α-Adrenoceptor activity of arylalkylimidazoles is improved byα-methylation and impaired byα-hydroxylation

Summary To investigate the effects of hydroxyl and methyl substitution of the alkyl bridge bond on the-adrenoceptor activity of arylalkylimidazole derivatives, the cardiovascular effects of the molecules were studied in anaesthetized and pithed rats. The compounds studied were 4(5)-substituted imidazole derivatives with a methano, ethano or etheno bridge between the imidazole and the 2-, 2,3- or 2,6-methyl substituted phenyl rings. The hypotensive and bradycardic activities of the molecules in the anaesthetized rat were always reduced by-hydroxylation and usually augmented by-methylation of the bridge between the imidazole and phenyl rings. Hydroxylation was associated with a consistent, marked decrease in vasopressor and sympatho-inhibitory activity in the cardiovascular system of the pithed rat, but a methyl moiety as a bulky substituent in the-position of the alkyl bridge did not decrease but even caused an increase in-adrenoceptor activity in this test system. The detrimental effect of-hydroxylation of the compounds at ₁- and ₂-adrenoceptors supports the notion that the interaction of the imidazoles at-adrenoceptor is different from that of the classical, noradrenaline-like phenethylamines. The results also suggest that the alkyl bridge between the phenyl and imidazole rings of the imidazoles may contribute directly to the binding process.     

Valerian-Derived Sedative Agents. I. On the Structure and Spectral Assignment of the Constituents of Valmane Using the Selective INEPT Nuclear Magnetic Resonance Technique

The valepotriates, a group of chemically unstable iridoid triesters possessing sedative activity, contain various ester groups at the C-l, C-7, and C-11 positions. Using the selective INEPT NMR technique and employing a suitable polarization delay for long-range coupling, it was possible to achieve the assignment and location of the ester groups directly, without ambiguity, and without chemical modification. Six valepotriates isolated from Valmane tablets served as examples to demonstrate the utility of this NMR technique. During the course of this work, the acevaltrate fraction was shown to be a mixture of 1--ace valtrate (3) and 7--acevaltrate (4), the structures of valtrate (1) and didrovaltrate (2) were confirmed directly, and two new valepotriates, 5a and 5b, were obtained as an inseparable mixture and characterized.     

Antifungal Activity of a New Triterpenoid Glycoside from Pithecellobium racemosum (M.)

Purpose. In a continuation of our search for novel antifungal compounds from higher plants, the standard extract of the bark of Pithecellobium racemosum was found to have good activity against important AIDS-related opportunistic yeasts. Methods. The extract was subjected to bioguided fractionation using silica gel column chromatography which led to purification of triterpene glycosides. The structures of these compounds were determined by a combination of spectroscopic (IR, NMR, HRMS) and chemical methods. Results. Compound 1 is a new glycoside, 3-O[-L-arabinopyranosyl (1 -2)][-L arabinopyranosyl (1 -6)]2-acetoamido-2-deoxy--D-gluco-pyranosyl oleanolic acid and Compound 2 was identified as the known compound 3-O-[-L-arabinopyranosyl (l-2)]-L-arabinopyranosyl (1-6)] 2-acetamido-2-deoxy--D-glucopyranosyl echinocystic acid. Conclusions. Compound 1 is a new glycoside, 3-O-[-L-arabinopyranosyl (1-2)]-L-arabinopyranosyl (l-6)]-2-acetoamido-2-deoxy--D-glucopyranosyl oleanolic acid and exhibits moderate antifungal activity against T. mentogrophytes, C. albicans and S. cerevisiae with MIC values of 6.25, 12.5 and 12.5 g/ml respectively.     

