EFFECT OF HYPOXIA ON NEUROPEPTIDE GENE EXPRESSION IN CHANNEL CATFISH
Maximizing appetite is critical for intensive production of catfish; a reduction in feed consumption means a longer production cycle with higher mortalities. When the minimum dissolved oxygen (DO) concentration falls below 3.0 mg/L there is a decrease in feed consumed. The primary objective of this project was to examine regulation of the neuropeptides urotensin I (UI) and corticotropin-releasing factor (CRF) during a short bout of hypoxia that replicated the daily conditions of a catfish production pond. Dissolved oxygen concentration was maintained in control aquaria at 95% saturation. Hypoxia tanks were maintained at 95% saturation, dropped to 20% saturation for 12 hours then returned to saturation in replicate aquaria. Fish were sampled at 0, 6, 12, 18, and 24 hours. Venous PO2 was the same after 6 hours of hypoxia, 60% lower in the hypoxia group after 12 hours of hypoxia, and the same 6 hours after the DO returned to saturation. Gene expression for CRF did not significantly change during hypoxia at any measured time point. There was a significant increase in Urotensin I gene expression (1.6-fold higher) in the hypoxia group 18 hours after the onset of the experiment but fell to pre-hypoxia level by 24 hours. At the time points sampled, the anorectic neuropeptide UI was significantly upregulated six hours after a 12-hour bout of hypoxia. This data suggests that urotensin I may act to decrease appetite after periods of hypoxia.