The effect of reserpine on the pressor responses to angiotensin in the conscious cat

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Abstract
1 Blood pressure recordings have been made in conscious cats in an attempt to reveal a possible indirect component to the angiotensin pressor response. 2 Reserpine (50 to 250 μg/kg per day) caused a maximal reduction of about 50% in the pressor response to angiotensin whilst virtually abolishing the responses to tyramine and McN-A-343. Responses to noradrenaline were only slightly and transiently reduced. 3 Syrosingopine (0.5 mg/kg) and reserpine (250 μg/kg) reduced the responses to angiotensin, McN-A-343 and tyramine to much the same extent, but tetrabenazine only reduced the responses to all these agents in a dose (25 mg/kg) which probably had effects on the catecholamine stores of smooth muscle. 4 The reduction in the responses to angiotensin, tyramine and McN-A-343 by reserpine was partly reversed by tranylcypromine. Noradrenaline and (±)-dopa infusions were ineffective by themselves, but increased the effects of tranylcypromine in restoring the responses to angiotensin, tyramine and McN-A-343 after reserpine. 5 Infusion of α-methyldopa markedly increased the responses to angiotensin, tyramine and McN-A-343 after these had been reduced by reserpine. 6 The results suggest that the pressor response to angiotensin in the conscious cat is partly mediated by release of noradrenaline from peripheral neuronal stores.