Ablation of the area postrema causes exaggerated consumption of preferred foods in the rat

Abstract

The area postrema (AP) is a hindbrain circumventricular organ (CVO) with apparent chemoreceptive function. The AP has demonstrated neural and vascular connections with the nucleus of the solitary tract (SOL), a structure which receives the primary visceral afferents from the oral cavity and gastrointestinal tract. The anatomical structure and connections of the AP suggests a potential role for this CVO in the control of feeding behavior. We have found that rats with surgically produced AP lesions consumed the same amounts of pelleted food ad libitum as control rats. Lesioned and control rats also consumed equal amounts of lab chow after 21 h food deprivation. However, when presented with a preferred food (instant breakfast or cookies), AP-lesioned rats consumed at least double the amount consumed by control rats. It is possible that AP lesions impair sensitivity to satiety cues. However, lesion rats did decrease their instant breakfast intake in response to cholecystokinin injections or gastric preloads. Furthermore, overingestion by AP-lesioned rats occurred only in response to preferred (highly palatable) foods and not in response to lab chow. Lesioned rats rejected quinine-adulterated instant breakfast at the same adulterant concentration as controls. Therefore, the lesioned rats do not suffer from ageusia or from enhanced responsiveness to bitter taste. Rather, the selective overeating by AP-lesioned rats may reflect an enhanced behavioral response to the sensory qualities of normally preferred foods. The close association of the AP with the SOL provides a neuroanatomical avenue by which a putative AP-chemoreceptor could alter the quality or intensity of information arriving via the taste afferents. Such tuning of gustatory mechanisms could be an important component of ingestive control.