The interaction between endogenous opioids and central alpha2-adrenoreceptors was studied in seven patients with uncomplicated essential hypertension by giving clonidine (0.15 mg i.v.), naloxone (0.4 mg i.v.) and both drugs at the same doses. Data were compared with those after placebo (saline i.v.). The study has a randomized cross-over design and treatments were two days apart. Blood pressure, heart rate, human growth hormone (HGH) and plasma renin activity (PRA) were measured every 7 1/2 , 15 and 30 min respectively over a 2-h period. Clonidine significantly reduced mean blood pressure, increased HGH and did not change heart rate and PRA. Naloxone alone did not change these variables, but when added to clonidine, it caused a further decrease in mean blood pressure, without changing heart rate and PRA and without affecting the HGH increase induced by clonidine. These results suggest that μ opioid receptor blockade does not influence the humoral effect of clonidine, but enhances its hypotensive action. There may be a negative interaction between endogenous opioids and central alpha2-adrenoreceptors in the control of blood pressure.
Interaction between central alpha-adrenergic stimulation and endogenous opioids in hypertensive humans
PEDRINELLI, ROBERTO;BERNINI, GIAMPAOLO;SALVETTI, ANTONIO
1983-01-01
Abstract
The interaction between endogenous opioids and central alpha2-adrenoreceptors was studied in seven patients with uncomplicated essential hypertension by giving clonidine (0.15 mg i.v.), naloxone (0.4 mg i.v.) and both drugs at the same doses. Data were compared with those after placebo (saline i.v.). The study has a randomized cross-over design and treatments were two days apart. Blood pressure, heart rate, human growth hormone (HGH) and plasma renin activity (PRA) were measured every 7 1/2 , 15 and 30 min respectively over a 2-h period. Clonidine significantly reduced mean blood pressure, increased HGH and did not change heart rate and PRA. Naloxone alone did not change these variables, but when added to clonidine, it caused a further decrease in mean blood pressure, without changing heart rate and PRA and without affecting the HGH increase induced by clonidine. These results suggest that μ opioid receptor blockade does not influence the humoral effect of clonidine, but enhances its hypotensive action. There may be a negative interaction between endogenous opioids and central alpha2-adrenoreceptors in the control of blood pressure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
