The 5-HT(1A)Receptor agonist 8-OH-DPAT lowers intraocular pressure in normotensive NZW rabbits

The aims of this study were first to investigate the effect of topical instillation of the 5-HT(1A)receptor agonist 8-OH-DPAT on intraocular pressure (IOP) in normotensive rabbits and second to establish whether the drug reaches the aqueous humour of treated and contralateral eyes at concentrations sufficient to activate ciliary epithelial 5-HT(1A)receptors. Following topical unilateral instillation of (+/-), (+) or (-)8-OH-DPAT, the IOP of rabbits was measured using an applanation tonometer. For the penetration study, [(3)H]8-OH-DPAT was instilled into one eye of each rabbit. Animals were killed after 30 min and the radioactive content of treated and contralateral ocular tissues was assessed. Administration of (+/-)8-OH-DPAT caused dose-dependent decreases in IOP in treated eyes of rabbits during the light and dark. The full 5-HT(1A)agonist (+)8-OH-DPAT was shown to be a more effective hypotensive agent than the partial agonist (-)8-OH-DPAT. The effect of (+/-)8-OH-DPAT on IOP was blocked by pretreatment with pindolol, a mixed 5-HT(1A)antagonist/beta-blocker, but not by the specific beta-blocker betaxolol. After instillation of [(3)H]8-OH-DPAT, peak levels of radioactivity were found in the cornea, followed by similar amounts in the iris-ciliary body and aqueous. There was negligible radioactivity present in tissues of the contralateral eye. This study demonstrates that topical administration of the 5-HT(1A)agonist 8-OH-DPAT dose-dependently decreases IOP in normotensive rabbits during the light and dark. The action of 8-OH-DPAT is presumably local to the anterior uvea as IOP was reduced only in treated eyes and [(3)H]8-OH-DPAT failed to reach the contralateral eye after unilateral instillation. Moreover, since 5-HT(1A)receptors are located in the rabbit ciliary epithelium and the effect of 8-OH-DPAT is blocked by a recognized 5-HT(1A)antagonist, the mechanisms of action of 8-OH-DPAT may well involve a decreased secretion of aqueous humour.     

Aqueous humor dynamics in monkeys after topical R-DOI

PURPOSE: To determine the effects of R-DOI, a selective 5-HT2 agonist, on intraocular pressure (IOP) and aqueous humor dynamics in monkeys. METHODS: Normotensive cynomolgus monkeys (n = 8) were treated topically once daily with four 5-muL drops of 0.5% R-DOI in one eye, vehicle in the opposite eye. The 6-hour IOP response (Goldmann applanation tonometry) was determined before the drug application and on the third day of treatment. Aqueous humor formation, or flow (AHF, measured by fluorophotometry), was measured from hours 3 to 8 after the third dose. Beginning 3.5 hours after the fourth or fifth dose, AHF was measured by dilution of radio-iodinated monkey albumin perfused through the anterior chamber and flow to blood by accumulation of albumin in the general circulation. Uveoscleral outflow (Fu) was calculated. Flow to blood was determined at spontaneous and elevated pressures, allowing calculation of trabecular outflow facility. Total outflow facility was determined by two-level constant pressure perfusion from 3.5 to 5 hours and from 5.5 to 6.25 hours after R-DOI treatment. RESULTS: Reduction of IOP in treated eyes was compared to the opposite control eyes corrected for the 6-hour IOP baseline before the first dose. After the third dose of R-DOI, IOP was significantly (P < 0.01, n = 7) decreased by 1.4 to 4.7 mm Hg over the 6 hours. AHF (by fluorophotometry) increased by 13% (P < 0.05, n = 8) in treated compared with control eyes corrected for baseline. AHF (isotope dilution) increased by 30% (P < 0.01, n = 8), flow to blood decreased by 28% (n = 5), and Fu increased by 241% (P < 0.05, n = 5). Total and trabecular outflow facility were unchanged. CONCLUSIONS: R-DOI caused a small but significant increase in AHF and lowered IOP in normotensive monkeys primarily by increasing Fu.     

Biodegradable calcium phosphate nanoparticles as a new vehicle for delivery of a potential ocular hypotensive agent.

