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Endogenous opioid peptides contribute to suckling-induced prolactin release by suppressing tyrosine hydroxylase activity and messenger ribonucleic acid levels in tuberoinfundibular dopaminergic neurons.
Endocrinology. 1998 Jun; 139(6):2857-62.E

Abstract

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 mg/kg x h; i.v.), an opioid receptor antagonist, or saline was infused for 12 h. Blood was collected before and at 2-h intervals during the infusion. NAL suppressed circulating PRL levels to less than 36% of control values at 4, 6, 8, and 12 h after the onset of the infusion. Tyrosine hydroxylase (TH) activity in the stalk-median eminence and TH messenger RNA signal levels in the arcuate nucleus were determined at the end of the NAL infusion. TH activity and TH messenger RNA signal levels were increased 2.5- and 2.7-fold, respectively, after the 12-h NAL infusion. Even though the time spent with their pups was similar between the two groups, the pups in the NAL-treated group failed to gain weight during the 12-h NAL infusion period, whereas the control litters (8 pups) gained 5 g. In a second experiment, pups were removed from the dams before the 12-h NAL infusion and were returned after 11 h. Blood was collected before the infusion, at 3-h intervals during the pup separation period, and at 15-min intervals after reunion with the pups. Plasma PRL in control and NAL-treated rats was low (1-15 ng/ml) and similar during the separation period. The suckling-induced PRL surge in NAL-treated rats was markedly attenuated to 9-25% of control levels (350-650 ng/ml). After a 1-h suckling episode, TH activity in the stalk-median eminence of NAL-treated rats was 4.5-fold greater than controls. Litter weight gains were significantly less in NAL-treated rats during the 1-h suckling episode. These data indicate that the endogenous opioid peptides are an integral component for increasing PRL release in response to suckling and they act to decrease tuberoinfundibular dopaminergic neuronal activity during lactation, in part, by suppressing TH gene expression.

Authors+Show Affiliations

Department of Physiology, University of Kansas Medical Center, Kansas City 66160-7401, USA. larbogast@som.siu.eduNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9607794

Citation

Arbogast, L A., and J L. Voogt. "Endogenous Opioid Peptides Contribute to Suckling-induced Prolactin Release By Suppressing Tyrosine Hydroxylase Activity and Messenger Ribonucleic Acid Levels in Tuberoinfundibular Dopaminergic Neurons." Endocrinology, vol. 139, no. 6, 1998, pp. 2857-62.
Arbogast LA, Voogt JL. Endogenous opioid peptides contribute to suckling-induced prolactin release by suppressing tyrosine hydroxylase activity and messenger ribonucleic acid levels in tuberoinfundibular dopaminergic neurons. Endocrinology. 1998;139(6):2857-62.
Arbogast, L. A., & Voogt, J. L. (1998). Endogenous opioid peptides contribute to suckling-induced prolactin release by suppressing tyrosine hydroxylase activity and messenger ribonucleic acid levels in tuberoinfundibular dopaminergic neurons. Endocrinology, 139(6), 2857-62.
Arbogast LA, Voogt JL. Endogenous Opioid Peptides Contribute to Suckling-induced Prolactin Release By Suppressing Tyrosine Hydroxylase Activity and Messenger Ribonucleic Acid Levels in Tuberoinfundibular Dopaminergic Neurons. Endocrinology. 1998;139(6):2857-62. PubMed PMID: 9607794.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Endogenous opioid peptides contribute to suckling-induced prolactin release by suppressing tyrosine hydroxylase activity and messenger ribonucleic acid levels in tuberoinfundibular dopaminergic neurons. AU - Arbogast,L A, AU - Voogt,J L, PY - 1998/6/2/pubmed PY - 1998/6/2/medline PY - 1998/6/2/entrez SP - 2857 EP - 62 JF - Endocrinology JO - Endocrinology VL - 139 IS - 6 N2 - 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 mg/kg x h; i.v.), an opioid receptor antagonist, or saline was infused for 12 h. Blood was collected before and at 2-h intervals during the infusion. NAL suppressed circulating PRL levels to less than 36% of control values at 4, 6, 8, and 12 h after the onset of the infusion. Tyrosine hydroxylase (TH) activity in the stalk-median eminence and TH messenger RNA signal levels in the arcuate nucleus were determined at the end of the NAL infusion. TH activity and TH messenger RNA signal levels were increased 2.5- and 2.7-fold, respectively, after the 12-h NAL infusion. Even though the time spent with their pups was similar between the two groups, the pups in the NAL-treated group failed to gain weight during the 12-h NAL infusion period, whereas the control litters (8 pups) gained 5 g. In a second experiment, pups were removed from the dams before the 12-h NAL infusion and were returned after 11 h. Blood was collected before the infusion, at 3-h intervals during the pup separation period, and at 15-min intervals after reunion with the pups. Plasma PRL in control and NAL-treated rats was low (1-15 ng/ml) and similar during the separation period. The suckling-induced PRL surge in NAL-treated rats was markedly attenuated to 9-25% of control levels (350-650 ng/ml). After a 1-h suckling episode, TH activity in the stalk-median eminence of NAL-treated rats was 4.5-fold greater than controls. Litter weight gains were significantly less in NAL-treated rats during the 1-h suckling episode. These data indicate that the endogenous opioid peptides are an integral component for increasing PRL release in response to suckling and they act to decrease tuberoinfundibular dopaminergic neuronal activity during lactation, in part, by suppressing TH gene expression. SN - 0013-7227 UR - https://www.unboundmedicine.com/medline/citation/9607794/Endogenous_opioid_peptides_contribute_to_suckling_induced_prolactin_release_by_suppressing_tyrosine_hydroxylase_activity_and_messenger_ribonucleic_acid_levels_in_tuberoinfundibular_dopaminergic_neurons_ L2 - https://academic.oup.com/endo/article-lookup/doi/10.1210/endo.139.6.6052 DB - PRIME DP - Unbound Medicine ER -