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 active neurons in the nucleus reticularis gigantocellularis (NRGC) of male, adult Sprague-Dawley rats anesthetized with pentobarbital sodium. In NRGC neurons that responded to both nociception (tail clamp) and transient hypertension elicited by phenylephrine (5 μg/kg, i.v.), the responsiveness to tail clamp was reduced upon simultaneous elevation in arterial pressure. This preferential response pattern did not appear to be affected by the level of anesthesia, since it was demonstrated in animals that were maintained by hourly bolus supplements or continuous infusion of pentobarbital sodium. These data offer a feasible cellular explanation for the documented correlation between elevated nociceptive threshold and hypertension. They also showed that NRGC may be a central integrator for the processing of nociceptive and cardiovascular information.