The purpose of this study was to determine the efficacy of a newly prepared formulation containing biodegradable calcium phosphate nanoparticles (CAP) and 7-hydroxy-2-dipropyl-aminotetralin (7-OH-DPAT) in pigmented and non-pigmented rabbits using the surrogate end points of intraocular pressure (IOP) and aqueous flow rate. IOP (mmHg) was measured by utilizing a manometrically calibrated Mentor pneumatonometer. Rates of aqueous humor flow were measured with a Fluorotron Master by estimating the dilution rate of fluorescein. In non-pigmented rabbits, the ocular hypotension induced by topical administration of 7-OH-DPAT (75 microg) with CAP (115 microg) was more pronounced and sustained than that of 7-OH-DPAT without CAP. Furthermore, IOP-lowering effects of topically administered 7-OH-DPAT (125 microg) alone were markedly diminished in pigmented rabbits compared to non-pigmented rabbits. However, topical application of 7-OH-DPAT formulated with CAP produced significant dose-related (37.5, 75, 125 microg) reductions of IOP accompanied by suppression of aqueous humor flow rates in pigmented rabbits. It is postulated that 7-OH-DPAT in vehicle without CAP binds to pigments in the anterior segment of the pigmented rabbit's eyes, and this binding limits the 7-OH-DPAT's action. Pretreatment with raclopride, a dopamine D2/D3 receptor antagonist, reduced the ocular hypotensive effect induced by 7-OH-DPAT in vehicle containing CAP thereby supporting the role for dopamine D2/D3 receptors in modulating IOP. It is concluded that CAP, as a delivery system, enhances activity by 7-OH-DPAT in pigmented rabbit eyes suggesting that CAP is potentially useful for achieving controlled and targeted drug delivery for treatment of ocular diseases.     

Effect of flunarizine, a calcium channel blocker, on intraocular pressure and aqueous humor dynamics in monkeys

PURPOSE: To evaluate the effects of flunarizine, a nonselective calcium channel blocker, on intraocular pressure (IOP) in monkeys with laser-induced unilateral glaucoma and on aqueous humor dynamics in normal monkeys. METHODS: The IOP was measured before and hourly for 6 hours after single-dose administration of 0.5%, 1%, or 2% flunarizine to the glaucomatous eye of 8 monkeys with unilateral laser-induced glaucoma. In a separate multiple-dose study, 0.5% flunarizine was applied twice daily for 5 consecutive days to the glaucomatous eye of the same 8 monkeys. IOP was measured at untreated baseline, after treatment with vehicle only, and on treatment days 1, 3, and 5. Tonographic outflow facility and fluorophotometric flow rates of aqueous humor were measured in 7 normal monkeys before and after the fifth dose of twice-daily treatment with 0.5% flunarizine. RESULTS: Unilateral application of 50 microL of 0.5%, 1%, or 2% flunarizine reduced IOP bilaterally. In the treated glaucomatous eyes, flunarizine reduced the IOP for 2, 3, or 5 hours, with a maximum reduction of 2.5+/-0.5 (mean+/-SEM) mm Hg (9%), 3.0+/-0.4 mm Hg (10%), and 5.0+/-0.8 mm Hg (18%) following the 0.5%, 1%, and 2% concentrations, respectively (P<0.01). The maximum reductions in IOP in the contralateral untreated eyes were 1.3+/-0.5 mm Hg, 1.5+/-0.3 mm Hg, and 2.9+/-0.7 mm Hg following the 0.5%, 1%, and 2% concentrations, respectively (P<0.05). Both the magnitude and duration of the ocular hypotensive effect of 0.5% flunarizine were enhanced with twice-daily administration for 5 days. Outflow facility in normal monkey eyes was increased (P<0.05) by 39% in the treated eyes compared with vehicle-treated contralateral eyes and by 41% compared with baseline values, and aqueous humor flow rates were unchanged (P>0.30). CONCLUSIONS: Flunarizine reduces IOP in a dose-dependent manner when administered to glaucomatous monkey eyes, but also has an ocular hypotensive effect on the contralateral untreated eyes. An increase in tonographic outflow facility seems to account for the IOP reduction in normal monkey eyes.     

The effect of bunazosin hydrochloride on intraocular pressure and aqueous humor dynamics in human]

The effects of bunazosin hydrochloride, a new highly selective alpha 1 adrenergic antagonist, on the intraocular pressure (IOP) and aqueous humor dynamics in healthy human volunteers were studied. Unilateral topical administration of 0.1% bunazosin significantly lowered IOP from 1 to 10 hrs in bunazosin-treated eyes, and from 2 to 8 hrs in contralateral placebo-treated eyes, with its maximum reduction at approximately 3 hrs, when the IOP decreased 5.0 mmHg in treated eyes, and 3.5 mmHg in contralateral eyes from the baseline, respectively. Fluorophotometrically measured aqueous humor flow rates did not change significantly either in treated or contralateral eyes. Bunazosin caused significant reduction of systolic and diastolic blood pressure 5 hr after application. The difference in pupil diameter between treated and contralateral eyes was found to be statistically significant from 1 to 5 hrs. A small but significant increase in anterior chamber depth also was observed from 2 to 6 hrs. Pulse rate and refraction were not substantially altered. There was moderate conjunctival vessel dilation, however, no serious complications were encountered. The results suggest that bunazosin hydrochloride appears to have great clinical potential for ocular hypotensive therapy.     

