Distributions of mu and delta opioid receptors in central nervous system of SHR rats and normotensive WKY rats.

AIM

To compare the distributions of opioid receptor subtypes in central nervous system of spontaneously hypertensive rat (SHR) and normotensive Wistar-Kyoto (WKY) rat.

METHODS

[3H] Ohmefentanyl (OMF), [3H]N-methyl-N-[7-(I-pyrrolidinyl)-1-oxaspiro (4,5)dec-8-yl] benzeneacetamide (U-69593) and [3H]etorphine after suppression of mu and kappa-sites by 15 mumol.L-1 each of unlabeled OMF and trans-(1R,2R)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]-benzeneacetamide hydrochloride (U-50 488H) were used as ligands for mu, kappa, and delta opioid receptor subtypes in autoradiography, respectively.

RESULTS

Delta receptors had an increase in hypothalamic nuclei, periaqueductal gray, caudate and interpeduncular nuclei, and a decrease in substantia nigra in SHR than in those of WKY rat. Mu receptors were less concentrated in basolateral amygdaloid nucleus, habenular nuclei and nucleus of solitary tract of SHR than in those of WKY rats. Kappa receptor density was not checked out in the present study.

CONCLUSION

Distribution of opioid receptor subtypes is related to hypertension of SHR, and delta opioid receptor is more important than mu opioid receptor in the maintenance of hypertension in SHR.