title: Relationship between endogenous opioids and the oestrous cycle in the rat.
abstract: The aim of this study was twofold: (1) to document changes in levels of immunoreactive beta-endorphin (Ir-beta-EP) in the hypothalamus, anterior pituitary gland, neurointermediate lobe and plasma during the oestrous cycle of the rat and (2) to investigate stress-induced changes in plasma Ir-beta-EP at different stages of the oestrous cycle. Evidence was found that Ir-beta-EP levels in the hypothalamus, anterior pituitary gland and plasma are not constant during the oestrous cycle and that the Ir-beta-EP response to stress is a function of the phase of the oestrous cycle at which stress is applied. It is suggested that fluctuations in ovarian hormones may influence oestrous Ir-beta-EP levels both under normal conditions and after exposure to stress.
mesh_terms: D000818:Animals; D004723:Endorphins / Q000097:blood / Q000378:metabolism*; D004971:Estrus; D005260:Female; D007031:Hypothalamus / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D001615:beta-Endorphin