LIVER DENERVATION, 5-HT3 RECEPTOR ANTAGONIST, AND INTAKE OF IMBALANCED AMINO-ACID DIET

The serotonin3 receptor antagonist ICS 205-930 (ICS) may act peripherally to attenuate the anorectic response of rats given an imbalanced amino acid (IMB) diet. Rats were divided into four groups: SHAM + saline (sal); SHAM + ICS; total liver denervation (TLD) + sal; and TLD + ICS. Rats were then given a purified basal diet for 16 days. Next, the groups were injected with sal or 9 mg/kg BW of ICS at 0800 h and at 0900 h (lights out) an isoleucine IMB diet was presented. By 12 h postinjection, the food intake (FI) of TLD and SHAM rats receiving ICS was similarly higher (p < 0.02) than sal-injected counterparts whose FI was also similar; BW followed FI. By day 3, the SHAM groups had similar low FI, whereas the FI of the TLD groups was increasing. The above study was repeated with similar results. Liver innervation is not required for ICS attenuation of IMB diet-induced hypophagia. Also, while sal-injected TLD rats show a normal attenuation of consumption of the IMB diet on the first day of exposure, they subsequently consume more of the IMB diet than SHAM rats. The reason for this difference in TLD rats is not clear but may be related to metabolism of the IMB diet or possibly learning.