Pressor and sympathetic responses to dorsal raphe nucleus infusions of TRH in rats.
Pressor, tachycardic, and sympathoexcitatory responses to intracerebroventricularly (icv) infused thyrotropin-releasing hormone (TRH) were recorded in urethan-anesthetized rats to identify where centrally administered TRH acts in the brain. None of these responses was altered either by electrolytic lesions in the medial preoptic, posterior, or paraventricular hypothalamus or by chemical lesions produced by destroying catecholaminergic neurons with icv infused 6-hydroxydopamine. By contrast, when serotonergic neurons were similarly destroyed with 5,7-dihydroxytryptamine, TRH-induced tachycardia was inhibited. Attendant pressor responses were also inhibited by electrolytic lesions of the dorsal, but not of the median, raphe nucleus. Pressor and sympathoexcitatory responses elicited by infusing TRH directly into the dorsal raphe nucleus resembled those produced by icv infusion, and their magnitude diminished after pentolinium-induced ganglioplegia. These results are compatible with the interpretation that icv infused TRH may produce its cardiovascular and sympathetic effects by acting, at least in part, on serotonergic mechanisms located in the dorsal raphe nucleus.
Mattila
J
J
Department of Pharmacology, College of Health Sciences and Hospital, University of Kansas Medical Center, Kansas City 66103.
Buñag
R D
RD
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002319:Cardiovascular System / Q000187:drug effects; D006892:Hydroxydopamines / Q000494:pharmacology; D007031:Hypothalamus / Q000502:physiology; D007267:Injections; D007276:Injections, Intraventricular; D008297:Male; D016627:Oxidopamine; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000187:drug effects*; D013610:Tachycardia / Q000139:chemically induced / Q000517:prevention & control; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D006892:Hydroxydopamines; D015116:5,7-Dihydroxytryptamine; D013973:Thyrotropin-Releasing Hormone; D016627:Oxidopamine