Aqueous humor dynamics in monkeys after topical 8-iso PGE(2)

PURPOSE: To determine in normotensive cynomolgus monkeys, the effects of topical 8-iso prostaglandin (PG)E(2) on intraocular pressure (IOP), aqueous humor formation (AHF), uveoscleral outflow (Fu), and total and trabecular outflow facility. METHODS: IOP was measured by Goldmann applanation tonometry under ketamine anesthesia after single or twice-daily topical treatments with 8-iso PGE(2). With animals under pentobarbital anesthesia, AHF and flow to blood (equated to trabecular outflow) were determined by anterior chamber perfusion with radioactively labeled albumin solution. Fu and trabecular outflow facility were calculated from these measurements. Total outflow facility was measured by two-level, constant-pressure perfusion. RESULTS: IOP was not significantly changed after single or multiple 10- micro g doses of 8-iso PGE(2). The 25- micro g dose significantly decreased IOP by 2 to 3 mm Hg compared to the contralateral vehicle-treated control 4 to 6 hours after a single dose and by 3 to 5 mm Hg within 1.5 hours after twice-daily treatments for 4 to 5 days. Total outflow facility corrected for control eye washout was increased by an apparent 37% (P < 0.02, n = 7) from 2 to 3.5 hours after the ninth dose, largely due to outlier values obtained in one monkey. Isotope studies performed after twice-daily treatments totaling 9 to 29 doses showed no change in AHF, trabecular outflow facility, or total outflow facility. Relative to AHF, trabecular outflow was significantly decreased, and the calculated Fu was significantly increased when all data were analyzed. CONCLUSIONS: The present findings are consistent with lowering of IOP by 8-iso PGE(2), primarily by increasing Fu. A direct effect on the trabecular meshwork was not indicated by these in vivo studies.     

HSV-1 recovery from ocular tissues after viral inoculation into the superior cervical ganglion

New Zealand albino rabbits were inoculated in the right superior cervical ganglion with 25 microliter of herpes simplex virus type 1 (HSV-1) (McKrae strain; 10(3) or 10(5) PFU/ml). Positive tear film swabs were detected at least once in 28/32 (88%) of ipsilateral eyes and 6/32 (19%) of contralateral eyes beginning on postinoculation (PI) day 2-6. The average HSV-1 titer in the tear film was 4.0 X 10(3) PFU in ipsilateral eyes and 2.7 X 10(3) PFU in contralateral eyes, determined from eye washes after inoculation of 25 PFU of HSV-1. In selected rabbits, the aqueous humor was positive for virus on PI days 3, 4, 5, 6, and 8. the aqueous humor in ipsilateral eyes showed positive results in 9/11 (82%) of the eyes tapped on PI 3, 13/18 (72%) on PI 4, 5/11 (45%) on PI 5, 1/6 (17%) on PI 6, and 1/2 (50%) on PI 8. No virus was detected in aqueous humor tappings in any contralateral eyes (0/65). Conjunctivitis and iritis (iris hyperemia) appeared in all ipsilateral eyes beginning as early as PI day 1. Conjunctivitis occurred in 1/21 (4.8%) of contralateral eyes. Cells and flare appeared in 18/21 (86%) of ipsilateral eyes and 2/21 (9.5%) of contralateral eyes. Hyphema was noted in 3/21 (14%) of ipsilateral eyes. Of the eyes with iritis, 12/21 (57%) developed corneal edema. Corneal dendritic ulcers were observed in 4/21 (19%) of ipsilateral eyes and 2/21 (9.5%) of contralateral eyes. No ocular fundus changes were seen in any contralateral or ipsilateral eyes.(ABSTRACT TRUNCATED AT 250 WORDS)     

改良式前房放液在白内障超声乳化术后早期高眼压中的应用

目的:探讨改良式前房放液法在白内障超声乳化吸出术后早期高眼压的应用价值。方法:对我院3170眼白内障超声乳化吸出术患者中14眼出现术后早期高眼压的患者经过一次性注射器针头轻压角膜侧切口放出部分房水,降低眼压,减轻角膜水肿。结果:经过上述处理后14眼眼压下降为(11.4±5.1)mmHg,角膜透明;视力大于或等于0.7者8眼,0.3～0.5者5眼,0.2者1眼;未出现与改良式前房放液相关并发症。结论:改良式前房放液治疗白内障超声乳化术后早期高眼压简单易行、安全有效,值得推广。     

