Studies on the effects of histamine on cholinergic transmission to the heart and vasculature in the anesthetized cat.
Intravenous infusion of histamine, 2 to 16 micro g/kg/min, failed to alter bradycardic responses to electrical stimulation of the vagus in anesthetized cats. In this respect, effect of this substance differed from those observed in anesthetized dogs. However, infusion of histamine, 2 micro g/kg/min, significantly attenuated vasodilator responses induced by electrical stimulation of the lumbar sympathetic chain in bretylium pretreated cats. This action of histamine on the cholinergic vasodilator system could be completely antagonized by the simultaneous administration of pyrilamine and metiamide. Histamine also inhibited vascular effects of acetylcholine and prostaglandin E1(PGE1). Thus it appears that the ability of histamine to attenuate cholinergic vasodilatation is due to a nonspecific antagonism of the neurohumor at the level of blood vessels. Since histamine has been shown also to inhibit sympathetic transmission by a presynaptic mechanism, it is suggested that histamine could influence vascular effects of both components of the autonomic nervous system.
D000758:Anesthesia; D000818:Animals; D001808:Blood Vessels / Q000294:innervation*; D002415:Cats; D004558:Electric Stimulation; D005260:Female; D006321:Heart / Q000294:innervation*; D006439:Hemodynamics / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology*; D008297:Male; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D013116:Spinal Cord / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects; D014630:Vagus Nerve / Q000502:physiology*
D006632:Histamine