The neural distribution of the avian homologue of oxytocin, mesotocin, in two songbird species, the zebra finch and the canary: A potential role in song perception and production

Abstract

The avian homologue of oxytocin (OT), formerly called mesotocin, influences social behaviors in songbirds and potentially song production. We sought to characterize the distribution of OT peptide in the brain of two songbird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). To visualize OT, we performed immunocytochemistry using an antibody previously shown to identify OT in avian species. In both canaries and zebra finches, dense OT‐ir perikarya were located in the paraventricular nucleus (PVN), preoptic area (POA), supraoptic nucleus (SON), and medial bed nucleus of the stria terminalis (BNSTm). We also observed morphologically distinct OT‐ir cells scattered throughout the mesopallium. OT‐ir fibers were observed in the PVN, ventral medial hypothalamus (VMH), periaqueductal gray (PAG), intercollicular nucleus (ICo), and ventral tegmental area (VTA). We also observed punctate OT‐ir fibers in the song control nucleus HVC. In both male and female canaries, OT‐ir fibers were present in the lateral septum (LS), but innervation was greater in males. We did not observe this sex difference in zebra finches. Much of the OT staining observed is consistent with general distributions within the vertebrate hypothalamus, indicating a possible conserved function. However, some extra‐hypothalamic distributions, such as perikarya in the mesopallium, may be specific to songbirds and play a role in song perception and production. The presence of OT‐ir fibers in HVC and song control nuclei projecting dopaminergic regions provides anatomical evidence in support of the idea that OT can influence singing behavior—either directly via HVC or indirectly via the PAG, VTA, or POA.

Exploring neuronal markers and early social environment influence in divergent quail lines selected for social motivation

“…No difference in MT-ir was found in the BNST and LS. Although sex differences in oxytocin expression have rarely been described in mammals and birds 51,52 , we observed, for the rst time in quail, a higher density of MT-ir bers in MPN, BNST, and LS in males compared to females, while no sex difference was found in the number of neurons in the PVN (Fig. 2 and Supplementary Table S2).…”

“…Antifreeze was prepared using 40% v/v PBS 0.01M, 1% polyvinylpyrrolidone (Sigma-Aldrich, P5288), 30% saccharose (VWR Chemicals BDH, 27478.296), 30% v/v ethylene glycol (VWR Chemicals BDH, 24041.297), which was adjusted with PBS to achieve the nal volume. Brain sections were immunostained for each neuronal marker using validated antibodies against MT, VT and ARO according to previous studies 37,51,55 . Sections were rst rinsed three times in 0.01 M tris-buffered saline (TBS, pH 7.6) for 5 minutes each (same duration applied for all following rinses).…”

Oxytocin receptor antagonism during early vocal learning reduces song preference and imitation in zebra finches

“…In birds, OTR is thought to serve as a common receptor for both nonapeptides 52 , which are predicted to bind equally well to this receptor 22 . Brain regions associated with sociality, such as the lateral septum and bed nucleus of the stria terminalis, contain dense immunoreactivity for both nonapeptides; regions associated with auditory processing and song learning, however, likely receive denser oxytocinergic than vasopressinergic input 21 , 54 .…”

“…Thus, the role of oxytocin in attraction to social cues may be conserved across species and developmental stages. Accordingly, we and others have hypothesized that, in songbirds, oxytocin receptors (OTR) mediate attraction and attention to tutor song, thus facilitating song learning 1 , 8 , 18 – 21 .…”

The Theory of Co-opting Mother-infant Bonding Informs a New Approach to the Science of Romantic Love (Published in Frontiers in Psychology: https://www.frontiersin.org/articles/10.3389/fpsyg.2023.1176067/full)

“…I would assert that the mallard duck was not experiencing romantic love -a potentially uniquely human experience (or at least confined to some primate species that pair bond and have a neurobiology proximate to humans, (see Grebe et al, 2021 for indications non-human primates possess social monogamy mechanisms that differ substantially from rodents). Rather, she was experiencing an acute courtship attraction episode (i.e., mate choice in female ducks) that subsequently led to pair bonding and the activation of an avian attachment system largely resulting from activity of an oxytocin variant, usually referred to as mesotocin (see Haakenson, Balthazart, Madison, & Ball, 2022).…”