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An endogenous cholinergic rhythm may be involved in the circadian changes of tuberoinfundibular dopaminergic neuron activity in ovariectomized rats treated with or without estrogen. 1995

K R Shieh, and J T Pan
Department of Physiology, School of Medicine, National Yang-Ming University, Shihpai, Taipei, Taiwan, Republic of China.

We recently reported that a circadian change in the activities of hypothalamic tuberoinfundibular dopaminergic (TIDA) neurons exists in ovariectomized (OVX) rats treated with or without estrogen. The involvement of an endogenous cholinergic control mechanism was the focus of this study. Adult female Sprague-Dawley rats OVX for 2 weeks and treated with or without a long-acting estrogen (poly-estradiol phosphate, 0.1 mg/rat, sc) were used in the study. An intracerebroventricular cannula for drug injection was implanted into the lateral cerebroventricle of each rat 6 days before experiment. TIDA neuron activity was determined by measuring the concentrations of 3,4-dihydroxyphenylacetic acid and 3,4-dihydroxyphenylalanine in the median eminence by HPLC plus electrochemical detection. Serum PRL levels were determined by RIA. Neither atropine nor mecamylamine, two cholinergic receptor antagonists, had any effect on TIDA neuron activity in the morning before 1200 h, when endogenous TIDA neuron activity is high. Both drugs, however, exhibited a dose-related stimulating effect on the TIDA neuron activity in the afternoon, when endogenous activity is low. The estrogen-induced afternoon PRL surge was also blocked by a single injection of atropine or mecamylamine at 1300 h. The rhythmic changes in endogenous TIDA neuron activity and their responses to atropine were also observed in OVX rats with no estrogen replacement. In conclusion, a daily change in endogenous cholinergic neuron activity may be responsible for the change in TIDA neuron activity in female rats, which is a prerequisite for the PRL surge.

UI MeSH Term Description Entries
D007031 Hypothalamus Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE. Lamina Terminalis,Preoptico-Hypothalamic Area,Area, Preoptico-Hypothalamic,Areas, Preoptico-Hypothalamic,Preoptico Hypothalamic Area,Preoptico-Hypothalamic Areas
D008464 Mecamylamine A nicotinic antagonist that is well absorbed from the gastrointestinal tract and crosses the blood-brain barrier. Mecamylamine has been used as a ganglionic blocker in treating hypertension, but, like most ganglionic blockers, is more often used now as a research tool.
D010052 Ovariectomy The surgical removal of one or both ovaries. Castration, Female,Oophorectomy,Bilateral Ovariectomy,Bilateral Ovariectomies,Castrations, Female,Female Castration,Female Castrations,Oophorectomies,Ovariectomies,Ovariectomies, Bilateral,Ovariectomy, Bilateral
D010053 Ovary The reproductive organ (GONADS) in female animals. In vertebrates, the ovary contains two functional parts: the OVARIAN FOLLICLE for the production of female germ cells (OOGENESIS); and the endocrine cells (GRANULOSA CELLS; THECA CELLS; and LUTEAL CELLS) for the production of ESTROGENS and PROGESTERONE. Ovaries
D011388 Prolactin A lactogenic hormone secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). It is a polypeptide of approximately 23 kD. Besides its major action on lactation, in some species prolactin exerts effects on reproduction, maternal behavior, fat metabolism, immunomodulation and osmoregulation. Prolactin receptors are present in the mammary gland, hypothalamus, liver, ovary, testis, and prostate. Lactogenic Hormone, Pituitary,Mammotropic Hormone, Pituitary,Mammotropin,PRL (Prolactin),Hormone, Pituitary Lactogenic,Hormone, Pituitary Mammotropic,Pituitary Lactogenic Hormone,Pituitary Mammotropic Hormone
D002799 Cholinergic Fibers Nerve fibers liberating acetylcholine at the synapse after an impulse. Cholinergic Fiber,Fiber, Cholinergic,Fibers, Cholinergic
D002940 Circadian Rhythm The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs or environmental and physiological stimuli. Diurnal Rhythm,Nyctohemeral Rhythm,Twenty-Four Hour Rhythm,Nycthemeral Rhythm,Circadian Rhythms,Diurnal Rhythms,Nycthemeral Rhythms,Nyctohemeral Rhythms,Rhythm, Circadian,Rhythm, Diurnal,Rhythm, Nycthemeral,Rhythm, Nyctohemeral,Rhythm, Twenty-Four Hour,Rhythms, Circadian,Rhythms, Diurnal,Rhythms, Nycthemeral,Rhythms, Nyctohemeral,Rhythms, Twenty-Four Hour,Twenty Four Hour Rhythm,Twenty-Four Hour Rhythms
D004298 Dopamine One of the catecholamine NEUROTRANSMITTERS in the brain. It is derived from TYROSINE and is the precursor to NOREPINEPHRINE and EPINEPHRINE. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (RECEPTORS, DOPAMINE) mediate its action. Hydroxytyramine,3,4-Dihydroxyphenethylamine,4-(2-Aminoethyl)-1,2-benzenediol,Dopamine Hydrochloride,Intropin,3,4 Dihydroxyphenethylamine,Hydrochloride, Dopamine
D004958 Estradiol The 17-beta-isomer of estradiol, an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position. Estradiol-17-beta is the most potent form of mammalian estrogenic steroids. 17 beta-Estradiol,Estradiol-17 beta,Oestradiol,17 beta-Oestradiol,Aerodiol,Delestrogen,Estrace,Estraderm TTS,Estradiol Anhydrous,Estradiol Hemihydrate,Estradiol Hemihydrate, (17 alpha)-Isomer,Estradiol Monohydrate,Estradiol Valerate,Estradiol Valeriante,Estradiol, (+-)-Isomer,Estradiol, (-)-Isomer,Estradiol, (16 alpha,17 alpha)-Isomer,Estradiol, (16 alpha,17 beta)-Isomer,Estradiol, (17-alpha)-Isomer,Estradiol, (8 alpha,17 beta)-(+-)-Isomer,Estradiol, (8 alpha,17 beta)-Isomer,Estradiol, (9 beta,17 alpha)-Isomer,Estradiol, (9 beta,17 beta)-Isomer,Estradiol, Monosodium Salt,Estradiol, Sodium Salt,Estradiol-17 alpha,Estradiol-17beta,Ovocyclin,Progynon-Depot,Progynova,Vivelle,17 beta Estradiol,17 beta Oestradiol,Estradiol 17 alpha,Estradiol 17 beta,Estradiol 17beta,Progynon Depot
D005260 Female Females

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