Chaganty, V. | Search bioRxiv

bioRxiv2025

Comparative transcriptomics of lateral hypothalamic cell types reveals conserved growth hormone-tachykinin dynamics in feeding

The lateral hypothalamus (LH) is a highly heterogeneous brain region regulating hunger and motivated behaviors. In zebrafish, the LH shows distinct neural activity across hunger, feeding, and satiety states. However, the functional and evolutionary conservation of relevant neural circuits remain unclear. Using integrative transcriptomics of zebrafish and mouse LH, we identify conserved cellular clusters with shared molecular markers, particularly within GABAergic neurons. We highlight a conserved GABAergic population expressing tachykinin and growth hormone receptors, which is responsive to food cues and modulated by hunger and feeding states. This cluster may mediate acute appetite-enhancing effects of growth hormone. In both species, feeding elevates growth hormone receptor and tachykinin expression and activates these neurons, while human growth hormone increases their activity and food intake in zebrafish. These findings suggest a conserved neural mechanism by which metabolic hormones influence feeding behavior. Our comparative LH atlas highlights the evolutionary biology of appetite regulation and the integration of hormonal and neural signals driving energy homeostasis.

neuroscience↗

bioRxiv2023

Dynamics of endogenous and water cortisol release in Asian Seabass Lates calcarifer after acute stress in a farm scale recirculating aquaculture system

Stress in farmed fish is associated with poor feeding, slow growth, disease, and mortality. Therefore, it is essential to closely monitor the stress levels in fish to optimize farming practices which could then enhance productivity and welfare in aquaculture operations. Cortisol, a stress hormone that can be found in the blood, is a reliable biomarker for evaluating fish stress. As blood sampling is highly invasive, alternative cortisol sampling methods such as fin, mucus, and the surrounding water which contains released cortisol, have been proposed as less invasive or non-invasive sampling methods. However, a comprehensive understanding of their temporal dynamics and associations with plasma cortisol levels is still lacking. In this study, we subjected Lates calcarifer, Asian sea bass within a farm-scale (3,000 L tank, 9,000 L system) high-flow rate (8,000 L/hour) Recirculating Aquaculture System (RAS) to an acute handling stress challenge specifically involving chasing and air exposure, and quantified cortisol dynamics both within different biological samples including blood, fin, and mucus and in tank water from multiple sampling points. We showed that handling stress induced an expected increase in plasma and mucosal cortisol, peaking at 1 hour and 24-48 hours, respectively, and that plasma and mucus cortisol were moderately correlated, especially during the stress period. Fin cortisol did not show consistent dynamics. Water cortisol similarly rose, but peaked within 40 minutes from the start of the stressor, in a pattern that was dependent on the site of sampling within the RAS system, likely due to RAS circulation dynamics. Our study is the first to examine the impact of stress on cortisol accumulation and release in Asian Sea bass in a farm-scale RAS, thus complementing existing research on the efficacy of fin, mucus, and water cortisol as stress indicators that could help optimize aquaculture productivity and welfare.

physiology↗