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

PENNACCHIO GE; ORTIZ MS; AYALA C; JAHN GA; VALDEZ SR; SOAJE M

Estancia Grande

Congreso; XXXII REUNIÓN CIENTÍFICA ANUAL DE LA SOCIEDAD DE BIOLOGÍA DE CUYO; 2014

SOCIEDAD DE BIOLOGÍA DE CUYO

During normal lactation, sustained hyperprolactinemia is due to suckling stimulus and decreased sensitivity to prolactin (PRL) negative feedback. OFA (hr/hr) rats are derived of Sprague Dawley (SD) strain. They have deficient lactation, a high hypothalamic dopaminergic tone and a blockade of milk ejection. In previous studies, we have demonstrated that OFA rats have an 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 also involved. Our aim was to investigate the changes in pituitary receptors expression involved in the synthesis and secretion of PRL in response to suckling stimulus in OFA rats compared to SD rats (normal lactation). Using real time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), we measured the changes in mRNA expression of dopamine receptor (D2 R), estrogen receptor (EαR) and long PRL receptor (PRLR) in anterior pituitary of OFA and SD rats separated from their pups for 12 h (S/ss) and rats subject to suckling during 4 h. Serum PRL and estradiol levels were measured by RIA and weight gain of the litters were obtained. After suckling, PRL release was higher in SD than OFA rats in correlation with a higher weight gain obtained. Removal the litters induced an increase in EαR expression only in OFA rats. After suckling, a decreased of D2R was obtained in OFA rats compared with SD rats. No change in PRLR was observed in both strains of rats in response to 4 h of suckling. The results show that suckling stimulus modifies differentially D2R and EαR expression in both strains. Like no changes on PRLR expression were observed, the decrease of D2R in OFA rats could reflect a compensatory effect rather a primary change of pituitary receptors supporting the hypothesis that PRL negative feedback acting at hypothalamic level is activated in these rats during lactation.