Observations on pain perception and hypertension in spontaneously hypertensive rats.

Pain sensitivity in Spontaneously Hypertensive Rats (SHR) and normotensive Wistar-Kyoto controls (WKY) as well as in experimentally hypertensive Wistar rats has been studied. Results indicate a diminished responsiveness to noxious stimuli in SHR when compared with WKY. This hypoalgesia is altered neither by chronic treatment with the antihypertensive drugs hydralazine and captopril nor by the peripherally acting opiate antagonist N-methylnaloxone. Induction of renal and DOCA-salt hypertension in Wistar rats and Wistar-Kyoto rats did not affect nociceptive responsiveness. It is concluded that opiate receptors within the central nervous system are involved in the hypoalgesia in SHR and that pain perception appears to be dissociated from blood pressure regulation in the rat strains used.