Mild hyperthyroidism regulates the response to acute stress in established lactation of the rat.

NEIRA, F.; SANCHEZ, MB.; MICHEL, C.; TRONCOSO M.; MARTINELLI, G; PIETROBON, E.; SOAJE, M.; MACKERN, JP; JAHN, GA.; VALDEZ, SR.

San Juan

Congreso; XLI Reunión Científica Anual de la Sociedad de Biología de Cuyo.; 2023

Sociedad de Biología de Cuyo

Hyperthyroidism (HyperT) affects women reproductive health and can impair the establishment of lactation. This reproductive event is regulated at the CNS by neuroendocrine mechanisms present in brain areas such as the Medial Basal Hypothalamus (MBH). In this region, there is a group of dopaminergic neurons responsible for regulating the secretion of prolactin (PRL). In previous studies, we determined that HyperT affects the regulation of PRL secretion and circulating levels of glucocorticoids (Gs) during the transition between gestation and lactation. PRL has anxiolytic functions and its receptor is expressed in the hippocampus (HpC), an area of great interest in the regulation of the stress response. We evaluated the effect of mild HyperT on the response to acute stress by restrain in different reproductive states, focalizing in established lactation of the female rat. HyperT was induced with T4 (0,1 mg/kg/day, s.c.) a dose that allows the maintenance of lactation. Control (Co) and HyperT female Wistar rats were bled from the tail vein during the first 5-10 m and 60 m of restraint stress, M1 and M2 respectively. We analyzed serum PRL and corticosterone (CORT) levels on virgin rats in estrus, day 19 of gestation (G19), day 2 (L2) and 12 (L12) of lactation, in response to acute stress. To explore the neuroendocrine mechanisms of PRL release during lactation, we also determined the expression of thyroid receptor (TR), the long isoform of the prolactin receptor (PRLLR), members of the PRL signaling pathway (STAT5b, CIS and SOCS) and glucocorticoid receptor (GR) in HMB and HpC in virgin rats, G19, L2 y L12 in Co and HyperT groups. Virgin, G19, L2 and L12 Co and HyperT rats increased serum CORT release induced by restraint stress. Serum PRL levels increased in response to stress virgin Co and HyperT groups, while in G19, L2 and L12, PRL levels were not modified by stress (p