This dualism only partially extended to Siberian hamsters here as PYY(3-36) microinjections into the Arc inhibited food intake and especially food hoarding, but the NPY-Y2R antagonist BIE0246 did not stimulate food foraging, intake, or hoarding. This lack of effect of BIIE0246 on baseline food intake also has been reported for laboratory rats [40]. It is possible that our BIIE0246 dose was insufficient to block endogenous Y2 signaling, although selleckchem this seems somewhat unlikely because we used a dose 5-times greater than a dose effective in rats [1]. In two pilot studies,

we injected the highest dose of BIIE0246 (5.0 nmol) used here into the Arc followed 2–3 min later by PYY(3-36) peripherally (7.5 nmol/kg) or into the Arc (0.1 nmol). In both studies, BIIE0246 co-administered with PYY(3-36) resulted in no significant change in ingestive behaviors when compared to saline-treated Siberian hamsters. These data suggest that our dose BIIE0246 is able to prevent the inhibition of ingestive behaviors

caused by Y2 agonism. The present data suggests that there is not a chronic stimulation of Y2 signaling in non-energetically challenged (i.e., ad libitum-fed) Siberian hamsters similar to laboratory rats [40], which is unlike the apparent underlying inhibition of ingestive behaviors by leptin [30] and cholecystokinin [46] in Siberian hamsters. check details It is worth noting the large standard Molecular motor error values found in most of the variables measured after Arc administration of the Y2 antagonist. The animals exhibited a dichotomous split into high and low levels of food foraging, intake, and hoarding, but hamsters showing high

or low levels of one behavior did not necessarily predict high or low levels of the other behaviors as seems apparent for food hoarding by Syrian hamsters [12]. In addition, the exact location of the cannula within the Arc also was not associated with a particular ingestive behavioral response or the magnitude of the response. Large variations in food hoarding both within and between animals from day-to-day are common, quite unlike that of food intake studies in this species in our experience. The cause of the variations in spontaneous food hoarding by Siberian hamsters remains a mystery presently and is not due to differences in body fat (for example: fat hamsters hoarding less than lean animals because they possess greater internal energy stores). The second experiment was designed to test the inhibitory role of the Y2-R signaling using the naturally occurring NPY Y2-R agonist PYY(3-36). PYY(3-36) has potent anorexigenic effects whether administered peripherally or centrally in laboratory rats and mice [for review: [35]], with few exceptions [47].

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