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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)
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 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)
Prolactin (PRL) and other lactogenic hormones feed back at the hypothalamus to inhibit PRL release. At midpregnancy, high circulating levels of placental lactogens (PL) terminate the mating-induced biphasic PRL surges in female rats. In the dark period preceding parturition, however, an ante-partum PRL surge occurs despite continuously high levels of PL.(More)
The Nb2 node lymphoma cell bioassay was verified in our laboratory as a sensitive, reproducible, and accurate bioassay for measurement of serum rat placental lactogen (rPL). Blood samples taken every 6 hr during pregnancy showed a significant peak of rPL secretion in the late afternoon on Day 11. The inverse relationship between rPL and nocturnal prolactin(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)
PRL in the rat exerts its luteotropic action during the first half of pregnancy. After midpregnancy, placental lactogens (PLs) take the place of PRL to stimulate progesterone secretion from the corpus luteum. Simultaneously, PLs trigger a negative feedback on PRL secretion. However, the brain mechanisms for the negative feedback induced by PLs are not fully(More)