Aporphine derivatives affect ocular function in diverse ways

The sympathetic nervous system has been implicated in the ocular effects of several classes of dopamine receptor agonists. Two agonists of the aporphine class, (-) N-propylnorapomorphine [-)NPA) and norapomorphine (NA), were evaluated for effects on intraocular pressure (IOP) and pupil diameter (PD) in cats and normal (NL) and sympathectomized (SX) rabbits and on contractions of the cat nictitating membrane (CNM). Topically administered (-)NPA produced a monophasic IOP drop in the ipsilateral eye and a biphasic (increase, decrease) IOP response in the contralateral eye of normal rabbits. Pupil diameter increased bilaterally. In NL cats, the ipsilateral IOP and PD response to (-)NPA was biphasic (increase, decrease) and the contralateral IOP response was monophasic (increase). (-)NPA produced an increase in spontaneous motor activity (SMA) in rabbits and cats. NA lowered IOP unilaterally in NL rabbits. In SX rabbit eyes, (-)NPA lowered IOP as much as in NL eyes but with less mydriasis. NA did not lower IOP in SX rabbit eyes. Both (-)NPA and NA inhibited contractions of the CNM elicited by electrical stimulation of the pre- and post-superior cervical ganglionic nerves. (-)NPA, but not NA, inhibited contractions elicited by exogenous norepinephrine. These results suggest that aporphine derivatives produced two diametrically opposed effects on ocular function; 1) a centrally mediated effect that enhanced noradrenergic activity to elicit mydriasis, SMA and ocular hypertension, and 2) a peripherally mediated effect to produce miosis and ocular hypotension.     

Pharmacology of serotonin receptors modulating electrically-induced [3h]-norepinephrine release from isolated mammalian iris-ciliary bodies.

The pharmacology of prejunctional serotonin (5-HT) heteroreceptors that regulate the release of norepinephrine (NE) was studied in isolated bovine and human iris-ciliary bodies. The effect of exogenous 5-HT and various 5-HT receptor agonists was examined on the release of [3H]-norepinephrine ([3H]NE). Both 5-HT and m-chlorophenyl-biguanide (m-CPBG) caused enhancement in the field-stimulated release of [3H]NE from bovine tissues whereas 5-carboxamidotryptamine (5-CT) had no such effect. On the other hand, 8hydroxy-dipropylaminotetralin (8-OH-DPAT), caused a significant dose-related inhibition of evoked [3H]NE release. In human iris-ciliary bodies, 5-HT caused an inhibitory response on electrically-evoked [3H]NE release at low concentrations but produced an excitatory action at concentrations greater than 3 microM. To further confirm the nature of the prejunctional 5-HT heteroreceptors regulating [3H]NE release, effects of 5-HT3, 5-HT6 and 5-HT7 receptor antagonists were examined on a standard response to 5-HT. All antagonists examined caused a concentration-dependent inhibition of the response elicited by the standard 5-HT-induced response with the following rank order of potency (as measured by IC30 values): MDL-72222 > SB-258719 > RO-04-690. We conclude that the excitatory prejunctional 5-HT heteroreceptors present in bovine iris-ciliary bodies belong to the 5-HT3 receptor subtype.     

8OH-DPAT-Induced ocular hypotension: sites and mechanisms of action.

The purpose of this study was to define the ocular actions of 8-OH-DPAT(DPAT), a 5-HT(1A)receptor agonist. The intraocular pressure responses to topically applied DPAT were dose related (25, 125, 250 microgram) and bilateral in normal rabbits but of relatively short duration. Ocular hypotension induced by topical, unilateral DPAT (125 microgram) in normal eyes did not occur in sympathetically denervated eyes. DPAT-induced ocular hypotension was inhibited by pretreatment with spiroxatrine, a 5-HT(1A)and alpha(2C)receptor antagonist, but not spiperone, a 5-HT(2A)receptor antagonist. In contrast, the hypotensive effect produced by unilaterally applied DPAT in the contralateral eye was abolished following pretreatment with rauwolscine, an alpha(2)-receptor antagonist, but the DPAT-induced ocular hypotension was not antagonized in the treated (ipsilateral) eye. Following central administration of DPAT (3 microgram) into the lateral ventricle, intraocular pressure was lowered bilaterally at 10 min and the effect lasted for 2 hr. In in vitro experiments, DPAT (0.1, 1, 10 micrometer) failed to alter norepinephrine release in rabbit iris-ciliary bodies. However, DPAT depressed basal cAMP levels in rabbit iris-ciliary bodies and also caused a dose-related (1, 10, 100 micrometer) inhibition of isoproterenol (1 micrometer)-stimulated cAMP accumulation by 26%, 58% and 82%, respectively. These findings indicate that: (1) based upon bilateral activity by the topical route, DPAT-induced ocular hypotension could result, in part, through activation of 5-HT(1A)receptors in the eye and 5-HT(1A)receptors and/or alpha(2C)adrenoreceptors in the central nervous system, (2) the activity of DPAT on 5-HT(1A)and/or alpha(2C)receptors was confirmed by antagonism of the ocular hypotensive response by spiroxatrine, (3) although there is no apparent prejunctional effect of DPAT on sympathetic nerves of iris-ciliary bodies, the accumulation of basal and isoproterenol-stimulated cAMP levels were depressed by DPAT, and (4) as a result of inhibition by rauwolscine, the ocular hypotensive effect of DPAT in the contralateral eye could involve an action on alpha(2)adrenoreceptors in the central nervous system.     

