Roles of dopamine D1 and D2, opiod and glutamate NMDA receptor signaling in the acquisition and expression of fat- and glucose-conditioned flavor preferences in rats and c-Fos analysis of the dopamine mesotelencephalic and nigrostriatal pathways following intake of sugars and fats in rats.

摘要

Systemic administration of the non-competitive NMDA antagonist, MK-801, demonstrated that acquisition, but not expression, were found to affect the orosensory-mediated (flavor/flavor: f/f) fructose-conditioned flavor preference (CFP). The present studies demonstrated a similar outcome when f/f and f/n processes were combined. Fat-CFP and glucose-CFP studies indicated that systemic injections of the NMDA antagonist, MK-801, were able to significantly reduce acquisition, but not expression, of Corn-Oil (CO)-CFP and glucose-CFP. Both studies appear to have mitigated effects on acquisition as compared to the separate orosensory and postingestive CFP studies.;Previous studies found that systemic administration of dopamine (DA) D1 (SCH23390) and D2 (raclopride) antagonists blocked both the acquisition and expression of the orosensory-mediated fructose-CFP and sham sucrose-CFP. DA D1, but not D2, blocked the f/n acquisition, and to a lesser degree, expression, of IG sucrose-CFP. The current study of both fat-CFP and glucose-CFP found that DA D1 and D2 antagonists did attenuate the acquisition and expression of conditioned flavor preference of CO-CFP and oral glucose-CFP, but to a lesser degree. Similar to how a combined f/f and f/n solution is affected by an NMDA antagonist, DA D1 and D2 antagonists do affect the combined f/f and f/n solutions of CO and glucose, but not to the degree observed for fructose-CFP or IG glucose-CFP.;It is suspected that certain areas of the mesotelencephalic and nigrostriatal DA pathways affect CFP, such as the nucleus accumbens (NAc), the amygdala (AMY), the medial prefrontal cortex (mPFC), or the dorsal striatum (caudate and putamen: CPu). The present study examined the origin of DA (ventral tegmental area: VTA) and the five projection zones (NAc shell, NAc core, AMY, mPFc and CPu) simultaneously for fos-like immunoreactivity (FLI) following oral ingestion of CO (f/f and f/n), glucose (f/f and f/n), fructose (f/f) and three controls (water, saccharin and xanthan gum). CO, which was isocaloric to fructose and glucose, elicited significantly higher FLI in the NAc core, the AMY, the mPFC, the VTA and the CPu than the controls. Glucose elicited significantly higher FLI in the AMY, the CPu and the NAc core than the controls. Fructose elicited significantly higher FLI in the AMY and the CPu than the controls.