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Inhibition of serotonin-induced increase in canine external carotid blood flow by drugs that decrease the sympathetic
J A Terrón1, E Hong, F J López-Muñoz
1Departamento de Farmacología y Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México, D.F., México.
Journal of Autonomic Pharmacology
|June 1, 1994
Summary
Central sympatho-inhibitory drugs, prazosin and ketanserin, reduce 5-hydroxytryptamine (5-HT)-induced increases in external carotid blood flow by decreasing sympathetic tone, not by blocking 5-HT receptors.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Neuroscience
Background:
- 5-hydroxytryptamine (5-HT) increases external carotid blood flow (external CBF) in dogs.
- The precise mechanism of this 5-HT-induced increase in external CBF is not fully understood.
- Centrally-acting sympatho-inhibitory drugs may influence this response.
Purpose of the Study:
- To investigate the effect of prazosin and ketanserin on 5-HT-induced external CBF.
- To determine if the mechanism involves 5-HT receptor blockade or sympathetic tone modulation.
Main Methods:
- Administered 5-HT intracarotidly to anesthetized dogs.
- Infused prazosin and ketanserin intravenously to assess their blocking effects.
- Utilized other agents like mecamylamine, methiothepin, and spiroxatrine to probe receptor involvement.
Main Results:
- 5-HT significantly increased external CBF without altering blood pressure or heart rate.
- Prazosin and ketanserin dose-dependently blocked the 5-HT response.
- Mecamylamine, methiothepin, and spiroxatrine also inhibited the 5-HT effect, while ritanserin did not.
Conclusions:
- The inhibition of 5-HT-induced external CBF by prazosin, ketanserin, mecamylamine, and spiroxatrine is mediated by a reduction in sympathetic tone.
- This suggests the effect is not due to direct blockade of 5-HT receptors.