Pharmacological characterization of a serotonin receptor (5-HT7) stimulating cAMP production in human corneal epithelial cells

PURPOSE: To study the mRNA and pharmacology of a serotonin (5-HT) receptor positively coupled to adenylyl cyclase in normal, primary (P-CEPI), and immortalized human corneal epithelial cells (CEPI-17-CL4), by using numerous 5-HT agonists and antagonists. To determine and compare cloned human 5-HT7 receptor binding affinities of compounds with their functional potency data. METHODS: RT-PCR was used to detect the presence of an mRNA for the human 5-HT7 receptor in CEPI-17-CL4 cells. Receptor-mediated production of cAMP in cultured cells was measured using an enzyme immunoassay. Compound binding affinities were determined using [3H]-lysergic acid diethylamide ([3H]-LSD) binding to cell membranes of human embryonic kidney (HEK-293) cells expressing the cloned human 5-HT7 receptor. RESULTS: RT-PCR revealed the presence of a 5-HT7 receptor mRNA in CEPI-17-CL4 cells. Normal P-CEPI cells generated cAMP in response to 5-HT (-log EC50; pEC50=7.6), 5-carboxamidotryptamine (5-CT; pEC50=7.8), 5-methoxy-tryptamine (pEC50=7.0) and 5-methoxy-dimethyl-tryptamine (pEC50=5.7). In CEPI-17-CL4 cells, serotonergic agonists also stimulated cAMP production with different potencies (pEC50): 5-CT (7.4)>5-HT (6.5)> or =5-methoxy-tryptamine (6.1)>5-methoxy-dimethyl-tryptamine (5.4)> or =8-OH-DPAT (<5.0)=alpha-methyl-5-HT (<5.0). Various 5-HT receptor antagonists inhibited cAMP production induced by 5-CT in CEPI-17-CL4 cells with different potencies (pKi): methiothepin (8.5)>mesulergine (8.1)=metergoline (8.0)>spiperone (7.4)> or =clozapine (7.2)=SB-258719 (7.2)>mianserin (6.9)>ketanserin (6.3). Antagonist pKi values in P-CEPI cells were methiothepin (8.7), spiperone (7.4) and SB-258719 (6.6). The rank order of affinity for displacement of [3H]-LSD from the cloned human 5-HT7 receptor was: methiothepin>ritanserin>mesulergine=clozapine> or =metergoline=5-HT>SB-258719> or =spiperone>mianserin> or =ketanserin. The functional agonist and antagonist potency data obtained from CEPI-17-CL4 cells correlated well with cloned human 5-HT7 receptor binding affinity data (r=0.69), with P-CEPI cell functional data (r=0.85), and with functional potency data in the literature for the cloned human 5-HT7 receptor (r=0.88). CONCLUSIONS: These collective data support the presence of a pharmacologically defined, adenylyl cyclase-coupled 5-HT7 receptor in the CEPI-17-CL4 cells that may have relevance to physiological and/or pathologic functions of 5-HT7 receptors in the human cornea.     

The prostanoid EP2 receptor agonist butaprost increases uveoscleral outflow in the cynomolgus monkey

PURPOSE: To investigate the ocular hypotensive effect of the prostanoid EP2 receptor agonist butaprost and to establish its mechanism of action. METHODS: All experiments were performed in cynomolgus monkeys after topical application of butaprost (0.1%). The effects of butaprost on aqueous humor flow were determined by fluorophotometry. Total outflow facility was measured by the two-level, constant-pressure perfusion method, and uveoscleral outflow was determined by perfusion of FITC-labeled dextran through the anterior chamber. Effects on ocular morphology were studied after tissue fixation with transcardial perfusion by paraformaldehyde and immersion fixation of the globe, in animals subjected to long-term treatment with butaprost. Conscious ocular normotensive monkeys and monkeys with unilateral ocular hypertension were used for intraocular pressure (IOP) studies. RESULTS: Butaprost had no significant effect on aqueous humor flow or total outflow facility in ocular normotensive monkeys. Uveoscleral outflow was significantly higher in the butaprost treated eyes than in vehicle treated eyes, 1.03 +/- 0.20 vs. 0.53 +/- 0.18 microL.min(-1). After a 1-year treatment with butaprost, the morphology of the ciliary muscle was changed, showing increased spaces between ciliary muscle bundles and the apparent formation of new outflow channels. In many instances, changes were observed in the trabecular meshwork as well. Butaprost, in a single 0.1% dose, decreased IOP significantly in ocular normotensive monkeys and reduced IOP in laser-induced glaucomatous monkey eyes to the same level as that in the ocular normotensive contralateral eyes. CONCLUSIONS: The prostanoid EP2 receptor agonist butaprost appears to lower IOP by increasing uveoscleral outflow, according to both physiological and morphologic findings. Although the prostanoid EP2 receptor is structurally and functionally distinct from the FP receptor, the effects of EP2 and FP receptor stimulation on aqueous humor outflow are similar.     

