Abstracts of papers pharmacological meeting

s of papers ANTI-ISCHAEMIC ACTIVITY OF NIFEDIPINE AND R 58735 IN THE GUINEA-PIG HEART-LUNG PREPARATION H.W.G.M. Boddeke, T.J.W. Jap, J.G. Nugtenbur& R.D. Veldsema-Currle and P.A. van Zwieten R 58735 (4-[(2-henzothiazolyl)methylamlno]-~[(4-fluorophenoxy)methyl]-1-plperidine-ethanol) has been demonstrated to possess anti-lsehaemic activity in isolated gulnea-pig hearts 9 In order to further investigate the anti-isehaemic activity of R 58735, the protective effects of nifedipine and g 58735 upon 35 and 60 mln of ischaemia and reperfusion (30 min) in the gulnea-plg heart-lung preparation were compared. Guinea pigs were anaesthetized with urethane (1.5 9 g/kg) and respirated at positive pressure with carbogen. Cardiac preload and afterload were 14 and 53 cm H20, and the hearts were paced at 5 Hz. Global ischaemia (35 or 60 min) was induced by clamping the venous and aortic cannulae. After 30 min Of reperfusion functional recovery (LVP, dp/dt and cardiac output) was calculated as a percentage of the pre-ischaemic value and tissue Cr~ ATP and adenylate charge were determined. Both in 35 and 60 min ischaemia experiments maximal protective concentrations of nifediplne and R 58735 were used. Upon 35 min of Ischaemia nifedipine and R 58735 at concentrations that did not affect contractility (10-' and I 0-' ~ respectively) improved the postischaemie recovery of functional and biochemical parameters to a similar extent. After ischaemia for 60 min g 58735 (10-' M) induced a pronounced recovery of functional parameters. Nifedlpine exerted a smaller recovery of functional parameters, this effect was observed at a higher concentratlon of 10-' ~ which induced a cardlodepressant effect by approximately 14%. No differences in recovery of biochemical parameters between nlfedipine and R 58735 were found after 60 min of ischaemia. These results may indicate a more pronounced effect of R 58735 on prevention of irreversible ischaemia. Division of Pharmacotherapy/Pharmacology, Academic Medical Centre, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands. ERGOTAMINE-INDUCED CHANGES IN CAROTID BLOOD FLOW AND ITS DISTRIBUTION IN THE ANAESTHETIZED PIG. A.R. Bum, P.D. Verdouw, A.M. Rutteman, P.R. Saxena. During anaesthesia the arterlovenous anastomoses (AVAS) in the cranial circulation of the pig are opened. This allows the study of the effects of drugs on AVAS, arterioles and large arteries, resulting in changes in carotid blood flow (CBF), measured with an electromagnetic flowmeter, and CBF distribution determined with the radioactive microsphere technique. 5-Nydroxytryptamlne (5-HT), which plays a role In the pathophyslology of migraine, constricts AVAS and large arteries and dilates arterioles I by activating a 5-HTl-llke receptor 2 . Ergotamlne, which is still the drug of choice for the treatment of the acute attack of migraine, also acts on 5-HT receptors. In 6 pentobarbltal-anaesthetized pigs ergotamine (2.5, 5, [O and 20 ~g/kg i.v.) induced a dosedependent decrease in heart rate, CBF and AVA flow. Mean arterial blood pressure remained stable, whereas the nutrient (capillary) flow showed a tendency to increase, especially in the tongue (see Table). Baseline Ergotamine (~g/kg i.v.) 2.5 5 I0 20 CBF 164 132 w 115" 104" 85" AVA Flow 123 80* 63* 48* 30* Nutrient Flow 40 52 52 57 56 Ears 1.9 3.0 3.9 4.1 4.4 Skin 1.4 1.9 2.6 3.5 5.6* Muscle 5.1 5.3 4.4 3.8 3.2* Tongue 1.4 2.6* 2.8* 3.0* 3.0* Total brain 5.6 6.1 7.4 7.1 6.4 ~: p < 0.05 vs baseline; mean values in ml/mln. We conclude that ergotamine mimicks the effect of 5-HT on AVAS, whereas, in contrast to 5-HT, it has only minimal effects on the arterioles. This effect on AVAS might explain the therapeutic effect of ergotamine in the acute attack of migraine. I) P.R. Saxena & P.D. Vardouw, J Physiol 1982,332:501-520 2) P.R. Saxena et al., Naunyn-S Arch Pharm 1986,333:198-204 Depts of Pharmacol & Exp Cardlol, Erasmus Unlv, Rotterdam *Secretary, Laboratory of Pharmacology, Faculty of Medicine, Free University, Van der Boechorststraat 7, Io81 BD Amsterdam, the Netherlands. 292 V o l . [ o 1987 Pharmaceutisch Weekblad Scientific Edition SELECTIVITY OF MUSCARINIC AGONISTS: A FUNCTIONAL STUDY ON ISOLATED ILE& ATRIA AND URINARY BLADDER OF THE RAT D. Davldesko, K.J. van Charldorp, P.H. 0verhaus, H.D.Batink and P.A. van Zwleten The current subolassification of musearinic receptors is based upon their affinity towards the selective antagonist plrenzeplne. High affinity exists between pirenzepine and the Mr-receptor type, while that between the Me-receptor and the antagonist is low (Ha~mer & Giachetti, 1 982). Only few agonists have been reported to show s(xne degree of selectivity in certain tissues and organs. MeN-A-3~3 (~-[mchloro-phenylcarbamoyloxy]-2-butynyltrimethylammoniumchloride) is the best known example. However, its usefulness as a tool has been questioned because of its low efficacy (E glen & Wh/tin& 1985). It was the aim of the present study to compare the functional data of ten muscarinie agonlsts in order to investigate their potential selectivity. R. Hammer and A. Giachetti, Life Sci. 31 (1982) 2991 R.M. Eglen and R.L. Whitin& Br. J. Pharmac. 