Experimental studies on the control and regulation of feeding in the common carp, Cyprinus carpio (L. )
The aims of this work were three-fold, to investigate the patterns of food intake exhibited by carp (Cyprinus carpio) feeding on an operant regime, to investigate the role of the nucleus posterior thalamicus (NPTh) in the control of food intake, and to investigate the role of gut peptides in the control of food intake. A range of techniques were employed in pursuit of these objectives. Behavioural studies were used to investigate feeding patterns, and to assess the effects of small electrolytic lesions placed in the region of the NPTh. Histological and physiological techniques were employed to investigate the cellular morphology of the NPTh and its relationship with both hindbrain and telencephalon. Pharmacological and behavioural techniques were employed to obtain a dose response characteristic for the peripheral administration of bombesin and its effect on food intake. Animals held individually and feeding on an operant regime showed no indication that they were feeding in bouts. Satiety was seen to increase exponentially or logarithmically over the course of a feeding session. Small lesions of the NPTh caused a highly significant and variable period of anorexia or hypophagia. On recovery of feeding behaviour in lesioned animals, satiety was seen to increase in a linear fashion over the course of a feeding session. Histologically the cell bodies within the NPTh are seen to be morphologically homogenous. Physiologically it is probable that the NPTh efferent fibres are of small diameter and unmyelinated, projecting to the vagal and facial lobes of the medulla. There is some evidence that the NPTh operates as a single unit providing the same function in both internal and external chemosensory systems. The hypothesis is advanced that the NPTh has a role in the determination of palatability in both internal and external chemosensory systems. Intra-peritoneal administration of the peptide bombesin was shown to reduce food intake in animals feeding on an operant regime, in a dose dependent manner. This result is very similar to the effects of bombesin administration seen in the higher vertebrates. A further result of bombesin administration demonstrated in these experiments is the appearance of a bout feeding pattern, effects of bombesin administration on the micro-structure of food intake have not been reported in other species.
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