Ocular effects associated with the chronic administration of the adenosine A(1) agonist cyclohexyladenosine

PURPOSE: To investigate changes in ocular responses associated with the chronic administration of the adenosine A(1) agonist cyclohexyladenosine (CHA). METHODS: New Zealand White rabbits were treated unilaterally twice-a-day for 30 days with CHA (165 or 500 microg) or vehicle. Intraocular pressures (IOPs) and pupil diameters (PDs) were evaluated over the course of the study. At the end of the study period, outflow facility was determined in selected animals and compared to na?ve vehicle- and CHA-treated animals. RESULTS: In rabbits receiving 165 microg of CHA, ipsilateral IOPs at 2 and 6 hours post-drug exhibited progressively greater reduction over the course of the study. Regression analysis demonstrated a significant correlation between study duration and lower IOP at 2 and 6 hours post-drug. In rabbits receiving 500 microg of CHA, ipsilateral IOP reductions at 2 hours post-drug were similar throughout the 30-day study. However, analysis of ipsilateral IOPs 6 hours following CHA administration, demonstrated a significant correlation between study duration and lower IOPs. Enhanced contralateral responses at 2 hours post- drug, were also measured in rabbits receiving 165 or 500 microg of CHA. In animals receiving chronic CHA treatment for 30 days, outflow facility 3 hours post-CHA was significantly elevated over that measured in na?ve vehicle-treated rabbits. Although mean outflow facility in chronic treatment animals was slightly elevated over CHA-induced increases in na?ve rabbits, this difference was not significant. No evidence of tolerance was observed for either dose during the course of these studies. No change in PD during the course of these studies was measured. CONCLUSIONS: The chronic administration of the adenosine A(1) agonist CHA twice daily produced no evidence of tolerance. Unexpectedly, the IOP response to CHA was enhanced with chronic administration. These data provide evidence that the use of adenosine A(1) agonists may be useful in the chronic treatment of ocular hypertension at doses lower than those identified in acute IOP studies.     

Modulation of ocular hydrodynamics and iris function by bremazocine, a kappa opioid receptor agonist

This study was designed to determine the activity of bremazocine (BRE), a relatively selective kappa opioid receptor agonist, on intraocular pressure (IOP), aqueous humor formation and pupil diameter (PD) in conscious, normal, dark-adapted New Zealand white (NZW) rabbits. IOP was measured in normal and unilaterally sympathectomized rabbits using a calibrated pneumatonometer and the aqueous flow rate was determined by the use of a Fluorotron Master. A masked-design study was conducted in which the rabbits' eyes were treated with BRE topically and unilaterally; the fellow eyes received vehicle. IOP and PD measurements were taken at 0.5 hr and 0 time before BRE and 0.5, 1, 2, 3, 4 and 5 hr post-treatment. Fluorophotometry recordings were taken at 1 hr before and 0.5, 1.5, 2.5 and 3.5 hr after topical application of the drug or vehicle. The effect of the relatively selective kappa opioid receptor antagonist, nor-binaltorphimine (nor-BNI), on bremazocine-induced changes in IOP, PD and aqueous flow was also determined. BRE (10 and 100 micrograms 25 microliters-1 vehicle) produced dose-related, bilateral reductions in IOP, PD and aqueous humor flow. A large increase in IOP (14 mmHg) was observed when BRE (100 micrograms) was applied to sympathectomized eyes. This ocular hypertensive effect was antagonized when the sympathectomized eyes were pretreated with naloxone (200 micrograms), a non-selective opioid receptor antagonist. BRE (10 and 100 micrograms) decreased the aqueous humor flow rate bilaterally by approximately 48 and 60%, respectively, at 0.5 hr after administration to the ipsilateral eye. Nor-BNI (100 micrograms) antagonized the effect of BRE (10 micrograms) on IOP and aqueous flow rates more effectively than on PD. These data indicate that bremazocine causes reductions in IOP by suppressing aqueous flow, but the ocular hypotensive effects are dependent on the presence of intact sympathetic nerves. Antagonism of BRE's effects on aqueous humor dynamics by nor-BNI suggests that the mechanism of IOP and aqueous flow reduction may involve, in part, an action on kappa receptors. Further experiments are necessary to fully define the opioid receptor populations in the ciliary body.     

