Reproductive roles of the vasopressin/oxytocin neuropeptide family in teleost fishes

Abstract

The vertebrate nonapeptide families arginine vasopressin (AVP) and oxytocin (OXT) are considered to have evolved from a single vasopressin-like peptide present in invertebrates and termed arginine vasotocin in early vertebrate evolution. Unprecedented genome sequence availability has more recently allowed new insight into the evolution of nonapeptides and especially their receptor families in the context of whole genome duplications. In bony fish, nonapeptide homologues of AVP termed arginine vasotocin (Avp) and an OXT family peptide (Oxt) originally termed isotocin have been characterized. While reproductive roles of both nonapeptide families have historically been studied in several vertebrates, their roles in teleost reproduction remain much less understood. Taking advantage of novel genome resources and associated technological advances such as genetic modifications in fish models, we here critically review the current state of knowledge regarding the roles of nonapeptide systems in teleost reproduction. We further discuss sources of plasticity of the conserved nonapeptide systems in the context of diverse reproductive phenotypes observed in teleost fishes. Given the dual roles of preoptic area (POA) synthesized Avp and Oxt as neuromodulators and endocrine/paracrine factors, we focus on known roles of both peptides on reproductive behaviour and the regulation of the hypothalamic-pituitary-gonadal axis. Emphasis is placed on the identification of a gonadal nonapeptide system that plays critical roles in both steroidogenesis and gamete maturation. We conclude by highlighting key research gaps including a call for translational studies linking new mechanistic understanding of nonapeptide regulated physiology in the context of aquaculture, conservation biology and ecotoxicology.

Adult sex change leads to extensive forebrain reorganization in clownfish

“…6). Putatively POA-derived cluster 13d was enriched for all sex steroid receptors ( ar1 , ar2 , esr2a , esr2b , and pgr ), consistent with known steroid hormone sensitivity of the POA in teleosts and other vertebrates species (4, 51, 52). Notably, all radial glial child clusters (including putative ependymal cells) were enriched for esr2b and ar2 , consistent with steroid modulation of neurogenesis (53).…”

Perinatal exposure to the fungicide ketoconazole alters hypothalamic control of puberty in female rats

“…In rats, oxytocin facilitates female pubertal development through a mechanism involving Pge2 release by glial cell and increases the expression of several actors of the GnRH network including kisspeptin ( 85 – 87 ). In fish, studies suggest a modulation of the hypothalamo-pituitary-gonadal axis by oxytocin ( 88 ). In women, oxytocin is involved in the physiological regulation of LH through the ovulatory cycle ( 89 ).…”

Male-specific vasotocin expression in the medaka tuberal hypothalamus: androgen dependence and probable role in aggression

“…Nonapeptides, namely, vasotocin (VT, also called vasopressin in mammals) and oxytocin (OT), are evolutionarily conserved neuropeptides that have been associated with a wide range of social behaviors, including aggression (Theofanopoulou et al ., 2021; Mennigen et al ., 2022). The largest population of neurons expressing VT and that expressing OT both lie in the paraventricular nucleus (PVN), where they project throughout the brain, as well as to the pituitary, to modulate behavior (Rigney et al ., 2022).…”