Energetic dependence of NPY-induced LH secretion in a teleost fish (Dicentrarchus labrax)

The purpose of this work was to examine the role of energetic status in neuropeptide Y (NPY)-induced luteinizing hormone (LH) secretion and glucose metabolism in fish. Fasted juvenile sea bass (Dicentrarchus labrax) were injected intraperitoneally with pig (p) NPY or pNPY + glucose, whereas fed animals were injected with pNPY alone and plasma glucose, insulin, and LH levels were examined. pNPY alone or in combination with glucose was found to induce a dose-dependent increase in LH secretion in fasted animals. Similar LH responses to pNPY were observed in vitro in dispersed pituitary cells isolated from fed and fasted animals incubated in L-15 and restricted media. Injection of pNPY + glucose in fasted animals resulted in depletion of glucose. Insulin plasma levels decreased in fasted animals coinjected with pNPY + glucose but remained stable when NPY was administrated alone to fed and fasted animals. Results suggest that 1) NPY-induced LH secretion in fish is dependent on energetic status and 2) NPY is capable of modifying glucose metabolism.