Abstract
Changes in rectal and skin temperatures following intraventricular injection of norepinephrine and receptor specificity of the response in the rat were investigated.
Intraventricular injection of norepinephrine in a small dose (6μg) produced a slight elevation in rectal temperature, but in larger amounts (25-50μg) the result was a dose-dependent hypothermia associated with a marked rise in skin temperature. No change was observed in oxygen consumption after intraventricular injection of norepinephrine (25μg).
Intraventricular injection of phenoxybenzamine prior to norepinephrine blocked hypothermia and skin temperature elevation which are normally observed following norepinephrine injection, while propranolol given in the same way showed less or no effect. Intraventricular injection of phenylephrine produced a dose-dependent hypothermia, whereas a no does-response relationship was obtained with isoproterenol.
These results suggest that in the rat the hypothermic effect of norepinephrine injected intraventricularly is mediated by the action of central alpha receptors.
