The effect of prostaglandin F2 alpha on trabecular outflow facility in cynomolgus monkeys

Cynomolgus monkeys were treated topically in one eye with 2 micrograms of prostaglandin F2 alpha -l-isopropylester (PGF2 alpha-IE) twice daily. On day 4, 3 hr after the seventh dose, intraocular pressure (IOP) was 8.1 +/- 0.7 mmHg lower in the treated than in the control eyes. On day 5, after the ninth PGF2 alpha dose, gross facility was measured in both eyes by determining the rate of fluid flow from an external reservoir into the eye at two different IOP levels. Simultaneously, trabecular facility was measured by determining the rate of accumulation of intracamerally infused radioiodinated albumin in the general circulation. Gross facility was 40-60% higher in PGF2 alpha treated than in control eyes, but there was no difference in trabecular facility. The increase in gross facility sometimes reported following PGF2 alpha probably represents increased pseudofacility or uveoscleral facility, rather than true facility of outflow through the trabecular meshwork and Schlemm's canal.     

Effects of topical PGF2 alpha on aqueous humor dynamics in cynomolgus monkeys

Single topical applications of prostaglandin F2 alpha (PGF2 alpha) tromethamine salt to living cynomolgus monkey eyes reduced intraocular pressure (IOP). Twice daily topical application was far more effective, so that after the 7th 50 micrograms or 100 micrograms dose on day 4, IOP fell 40-50%, to 8-10 mm Hg. Following twice daily application of 50 or 100 micrograms for greater than 3 days: (1) no increase in total outflow facility could be demonstrated by 2-level constant pressure perfusion or Schiotz tonography; (2) no decrease in aqueous humor formation rate could be demonstrated by fluorophotometry--rather, aqueous flow may have increased; (3) anterior chamber aqueous humor protein concentration was unaltered, but entry of intravenously injected fluorescein into the cornea and anterior chamber tended to increase; (4) there was a weak but sometimes statistically significant miosis of up to approximately 0.5 mm. We conclude that in the cynomolgus monkey: (1) PGF2 alpha is a potent ocular hypotensive agent with only very weak miotic and blood-aqueous barrier-disrupting effects; (2) the ocular hypotensive action of PGF2 alpha is definitely not due to increased conventional outflow facility or decreased aqueous production, but probably to increased uveoscleral drainage of aqueous humor.     

Prostaglandin F2 alpha increases uveoscleral outflow in the cynomolgus monkey

Cynomolgus monkeys were treated topically in one eye twice daily with prostaglandin F2 alpha-l-isopropylester (PGF2 alpha-IE) for nine doses. On treatment day 4, 3 hr after the seventh dose, intraocular pressure (IOP) in the treated eye was reduced by 65% compared to the controls, to less than 5 mmHg. On treatment day 5, 3 hr after the ninth dose, total outflow facility was determined by two-level constant pressure perfusion of the anterior chamber. Immediately thereafter, uveoscleral outflow was determined by intracamerally infusing [125I]- or [131I]-albumin and fluoresceinated dextran, and calculating the volume of anterior chamber fluid required to have deposited the quantity of tracer recovered from the various ocular and periocular tissues. Simultaneously, trabecular outflow was determined by calculating the volume of anterior chamber fluid required to have deposited the quantity of tracer recovered from the general circulation. Total facility was approximately 50% higher in treated than in control eyes, but the effect was variable, of marginal statistical significance, and perhaps due to increased pseudofacility or uveoscleral facility. Uveoscleral outflow was approximately two to three-and-a-half times higher in treated than in control eyes, the magnitude of the effect being dependent upon the timing and pressure at which the perfusion was conducted. Trabecular outflow was reduced by approximately 75% in the treated eyes relative to control so that the proportion of total outflow comprised by trabecular outflow in the treated eyes was only one third that in the controls. Total aqueous flow was slightly (approximately 20%) but not significantly reduced in the treated eyes. The IOP lowering effect of PGF2 alpha in the cynomolgus monkey is due largely if not exclusively to an increase in uveoscleral outflow of aqueous humor, with aqueous outflow being redirected from the trabecular to the uveoscleral route.     

