Gyroxin fails to modify in vitro release of labelled dopamine and acetylcholine from rat and mouse striatal tissue

Gyroxin fails to modify in vitro release of labelled dopamine and acetylcho line from rat and mouse striatal tissue. Gyroxin is a thrombin-like peptide with amidasic, esterasic and fibrinogenolitic activities, found in the ven om of snakes like Lachesis muta muta and Crotalus durissus terrificus. Intr avenous injections of small doses of gyroxin induce a typical barrel rotati on behaviour that has been thought to be a neurotoxic effect. The aim of th is study was to determine whether gyroxin-induced barrel rotation behaviour involves changes in neurotransmitter release. Gyroxin was isolated from cr ude venoms by gel filtration and affinity chromatography. Its properties we re determined by assaying esterasic, amidasic and fibrinogenolitic enzymati c activities and tested for barrel rotation behaviour. Neurotransmitter rel ease tests employed rat and mouse superfused brain striatal chopped tissue preloaded with [H-3]-dopamine, [H-3]-acetylcholine or in a double labelling procedure. They were stimulated by 20 mM K+ in control conditions or in th e presence of several concentrations of toxins. Crotoxin and crotamine were used as positive controls. Gyroxins failed at modifying both basal and sti mulated neurotransmitter releases, suggesting a lack of direct neurotoxic e ffect. We therefore suggest that gyroxin may not be a neurotoxin but rather , induces this behavioural syndrome by other means possibly related to haem odynamic disturbance. The possible role of vasopressin is discussed. (C) 20 01 Elsevier Science Ltd. All rights reserved.