Cortisol stimulates arginine vasotocin and isotocin release from the hypothalamo‐pituitary complex of round goby (Neogobius melanostomus): Probable mechanisms of action

Abstract

There were two aims of this in vitro perfusion study. Firstly, to determine which class of receptors, glucocorticoid (GRs) or mineralocorticoid (MRs), are involved in cortisol regulation of arginine vasotocin (AVT) and isotocin (IT) release from the hypothalamo-pituitary (H-P) complex of round goby (Neogobius melanostomus). Secondly, to determine which pathways, genomic or non-genomic, are involved in the aformentioned process.The H-P explants were perfused with cortisol (1.4 × 10(-) (7) M, 2.8 × 10(-7) M, 0.4 × 10(-6) M); only the highest dose significantly increased a release of both nonapeptides. In the perfusion of H-P explants, we used cortisol (0.4 × 10(-6) M) in combination with GRs antagonist RU486 (0.3 × 10(-6) M) or MRs antagonist C03DA01 (0.36 × 10(-6) M) or transcription inhibitor Actinomycin D (1 × 10(-7) M). All inhibitors were also tested seperately. The contents of AVT and IT in the perfusion media was determined by high-performance liquid chromatography (HPLC) with UV detection. This study suggested that different mechanisms were involved in the regulation of AVT and IT release from H-P complex in round goby. Apparently it was GRs but not MRs that were involved in cortisol regulation of AVT and IT release. In the case of AVT, our data points to both genomic and non-genomic pathways mediating the effect of cortisol; in the case of IT, it is only the non-genomic pathway. This study presents the first feasible mechanisms of cortisol action on AVT and IT release from the H-P complex in round goby.

How does oestradiol influence the AVT/IT system in female round gobies during different reproductive phases?

“…Fish were fed frozen mussels ad libitum . Studies were performed on round goby due to their availability and proper size for in vitro studies and plasma sample collections and our experience with this species ( Kalamarz-Kubiak et al, 2011 , 2015 ; Sokołowska et al, 2015 ). Before conducting experiments, 20 randomly selected fish were anaesthetized in MS 222 (tricaine methanesulfonate) water solution (50 mg l –1 ) (A5040; Sigma-Aldrich) and blood samples were collected by cardiac puncture.…”

“…In our experiments, two brain explants were perfused simultaneously in a single gradient perfusion container. Brain explants were perfused with Ringer buffer (pH 7.4) prepared according to the composition previously described by Kalamarz-Kubiak et al (2015) . Explants were put on the 20 µm Nylon Net Filter (NY2002500; Merck Millipore, Darmstadt, Germany) placed between the base and tension rings of the tissue carrier (MINUSHEET; diameter of 13 mm) in a gradient culture container.…”

“…The 17β-oestradiol doses were established based on their concentrations measured in plasma samples collected during the spawning-capable phase (10±1.2 ng ml –1 ) and the regressing phase (5±1.6 ng ml –1 ). The dose of inhibitors was selected based on available data for Fulvestrant ( Bouma et al, 2003 ; Pang and Thomas, 2009 ; Notch and Mayer, 2011 ) or our previous experiments for Actinomycin D ( Kalamarz-Kubiak et al, 2015 ). Moreover, before experiments, different doses of inhibitors (1×10 –6 M; 1×10 –7 M) were tested (data not shown).…”

Introducing the Amphibious Mudskipper Goby as a Unique Model to Evaluate Neuro/Endocrine Regulation of Behaviors Mediated by Buccal Sensation and Corticosteroids

“…The simple aquatic preference of mudskippers may also reflect these behaviors. Furthermore, most GR/MR-expressing PM and PP nuclei produce vasotocin and its paralogue, isotocin [82], and the cortisol-GR system regulates the expressions of vasotocin and isotocin [98]. These neuropeptides also promote migration to water in mudskippers, similarly to angiotensin II [26].…”

The Amphibious Mudskipper: A Unique Model Bridging the Gap of Central Actions of Osmoregulatory Hormones Between Terrestrial and Aquatic Vertebrates

“…Such a system that is responsive to external stressors can also mediate the start of migration from river to ocean in salmon ( Clements and Schreck, 2004 ; Flores et al, 2012 ). The expression of GRs and MRs mRNA were observed in most of the PM and PP, known to produce VT and IT ( Teitsma et al, 1998 ), and the cortisol-GR system regulated VT and IT release from the hypothalamus-pituitary complex ( Kalamarz-Kubiak et al, 2015 ). Thus, future studies should focus on the “cross-talk” among these hormones in the brain to clarify the link between osmoregulation and stress response, both of which are primarily regulated by the neurohypophysial hormones and corticosteroids.…”