Two distinct adrenoceptor-biophases in the vasculature: One for α-and the other for β-agonists

Summary Strips of two canine vessels with different patterns of sympathetic innervation were used: the mesenteric artery which has an adventitio-medial plexus and the saphenous vein in which nerve terminals are distributed throughout the media.The pD₂ of (–)-adrenaline for -and -adrenoceptors was determined for both vessels (in the presence of 0.5 M propranolol and 7 M phentolamine, respectively; in the latter case the strips were contracted by 0.28 M prostaglandin F2) and found to be very similar: 6.96 and 7.01 in the saphenous vein and 6.77 and 6.91 in the mesenteric artery, respectively. The similarity of pD₂ for adrenaline acting on -and -adrenoceptors in both preparations allowed us to compare the effect of inhibition of neuronal uptake by 12 M cocaine with that of inhibition of COMT by 50 M dihydroxy-2-methyl propiophenone (U-0521) on: a) the potency of adrenaline (noradrenaline was used in the saphenous vein only) acting on -and -adrenoceptors and b) the time required by the strips to recover 50% in oil (t ₅₀) after contractions or relaxations caused by 0.23 M adrenaline. In the saphenous vein cocaine increased the potency of both adrenaline and noradrenaline for -effects more than for -effects (2.8 times vs. no increase for adrenaline; 7.1 vs. 1.9 times for noradrenaline) and U-0521 increased the potency of both adrenaline and noradrenaline for -effects more than for -effects (4.1 vs. 2.6 times for adrenaline; 1.8 times vs. no increase for noradrenaline); regarding the termination of action of adrenaline, cocaine prolonged the t ₅₀ 1.6 times after contraction and did not change it after relaxation, whereas U-0521 prolonged the t ₅₀ 6.9 times after relaxation and only 1.8 times after contraction.In the mesenteric artery only sensitivity experiments were done. Cocaine increased the potency of adrenaline by a factor of 2.1 for the -effects while there was no influence on its potency with regard to its -effects, and U-0521 increased the potency of adrenaline for the -effects more than for -effects (3.9 vs. 1.8 times, respectively).These results show that there are two different biophases for sympathomimetic agonists in the vasculature: one for -adrenoceptors which is more under the influence of the neuronal uptake and one for -adrenoceptors which is more under the influence of COMT activity. We conclude that -adrenoceptors are situated close to the nerve endings and -adrenoceptors close to COMT sites. Since these results do not differ qualitatively in two vessels with different patterns of innervation, we conclude that this asymmetry in the distribution of -and -adrenoceptors may be due to either an uneven distribution of cells with only one type of receptors each or due to an uneven distribution of receptors on the same cell.     

Effects of Δ8-THC,and Δ9-THC on the acquisition of a discriminative positional habit in rats

Using a reversal learning paradigm the dissociative effects of two tetrahydrocannabinols (THC) on the acquisition and reversal of a discriminative positional habit in rats were studied. A T-shaped water maze was used. From these experiments it is concluded that learning under the influence of ⁸-THC (10 and 20 mg/kg), and ⁹-THC (5 mg/kg) is state-dependent (StD) in the rat.Numbering system according to IUPAC rules.Parts of the results were presented at the Symposium on the chemistry and biological activity of cannabis, Stockholm, October 26–28, 1971 and at the Symposium on medical plants of Brazil, Sao Paulo, April 17–20, 1972.     

Motor disturbance induced by tremorine and oxotremorine

Summary The action of tremorine and oxotremorine on spinal motor activity was studied in the rat. Both tremorogenio agents increased a reflex activity and spontaneous activity. The increase in spontaneous activity consisted of rhythmic bursts of discharges. The increase in a reflex activity was accompanied by rigidity, which manifested itself by the appearance of tonic muscle activity.Tremorine and oxotremorine-induced tremor was depressed by the antitremor agents metixene and Kr 339, the antiparkinson drugs atropine and biperiden, and the adrenergic receptor blocking agents propranolol and pronethalol. The adrenergic. receptor blocking agents azapetine, dihydroergotamine, haloperidol, phenoxybenzamine and phentolamine failed to inhibit tremor activity. Chlorpromazine, however, as well as procaine, verapamil and DOPA, diminished the intensity of tremor activity without blocking the generation of tremor bursts.Drugs which depressed tremor activity also antagonized the effect of oxotremorine on and motor activity, whereas the drugs, which only diminished tremor intensity, depressed the increased reflex discharge without reducing spontaneous activity. Rigidity disappeared when reflex discharge was normalized.It is concluded that experimental parkinsonlike rigidity may be interpreted in terms of a disturbed balance between monoaminergic and cholinergic mechanisms in the brain.The authors are grateful to KnolI-Ludwigshafen for the support of the investigation.     

