ALTERATIONS IN BRAIN AND PITUITARY BETA-ENDORPHIN CONTENT IN GENETICALLY EPILEPSY-PRONE RATS

We measured beta-endorphin concentrations in the anterior and neuroint ermediate lobes of the pituitary gland and in microdissected brain reg ions of moderate-seizure genetically epilepsy-prone rats (GEPR-3), sev ere-seizure GEPR-9s and Sprague-Dawley non-epileptic control rats. Pla sma concentrations of beta-endorphin and alpha-melanocyte-stimulating hormone (alpha-MSH) were also measured as indicators of pituitary POMC -peptide secretion. Concentrations of beta-endorphin in the anterior l obe of GEPR-3s were 53% higher compared to controls and 57% higher com pared to GEPR-9s. There were no differences in neurointermediate lobe beta-endorphin concentrations between control and either GEPR strain. Plasma beta-endorphin concentrations were significantly lower in GEPR- 9s than controls. Plasma levels of alpha-MSH did not differ between co ntrol and GEPRs. In the hypothalamus of GEPR-9s beta-endorphin concent rations in the arcuate nucleus were significantly greater than in GEPR -3s. Concentrations of beta-endorphin in the central amygdala of GEPR- 9s were two- to threefold greater than in control or GEPR-3s. beta-End orphin concentrations in the central gray of GEPR-3s were 58% lower th an control or GEPR-9s. These data suggest that anterior lobe beta-endo rphin secretion is reduced in GEPR-9s. Furthermore, brain endorphinerg ic pathways appear to be differentially altered in GEPR-3s and GEPR-9s . Alterations in pituitary beta-endorphin secretion and brain endorphi nergic systems may contribute to seizure susceptibility in GEPRs and t o differences in seizure severity between GEPR-3s and GEPR-9s. (C) 199 8 Elsevier Science B.V. All rights reserved.