title: The effects of intraventricular injection of beta-endorphin on initial estrogen action to induce lordosis behavior.
abstract: Ovariectomized female rats subcutaneously (SC) injected or intracerebrally implanted with estradiol benzoate (EB), and given progesterone SC were used as experimental animals to assess the effects of the beta-endorphin (beta-EP) neuronal system on lordosis behavior. In intraventricular (IV) injection of beta-EP at the onset of sc EB priming, the lordosis behavior was significantly (p < 0.001) facilitated. In contrast, the lordosis behavior was significantly (p < 0.001) inhibited by IV injection of naloxone, an opioid receptor antagonist. beta-EP facilitation of lordosis was observed exclusively within the initial stage of estrogen action. The behavior was significantly (p < 0.001) facilitated by IV injection of beta-EP given with an intracerebral implantation of crystalline EB into the septal-preoptic regions. However, the lordosis behavior was significantly (p < 0.001) inhibited by beta-EP when EB was implanted into the ventromedial hypothalamus. Animals receiving EB implants into the mesencephalic reticular formation were not affected by beta-EP. The present study suggests that the beta-EP neuronal system stimulates sexual receptivity through an action on the central nervous system in relation to the site of estrogen-initial activation to induce the lordosis reflex. The sites of beta-EP action may be the estrogen receptive septal-preoptic and hypothalamic regions; the former for facilitatory effect and the latter for inhibitory effect.
authors.affiliation: Physical Fitness Laboratory, Faculty of Engineering, Kyushu Institute of Technology, Fukuoka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Torii
authors.forename: K
authors.initials: K
authors.lastname: Kubo
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004967:Estrogens / Q000502:physiology*; D005260:Female; D009433:Neural Inhibition / Q000502:physiology; D009474:Neurons / Q000502:physiology; D011301:Preoptic Area / Q000502:physiology; D011374:Progesterone / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000502:physiology; D012686:Septal Nuclei / Q000502:physiology; D012726:Sexual Behavior, Animal / Q000502:physiology*; D014697:Ventromedial Hypothalamic Nucleus / Q000502:physiology; D001615:beta-Endorphin / Q000502:physiology*
chemical_list: D004967:Estrogens; D011957:Receptors, Opioid; D011374:Progesterone; D001615:beta-Endorphin