Influence of Chronic Opioid Delta Receptor Antagonism on Blood Pressure Development and Tissue Contents of Catecholamines and Endogenous Opioids in Spontaneously Hypertensive Rats

Abstract

Opioid δ receptors seem to be involved in blood pressure regulation of spontaneously hypertensive rats (SHR), possibly by an interaction with the sympathetic nervous system. In the present study the effect of four weeks' chronic δ receptor antagonism with ICI 154 129 on development of blood pressure was evaluated in young SHR. Contents of adrenaline and noradrenaline and the opioid peptides β-endorphin and leucine-enkephalin were measured in brain stem, mid brain, hypothalamus, and adrenal glands. After four weeks' treatment, systolic blood pressure was lower when compared with control SHR. During chronic δ antagonism, concentrations of adrenaline were higher in hypothalamus, mid brain and adrenal glands, contents of noradrenaline were higher in hypothalamus and adrenal glands than in control rats, contents of opioid peptides were not altered with the exception of an increase of β-endorphin concentration in the hypothalamus. The changes in concentrations of catecholamines following chronic β antagonism may reflect an alteration of sympathetic activity and could contribute to the retardation of blood pressure development.

Key Words:

• spontaneously hypertensive rat
• β receptor-antagonism
• cate-cholamines
• blood pressure
• β-endorphin