Hypothalamic chemostimulation and autonomic changes in curarized rats.

Rats previously implanted with chronic double walled cannulae aimed at the lateral hypothalamic area (LHA) ate and drank reliably after minute injections of norepinephrine and carbachol respectively. Later on the rats were curarized and artificially respirated. After an habituation period during which rectal temperature, cardiac rate and peripheral vasomotor activity were continuously recorded, half of the subjects were injected with 1 mul of norepinephrine (40 x 10(-9) moles) and the other half with 1 mul of carbachol (2.4 x 10(-9)moles). Both drugs elicited hypothermia, bradycardia and vasodilatation. Bradycardia after carbachol was significantly greater than after norepinephrine and hypothermia and vasodilatation after norepinephrine were significantly greater than after carbachol. When the treatments were reversed essentially the same effects were observed.