Related Experiment Video
Updated: Jun 12, 2026

Behavioral Approaches to Studying Innate Stress in Zebrafish
Published on: May 1, 2019
The serotonin subtype 1A receptor regulates cortisol secretion in the Gulf toadfish, Opsanus beta
Lea R Medeiros1, Edward M Mager, Martin Grosell
1Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA. lmedeiros@rsmas.miami.edu
Abstract:
It is well established that serotonin (5-HT; 5-hydroxytryptamine) plays a role in mammalian regulation of the hypothalamic-pituitary-adrenal (HPA) axis via the 5-HT receptor subtype 1A (5-HT(1A)). To date, there has not been a comprehensive investigation of the molecular, pharmacological and physiological aspects of the 5-HT(1A) receptor and its role in the activation of the hypothalamic-pituitary-interrenal (HPI) axis in teleost fish. The 5-HT(1A) receptor of the Gulf toadfish (Opsanus beta) was cloned and sequenced, showing 67.5% amino acid similarity to the human homologue. The 5-HT(1A) receptor was distributed throughout the brain, with the whole brain containing significantly higher levels of 5-HT(1A) mRNA compared to all other tissues and the midbrain/diencephalon region containing significantly higher levels of transcript than any other brain region. Substantial levels of transcript were also found in the pituitary, while very low levels were in the kidney that contains the interrenal cells. Xenopus oocytes injected with toadfish 5-HT(1A) receptor cRNA displayed significantly higher binding of [(3)H]5-HT that was abolished by the mammalian 5-HT(1A) receptor agonist, 8-OH-DPAT, indicating a conserved binding site of the toadfish 5-HT(1A) receptor and a high specificity for the agonist. Supporting this, binding of [(3)H]5-HT was not affected by the mammalian 5-HT(1B) receptor agonist, 5-nonyloxytryptamine, the 5-HT(7) receptor antagonist, SB269970, or the 5-HT(2) receptor agonist, alpha-methylserotonin. Confirming these molecular and pharmacological findings, intravenous injection of 8-OH-DPAT stimulated the HPI axis to cause a 2-fold increase in circulating levels of cortisol. The present study of the 5-HT(1A) receptor in a single teleost species illustrates the high conservation of this 5-HT receptor amongst vertebrates.
Related Concept Videos
Hypothalamic-Pituitary Axis
Regulation of Hormone Secretion
Humoral stimuli,...
G-protein Coupled Receptors
Hormones of the Adrenal Glands
The adrenal cortex, a powerhouse of hormone synthesis, generates over two dozen corticosteroid hormones. The zona glomerulosa produces mineralocorticoids, exemplified by aldosterone, influencing the electrolyte composition of body fluids. The synthesis of glucocorticoids such as cortisol and corticosterone...
Adrenergic Receptors: β Subtype
Isoprenaline > Adrenaline > Noradrenaline
Neurotransmitter binding to these receptors causes activation of adenylyl cyclase resulting in increased concentrations of cAMP and modulation of calcium ion channels within the cell. They are further classified into β1, β2, and β3 subtypes.
β1-adrenoceptors: β1-adrenoceptors have equal affinities for...
Major Hormones and Their Functions
Oxytocin, produced in the hypothalamus and released by the pituitary gland, plays a role in social bonding, childbirth, and lactation.
