SUCKLING MODULATES PITUITARY RECEPTORS EXPRESSION IN RATS WITH DEFICIENT LACTATION (OFA hr/hr)

PENNACCHIO GISELA E; ORTÍZ MARÍA SOL; AYALA CAROLINA; JAHN GRACIELA A; VALDEZ, SUSANA R; SOAJE MARTA

San Luis

Congreso; Sociedad de Biología de Cuyo; 2014

Sociedad de Biología de Cuyo

<!-- /* 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-fareast-font-family:"Times New Roman";mso-bidi-font-family:"Times New Roman";}@page Section1{size:612.0pt 792.0pt;margin:70.85pt 3.0cm 70.85pt 3.0cm;mso-header-margin:36.0pt;mso-footer-margin:36.0pt;mso-paper-source:0;}div.Section1{page:Section1;}-->During normal lactation, sustainedhyperprolactinemia is due to suckling stimulus anddecreased sensitivity to prolactin (PRL) negative feedback. OFA (hr/hr) rats derived from the SpragueDawley (SD) strain. They have deficient lactation, a high hypothalamicdopaminergic tone and a blockade of milk ejection. In previous studies, we have demonstrated that OFA rats havean increased sensitivity to PRL negative feedback acting at hypothalamic level,also responsible to the decreased PRL release of these rats. However,this evidence not rejects the hypothesis that pituitary mechanisms may be alsoinvolved. Our aim was to investigate the changes in pituitary receptorsexpression involved in the synthesis and secretion of PRL in response tosuckling stimulus in OFA rats compared to SD rats (normal lactation). Usingreal time quantitative reverse transcriptase-polymerase chain reaction(RT-PCR), we measured the changes in mRNA expression of dopamine receptor (D2 R), estrogen receptor (ERα) and long PRLreceptor (PRLR) in anterior pituitary of mid-lactating OFA and SD rats separatedfrom their pups for 12 h and rats and subsequently subject to suckling during 4h. Serum PRL and estradiol levels were measured by RIA and weight gain of the litterswere determined. After suckling, PRL release was higher in SD than OFA rats incorrelation with a higher weight gain obtained. Removal the litters induced anincrease in ERα expression only in OFA rats. After suckling, a decreased of D2Rwas detected in OFA rats compared with SD rats. No change in PRLR was observedin both strains of rats in response to 4 h of suckling. The results show thatsuckling stimulus modifies differentially D2R and ERα expression inboth strains. Since no changes on PRLR expression were observed, the decreaseof D2R in OFA rats could reflect a compensatory effect rather a primarychange of pituitary receptors supporting the hypothesis that PRL negative feedback acting athypothalamic level is activated in these rats during lactation.