Serum glycoside concentrations after single or repeated intravenous doses ofβ-methyl-digoxin and digoxin

Summary The aim of the present investigation was to estimate the ratio of the intravenous doses of-methyl-digoxin and digoxin required to produce identical serum glycoside concentrations in man.20 patients on intravenous maintenance therapy were changed from-methyl-digoxin to the identical dose of digoxin or vice versa. Each drug was given for 7 days. Serum concentrations 13% higher were found during administration of-methyl-digoxin. Assuming a half life of 60 h after with drawal, the dose of digoxin producing the same minimum serum concentration was estimated to be 1.16 times higher than that of-methyl-digoxin.18 healthy volunteers received 0.4 mg -methyldigoxin, and 23 the same dose of digoxin, as an intravenous infusion over 2 h. The serum concentrations and urinary glycoside excretion were measured over a period of 32 hrs. During the first hour after the infusion the serum concentration of digoxin declined more rapidly than that of-methyl-digoxin. Thereafter, the ratio of the serum concentrations did not change appreciably up to the end of the investigation. The area under the serum concentration/time curve was about 13% greater for-methyl-digoxin than for digoxin; this difference was not significant.The average renal clearance was 96±9 ml for-methyl-digoxin, 151±13 ml for digoxin. Since the total body clearance of digoxin is only about 1.16 times higher than that of-methyl-digoxin, the lower renal clearance of-methyl-digoxin must partly be compensated by higher extrarenal clearance.From the ratios of the areas under the serum concentration/time curves after single doses of -methyldigoxin and digoxin, and the minimum serum concentrations during maintenance therapy, it was concluded that the dose of digoxin to produce the same average serum concentrations would be about 1.15 times higher than that of-methyl-digoxin. In comparison with the large variations in individual dosage of digoxin and-methyl-digoxin, this difference is too small to be of practical importance.     

Neonatal exposure to zearalenone causes persistent anovulatory estrus in the rat

The effect of neonatal administration of zearalenone on the female reproductive system was studied in the rat. A single subcutaneous injection of 1.0 mg zearalenone to 3- or 5-day-old rats caused persistent vaginal estrus in adulthood. Ovaries in these animals contained many large follicles but no newly formed corpora lutea. The same effects were observed in rats which had received 100 g estradiol-17 in the neonatal period. Most rats which had received 100 g zearalenone or 10 g estradiol-17 showed regular 4-day estrous cycles and had newly formed corpora lutea in their ovaries. These results demonstrate that neonatal exposure to zearalenone produces persistent anovulatory estrus in the rat, the potency being about one tenth that of estradiol-17.     

The influence of hyperthyroidism on β-adrenoceptor-mediated relaxation of isolated small mesenteric arteries

