• The Korean Journal of Pharmacology
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• v.27 no.1
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• pp.21-31
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• 1991

When administered intracerebroventricularly (icv), cholinergic nicotinic agents, nicotine and DMPP, as well as cholinergic muscarinic agents, muscarine and bethanechol, produced pressor responses in urethane-anesthetized vagotomized rabbits. The response patterns to nicotine and to DMPP were similar, while the bethanechol response resembled the muscarine pattern. The pressor response to nicotine and DMPP was markedly inhibited by icv mecamylamine but not by icv pirenzepine, whereas the response to muscarine and bethanechol was inhibited by icv pirenzepine but not by icv mecamylamine, suggesting that both nicotinic and muscarinic receptors in the brain are involved in the action. Intravenous pretreatments of animals with regitine, reserpine, enalapril, saralasin, both regitine and enalapril, both regitine and saralasin, SK&F-100273 did not prevent the pressor response to nicotine and muscarine. Iv pretreatments with both regitine and SK&F-100273 inhibited the nicotine response without affecting the muscarine response, whereas pretreatments with three agents, regitine, enalapril and SK&F-100273, inhibited the muscarine response. The nicotine-induced elevated blood pressure as well as the muscarine-induced were lowered by regitine but not by enalapril or by SK&F-100273. Enalapril was without effect on the nicotine hypertension in rabbits treated with regitine or both regitine and SK&F-100273, whereas SK&F-100273 lowered the nicotine hypertension in regitine-treated animals. Enalapril did not enhance the lowering effect of SK&F-100273 in regitine-treated ones, nor did it cause a fall of the muscarine hypertension induced in regitine-treated rabbits, but it did lower the blood pressure in animals treated with both regitine and SK&F-100273. Likewise, SK&F-100273 did not cause a fall of the muscarine hypertension induced in regitine-treated rabbits, but it did lower the blood pressure in animals treated with both regitine and enalapril. These data suggest that the nicotine-induced hypertensive state is related to at least two systems in the periphery-sympathetic and vasopressin, whereas in the muscarine-induced hypertensive state three systems in the periphery are involved, i.e., the sympathetic, vasopressin and angiotensin system. The hypotensive effect of regitine on basal arterial blood pressure levels of rabbits was not influenced by pretreatment with either of enalapril or SK&F-100273, but significantly potentiated by treating with both enalapril and SK&F-100273, suggesting participation of the sympathetic and the renin-angiotensin system as well as the vasopressin system in maintenance of arterial blood pressure.