Cardiovascular responses to centrally administered serotonin in conscious normotensive and spontaneously hypertensive rats |
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Authors: | T Sukamoto T Yamamoto S Watanabe S Ueki |
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Affiliation: | Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812, Japan |
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Abstract: | Serotonin (5-HT, 1-10 micrograms), injected into the lateral ventricle of the urethanized, and conscious normotensive and spontaneously hypertensive rats produced a dose-dependent increase in blood pressure. In conscious rats, there was mainly a decrease in heart rate while variable changes in heart rate were elicited by intraventricular (i.c.v.) administration of 5-HT in anesthetized animals. These pressor responses and bradycardia caused by 5-HT in conscious rats were reduced by pretreatment with i.c.v. methysergide (25 micrograms). Microinjection of 5-HT (2.5-5 micrograms) directly into the medial hypothalamus and the anterior hypothalamus/preoptic area of conscious normotensive rats caused a pressor response accompanied by variable changes in heart rate. The present results indicate that urethane can affect the HR response to 5-HT injected i.c.v. without having a marked influence on the pressor response. These findings, which show that 5-HT produced a rise in BP independent of the anesthetized or conscious state and of normotension or hypertension, further confirm the idea that 5-HT plays a pressor role in the central regulation of the cardiovascular system. |
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Keywords: | Serotonin Central cardiovascular control Central drug administration Rats |
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