Central hypotensive effect of diprenorphine in normotensive rat and SHR.

Opioid compounds injected intracisternally in rats induce a centrally-mediated increase in blood pressure. In the present study, the intracisternal injection of an antagonist of opioid compounds, diprenorphine was examined. Diprenorphine caused a similar blood pressure decrease in spontaneously hypertensive rats and normotensive control Wistar Kyoto rats both in young and adult animals. This represents an important argument concerning a role of endogenous opioids in blood pressure control in anaesthetized rats but suggests that brain stem endogenous opioids may not be involved in the mechanism of hypertension.