The parathyroid hormone 2 receptor participates in physiological and behavioral alterations of mother mice

Abstract

Parathyroid hormone 2 receptor (PTH2R) and its ligand, tuberoinfundibular peptide of 39 residues (TIP39) have been implicated in the maintenance of homeostasis including body temperature in males. The system was recently shown to be activated in mothers. Therefore, we addressed some of its functions during pregnancy and lactation, comparing PTH2R-knockout (PTH2R-KO) mice with their wild type (WT) littermates. Core body temperature (Tc) was recorded via a telemetric device, anxiety was assessed in an open field, depression-like behavior in the forced-swim test while spontaneous and pup retrieval-induced maternal behavior was also observed. Nulliparous virgin KO and WT mice showed a circadian pattern of Tc and locomotion with no differences between groups. WT mothers had an increased Tc during pregnancy and lactation as compared to virgins. This peripartum elevation of Tc was present but reduced in KO mice, even though their locomotor activity was increased. The greater locomotor activity of the KO mice was confirmed in the open field test but no other behavior differences were detected in the test. The maternal behavior was similar in the 2 genotypes except that the KO mice spent more time in the nest. In turn, a marked difference was found in the forced-swim test as the KO mice spent significantly less time struggling and more time floating compared to the WT littermates. The data suggest that the PTH2R contributes to the elevated Tc and reduced depression-like behavior of mother mice. These findings are consistent with specific maternal functions of the activated TIP39-PTH2R neuromodulator system in mothers.