OPIOID RECEPTOR SUBTYPE CONTROL OF GALANIN-INDUCED FEEDING

This study examined the effects of specific antagonists to kappa- and mu-opioid receptors on the feeding induced by injecting galanin into t he lateral cerebral ventricle (LCV). Galanin injected into the lateral cerebral ventricle of sated rats stimulated the consumption of high-f at diet when compared to controls injected with saline vehicle. The mu -opioid receptor antagonist, CTOP, completely abolished galanin-induce d feeding in sated rats whereas the kappa-opioid receptor antagonist, nor-BNI, had no effect on galanin-induced feeding. Neither CTOP nor no r-BNI alone produced any change in food consumption in sated rats. In fasted rats, on the other hand, nor-BNI significantly decreased consum ption of a high-fat diet (>83%) when compared to animals treated with the saline vehicle, whereas CTOP had no significant effect. These find ings suggest that galanin-induced feeding of a high-fat diet is select ively modulated by a pathway involving mu-opioid receptors whereas fee ding induced by fasting is dependent on a pathway mediated by kappa-op ioid receptors. These data also suggest that galanin does not mediate the feeding response after fasting.