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L‐TRYITOPHAN‐INDUCED DEPRESSION OF THE PRESSOR RESPONSE TO CLONIDINE IN ANAESTHETIZED RATS
Author(s) -
Nolan P. L.,
Brazenor R. M.
Publication year - 1978
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1978.tb00672.x
Subject(s) - clonidine , methysergide , serotonin , endocrinology , medicine , angiotensin ii , pressor response , tryptophan , carbidopa , renin–angiotensin system , chemistry , blood pressure , heart rate , receptor , levodopa , biochemistry , disease , amino acid , parkinson's disease
SUMMARY 1. The interaction of the serotonin precursor L‐tryptophan with the pressor responses of the anaesthetized rat to the intravenous injection of clonidine, adrenaline and angiotensin has been studied. 2. Pretreatment of rats with L‐tryptophan (100 mg/kg) depressed the pressor response to clonidine but had no effect on the responses elicited by adrenaline or angiotensin. 3. The L‐tryptophan‐induced depression of the clonidine response was prevented by pretreating rats with either Rö 44602, carbidopa, BW 172C58, methys‐ergide or by pithing. 4. Intravenous infusions of serotonin depressed the pressor responses to clonidine, adrenaline and angiotensin in both intact anaesthetized and pithed rats. 5. It is concluded that the depressant action of L‐tryptophan is dependent on its conversion within the periphery to serotonin. This action is also dependent on or mediated by the sympathetic nervous system.