Hypothalamic chemostimulation and autonomic changes in curarized rats

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Abstract
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 continously recorded, half of the subjects were injected with 1 μl of norepinephrine (40×10-9 moles) and the other half with 1 μl of carbachol (2.4×10-9 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.