We investigated the influence of hyperthyroidism on relaxant responses of small mesenteric resistance arteries to -adrenoceptor agonists and to compounds stimulating the corresponding second-messenger system. Hyperthyroidism was induced by feeding rats for 28 days with 5 mg/kg L-thyroxine (T4)-containing rat chow. This treatment produced a stable hyperthyroid state, as indicated by several biochemical/metabolic and haemodynamic parameters. Preparations of small mesenteric arteries were mounted in an isometric wire myograph. Subsequently, concentration-effect curves were determined for isoproterenol, noradrenaline and salbutamol as well as for forskolin, dibutyryl-cAMP and theophylline. We also determined concentration-effect curves to the -adrenoceptor agonists in the presence of ICI 118,551 and CGP 20712A (i.e., in the presence of a selective ₂- and ₁-adrenoceptor antagonist, respectively). Apparent pA₂-values were calculated to determine which -adrenoceptor subtype causes vasodilation. These experiments indicate that -adrenoceptor-mediated vasodilation involves both ₁- and ₂-adrenoceptors in mesenteric resistance vessels of both hyperthyroid and control rats. In our experiments hyperthyroidism has a sensitizing influence on vascular responses induced by the -adrenoceptor agonist isoproterenol and the selective ₂-adrenoceptor agonist salbutamol. Sensitization to isoproterenol was abolished in the presence of ICI 118,551, whereas it was emphasized in the presence of CGP 20712A. Although this was not fully supported by the results obtained with noradrenaline, these results indicate that the sensitization to -adrenoceptor agonists is probably limited to the ₂-adrenoceptor/G-protein complex and not associated with alterations of the corresponding second messenger system.     

The physiological disposition of p-octopamine in man

Summary After oral administration of ³H-p-octopamine (8 mg300 Ci) more ³H-activity (93% of the dose) is excreted in the urine within 24 h than after intravenous infusion (2 mg300 Ci) over 2.5 h (82% of the dose). This proves that p-octopamine is absorbed quantitatively in man. The absorption proceeds rapidly, peak plasma levels are reached between 30 and 60 min.The only metabolic pathways for p-octopamine are deamination and conjugation. The predominant step is oxidative deamination by monoamine oxidase (MAO) to p-hydroxymandelic acid. This acid represents 2/3 of the urinary ³H-activity after both routes of admistration.A quantitative difference is seen in the fraction of free p-octopamine which equals the amount of conjugated amine after infusion but is only 1/20 after oral administration. This indicates a higher total clearance after an oral dose which consequently explains the diminished efficacy on blood pressure after this route.Hydroxylation to catecholamines was not found.     

Population Genetic Structure of the Western Mosquitofish,Gambusia Affinis,In a Highly Channelized Portion of the San Antonio River in San Antonio,TX

Population genetic assessments were performed on populations of the mosquitofish, Gambusia affinis, sampled at seven sites along a 10km reach of the upper San Antonio River in San Antonio, TX. Mosquitofish populations were sampled from the downtown area, known as the Riverwalk, where the river is concrete lined, deeply pooled, and receives heavy tour boat traffic. Populations were also sampled from sites upstream and downstream from the Riverwalk. Allozyme electrophoresis was performed on approximately 50 individuals from each site. Five of 12 loci surveyed were polymorphic (95% criterion). Exact tests over all loci for all populations indicated that allele frequencies differed significantly among sites. Allele frequencies of the upstream population were significantly different from the Riverwalk populations. Differences resulted primarily from significant decreases in frequencies of rare alleles at MDH-2* and two GPI* loci in the downtown area. Mean dissolved oxygen measurements were also significantly lower at Riverwalk sites. These results suggest that selective forces such as non-point source runoff or low dissolved oxygen, perhaps in combination with limited migration due to numerous dams, have reduced genetic diversity of populations in the downtown area.     

Activation of β2-adrenoceptors by isoprenaline and adrenaline enhances noradrenaline release in cortical kidney slices of young spontaneously hypertensive rats

