Role of the medullary raphé in thermoregulatory vasomotor control in rats.
To investigate the involvement of the medullary raphé in thermoregulatory vasomotor control, we chemically manipulated raphé neuronal activity while monitoring the tail vasomotor response to preoptic warming. For comparison, neuronal activity in the rostral ventrolateral medulla (RVLM) was manipulated in similar experiments. Injections of D,L-homocysteic acid (DLH; 0.5 mM, 0.3 microl) into a restricted region of the ventral medullary raphé suppressed the tail vasodilatation normally elicited by warming the preoptic area to 42 degrees C. DLH injection into the RVLM also suppressed the vasodilatation elicited by preoptic warming. Injection of bicuculline (0.5 mM, 0.3 microl) into the same raphé region suppressed the vasodilatation elicited by preoptic warming. Bicuculline injection into the RVLM did not suppress tail vasodilatation. These results suggest that neurones in both the medullary raphé and the RVLM are vasoconstrictor to the tail, but only those in the raphé receive inhibitory input from the preoptic area. That input might be direct and/or indirect (e.g. via the periaqueductal grey matter).
Tanaka
Mutsumi
M
Department of Physiology, School of Allied Health Sciences, Osaka University Faculty of Medicine, Yamadaoka 1-7, Suita, 565-0871 Osaka, Japan.
Nagashima
Kei
K
McAllen
Robin M
RM
Kanosue
Kazuyuki
K
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006358:Hot Temperature; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011301:Preoptic Area; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D018756:GABA Antagonists; D006710:Homocysteine; C007956:homocysteic acid; D001640:Bicuculline