Arginine Vasotocin and Cortisol Co-regulate Vasotocinergic, Isotocinergic, Stress, and Thyroid Pathways in the Gilthead Sea Bream ( Sparus aurata )

• Published in: Frontiers in physiology Vol. 10; p. 261
• Main Authors: Martos-Sitcha, Juan Antonio, Cádiz, Laura, Gozdowska, Magdalena, Kulczykowska, Ewa, Martínez-Rodríguez, Gonzalo, Mancera, Juan Miguel
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 21-03-2019
• Subjects: arginine vasotocin; cortisol; Crh; isotocin; Physiology; receptors; Sparus aurata; isotocin; cortisol; stress; Sparus aurata; receptors; arginine vasotocin; Crh; thyroid system
• ISSN: 1664-042X; 1664-042X
• DOI: 10.3389/fphys.2019.00261

In teleosts, a complex interaction between several endocrine axes modulates physiological functions related to metabolism, stress, and osmoregulation. Although many studies in fish underline the interconnection between the hypothalamic-pituitary-interrenal (HPI) and hypothalamic-pituitary-thyroid (HPT) endocrine axes, their relationship with the vasotocinergic and isotocinergic systems remains unknown. The aim of the present study is therefore to shed light on the potential cross-regulations between HPT, HPI, and the vasotocinergic and isotocinergic axes in gilthead sea bream (
) at hypothalamic, hypophyseal, and plasma levels. Sea breams were administered with intraperitoneal slow-release implants containing different doses of vasotocin (the active peptide in vasotocinergic system) or cortisol (the last component of HPI axis). Plasma osmolality was higher in active neuropeptides vasotocin (Avt)-treated fish, indicating an osmoregulatory function of this hormone. Low concentrations of Avt increased hypothalamic
(
) mRNA levels and increased Avt storage in the pituitary. Avt treatment down-regulated hypothalamic
(
), suggesting a negative paracrine co-regulation of the HPI axis due to the close location of
and adrenocorticotropin hormone (Acth) cells in the anterior pituitary. Furthermore, the up-regulation observed in
(
) suggests their involvement in metabolic and cortisol-related pathways in the hypothalamus. The decrease in isotocin (It) pituitary storage and the up-regulation of
receptor, observed in the Avt-treated group, reinforce the idea of an interconnection between the vasotocinergic and isotocinergic systems. Cortisol and Avt administration each inhibited the HPI axis, down-regulating
gene expression in the absence of variations in
(
). Finally, both hormonal treatments activated the HPT axis via up-regulation of
and down-regulation of
. Our results provide evidence for strong interactions among the Avt/It, HPI, and HPT axes of marine teleosts, particularly at the hypothalamic level.