Premium
Comparison of the antagonistic effects of phentolamine on vasoconstrictor responses to exogenous and neurally released noradrenaline in vivo
Author(s) -
Bell C.
Publication year - 1985
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1985.tb08853.x
Subject(s) - phentolamine , stimulation , endocrinology , medicine , chemistry , norepinephrine , vasoconstrictor agents , vasoconstriction , dopamine
1 The antagonistic effects of the α‐adrenoceptor blocking agent phentolamine on vasoconstrictor responses to intraluminal noradrenaline and lumbar sympathetic nerve stimulation were compared in the hindlimb of the anaesthetized dog. 2 Sympathetic stimulation with 1 pulse or trains of 4–10 pulses at 0.4–40 Hz produced graded vasoconstrictor responses that were matched in amplitude by intra‐arterial injections of 10 −8– 10 −6 g noradrenaline. Phentolamine (0.5 mg kg −1 i.v.) attenuated amplitude‐matched responses to both types of stimuli to quite similar extents. 3 The extent of the effect of phentolamine on neurogenic responses was greater with 1 pulse stimulation than with trains, and greater with 4 pulse than with 10 pulse trains. The effect was maximal within 2 min of phentolamine administration and wore off in parallel with that on responses to injected noradrenaline. 4 The results are consistent with the view that transmitter released from noradrenergic vasoconstrictor nerves acts primarily on subjunctional α‐adrenoceptors.