Summary The aim of the present study was to investigate -adrenoceptor modulation of noradrenaline release from sympathetic nerves in superfused cortical kidney slices of 4-week-old spontaneously hypertensive rats (SHR) and age-matched controls (WKY). After preincubation with ³H-noradrenaline the kidney slices were electrically stimulated in superfusion chambers. The stimulation induced (S-I) outflow of radioactivity was mainly composed of unmetabolized 3H-noradrenaline in both strains and thus taken as an index of noradrenaline release. There was a frequency-dependent (1.25–20 Hz) increase in the S-1 outflow of radioactivity. At all stimulation frequencies tested S-I outflow of radioactivity was similar or even slightly lower in SHR than in WKY kidney slices in either the absence or presence of cocaine (10 mol/l). The non-selective -adrenoceptor agonists isoprenaline (0.l gmol/1) and adrenaline (0.01 and 0.1 mol/l) enhanced S-I outflow of radioactivity. The facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) were blocked by the selective ₂-adrenoceptor antagonist ICI 118551 (0.1 mol/l) but not by the selective ₁-adrenoceptor antagonist atenolol (0.3 mol/l). The cell-permeable CAMP analogue 8-bromo-cAMP (300 mol/l) enhanced S-1 outflow of radioactivity to a similar extent in both SHR and WKY kidney slices. A combination of 8-bromo-cAMP (300 mol/l) and adrenaline (0.1 mol/l) did not enhance S-1 outflow of radioactivity to a greater extent than 8-bromo cAMP (300 mol/l) alone in both strains. However, the facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) but not that of adrenaline (0.01 mol/l) were significantly greater in SHR than in WKY. The results suggest that stimulation of prejunctional ₂-adrenoceptors by adrenaline even in the absence of a-adrenoceptor blockade enhances noradrenaline release in kidney cortex of young SHR and WKY. This ₂-adrenoceptor mediated effect may possibly be dependent on cAMP formation. The greater facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) in SHR as compared to WKY are in accord with receptor binding studies which show a higher density of ₂-adrenoceptors in SHR than in WKY kidney cortex.Abbreviations SHR Spontaneously hypertensive rats - WKY WistarKyoto rats - cAMP 3-5-cyclic adenosine monophosphate - S-I stimulation induced Send offprint requests to: L. C. Rump     

Liposomes Containing Interferon-Gamma as Adjuvant in Tumor Cell Vaccines

Purpose. Liposomal systems may be useful as a cytokine supplementin tumor cell vaccines by providing a cytokine reservoir at the antigenpresentation site. Here, we examined the effect of liposomeincorporation of mIFN on its potency as adjuvant in an established tumor cellvaccination protocol in the murine B16 melanoma model. Adjuvanticityof the mIFN-liposomes was compared to that achieved bymIFN-gene transfection of the B16 tumor cells. Furthermore, we studiedwhether liposomal incorporation of mIFN indeed increases theresidence time of the cytokine at the vaccination site. Methods. C57B1/6 mice were immunized with i) irradiated IFN-genetransfected B16 melanoma cells or ii) irradiated wild type B16 cellssupplemented with (liposomal) mIFN, followed by a challenge withviable B16 cells. The residence time of the (liposomal) cytokine at thesubcutaneous (s.c.) vaccination site was monitored using radiolabeledmIFN and liposomes. Results. Immunization with irradiated tumor cells admixed withliposomal mIFN generated comparable protection against B16 challenge asimmunization with mIFN-gene modified tumor cells. Irradiated tumorcells admixed with soluble mIFN did not generate any protectiveresponses. Radiolabeling studies indicated that free mIFN rapidlycleared from the s.c. injection site. Association of [¹²⁵I]-mIFNwith liposomes increased the local residence time substantially: liposomalassociation of mIFN resulted in a prolonged local residence time ofthe cytokine as reflected by a 4-fold increase of the area under thecurve. The amount of released cytokine in the optimal dose rangecorresponds to the amount released by the gene-transfected cells. Moderate but significant CTL-activity against B16 cells was found for miceimmunized with irradiated cells supplemented with mIFN-liposomescompared to untreated control animals. Conclusions. Prolonged presence of mIFN at the site of antigenpresentation is crucial for the generation of systemic immune responsesin the B16 melanoma model. These studies show that liposomalencapsulation of cytokines is an attractive strategy for paracrine cytokinedelivery in tumor vaccine development.     

