DIFFERENT DISTRIBUTIONS OF OPIOID RECEPTORS IN SPONTANEOUSLY HYPERTENSIVE RATS AND WISTAR-KYOTO RATS

AIM: To compare the densities of opioid receptors in spontaneously hyp ertensive rats (SHR) with those of normotensive Wistar-Kyoto (WKY) rat s in central nervous system which are related to the regulation of BP. METHODS: [H-3]Etorphine, a nonspecific opioid ligand, was used to det ermine the distributions of opioid receptors in 16-wk-old SHR and WKY rats by quantitative autoradiography. RESULTS: The densities of [H-3]e torphine in hippocampus (P< 0.01), periaqueductal gray, nucleus of the solitary tract, and thoracic (T4 - 6) spinal cord (P<0.05) of SHR wer e lower than those of WKY rats. But in basolateral amygdaloid nucleus (P<0.01), habenular nuclei (P<0.05), and hypothalamic nuclei including arcuate nucleus (P<0.01), higher densities of opioid receptors were f ound in SHR. No difference existed in interpeduncular nuclei between t he 2 groups. CONCLUSION: The difference in distributions of opioid rec eptors is related to the hypertension in SHR.