title: The effects of protease inhibitor homologues from mamba snake venoms on autonomic neurotransmission.
abstract: Five protease inhibitor homologues isolated from mamba venoms were tested for facilitatory actions on autonomic neurotransmission using isolated smooth muscle preparations. Dendrotoxin from the eastern green mamba (Dendroaspis angusticeps) was the most consistent in augmenting the responses to sympathetic stimulation in vas deferens preparations and to parasympathetic stimulation in chick oesophagus preparations. Toxin I from the black mamba (D. polylepis) venom augmented the neurally evoked responses in vas deferens preparations, and toxin K from the same venom augmented neurally evoked responses in chick oesophagus preparations. Proteins B and E from D. polylepis venom, as well as bovine pancreas trypsin inhibitor, had no significant facilitatory action on either smooth muscle preparation. The mechanism of the augmentation of neurally evoked responses produced by toxin I on vas deferens preparations, and dendrotoxin on chick oesophagus preparations, was investigated using a variety of drugs which interfere with cholinergic and adrenergic transmission. It is concluded that dendrotoxin and toxin I increase evoked transmitter release in the autonomic nervous system by a direct action on nerves.
mesh_terms: D000818:Animals; D001337:Autonomic Agents / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000187:drug effects*; D002645:Chickens; D004546:Elapid Venoms / Q000494:pharmacology*; D004558:Electric Stimulation; D004947:Esophagus / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D011480:Protease Inhibitors / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D009435:Synaptic Transmission / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D001337:Autonomic Agents; D004546:Elapid Venoms; D011480:Protease Inhibitors