A new procedure for the measurement of the outflow facility in conscious rabbits

A new procedure for measuring the outflow facility in conscious rabbits is described. The Langham pneumatic tonometer is applied horizontally against the eye; the intraocular pressure (IOP) is recorded before, during and immediately following 2 min of a pre-determined increased ocular pressure that is maintained at a fixed value by digital pressure applied through the eyelids. An increased volume of aqueous humor outflow resulting from the IOP increase is evaluated from the initial and final IOP values and the pressure volume relation for eyes of living rabbits. Close agreement in values of the outflow facilities in pairs of eyes of individual rabbits and excellent reproducibility of the procedure were found in repeated measurements made over a 24-hr period. The mean values of the IOP and the total outflow facility in 60 eyes of 30 rabbits were 20.5 +/- 0.2 mmHg and 0.17 +/- 0.01 microliter min-1 mmHg-1 respectively. Thirty minutes after an intravenous injection of acetazolamide, the IOP had decreased in both eyes of individual rabbits. This was associated with a decrease in the outflow facility and with a decrease of more than 50% in the rate of aqueous humor formation. One hour after the unilateral application of epinephrine the IOP had decreased in the treated eyes while the outflow facility remained unchanged.     

Effects of brinzolamide on aqueous humor dynamics in monkeys and rabbits.

This study examines the mechanisms by which brinzolamide reduces intraocular pressure (IOP) in healthy rabbits and in monkeys with unilateral ocular hypertension. Intraocular pressures were measured by pneumatonometry and aqueous flow was determined by fluorophotometry before and after three twice-daily drops of 1% brinzolamide to both eyes per monkey and after similar treatment to one eye per rabbit. In monkeys, outflow facility was determined by fluorophotometry and uveoscleral outflow was calculated. In rabbits, outflow facility was determined by two-level constant pressure infusion and uveoscleral outflow was measured by an intracameral tracer technique. Compared with contralateral vehicle-treated rabbit eyes, IOP was reduced in brinzolamide-treated eyes by 2.5 +/- 1.9 mmHg (mean +/- standard deviation; p =.006) at four hours after the second dose. Aqueous flow was reduced by 0.50 +/- 0.65 microl/min (p =.02). This effect was found in rabbits previously treated with brinzolamide but not in naive rabbits. Treated hypertensive eyes of monkeys had a reduction in IOP of 7.3 +/- 8.8 mmHg (p = 0.01) and aqueous flow of 0.69 +/- 1.10 microL/min (p = 0.05) when compared with baseline. Brinzolamide did not affect outflow facility or uveoscleral outflow in either rabbits or monkeys. It is concluded that, in normotensive eyes of rabbits and hypertensive eyes of monkeys, brinzolamide reduces IOP by reducing aqueous flow and not by affecting aqueous humor drainage.     

Topical verapamil lowers outflow facility in the rabbit eye.

Results of studies examining the mechanism of the ocular hypotensive effect of topical calcium channel blockers are controversial. Whereas evidence obtained in perfused human eyes indicates that these drugs lower intraocular pressure by increasing the aqueous humor outflow, tonographic studies in rabbits have revealed that they reduce both the aqueous humor outflow and inflow. In order to clarify such a discrepancy, the aim of this study was to assess whether the effect of topical verapamil on the facility of aqueous humor outflow in the rabbit eye was dose-related. Total outflow facility was determined by two-level constant pressure perfusion in anesthetized rabbits. The effect of 5 different concentrations on aqueous humor outflow at 60 minutes postdrug was studied in groups of 10 rabbits each. Baseline outflow facility was also determined in a group of 15 rabbits. In order to check the reliability of the method for detecting drug-induced changes in aqueous outflow, the effect of pilocarpine was also tested. Topical verapamil was shown to lower outflow facility in the rabbit eye in a dose-related fashion. On the contrary, topical pilocarpine was found to significantly increase outflow facility. Our data indicate that topical verapamil reduces outflow facility in the rabbit eye.     

