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The effect of β-bungarotoxin on neurotransmitter release from synaptosomes
Tenth World Congress
497
of a thrombin-like substance, resulting in defibrination and secondary fibrinolysis. All of these patients had increased blood concentrations of fibrin degradation products (FDP) ranging from 10-40/~g/1 to greater than 200/~g/1 (normal: < 10 #g/l). Ten patients (48%) had decreased blood concentrations of fibrinogen ranging from 0.3 g/1 to 1.9g/l (normal: 2~g/1). Fibrin monomer, consistent with fibrinogen activation and unstable clot formation, was detected in all affected patients. Euglobulin clot lysis time was shortened ( < 150 min) in 11 cases (52%), suggesting a degree of plasminogen activation with secondary fibrinolytic afibrinogenaemia. There was mild to moderate thrombocytopenia in five cases (85,000-130,000 x 109/1) (normal: 150-400 x 109/1). Only five (24%) patients had prolonged prothrombin time (PT) between 15 and 18.5 sec (control: 12-14 sec) and/or activated partial thromboplastin time (APTT) between 41.6 and 49.1 sec (control: 2 5 4 0 sec). Although the coagulation abnormalities are usually correctable by replacement therapy, envenomation by T. albolabris is frequently associated with a coagulopathy due to the presence of a thrombin-like substance. Increased blood concentration of FDPs remains the most sensitive test for detecting the abnormality. The effect o f fl-bungarotoxin on neurotransmitter release from synaptosomes, R. CHAPELLand P. ROSENBERG(The University of Connecticut, School of Pharmacy, Storrs, CT 06269, U.S.A.).
PRESYNAPTICALLY acting phospholipase A 2 (PLA2) neurotoxins such as fl-bungarotoxin (fl-BuTx) modify the release of only acetylcholine (ACh) in the periphery, whereas in the CNS the release of norepinephrine (NE) and serotonin (5-HT) are also modified. In addition, ACh release in the periphery is modified in a triphasic manner (decrease, then increase, then block), while in the CNS only the increase has been demonstrated. To determine the specificity of the central effects of fl-BuTx we compared the effects of fl-BuTx and Naja naja atra PLA 2 on the release from rat cortical synaptosomes of ACh, NE, and 5-HT. We also measured the release of lactate dehydrogenase (LDH) in order to determine whether membrane disruption was responsible for neurotransmitter leakage. Both the PLA 2 toxin (5.0 n M) and enzyme (0.5 nM) stimulated the release of NE and 5-HT, but only at concentrations which induced leakage of LDH. Conversely, fl-BuTx stimulated the release of ACh at a concentration (0.SnM) which caused no leakage of LDH, while N. n. atra PLA 2 (0.SnM) did not stimulate release of ACh. fl-BuTx thus exerts a specific effect on the cholinergic nerve terminals, while the leakage of NE and 5-HT induced by fl-BuTx and N. n. atra PLA 2 correlates with membrane disruption due to their PLA 2 activities, fl-BuTx (0.5 nM), within 20 min, increased the resting release of ACh and decreased the stimulated release of ACh induced by depolarization with 4-aminopyridine, while N. n. atra PLA 2 (0.5 nM), in 20min, had no effect on resting or stimulated release of ACh. It is concluded that fl-BuTx in the CNS acts specifically on cholinergic terminals, where it exerts both stimulatory and inhibitory effects. (Supported by NIH Research Grant ROlNS14521.) Stonustoxin contracts the anococcygeus muscle and then inhibits adrenergic transmission prejunctionally. L . S . CHEAH,m M . C . E . GWEE,I R. YUEN,2 P. GOPALAKRISHNAKONE 3 and K . S . Y . Low ~ (Departments of Ipharmacology, 2Biochemistry and 3Anatomy, Faculty of Medicine, National University of Singapore, Singapore 051 l).
STONUSTOYdN(SNTx) is a peptide toxin recently purified from the venom of the stonefish Synanceja horrida by the Venom and Toxin Multidisciplinary Research Group of NUS; its pharmacological properties are now being characterized. The effects of SNTx on the rat isolated anococcygeus muscle mounted in Krebs solution and gassed with 95% 02/5% CO 2 were studied. Motor responses were evoked via field stimulation (20-25V, 10Hz x 10sec, 1 ms pulse width) every 2min; contractile responses to noradrenaline (NA) 5/zM were also obtained when appropriate. Cumulative doses of SNTx (0.5-30/Lg/ml) produced an initial rapid and transient contracture of the anococcygeus, accompanied by a progressive decline of the motor responses to about 40% of the control height, without blocking the contractile responses to NA; recovery was poor on drug washout. 4-aminopyridine (5-100/~M) progressively reversed the partially inhibited motor responses, but the reversal was not sustained on washing out 4-aminopyridine. SNTx has a dual action on the field-stimulated anococcygeus muscle: it caused a concentration-dependent and transient contracture of the muscle accompanied by a progressive inhibition of adrenergic transmission which may be attributed to a prejunctional mechanism of action of SNTx. Aconite poisoning in a herb preparation. S.-S. CI~N, D.-Z. HUNG, J.-F. DENG and W.-J. TSAI (Department of Medicine, Veterans General Hospital-Taipei, Taiwan, R.O.C.).