90 (1985) 701 Division of Pharmacotherapy/Pharmacology, Academic Medical Centre, University of Amsterdam, Meibergdreef 15, ]105 AZ Amsterdam, The Netherlands THE R ~ PRODRUG CGP 22 979A. ITS t~(~ISM OF ACTION. J.C. Drieman and H.H.W. Thijssen The compound CGP 22 979A, a N-acetyl gamma glutamyl prodrug of the hydralazine-like vasodilator CGP ig 137A, was developed to act as a renal specific vasodilator. This prodrug approach, based on the fact that renal tissue is very rich in gaRl~a-glutamyl transpeptidase (~s appears to be successfull. However, theoretical considerations suggest that the ~ activity in the kidney alone cannot explain the renal selectivity. Therefore, a pharmacokinetic study was undertaken to elucidate the mechanism of the preferential effects of the prodrug. Male Wistar rats (+300 g) were used in this study. All drugs were administered i.v. Active drug was measured by HPLC following a reaction with p-anisaldehyde. The following pharmacokinetics of the active drug CGP 18 137A were observed in vivo: tl/2: ~ min, volume of distribution: 0.7 i, and clearance: 9 l.h. In vitro the tl/2 of the active drug was 2.5 and 60 ntin in blood and dialysed plasma respectively. Following prodrug administration no active drug could be detected in the circulation, but active drug was found in liver and kidney. At t-30 min the kidney contained 13.4+5.4 and the liver 2.2+0.9 #g C~P 18 137A/g tissue. Injection of glutath}one (2 -m~ol.kg) or buthionine sulfoximine (i mmol.kg) 15 min prior to prodrug administration caused significantly lower concentrations of active drug in the kidney (4.2+0.9 and 3.5+1.0 pg/g tissue), but only a minor nonsignificant change in liver concentrations (1.2+0.6 and 1.0+0.4 ~g/g tissue). These results suggest the ~ollowing features underlying the renal selectivity of CGP 22 979A: 1) facilitated or active uptake by renal tissue cells. This uptake can be blocked by glutathione or buthionine sulfoximine. 2) Higher conversion rate into active drug by the kidney. 3) Rapid clearance of active drug in the blood compartment by a chemical reaction. Dept. of Pharmacology, University of Limburg, P.O, Box 616, 6200 MDMaastricht, The Netherlands. PASSIVE AVOIDANCE BEHAVIOR AND THE IMMUNE SYSTEM Gerda Croiset I Cobi J. Heijnen 2, D. de Wled I It has been shown that stressful situations, induced by environmental stimuli may affect immune responsiveness. In the present study the influence of a short and mild form of emotional stress was studied on immune react iv i ty. To that end a step through type one-triallearning passive avoidance test was used. The react iv i ty of the immune system was determined by measuring the generation of the primary antibody response i_.qn vivo.. The results demonstrate that habituation trials in the passive avoidance apparatus is associated with an increase in immune react ivi ty. However, the ini t ia l ly enhanced immune response decreases in rats that show maxima] passive avoidance behavior. A negative c o r r e l a t i o n between the duration of the passive avoidance behavior and the react iv i ty or the immune system was demonstrated. These results point to the significance of tile capabil i ty of the immune system to respond in a specific way to dif ferent short term psychological stimuli. I Rudolf Magnus Institute for Pharmacology, Vondellaan 6, Utrecht 2 University Hospital for Children and Youth "Her Wilhelmina Kinderziekenhuis" dept. Immunology, Utrecht A ~IO-IOD]]~ATED OXYTOCIN (OT) RECEPTOR LIGAND: PPJ~AIMTION, M ~ BI]~)I~ AND AUTORADIO~ J. glands/ C. Barberis and E.R. de Kloet [3H]-OT has been used to characterize OT receptors in uterus, lactating mammary gland and central nervous system regions (f.i. the ventromedial nucleus of the hypothalamus and the ventral hlppoc~umpus). A detailed pharmacological characterization of brain OT binding sites is limited by their low maximal binding capacity and the small dimensions of OT receptor containing brain nuclei. Available tritium labelling techniques do not allow a higher specific radioactivity. Iodination (on the 2-tyrosyl residue), on the other hand, was impossible due to a dramatic loss of affinity of the existing OT receptor ligands. To circtuavent this fall in affinity a recently synthesized 9tyrosylemide containinR oxytocie antagonist, desGly(NH2)9d(CH2)5[Tyr(Me)2Thr4]OVT has been iodlnated on the 9 position. Competition experim@nts with vasopressin V Iand V 2and OT-receptor containing m~brane preparations revealed that the monoiodinatedantagonlst was about 30 times more selective than OT for uterine OT receptors. The inhibition constant for uterine OT receptors was 0.031• nM. Scatchard analyses with [1251J-labelled antagonist on uterine membranes showed a dissociation constant of 0.048• nM and a maximal binding capacity o