GPR39 and Anxiety: Interestingly, these peptide hormones bind their specific cognate receptors via the conformation of heteroreceptor complexes, as shown for OTR and D2R, 5-HT1A-GalR1, and 5-HT1A-GPR39 heterodimeric complexes, whose biased cell-signaling pathway may promote and favor the behavioral adaptations during the peripartum period, and which include several aspects of maternal care, maternal aggression, improved spatial memory, offspring recognition, including sensitive auditory processing of offspring vocalization, reduced anxiety and fear responses, and an attenuated neuroendocrine stress response.