Chronic administration of naltrexone alters central catecholamine levels but not the development of hypertension in spontaneously hypertensive rats.

The effect of chronic administration of the opiate antagonist naltrexone on the genesis and development of hypertension and correlated changes in central norepinephrine levels was evaluated in spontaneously hypertensive rats and Wistar-Kyoto controls. Capsules of poly-epsilon-caprolactone containing naltrexone in ethyl oleate or ethyl oleate alone were implanted in 4 week old SHR and WKY rats. Naltrexone failed to alter the genesis or magnitude of hypertension developed by the SHR and did not alter heart rates. Blood pressure and heart rate of WKY rats were also unaffected. A significant decrease in midbrain and hippocampal NE levels was observed in SHRs but not in WKYs following naltrexone.