TRH: cardiovascular and sympathetic modulation in brain nuclei of the rat.
The cardiovascular and sympathetic effects of TRH in discrete cardiovascular-related brain nuclei were studied. Microinjections of TRH were made into the nucleus preopticus medialis (POM) of conscious rats and the nucleus tractus solitarius (NTS) of pentobarbitone-anesthetized, artificially respired rats. POM injections (1 microliter, 0.8-80 nM) elicited dose dependent pressor and tachycardic responses which were accompanied by increased levels of norepinephrine (NE) and epinephrine (EPI) in the plasma. These pressor/tachycardic effects of TRH were also elicited in adrenal demedullated (ADM-x) rats, but completely abolished in ADM-x rats pretreated with bretylium (30 mg/kg, IA). NTS injections (0.1 microliter, 30 and 150 nM) had a short depressor effect on blood pressure (BP) and a delayed increase in heart rate (HR). From these findings we suggest that the POM, a central nucleus in the AV3V region, may be an important forebrain site for autonomic regulation by TRH, mediated through the sympathetic nervous system.
D000313:Adrenal Medulla / Q000502:physiology*; D000315:Adrenalectomy; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001949:Bretylium Compounds / Q000494:pharmacology; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D011301:Preoptic Area / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D001949:Bretylium Compounds; D013973:Thyrotropin-Releasing Hormone; D009638:Norepinephrine; D004837:Epinephrine