INTERACTION BETWEEN NEURONAL RESPONSES TO NOCICEPTION AND HYPERTENSION IN THE NUCLEUS-RETICULARIS GIGANTOCELLULARIS OF THE RAT

We evaluated the interactive effects of noxious stimuli and elevation in systemic arterial pressure on the responsiveness of spontaneously a ctive neurons in the nucleus reticularis gigantocellularis (NRGC) of m ale, adult Sprague-Dawley rats anesthetized with pentobarbital sodium. In NRGC neurons that responded to both nociception (tail clamp) and t ransient hypertension elicited by phenylephrine (5 mu g/kg, i.v.), the responsiveness to tail clamp was reduced upon simultaneous elevation in arterial pressure. This preferential response pattern did not appea r to be affected by the level of anesthesia, since it was demonstrated in animals that were maintained by hourly bolus supplements or contin uous infusion of pentobarbital sodium. These data offer a feasible cel lular explanation for the documented correlation between elevated noci ceptive threshold and hypertension. They also showed that NRGC may be a central integrator for the processing of nociceptive and cardiovascu lar information.