Effect of topical prostaglandin D2 on the aqueous humor dynamics in rabbits

Effects of topically applied prostaglandin (PG) D2 on the aqueous outflow facility, uveoscleral flow, and aqueous flow rate were studied in rabbits to reveal its intraocular pressure (IOP)-reducing mechanism. The outflow facility after PGD2 application (50 micrograms) as measured by 2-min tonography was 0.19 microliters/min/mm Hg and did not differ from that before the application (0.22) or from that of the control contralateral eye (0.21). Direct measurement of the uveoscleral flow by perfusion of the anterior chamber for 30 min with fluorescein isothiocyanate-labeled dextran solution showed the flow rate to be about 0.15 microliters/min in indomethacin-treated (10 mg/kg, i.p.) rabbits. In these animals, PGD2 (50 micrograms) was ineffective in changing the flow rate, while PGF2 alpha (50 micrograms) significantly increased the flow by about 35%. Indirect assessment of the effects of PGs on this flow system was made using the uveoscleral flow-antagonizing ability of topical pilocarpine (1.5 mg). IOP reduction by PGD2 (50 micrograms) was only slightly inhibited by pilocarpine, while that by PGF2 alpha (10 micrograms) was markedly reduced. Aqueous flow rate measured fluorophotometrically was about 3.5 microliters/min in normal eyes. After PGD2 (50 micrograms) the flow rate was significantly reduced to 3.0 microliters/min. The magnitude of this reduction was estimated to be enough to account for the IOP reduction after application of 50 micrograms of PGD2. These results indicate that IOP reduction caused by topical PGD2 application is due mostly to the inhibition of aqueous flow rate.     

Prostaglandin F2 alpha isopropyl ester versus iloprost phenacyl ester in rabbit and beagle eyes

One and 2 micrograms of prostaglandin F2 alpha isopropyl ester (PGF2 alpha -IE) applied topically to the rabbit eye caused a biphasic response. The hypotensive phase was dose-dependent with a maximum reduction in intraocular pressure (IOP) of 9.4 +/- 1.7 mmHg at a dose of 2 micrograms. In beagles, 0.4 to 2 micrograms topical PGF2 alpha-IE resulted in a sustained IOP reduction; 2 micrograms produced the maximum reduction of 7-9 mmHg. No initial hypertensive response was observed. Iloprost phenacyl ester (Iloprost-PE) caused a greater decrease in IOP when dissolved in 0.5% hydroxypropyl methylcellulose (AT) than in saline. In rabbits, doses of 0.1 to 1 microgram in AT caused a biphasic response with a sustained IOP decrease fluctuating between 7 and 8 mmHg. In beagles 1 and 2 micrograms Iloprost-PE resulted in a mean IOP reduction of 5.8 +/- 0.4 mmHg and 5.8 +/- 0.5 mmHg (P less than 0.005), respectively; the decrease persisted for 5 hrs. No initial hypertensive response was observed. In beagles PGF2 alpha-IE induced a strong miosis lasting more than 6 hours; Iloprost-PE had no effect on pupil size. Both PG-esters induced a slight hyperemia in rabbit and beagle eyes. In rabbits Iloprost-PE affects the blood-aqueous barrier more than PGF2 alpha-IE, since higher protein concentrations are seen in the aqueous humor after application of Iloprost-PE. Neither PG-ester had a noticeable effect on aqueous protein in beagles. In rabbits, both PG-esters led to slightly increased aqueous humor cyclic-AMP concentrations. In beagles aqueous humor cyclic-AMP was elevated only after Iloprost-PE.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Eicosanoids as a new class of ocular hypotensive agents. 2. Comparison of the apparent mechanism of the ocular hypotensive effects of A and F type prostaglandins

It has recently been shown that derived prostaglandins (PGs) of the A and B types are much more potent ocular hypotensive agents than primary PGs of the E, F, or D type. The purpose of this study was to determine whether two representatives of these structurally different PGs, namely PGA2 and PGF2 alpha-1-isopropyl ester (PGF2 alpha IE), reduce intraocular pressure (IOP) of the feline eye by similar or dissimilar mechanisms. Aqueous humor flow rate was determined by a fluorophotometric technique, Schiotz electronic tonography was used to measure outflow facility and venomanometry was done to measure episcleral venous pressure. Although at the doses used, both PGF2 alpha IE (2.5 micrograms/eye) and PGA2 (5.0 micrograms/eye) caused significant IOP reduction within 2.5 hr after their topical application, neither caused a significant decrease in aqueous humor flow rate, a significant increase in outflow facility or a change in episcleral venous pressure. It was concluded, therefore, that both of these PGs reduce IOP by an apparently similar mechanism, presumably by increasing uveoscleral outflow.     

