Abstract
GABAergic inhibition of neurons in the preoptic area (POA) is involved in thermogenesis elicited by cooling stimulation of the skin. In the present study, we investigated hypothalamic sites mediating thermogenesis induced by microinjection of GABA into the POA in urethane-chloralose-anesthetized rats. Unilateral microinjection of GABA (0.3 M, 100 nl) into the POA increased the rate of whole body oxygen consumption (VO2), colonic temperature, and temperature of brown adipose tissue. By pretreatment of the dorsomedial hypothalamic nucleus (DMH) with a microinjection of the local anesthetic lidocaine (10%, 100 nl), the thermogenic responses were largely attenuated although the injection of lidocaine alone had no significant effect on VO2. The magnitude of GABA-induced thermogenic responses recovered within 60 min after the lidocaine injection into the DMH. Microinjection of lidocaine into the ventromedial hypothalamic nucleus or lateral hypothalamic area, and microinjection of physiological saline into the DMH had no effect on the GABA-induced thermogenic responses. These results suggest that the DMH is, at least in part, involved in efferent pathways for the thermogenesis elicited by microinjection of GABA into the POA. [Jpn J Physiol 54 Suppl:S231 (2004)]
