Effects of Noradrenaline and 5－hydroxytryptamine on Thermoresponsive Neurons in Slice Preparations of Rat Brainstem

Noradrenaline (NA) and 5-hydroxytryptamine (5-HT) have been thought to be involved in thermoregulation. In the present study, using slice preparations. We observe that NA inhibits the activities of most of the warm-responsive neurons but that 5-HT facilitates those of most of the warm-responsive neurons in the preoptic and anterior hypothalamic region. This conclusion supports the previous which show that the serotonergic system activates heat-loss responses and that NA inhibits heat-loss responses during heat expouse.On the other hand, the result obtained in the dorsal raphe nucleus was opposite to that in the preopic and anterior hypothalamic region when 5-HT was applied. This observation may be in part related to the autoregulation of 5-HT containing neurons in the dorsal raphe nucleus. In addition, the dose-response relations were determined using in vitro slice preparations. In both regions, NA and 5-HT started to effect the activities of the warm-responsive neurons at minimum concentration of 5×1０　mol, while the maximum responses were obtained at a concentration of 5×10 mol.

Noradrenaline

5-hydroxytryptamine

Thermoresponsive Nuron

Slice Preparation