Metabolism,Distribution, and Transdermal Permeation of a Soft Corticosteroid,Loteprednol Etabonate

The soft corticosteroid, loteprednol etabonate (chloromethyl 17-ethoxycarbonyloxy-11-hydroxy-3-oxoandrosta-1,4-diene-17-carboxylate), I, was designed based on the inactive metabolite approach. Accordingly, I should be metabolized by hydrolysis to the corresponding inactive cortienic acid derivative, II. The in vitro and in vivo metabolism of I indeed yielded mainly this inactive metabolite, which is more hydrophilic and thus readily eliminated from the body. Relatively high levels of I were found in tissues after intravenous administration of the drug in rats. The permeability of I through hairless mouse skin was comparable to what has been found for related hard steroids, without significant metabolism taking place in the skin.     

Zinc,among a ‘cocktail’ of metal pollutants,is responsible for the absence of the terrestrial isopod Porcellio scaber from the vicinity of a primary smelting works

Porcellio scaber Latreille (Crustacea: Isopoda) of one month in age were reared for a year on leaf litter of field maple (Acer campestre) contaminated in the laboratory with a range of concentrations of cadmium, copper, lead or zinc. The metals were applied topically to the leaves as nitrates. Growth and survival, numbers of live offspring produced by females that matured, and concentrations of metals in adult isopods at the end of the experiment were measured.Critical concentrations of metals in food at which all the isopods died before producing offspring were 100 g Cd g^–1, 100 g Cu g^–1, 2000 g Pb g^–1 and 1000 g Zn g^–1 (on a dry weight basis). The relative toxicities of the four metals in the laboratory were compared with concentrations of cadmium, copper, lead and zinc in surface leaf litter in the vicinity of a primary smelting works at Avonmouth, South West England. The results support the hypothesis that the absence of Porcellio scaber from sites in the immediate vicinity of the factory is due to zinc poisoning. Although cadmium is approximately ten times more toxic to isopods than zinc in the laboratory, zinc is most likely to be killing isopods in the field because its concentration is always at least 30 times higher than cadmium in Avonmouth leaf litter, and more than 100 times higher at most sites.Populations of Porcellio scaber survive in field sites where surface leaf litter contains up to 5000 g Zn g^–1. This is at least five times higher than the critical concentration in laboratory experiments. Thus, the methodology for assessing metal toxicity described in this paper, exaggerates the potential effects of metals to isopods in the field. Such differences between laboratory and field toxicities of metals should be taken into account when environmental protection levels for metals are being proposed for soil invertebrates based on ecotoxicological tests conducted in the laboratory.     

A method to estimate the potency of the μ-component of an opioid having mixedμ-, andκ- and/orδ-agonist activities

The SC administration of either typical-agonists such as morphine, pethidine, fentanyl and levorphanol or a mixed- and-agonist like [d-Ala²,d-Leu⁵]-enkephalin to 10-day-old rats produced loss of righting reflex. Additionally, the loss of righting reflex induced by these opioid agonists was antagonized by naloxone, an opioid antagonist having a preference for-receptors, but by neither nor-binaltorphimine nor naltrindole, a specific- or-antagonist, respectively, indicating that the loss of righting reflex was produced by the interaction of an opioid with-receptors. Moreover, the potency of each opioid agonist relative to that of morphine estimated by the present in vivo method was similar to that determined by the traditional in vitro isolated preparation. In contrast to-agonists, neither typical-agonists such as U-50, 488H, ketocyclazocine, pentazocine and butorphanol, nor a selective-agonist like [d-Pen²,d-Pen⁵]-enkephalin affected the righting reflex of 10-day-old rats, indicating that-agonists, but neither- nor-agonists, produced the naloxone-reversible loss of righting reflex in infant rats. By employing the present in vivo method to estimate the-agonist activity of an opioid with mixed agonist activities, it was indicated that the-agonist activity of ethylketocyclazocine, which had been employed as a representative-agonist, was essentially the same as that of morphine, a representative-agonist.     