Effect of latanoprost on outflow facility in the mouse

PURPOSE: To assess the early effect of latanoprost on outflow facility and aqueous humor dynamics in the mouse. METHODS: Aqueous humor dynamics in NIH Swiss White mice were assessed with an injection and aspiration system, using fine glass microneedles. A single 200-ng (4 microL) dose of latanoprost was applied to one eye 2 hours before measurement. The fellow eye served as a control. Intraocular pressure (IOP) was measured by using an established microneedle procedure. Outflow facility (C) was determined by constant-pressure perfusion measurements obtained at two different IOPs. Aqueous humor flow (Fa) was determined by a dilution method using rhodamine-dextran. Conventional and uveoscleral outflow (Fc and Fu) were calculated by the Goldmann equation. RESULTS: Average IOP, Fa, and C of control eyes were 15.7 +/- 1.0 mm Hg, 0.144 +/- 0.04 microL/min (mean +/- SD, n = 8), and 0.0053 +/- 0.0014 microL/min per mm Hg (n = 21), respectively. Average IOP, Fa, and C of treated eyes were 14.0 +/- 0.8 mm Hg, 0.138 +/- 0.04 microL/min (n = 8 for each), and 0.0074 +/- 0.0016 microL/min per mm Hg (n = 21), respectively. The differences between treated and control eyes were significant for IOP and total outflow facility only. CONCLUSIONS: These data indicate that the early hypotensive effect of latanoprost in the mouse eye is associated with a significant increase in total outflow facility. Alterations in the aqueous dynamics induced by latanoprost can be measured reproducibly in the mouse and may provide a useful model for further determining the mechanism by which latanoprost reduces IOP and alters outflow facility.     

Inhibition by indomethacin of the increased facility of outflow induced by adrenaline

Topical adrenaline lowers intraocular pressure (IOP) in the rabbit largely due to an increase in facility of outflow of aqueous humour. This paper studies the inhibition by indomethacin or piroxicam of the adrenaline-induced rise in facility of outflow. Topical indomethacin is shown to reduce the acute IOP changes induced by adrenaline in conscious rabbits; both the early rise and the prolonged fall in pressure were inhibited. In anaesthetized rabbits, indomethacin pretreatment prevented the large rise in facility of outflow which normally follows topical adrenaline. Indomethacin did not block the mydriasis induced by adrenaline, nor did it significantly alter aqueous humour protein levels. Piroxicam, a cyclo-oxygenase inhibitor which, unlike indomethacin, does not block Ca2+ movements in some tissues, also blocked the adrenaline-induced rise in facility of outflow, suggesting that this increased facility depends on cyclo-oxygenase and not on Ca2+ movements. Verapamil, a drug which blocks Ca2+ channels, was shown to inhibit the brief ocular hypertensive effect of adrenaline in the conscious rabbit, but to leave the hypotensive phase unchanged. It is concluded that the hypotensive mechanism of adrenaline may depend on synthesis of a prostaglandin, since inhibition of the adrenaline-induced rise in facility is achieved by inhibitors of cyclooxygenase. Despite previous reports that a prostaglandin may be responsible for the brief hypertensive phase, the present evidence suggests that Ca2+ movements may be involved, perhaps in activation of the extraocular muscles.     

The effect of prostaglandin F2 alpha on intraocular pressure in normotensive human subjects

Hypotensive and other ocular effects were studied for 24 hr after topical application of prostaglandin F2 alpha as the tromethamine salt (PGF2 alpha) in 45 normotensive human subjects. After baseline intraocular pressure (IOP) measurements, 62.5 micrograms, 125 micrograms and 250 micrograms of PGF2 alpha dissolved in 50 microliter of saline was applied to one eye of 15 subjects for each dose tested. Contralateral control eyes received 50 microliter of saline. As compared with the IOP of the contralateral control eyes, topical application of 62.5 micrograms PGF2 alpha caused a significant IOP reduction at 1-12 hr, with a maximal IOP reduction of 2.2 mm Hg at 2 hr. Treatment with 125 micrograms of PGF2 alpha lowered IOP significantly at 1-21 hr, with a maximal reduction of 3.1 mm Hg at 9 hr. Administration of 250 micrograms PGF2 alpha produced a significant reduction of IOP, which lasted for at least 24 hr. A maximal IOP reduction of 2.9 mm Hg occurred at 7 hr. Pupillary diameter was not altered. Aqueous flare and anterior chamber cellular response were not seen in any of the eyes of the subjects at any time after topical application of 62.5-250 micrograms PGF2 alpha. The drug caused side effects consisting of reddened skin of lower lid, ocular irritation, conjunctival hyperemia and headache.     

