Search results for "Venoms"
showing 2 items of 52 documents
Comparison of the contractile effects of endothelin-1 and sarafotoxin S6b in goat isolated cerebral arteries
1992
1. The effects of endothelium-derived endothelin-1 and snake venom-derived sarafotoxin S6b, peptides with striking structural and functional similarities, were examined and compared in isolated middle cerebral arteries of goats. 2. Endothelin-1 and sarafotoxin S6b contracted cerebral arteries in a concentration-dependent manner. The potency of endothelin-1 (EC50 = 4.9 (3.9-6.2) x 10(-10) M) was about ten times higher than that of sarafotoxin S6b (EC50 = 5.5 (4.4-6.9) x 10(-9) M). The tension returned to basal values after repeated washings and contraction with endothelin-1 could be reproduced. Endothelin-1 and sarafotoxin S6b induced further contraction in arteries precontracted with prosta…
Differential blockade by nifedipine and ω-conotoxin GVIA of α1- and β1-adrenoceptor-controlled calcium channels on motor nerve terminals of the rat
1990
Electrically evoked release of [3H]acetylcholine ([3H]ACh) from the rat phrenic nerve and its facilitation by stimulation of presynaptic alpha 1- and beta 1-adrenoceptors were investigated in the absence and presence of nifedipine and omega-conotoxin GVIA. Both calcium channel antagonists did not modify electrically evoked [3H]ACh release, but selectively blocked the effect triggered by both facilitatory adrenergic receptors. The increase in [3H]ACh release mediated via beta 1-adrenoceptor activation was abolished by low concentrations (1 nM) of omega-conotoxin GVIA, whereas nifedipine (100 nM) abolished the facilitatory effect mediated via alpha 1-adrenoceptor stimulation. Therefore, the b…