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The endogenous opioid peptides have been implicated in the control of the suckling-induced PRL rise during lactation. This study examined the role of the endogenous opioid peptides in suppressing tuberoinfundibular dopaminergic neuronal activity during lactation. In the first experiment, lactating rats were constantly exposed to pups. Naloxone (NAL; 60(More)
Central catecholaminergic systems play an important role in the control of reproductive activities including sexual behavior, luteinizing hormone (LH) and prolactin secretion. It has been reported that catecholaminergic neurons in the locus coeruleus (A6) are activated by mating in rabbits and ferrets, animals known as reflex ovulators. This study used Fos(More)
The effects of experimentally produced hypoprolactinemia and hyperprolactinemia on tyrosine hydroxylase (TH) mRNA signal levels were examined in dopaminergic neurons ovariectomized rats. TH mRNA signal levels and relative TH quantity in the arcuate nuclei, zona incerta, and substantia nigra were evaluated by in situ hybridization and immunocytochemistry,(More)
This study examined the responsiveness of dopaminergic neurons to PRL and the expression of PRL receptors in fetal hypothalamic cells. Hypothalamic cells were cultured in medium containing 5 or 25 mM potassium (K+) with or without 5% FBS. Rat PRL (rPRL) treatment (10-1000 ng/ml) for 10 days increased tyrosine hydroxylase (TH) activity 1.6- to 1.8-fold in(More)
Lactation is a state of hyperprolactinemia resulting in part from suppressed tuberoinfundibular dopaminergic (TIDA) neuronal activity. The suckling stimulus contributes to this suppression despite the fact that the TIDA neurons are a potential site for PRL feedback to increase neuronal activity. This study examined the influence of PRL feedback and the(More)
In order to identify the distribution of prolactin-releasing peptide (PrRP) mRNA in the rat brain, we independently cloned cDNA of PrRP. Brains were removed from three adult males, and brains from three females each at 0200 and 1400 h on day 7 of pregnancy were obtained. By the nonradioactive in situ hybridization method, the location of PrRP mRNA was(More)
Endogenous opioids stimulate PRL release in the rat during proestrus, stress, and lactation. This study investigated the potential role of opioids in regulating the daily nocturnal PRL surges that occur during the first half of pregnancy. On day 8 of pregnancy, infusion of naloxone (NAL; 0.25, 1.0, or 2.0 mg/10 min), an opioid receptor antagonist, from(More)
Dopamine (DA) secreted by tuberoinfundibular dopaminergic (TIDA) neurons in the hypothalamus is the major inhibitory factor controlling prolactin (PRL) secretion from the anterior pituitary. Endogenous opioid peptides (EOPs), mainly the neuropeptide beta-endorphin, have a stimulatory influence on PRL secretion. During the first half of pregnancy in rats,(More)
Abstract The purpose of this study was to determine whether prolactin (PRL) could exert a negative feedback on it's own secretion during pregnancy and following ovariectomy, and to determine the possible mechanism by which this feedback acts. Implantation of ovine PRL into the arcuate nucleus-median eminence area of the hypothalamus completely inhibited the(More)