Apomorphine-induced growth hormone-release in African catfish (Clarias gariepinus) is related to the animal's nutritional status

In African catfish the dopamine agonist apomorphine (APO) stimulates in vivo growth hormone (GH) release. The present study demonstrates that the potency of APO to stimulate plasma GH levels is affected by the nutritional status of the fish. The effect of starvation on APO induced GH release was investigated in sexually mature and immature catfish. Administration of APO clearly stimulated plasma GH levels in mature catfish that had been starved for 3 and 5 weeks, while no effect could be observed prior to starvation. This increased responsiveness to the GH stimulating action of APO was also demonstrated in fasted immature fish, though it was only evident in fish starved for a prolonged period (19 days or more). The importance of the duration of the starvation period suggests that the enhanced responsiveness is the result of physiological adaptations to starvation rather than an acute effect of food deprivation.