Both β1- and β2-adrenoceptors mediate catecholamine-evoked arrhythmias in isolated human right atrium

Summary The involvement of ₁- and ₂-adrenoceptors in catecholamine-evoked arrhythmias was investigated in isolated human right atrial appendages obtained from 22 patients chronically treated with blockers (usually ₁-selective) and 9 patients not treated with blockers. A simple experimental model that assesses the incidence of arrhythmic contractions as a function of heart rate (pacing) is introduced. ₁-adrenoceptors were activated by (–)-noradrenaline during ₂-adrenoceptor blockade with 50 nmol/l ICI 118551. ₂-adrenoceptors were activated by (–)-adrenaline during ₁-adrenoceptor blockade with 300 nmol/l CGP 20712A. Both (–)noradrenaline and (–)-adrenaline caused arrhythmic contractions whose incidence was greater at low than at high pacing rates. CGP 20712A (300 nmol/l) blocked the (–)-noradrenaline-evoked contractions in 1/1 atrial strip from 1/1 patient not treated with a blocker and 17/17 atrial strips from 15/15 patients chronically treated with blockers. ICI 118551 (50 nmol/l) blocked the (–)-adrenaline-evoked contractions in 3/4 atrial strips from 3/4 patients not treated with blockers and 17/20 atrial strips from 15/18 patients chronically treated with blockers. The incidence of arrhythmic contractions evoked by both (–)-noradrenaline and (–)-adrenaline was higher in chronically blocked patients than in non blocked patients. We conclude that both ₁- and ₂-adrenoceptors mediate atrial arrhythmias and that the generation of these arrhythmias is facilitated by chronic ₁-adrenoceptor blockade. Correspondence to: A. J. Kaumann at the Clinical Pharmacology Unit, University of Cambridge, as above     

Frequency- and train length-dependent variation in the roles of postjunctional α1- and α2-adrenoceptors for the field stimulation-induced neurogenic contraction of rat tail artery

Summary The present paper examines the roles of postjunctional ₁- and ₂-adrenoceptors for the noradrenaline (NA)-induced neurogenic contractile response to field stimulation mainly with 1–100 pulses at 2 or 20 Hz, in the tail artery of adult normotensive rats. Pharmacological tools were employed to isolate and characterize the ₁- and ₂-adrenoceptor-mediated components of this response. The degree to which the drugs influenced NA release or reuptake was assessed by their effects on the electrochemically determined, stimulation-induced rise in the NA concentration at the innervated outer surface of the media. This response was unaffected by ,-methylene ATP (10 M) or suramin (500 M), added to desensitize or block P₂-purinoceptors, respectively prazosin (0.1 M) or SK&amp;F 104078 (6-chloro-9-[(3-methyl-2-butenyl)oxyl]-3-methyl-1H-2, 3, 4, 5-tetrohydro-3-benzazepine, 0.1 M), used to block postjunctional ₁- and ₂-adrenoceptors respectively, nifedipine (10 M), blocker of Ca²⁺ influx through L-type channels, and ryanodine (10 M), which blocks mobilization of Ca²⁺ from intracellular stores; it was moderately enhanced by yohimbine (0.1 M), blocker of pre- and postjunctional ₂-adrenoceptors, and strongly enhanced by cocaine (3 M) or desipramine (1 M), blockers of NA reuptake. Judging from their inhibitory effects on the contractile responses to the ₁- and ₂-adrenoceptor agonists, phenylephrine andxylazine, prazosin (0.1 M)and SK & F 104078 (0.1 M) could be used to selectively block ₁- and ₂-adrenoceptors respectively, while yohimbine (0.1 M) was less selective, strongly depressing ₂- and slightly depressing ₁-adrenoceptor-mediated responses. The ₁-adrenoceptor-mediated component of the contractile response to short trains at 20 Hz was fast in onset, brief in duration and abolished by ryanodine; that mediated by ₂-adrenoceptors was more delayed, prolonged and insensitive to ryanodine. Both components were dose-dependently depressed by nifedipine (0.1–10 M). The small contractile responses to single pulses, or up to 50 pulses at 2 Hz, or short train (< 4 pulses) at 20 Hz, were more markedly depressed by 0.1 M yohimbine or SK & F 104078 than by 0.1 M prazosin and, hence, mediated mainly by ₂-adrenoceptors. The reverse was true of the much larger response to longer trains at 20 Hz, which thus probably was mediated mainly by ₁-adrenoceptors. Cocaine or desipramine, as well as ,-methylene ATP or suramin, amplified both components of the NA induced contractile response especially that mediated via a₁-adrenoceptors and caused by single pulses or short trains.The main conclusions are (i) that the small NA-induced contractile responses of this artery to single pulses, or pulses at low frequency, or in short trains at high frequency, are mediated mainly via ₂-, and the larger responses to longer trains at high frequency increasingly via ₁-adrenoceptors, (ii) that the ₁- and ₂-adrenoceptor-mediated components interact cooperatively, probably at least in part by utilizing two different pathways to increase the intracellular Ca²⁺, (iii) that neuronal reuptake of NA strongly restricts both components of the NA-induced contraction, especially the ₁-adrenoceptor-mediated response to single pulses or short trains, and (iv) that both components of the NA-induced contraction, especially that mediated by ₁-adrenoceptors, may be depressed by ATP released by field stimulation and acting via P_2x-purinoceptors on smooth muscle. Based on these results a novel working hypothesis is proposed, in which it is assumed that the geometry of NA-mediated neuromuscular transmission in this vessel varies with the frequency and number of impulses in a stimulus train.Correspondence to J.-X. Bao at the above address     

