Sunayana B. Banerjee

Most birds are socially monogamous, yet little is known about the neural pathways underlying avian monogamy. Recent studies have implicated dopamine as playing a role in courtship and affiliation in a socially monogamous songbird, the zebra finch (Taeniopygia guttata). In the present study, we sought to understand the specific contribution to pair formation in zebra finches of the mesolimbic dopaminergic pathway that projects from the midbrain ventral tegmental area to the nucleus accumbens. We observed that paired birds had higher levels of dopamine and its metabolite 3,4‐dihydroxyphenylacetic acid in the ventral medial striatum, where the nucleus accumbens is situated, than unpaired birds. Additionally, we found that the percentage of dopaminergic neurons expressing immediate early gene Fos, a marker of neuronal activity, was higher in the ventral tegmental area of paired birds than in that of unpaired birds. These data are consistent with a role for the mesolimbic dopaminergic pathway in pair formation in zebra finches, suggesting the possibility of a conserved neural mechanism of monogamy in birds and mammals.

Early-life stress caused by the deprivation of maternal care has been shown to have long-lasting effects on the hypothalamic–pituitary–adrenal (HPA) axis in offspring of uniparental mammalian species. We asked if deprivation of maternal care in biparental species alters stress responsiveness of offspring, using a biparental avian species—the zebra finch,Taeniopygia guttata. In our experiment, one group of birds was raised by both male and female parents (control), and another was raised by males alone (maternally deprived). During adulthood, offspring of both groups were subjected to two stressors (restraint and isolation), and corticosterone concentrations were measured. Additionally, we measured baseline levels of the two corticosteroid receptors—glucocorticoid receptor (GR) and mineralocorticoid receptor (MR)—in the hippocampus, hypothalamus and cerebellum. Our results suggest that maternally deprived offspring are hyper-responsive to isolation in comparison with controls. Furthermore, mRNA levels of both GR and MR receptors are altered in maternally deprived offspring in comparison with controls. Thus, absence of maternal care has lasting consequences for HPA function in a biparental species where paternal care is available.