Elevated cortisol inhibits adrenocorticotropic hormone- and serotonin-stimulated cortisol secretion from the interrenal cells of the Gulf toadfish (Opsanus beta)

The relationship between handling time and cortisol release rates changes as a function of brain parasite densities in California killifishFundulus parvipinnis

“…Unexpectedly, plasma cortisol concentrations tended to be lower for stress treatment fish in experiment 1 relative to fish on day 4 of experiment 2. If plasma cortisol levels peak in 1–2 h following initiation of the stressor (Barton, ; Sharpe, ; Medeiros & McDonald, ), negative feedback may have been induced prior to the time when blood was drawn and water‐borne release rates would therefore reflect a previously achieved cortisol plasma peak. Alternatively, significant stressors may increase gill permeability (Sloman et al , ), allowing more cortisol to be released into the water for fish in the stress treatment of experiment 1.…”

“…This drop in cortisol on day 4 could indicate either acclimation or negative feedback inhibition in response to the procedure (Fryer & Peter, 1977;Bradford et al, 1992;Schreck, 2000;Ellis et al, 2012). While negative feedback inhibition can be induced in under 4 days (Medeiros & McDonald, 2012), differentiating between acclimation and negative feedback would require understanding the mechanisms through which cortisol release rates were reduced on day 4. Future studies should quantify these mechanisms and examine if different time courses (e.g.…”

The endocrine regulation of cichlids social and reproductive behavior through the eyes of the chanchita, Cichlasoma dimerus (Percomorpha; Cichlidae)

“…This would be particularly useful in those species in which, by a matter of size, it is difficult to obtain blood samples in order to asses cortisol plasma levels. On the other hand, the punctual localization of chanchitas' interrenal gland makes this species an excellent model to determine the effect of different metabolites and hormones upon cultured interrenal gland cells (e.g., Lim et al, 2013;Medeiros and McDonald, 2012).…”

Molecular and functional characterization of the Gulf toadfish serotonin transporter (SERT; SLC6A4)

“…At a functional level, fish SERTs appear to possess a lower affinity for 5-HT than mammalian SERTs (Wang et al, 2006;Severinsen et al, 2008), although they may be inhibited by SSRIs with similar effectiveness (Wang et al, 2006;Severinsen et al, 2008;reviewed by McDonald, 2017). SERT mRNA transcript has been documented both within the central nervous system and in peripheral tissues of teleost fish (Wang et al, 2006;Norton et al, 2008;Mennigen et al, 2010a), where it could be involved in such 5-HT-sensitive processes as catecholamine and cortisol secretion (Fritsche et al, 1993;Bernier and Perry, 1996;Medeiros and McDonald, 2012;Lim et al, 2013) or branchial (Fritsche et al, 1992;Sundin, 1995;Sundin et al, 1995;Forster et al, 1998;Nilsson and Sundin, 1998;McDonald et al, 2010), gastrointestinal (Kiliaan et al, 1989;Mori and Ando, 1991;Venugopalan et al, 1995;Buddington and Krogdahl, 2004;Velarde et al, 2010) or cardiovascular (Janvier et al, 1996;Pellegrino et al, 2003;McDonald et al, 2010) functions. Interestingly, teleost thrombocytes, the evolutionary precursors of plateletswhich are the primary circulating 5-HT storage pools in mammals (Mercado and Kilic, 2010)do not appear to play a 5-HT storage role in teleosts.…”