Lack of involvement of α‐adrenoceptors in sympathetic neural vasoconstriction in the hindquarters of the rabbit

• Published in: British journal of pharmacology 1987-01, Vol.90 (1), p.51-60
• Main Authors: Hirst, G.D.S., Lew, M.J.
• Format: Article
• Language: English
• Subjects: Adrenergic alpha-Antagonists - pharmacology; Animals; Biological and medical sciences; Blood vessels and receptors; Cystamine - analogs & derivatives; Cystamine - pharmacology; Electric Stimulation; Female; Fundamental and applied biological sciences. Psychology; Gagging - drug effects; Hindlimb - innervation; Male; Norepinephrine - pharmacology; Phenoxybenzamine - pharmacology; Phentolamine - pharmacology; Rabbits; Receptors, Adrenergic, alpha - drug effects; Receptors, Adrenergic, alpha - physiology; Vasoconstriction - drug effects; Vertebrates: cardiovascular system
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1987.tb16824.x

1 The hypothesis that sympathetic nerves in arterial blood vessels activate excitatory receptors distinct from α‐adrenoceptors was investigated in vivo in the rabbit. 2 In anaesthetized, ganglion‐blocked rabbits, graded stimulation of the lumbar sympathetic nerve chains caused graded hind limb vasoconstriction. The responses to single pulses and short trains of stimuli were unaffected by benextramine (10 mg kg‐1) and the longer trains were enhanced. Phenoxybenzamine (5 mg kg−1) slightly reduced the responses to short trains of stimuli and did not affect the responses to long trains. The dose‐response curve to intra‐arterial noradrenaline (after β‐adrenoceptor blockade) was shifted rightwards about ten fold by benextramine (10 mg kg−1) and by phenoxybenzamine (5 mg kg−1). 3 In conscious rabbits the vasoconstriction caused by the nasopharyngeal reflex initiated by smoke inhalation was unaffected by benextramine (10 mg kg−1). 4 Small mesenteric arteries (