EEG,heart rate and mood change (“high”) after Cannabis

Fourteen experienced marijuana users smoked marijuana, hashish, ⁹-THC, and placebo. EEG, ECG and ratings of subjective feelings of high and pleasantness were recorded. EEGs were processed by period analysis.In EEG, marijuana and ⁹-THC increased the amount of alpha activity, and the three Cannabis preparations decreased the amount of beta activity. The average frequency of alpha activity was decreased by 0.15–0.20 c/sec after marijuana, hashish and ⁹-THC. The peak EEG effect occurred during the first 10 min after smoking; most of the changes disappeared after 40 min. Heart rate was increased by all the three drugs, and the effect persisted for the entire observation period (50 min).Feelings of high were elicited by each Cannabis preparation. This was not true of the pleasantness of the experience: only marijuana and hashish were perceived as more pleasant than placebo. Intensity of high increased with the amount of alpha activity, and decreased with the average alpha frequency. Pleasantness was unrelated to the EEG.The high showed a linear increase with heart rate, whereas pleasantness of the experience was an inverted U-function of heart rate.Aided, in part, by MH 13358, 18172 and by a contract with the New York State Narcotic Addiction Control Commission.     

Studies on the effects ofl(αS,5S)-α-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125) on 4-aminophenol-induced nephrotoxicity in the Fischer 344 rat

4-Aminophenol (para-aminophenol; PAP) causes selective necrosis to the S₃ segment of the proximal tubule in experimental animals. The mechanism of PAP nephrotoxicity has not been fully elucidated, although it has been suggested to involve glutathione (GSH)-dependentS-conjugation followed by processing by the enzyme -glutamyl transpeptidase (GT) to the corresponding cysteineS-conjugate. This proposed toxicity mechanism was probed further by administering L-(S,5S)--amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125), a potent GT inhibitor, to Fischer 344 (F344) rats before treatment with PAP (100 mg/kg). AT-125 pretreatment did not appear to protect against PAP-induced nephrotoxicity as assessed by renal histopathology, clinical chemistry and proton nuclear magnetic resonance (¹H NMR) spectroscopy of urine. These data suggest that renal GT activity is not a prerequisite for PAP nephrotoxicity and that the generation of a cysteineS-conjugate is not a unique requirement for the induction of PAP nephrotoxicity.