Studies on the mechanism of action of timolol and on the effects of suppression and redirection of aqueous flow on outflow facility

Long-term use of drugs that suppress aqueous humor formation, such as timolol and dorzolamide, or that redirect aqueous humor outflow from the trabecular meshwork, such as prostaglandin F2alpha analogues, could cause underperfusion of the trabecular meshwork and a secondary decrease in outflow facility. We investigated the mechanism of suppression of aqueous humor formation by timolol in monkey eyes by measuring aqueous humor ascorbate levels. We also determined whether suppression of aqueous humor formation with and without redirection of aqueous humor away from the trabecular meshwork could lead to a subsequent reduction in outflow facility, and whether this reduction was correlated with increased fibronectin levels in anterior chamber aqueous humor. In cynomolgus monkeys, unilateral dose/aqueous humor formation response curves were generated for timolol, dorzolamide, and a combination of timolol + dorzolamide. Aqueous humor formation and/or outflow facility were measured in both eyes after approximately four days, four weeks and seven weeks of twice daily treatment with 3.5 microg timolol + 1.0 mg dorzolamide to one eye and 30% DMSO to the other. In some monkeys, 5 microg prostaglandin F2alpha-isopropyl ester (PG) was added to timolol + dorzolamide for 4-week treatments. Intraocular pressure and corneal endothelial transfer coefficients (k(a)) were also measured at four weeks. Aqueous humor fibronectin levels were determined in four monkeys after approximately 9.5 weeks of timolol + dorzolamide treatment. Aqueous humor formation, intraocular pressure, and aqueous humor ascorbate levels were also determined in rhesus monkeys at baseline and after a single unilateral topical administration of 25 microg timolol. Compared to baseline for the same eye, aqueous humor formation was significantly decreased in treated eyes at all doses of timolol and at 1.8 and 4 mg dorzolamide. Compared to the opposite control eye, aqueous humor formation was lower in treated eyes after 3.5 and 5 microg timolol and after all doses of dorzolamide. Aqueous humor formation after treatment with 3.5 microg timolol + 1.0 mg dorzolamide was decreased in treated vs. control eyes, after four days and was suppressed in both treated and control eyes after four weeks of treatment, but not when PG was added. There was no difference in k(a) values with or without the addition of PG. Intraocular pressure was significantly lower in both treated and control eyes vs. baseline after approximately 6.5 weeks treatment with timolol + dorzolamide when taken 2 hr after the last dose and after approximately 3.5 weeks treatment with timolol + dorzolamide + PG when measured 6 hr after the last dose. Outflow facility after treatment with timolol + dorzolamide was unchanged after four days, tended to be lower in the treated vs. control eyes after four and seven weeks, and was significantly lower in treated vs. control eyes after four weeks treatment with timolol + dorzolamide + PG (0.352 +/- 0.052 vs. 0.515 +/- 0.096 microl min(-1) mmHg(-1), p < or = 0.02). Both treated vs. control eye aqueous humor fibronectin levels were below the level of detection for our assay (0.01 microg ml(-1)). The 25 microg timolol dose decreased ipsilateral, but not contralateral intraocular pressure (12.6 +/- 1.7 vs. 15.2 +/- 0.9; p < 0.05) and aqueous humor formation (1.40 +/- 0.08 vs. 2.03 +/- 0.09 microg ml(-1), p < or = 0.01). There was no difference in anterior chamber ascorbate levels in treated vs. control eyes or compared to their respective baselines. Our findings indicate that timolol affects neither ciliary epithelial transport of ascorbate nor aqueous fibronectin levels. Our data also indicate that decreasing aqueous humor formation over a period of time can lead to reduction in outflow facility, particularly when combined with therapy that redirects aqueous from the trabecular meshwork. Future intraocular pressure-lowering therapies for glaucoma may better be directed at enhancing flow through the trabecular pathway as opposed to decreasing aqueous humor formation or rerouting aqueous humor away from the trabecular meshwork.     

Effect of the application of acetazolamide soaked contact lenses on intraocular pressure of rabbits

Topical application of acetazolamide has no known effect on intraocular pressure (IOP). We tried to detect the hypotensive effect on IOP of acetazolamide soaked onto soft contact lenses (CL). We applied CLs soaked in either 1%, 3%, or 5% acetazolamide solution onto one eye of 29 rabbits while the contralateral eye served as a control. There was an average 32% reduction of IOP amongst all acetazolamide applied eyes, and an average 19% reduction of IOP amongst all control eyes. Amongst the 1% acetazolamide-CL applied eyes there was a mean 37% reduction of IOP, amongst the 3% acetazolamide-CL applied eyes a mean 36% reduction, amongst the 5% acetazolamide-CL applied a mean 30% reduction, and a mean 19% reduction in control eyes. The longest period of IOP reduction followed the application of 1% acetazolamide-CLs, probably owing to improved drug corneal penetration at this concentration. Our results reveal that the application of acetazolamide soaked soft CLs has a significant hypotensive effect on IOP in both the applied and contralateral control eyes of rabbits.     