Diurnal variations in outflow facility

Tonography was carried out at 8 AM, 2 PM, and 8 PM on 43 normal eyes, 58 open-angle glaucomatous eyes and 10 ocular hypertensive eyes. Diurnal variations in outflow facility and their relation to those in intraocular pressure (IOP) were studied. Diurnal variations in outflow facility were present in almost all eyes, with approximately a 10% exception. The average diurnal variation in true outflow facility (deltaCtrue) was 0.10 microliter/min/mm Hg in normal eyes and 0.07 microliter/min/mm Hg in glaucomatous eyes. The average rate of diurnal variation in true outflow facility: formula: (see text) was 43.6% in normal eyes and 69.1% in glaucomatous eyes. The value was greater in glaucomatous eyes than in normal eyes. The curve of diurnal variations in true outflow facility was divided into 5 types, and in glaucomatous eyes the value of outflow facility was apt to increase in the morning and decrease in the evening. In 42% of the normal and 45% of the glaucomatous eyes, inverse relation was seen between diurnal variations in outflow facility and diurnal rhythm in IOP. It is thought that diurnal variations in outflow facility, along with diurnal fluctuations in the rate of aqueous formation, are one of the factors responsible for the diurnal rhythm found in IOP.     

Different Effects of Topical Prazosin and Pilocarpine on Uveoscleral Outflow in Rabbit Eyes

Purpose:To investigate the effects of topical prazosin and pilocarpine on uveoscleral outflow(Fu) in rabbits.Methods:Sixteen rabbits were randomly divided into the control group (5 rabbits, only topical application of normal saline in the fight eye of each rabbit), Prazosin (PZ) treated group (6 rabbits, only 0.1％ Prazosin eyedrop 0.1％ in the right eye of each one) and Pilocarpine (PC) treated group (5 rabbits, 1％ Pilocarpine eye drop in each fight eye). Intraocular pressure (IOP) of bilateral eyes of each rabbit was measured before and 1h after topical application of the eye drop. And the bilateral eyes were perfused with Fluorescein-isothiocyanate bovine serum albumin (FITC-BSA) as the tracer into the anterior chamber of each rabbit for 30 min at 90 min after topical treatment. Then the rabbits were killed for Fu measurement.Results:IOP of PZ-treated eyes decreased [(0.71±0.07)kPa] in 1 hour after PZ application. IOP of PC-treated eyes decreased [(0.70±0.08)kPa] in 1 hour after PC application. Th     

The effect of topical CS-088, an angiotensin AT1 receptor antagonist, on intraocular pressure and aqueous humor dynamics in rabbits

PURPOSE: To evaluate the ocular hypotensive effect of topical CS-088, an angiotensin AT1 receptor antagonist, and the effect of CS-088 on aqueous humor dynamics. METHODS: The effects of CS-088 on intraocular pressure (IOP) were studied in 2 models of rabbit ocular hypertension. Experimental ocular hypertension was induced in albino rabbits by injecting alpha-chymotrypsin into the anterior chamber (alpha-chymotrypsin rabbit). The effects of the single application of CS-088 were examined. Additionally, CS-088 was repeatedly administered over a period of 3 weeks to hereditary ocular hypertensive rabbits (buphthalmic rabbits, JWHR bu/bu) and the IOPs were monitored throughout the experiment. The effects of CS-088 on aqueous humor dynamics were also examined in normal rabbits. In this study, the methods of IOP recovery rate, two-level constant pressure perfusion and fluorescein-dextran perfusion were used respectively to determine the aqueous inflow, outflow facility and uveoscleral outflow (USF). RESULTS: CS-088 at 1% and 2% significantly lowered the IOP in the alpha-chymotrypsin rabbits with a maximum IOP reduction of 10.1 mmHg. The maximum effect obtained with 2% CS-088 was no greater than that with 1% CS-088. In the buphthalmic rabbits, 2% CS-088 also lowered IOP significantly. Timolol was effective in both models. In the study on aqueous humor dynamics, a slight increase in USF (17%) was seen after a topical application of CS-088 whereas changes in aqueous inflow or outflow facility were not observed. CONCLUSIONS: Topical CS-088 can decrease IOP in rabbits. Despite the USF change, the ocular hypotensive mechanism by CS-088 was not fully determined.     

Can UK-14, 304-18 lower IOP in rabbits by a peripheral mechanism?