ACONITE is the dried tuberous root of aconitum species. It has been used for thousands of years in Eurasia as a homicidal agent, arrow poison, and medicinal drug. Chinese medicine uses aconite to treat weak constitution, poor metabolism, dysuria, etc. Pharmacologically, aconite possesses analgesic, anaesthetic, anti-inflammatory and hypotensive effects. Its principal poison alkaloids are aconitine, mesaconitine and jesaconitine. Aconite intoxication may produce nausea, vomiting, weakness, paresthesias and cardiac dysrhythmias. Recently, we
497
of a thrombin-like substance, resulting in defibrination and secondary fibrinolysis. All of these patients had increased blood concentrations of fibrin degradation products (FDP) ranging from 10-40/~g/1 to greater than 200/~g/1 (normal: < 10 #g/l). Ten patients (48%) had decreased blood concentrations of fibrinogen ranging from 0.3 g/1 to 1.9g/l (normal: 2~g/1). Fibrin monomer, consistent with fibrinogen activation and unstable clot formation, was detected in all affected patients. Euglobulin clot lysis time was shortened ( < 150 min) in 11 cases (52%), suggesting a degree of plasminogen activation with secondary fibrinolytic afibrinogenaemia. There was mild to moderate thrombocytopenia in five cases (85,000-130,000 x 109/1) (normal: 150-400 x 109/1). Only five (24%) patients had prolonged prothrombin time (PT) between 15 and 18.5 sec (control: 12-14 sec) and/or activated partial thromboplastin time (APTT) between 41.6 and 49.1 sec (control: 2 5 4 0 sec). Although the coagulation abnormalities are usually correctable by replacement therapy, envenomation by T. albolabris is frequently associated with a coagulopathy due to the presence of a thrombin-like substance. Increased blood concentration of FDPs remains the most sensitive test for detecting the abnormality. The effect o f fl-bungarotoxin on neurotransmitter release from synaptosomes, R. CHAPELLand P. ROSENBERG(The University of Connecticut, School of Pharmacy, Storrs, CT 06269, U.S.A.).
PRESYNAPTICALLY acting phospholipase A 2 (PLA2) neurotoxins such as fl-bungarotoxin (fl-BuTx) modify the release of only acetylcholine (ACh) in the periphery, whereas in the CNS the release of norepinephrine (NE) and serotonin (5-HT) are also modified. In addition, ACh release in the periphery is modified in a triphasic manner (decrease, then increase, then block), while in the CNS only the increase has been demonstrated. To determine the specificity of the central effects of fl-BuTx we compared the effects of fl-BuTx and Naja naja atra PLA 2 on the release from rat cortical synaptosomes of ACh, NE, and 5-HT. We also measured the release of lactate dehydrogenase (LDH) in order to determine whether membrane disruption was responsible for neurotransmitter leakage. Both the PLA 2 toxin (5.0 n M) and enzyme (0.5 nM) stimulated the release of NE and 5-HT, but only at concentrations which induced leakage of LDH. Conversely, fl-BuTx stimulated the release of ACh at a concentration (0.SnM) which caused no leakage of LDH, while N. n. atra PLA 2 (0.SnM) did not stimulate release of ACh. fl-BuTx thus exerts a specific effect on the cholinergic nerve terminals, while the leakage of NE and 5-HT induced by fl-BuTx and N. n. atra PLA 2 correlates with membrane disruption due to their PLA 2 activities, fl-BuTx (0.5 nM), within 20 min, increased the resting release of ACh and decreased the stimulated release of ACh induced by depolarization with 4-aminopyridine, while N. n. atra PLA 2 (0.5 nM), in 20min, had no effect on resting or stimulated release of ACh. It is concluded that fl-BuTx in the CNS acts specifically on cholinergic terminals, where it exerts both stimulatory and inhibitory effects. (Supported by NIH Research Grant ROlNS14521.) Stonustoxin contracts the anococcygeus muscle and then inhibits adrenergic transmission prejunctionally. L . S . CHEAH,m M . C . E . GWEE,I R. YUEN,2 P. GOPALAKRISHNAKONE 3 and K . S . Y . Low ~ (Departments of Ipharmacology, 2Biochemistry and 3Anatomy, Faculty of Medicine, National University of Singapore, Singapore 051 l).
STONUSTOYdN(SNTx) is a peptide toxin recently purified from the venom of the stonefish Synanceja horrida by the Venom and Toxin Multidisciplinary Research Group of NUS; its pharmacological properties are now being characterized. The effects of SNTx on the rat isolated anococcygeus muscle mounted in Krebs solution and gassed with 95% 02/5% CO 2 were studied. Motor responses were evoked via field stimulation (20-25V, 10Hz x 10sec, 1 ms pulse width) every 2min; contractile responses to noradrenaline (NA) 5/zM were also obtained when appropriate. Cumulative doses of SNTx (0.5-30/Lg/ml) produced an initial rapid and transient contracture of the anococcygeus, accompanied by a progressive decline of the motor responses to about 40% of the control height, without blocking the contractile responses to NA; recovery was poor on drug washout. 4-aminopyridine (5-100/~M) progressively reversed the partially inhibited motor responses, but the reversal was not sustained on washing out 4-aminopyridine. SNTx has a dual action on the field-stimulated anococcygeus muscle: it caused a concentration-dependent and transient contracture of the muscle accompanied by a progressive inhibition of adrenergic transmission which may be attributed to a prejunctional mechanism of action of SNTx. Aconite poisoning in a herb preparation. S.-S. CI~N, D.-Z. HUNG, J.-F. DENG and W.-J. TSAI (Department of Medicine, Veterans General Hospital-Taipei, Taiwan, R.O.C.).
ACONITE is the dried tuberous root of aconitum species. It has been used for thousands of years in Eurasia as a homicidal agent, arrow poison, and medicinal drug. Chinese medicine uses aconite to treat weak constitution, poor metabolism, dysuria, etc. Pharmacologically, aconite possesses analgesic, anaesthetic, anti-inflammatory and hypotensive effects. Its principal poison alkaloids are aconitine, mesaconitine and jesaconitine. Aconite intoxication may produce nausea, vomiting, weakness, paresthesias and cardiac dysrhythmias. Recently, we