Effect of alpha-adrenergic and serotonergic blockers on the acute irritative response in the rabbit eye

The effect of alpha-adrenergic and serotonergic (5-HT) blockers on the acute irritative response in the rabbit eye elicited by topical, neutral formaldehyde (1%), was studied. In the control animals, the peak rise in the intraocular pressure (delta IOP) after irritation was 29.5 +/- 5.7 mm Hg, and the perfusion pressure of the eye at 1 min after irritation was 50.1 +/- 2.8 mm Hg. The peak rise in the IOP was inhibited by phentolamine (alpha- and 5-HT-antagonist, delta IOP = 6.6 +/- 2.1 mm Hg, P less than 0.01), methysergide (5-HT-antagonist, delta IOP = 10.6 +/- 4.4 mm Hg, P less than 0.05), and prazosin (alpha 1-antagonist, delta IOP = 12.8 +/- 3.7 mm Hg, P less than 0.05). Perfusion pressures of the eyes were decreased after pretreatment with phentolamine or prazosin, and were 35.2 +/- 4.8 mm Hg (P less than 0.05) and 25.7 +/- 3.7 mm Hg (P less than 0.01), respectively. Perfusion pressure in the methysergide group remained unchanged (75.4 +/- 14.2 mm Hg). Yohimbine (alpha 2-antagonist) and ketanserin (5-HT2-antagonist) did not inhibit the IOP response. None of the antagonists could inhibit the miosis or disruption of the blood-aqueous barrier induced by topical neutral formaldehyde. In the contralateral eyes, the changes in the IOP, in the integrity of the blood-aqueous barrier, and also in the pupil size, were enhanced by ketanserin. The present study demonstrates the inhibitory actions of methysergide, phentolamine, and prazosin on the neurally mediated, acute irritative response in the rabbit eye. Methysergide seems to inhibit the response, probably acting via the 5-HT1-receptors. A part of the effect of phentolamine might be explained by an inhibitory action via 5-HT1-receptors. The effect of phentolamine and prazosin on the alpha 1-receptors seems to create an inhibitory action on the irritative response by lowering the perfusion pressure of the eye.     

Flesinoxan, a 5-HT1A receptor agonist/alpha 1-adrenoceptor antagonist, lowers intraocular pressure in NZW rabbits

PURPOSE: alpha1-Adrenoceptor antagonists and 5-HT1A receptor agonists reduce intraocular pressure (IOP) in the rabbit. The aims of this study were firstly, to determine the IOP-lowering effects of flesinoxan and selected other hybrid 5-HT1A receptor agonists/alpha1-adrenoceptor antagonists, and secondly, to investigate the mechanism of action of the IOP response to flesinoxan. METHODS: IOP and total outflow facility were measured in rabbits after administration of hybrid drugs. Inositol phosphates accumulation assays were performed using standard methodologies. RESULTS: Topical unilateral instillation of the drugs caused dose-related reductions of IOP. Comparison of the compounds tested revealed a potency order of WB 4101 > flesinoxan > 5-methyl-urapidil > or = BMY7378 > urapidil. WB-4101 caused a small increase in total outflow facility whereas flesinoxan had no effect. Measurement of the IC50 values for inhibition of phenylephrine-stimulated inositol phosphates accumulation in rabbit iris-ciliary body revealed a potency order of WB 4101 > 5-methyl-urapidil > flesinoxan > BMY 7378 = urapidil. Topical flesinoxan was ineffective in reversing phenylephrine-induced mydriasis, yet, pretreatment with the 5-HT1A receptor antagonists MDL 73005EF and pindolol only partially blocked the hypotensive effect of topical flesinoxan. CONCLUSIONS: The present studies indicate the potent and efficacious IOP-lowering capabilities of flesinoxan and certain other ligands with affinity for 5-HT1A receptors/alpha1-adrenoceptors. The exact mechanisms by which these drugs lower IOP in the rabbit are complex but our results indicate that flesinoxan likely reduces aqueous secretion.     

晚期青光眼的房水动力学变化

目的：观察晚期青光眼高眼压对睫状体功能的损害作用及对角膜透明性的影响。方法：应用扫描荧光光度计及Ｓｃｈｉｏｔｚ电子眼压计分别测定１５只正常眼和１５只晚期原发性青光眼眼压、房水排出率和房水流畅系数,并观察角膜的透明性。结果：晚期青光眼眼房水排出率显著下降,下降程度与眼压水平及病程成正比。房水排出率降低至０．８μｌ／ｍｉｎ。角膜出现水肿混浊,房水排出率下降愈甚,角膜透明性改变愈明显。结论：持续高眼压将