Unilateral topical administration of alpha 2 adrenoceptor agonists lowers intraocular pressure (IOP) bilaterally in laboratory animals and man. Investigators have suggested that this decrease in IOP is mediated, in part, by alpha 2 adrenoceptors in the central nervous system (CNS). In the present study, the hypotensive activity of the alpha 2 agonist, UK-14,304-18 (UK), was evaluated following topical and intracameral administration. The unilateral administration of a relatively selective alpha 2 adrenoceptor agonist, UK (50 micrograms), lowered IOP bilaterally when applied topically to the eyes of rabbits. Intracamerally administered UK (0.05-50 ug) lowered IOP unilaterally in a dose-related manner with minimal pupillary and cardiovascular changes. The ocular hypotensive action of UK administered intracamerally was absent in rabbits that had been surgically sympathectomized. While these data demonstrate that UK can lower IOP in the rabbit independent of alpha 2 adrenoceptor stimulation in the CNS and other systemic sites, the expression of this response is dependent upon the presence of intact sympathetic innervation.     

Central imidazoline (I(1)) receptors modulate aqueous hydrodynamics

The purpose of this work is to determine the relative contributions of central imidazoline (I(1)) receptors to the ocular hydrodynamic action of moxonidine. Moxonidine (MOX), an alpha(2) and I(1) receptor agonist, and efaroxan (EFA), a relatively selective I(1) antagonist, were utilized to study alterations in intraocular pressure (IOP) and aqueous flow in New Zealand white rabbits subjected to intracerebroventricular (i.c.v.) cannulation and sympathectomy. Intracerebroventricular administration of MOX (0.033, 0.33 and 3.33 microg) to normal rabbits produced dose-dependent, bilateral IOP decreases of 3, 6, and 8 mmHg, respectively. The ocular hypotensive response to MOX was immediate (10 min. post drug), lasted for one hour, and was inhibited by prior administration of efaroxan (3.33 microg i.c.v.). In unilaterally sympathectomized (SX) rabbits, the ocular hypotensive response induced by i.c.v MOX in the denervated eye was attenuated approximately 50%, but the duration of ocular hypotension in the surgically altered eye was longer than that of the normal eye. MOX (0.33 microg i.c.v.), caused a statistically significant decrease (2.24 to 1.59 ml/min.) in aqueous flow in normal eyes. In SX eyes, there was no change in aqueous flow by MOX, suggesting that IOP effect in i.c.v. MOX observed in the SX eye might be mediated by changes in outflow resistance. Sedation was observed in all the rabbits treated with MOX (i.c.v.) and was dose-dependent. These in vivo data support the suggestion that centrally located I(1) receptors modulate the early contralateral response to topically administered MOX and are involved in lowering of IOP and aqueous flow in rabbit. In addition, expression of the full ocular hypotensive effect of centrally applied MOX depends on intact sympathetic innervation. Ocular hypotension induced by MOX in the SX eye may involve an effect on uveoscleral outflow.     

Prostaglandin F2 alpha-isopropylester eye drops: effects in normal human eyes.

The effects of PGF2 alpha-isopropylester eye drops on intraocular pressure (IOP) and aqueous humour dynamics were investigated in healthy male volunteers. The other eye was treated with vehicle and used as a control. Special attention was also paid to adverse effects. Single and repeated doses were tested. There was a dose related effect on IOP. Significant reductions were observed 4, 8, and 12 hours after application of 1.0, 2.5, or 10 micrograms PGF2 alpha equivalents of the drug. With 10 micrograms the effect lasted 24 hours. An initial tendency towards an increase in IOP was observed for these doses. Repeated doses of 1.0 microgram daily or 0.5 microgram twice daily produced a significant and lasting IOP reduction of about 2 mmHg for 1-2 weeks. Aqueous humour production was not altered, and outflow facility was not significantly changed. There was a dose dependent hyperaemia with a maximum within 2 hours after application. A foreign body sensation, some pain, and photophobia were noted with increasing doses. A slight miosis of 1 mm was seen in three of six eyes treated with 10 micrograms. No signs of intraocular inflammation were recorded, but a slight increase in penetration of fluorescein into the anterior chamber was observed after 16 days of treatment.     

A mechanism for reducing intraocular pressure in normal volunteers using UF-021, a prostaglandin-related compound]

The mechanism of reduction of intraocular pressure (IOP) and other ocular effects were studies after topical application of prostaglandin (PG) F2 alpha and UF-021, a new PG related compound, in eight normal volunteers. IOP, aqueous humor flow rate and outflow rate were evaluated during a period of four hours after the application. Both PGF2 alpha and UF-021 caused significant and similar IOP reduction for four hours. Neither compound produced any significant change in the aqueous humor flow rate or outflow rate, suggesting the increase of unconventional outflow rate as being the possible mechanism of IOP reduction in normal human eyes.