THE BLOCKADE OF OPIOID SYSTEM INCREASES OXYTOCIN SECRETION IN SUCKLING RATS WITH DEFICIENT LACTATION

PENNACCHIO GISELA E; NEIRA FLAVIA J; PIETROBON ELISA O; MORENO-SOSA MARÍA TAMARA; MACKERN OBERTI, JUAN PABLO; JAHN GRACIELA A; VALDEZ SUSANA R; SOAJE MARTA

Mendoza

Congreso; XXXIV Reunión Anual de la Sociedad de Biología de Cuyo; 2016

Sociedad de Biología de Cuyo

<!-- /* Font Definitions */@font-face{font-family:Cambria;panose-1:2 4 5 3 5 4 6 3 2 4;mso-font-charset:0;mso-generic-font-family:auto;mso-font-pitch:variable;mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-parent:"";margin:0cm;margin-bottom:.0001pt;mso-pagination:widow-orphan;font-size:12.0pt;font-family:"Times New Roman";mso-ascii-font-family:Cambria;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Cambria;mso-fareast-theme-font:minor-latin;mso-hansi-font-family:Cambria;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;mso-fareast-language:EN-US;}@page Section1{size:595.0pt 842.0pt;margin:70.85pt 3.0cm 70.85pt 3.0cm;mso-header-margin:35.4pt;mso-footer-margin:35.4pt;mso-paper-source:0;}div.Section1{page:Section1;}-->Oxytocin (OT) and prolactin (PRL)are essential hormones for a successful lactation and OT acting at pituitarylevel was proposed as a putative prolactin-releasing factor (PRF). An opioidrestraint of OT secretion is developed during late gestation but declines inthe postpartum. Our aim was to evaluate if blockade of opioid action mayinfluence OT regulation in response to suckling in hypoprolactinemic OFA hr/hrrats characterized by a failure in lactation compared with Sprague-Dawley rats(SD) their strain of origin. Mid-lactating OFA and SD rats separated from theirpups for 12 h and subsequently subject to suckling during 2 and 4 h weretreated with the opioid antagonista naltrexone (NTX; 5 mg/kg, ip; 8.00 h) orsaline and decapitated at 12.00 h. Serum OT levels were measured by RIA, weightgain of the litters was determined and the expression of OT receptor (OTR) inthe anterior pituitary was measured by western blot. After suckling OT releaseand litter weight gain were higher in SD rats compared with OFA rats. NTXtreatment increased OT secretion only in OFA rats and after 2 h of suckling anincrease in weight gain was observed. After suckling during 4 h an increase ofOTR expression was observed in OFA rats. The results obtained show that theopioid restrain of OT secretion is still operating during lactation in OFA ratssuggesting another mechanism involved in thefailure of the lactation observed in these rats. The higher OTR expression in anteriorpituitary in suckling rat supports the proposal that OT may act as a PRF.