Dynorphins and Leu-enkephalin in brain nuclei and pituitary of WKY and SHR rats.

The distribution of dynorphin 1-13 (Dyn-1-13, Dyn-(1-8) and Leu5-enkephalin (LE) immunoreactivities (ir) were determined in discrete brain nuclei of normotensive (WKY) and hypertensive (SHR) rats. The concentration of ir-Dyn-(1-13) and ir-Dyn-(1-8) varied markedly among the various nuclei studies with a predominance of ir-Dyn-(1-13) over ir-Dyn-(1-8) in all the nuclei of both WKY and SHR rats. Ir-LE also showed large variations in different sites and no consistent relationships were found between the distribution of ir-Dyn-(1-8), Dyn-(1-13) and LE. SHR rats had lower levels of ir-Dyn-(1-13), Dyn-(1-8) and LE in the suprachiasmatic nucleus compared with WKY rats. In addition, SHR rats had lower levels of ir-Dyn-(1-8)- in the paraventricular and central amygdala, and higher ir-Dyn-(1-13) levels in the substantia nigra. The level of ir-Dyn-(1-13) in the neurointermediate lobe (NIL) of SHR rats was decreased substantially compared with that of WKY rats. The localization of these opioid peptides suggests that dynorphin-like peptides may serve a variety of hypothalamic and extrahypothalamic functions which might differ between SHR and WKY rats.