Castillo-Ramírez, LA, Herget, U, Ryu, S and De Marco, RJ (2024) Early-life challenge enhances cortisol regulation in zebrafish larvae. Biology Open, 13 (12).

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Abstract

The hypothalamic-pituitary-adrenal (HPA) axis in mammals and the hypothalamic-pituitary-interrenal (HPI) axis in fish are open systems that adapt to the environment during development. Little is known about how this adaptation begins and regulates early stress responses. We used larval zebrafish to examine the impact of prolonged forced swimming at 5 days post-fertilization (dpf), termed early-life challenge (ELC), on cortisol responses, neuropeptide expression in the nucleus preopticus (NPO), and gene transcript levels. At 6 dpf, ELC-exposed larvae showed normal baseline cortisol but reduced reactivity to an initial stressor. Conversely, they showed increased reactivity to a second stressor within the 30-min refractory period, when cortisol responses are typically suppressed. ELC larvae had fewer corticotropin-releasing hormone (crh), arginine vasopressin (avp), and oxytocin (oxt)-positive cells in the NPO, with reduced crh and avp co-expression. Gene expression analysis revealed upregulation of genes related to cortisol metabolism (hsd11b2, cyp11c1), steroidogenesis (star), and stress modulation (crh, avp, oxt). These results suggest that early environmental challenge initiates adaptive plasticity in the HPI axis, tuning cortisol regulation to balance responsiveness and protection during repeated stress. Future studies should explore the broader physiological effects of prolonged forced swimming and its long-term impact on cortisol regulation and stress-related circuits.

Item Type:	Article
Uncontrolled Keywords:	Pituitary-Adrenal System; Hypothalamo-Hypophyseal System; Animals; Zebrafish; Hydrocortisone; Gene Expression Regulation; Larva; Stress, Physiological; Cortisol regulation; Developmental programming; Early-life challenge; HPI axis; Stress response; Zebrafish larvae; Animals; Zebrafish; Hydrocortisone; Larva; Stress, Physiological; Hypothalamo-Hypophyseal System; Gene Expression Regulation; Pituitary-Adrenal System; Neurosciences; Behavioral and Social Science; Genetics; Basic Behavioral and Social Science; Animals; Zebrafish; Hydrocortisone; Larva; Stress, Physiological; Hypothalamo-Hypophyseal System; Gene Expression Regulation; Pituitary-Adrenal System; 0699 Other Biological Sciences
Subjects:	Q Science > QH Natural history > QH301 Biology Q Science > QL Zoology
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	The Company of Biologists
SWORD Depositor:	A Symplectic
Date Deposited:	12 Dec 2024 10:29
Last Modified:	12 Dec 2024 10:30
DOI or ID number:	10.1242/bio.061684
URI:	https://researchonline.ljmu.ac.uk/id/eprint/25078

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