Feeding responses to perifornical hypothalamic injection of neuropeptide Y in relation to circadian rhythms of eating behavior

May 1, 1993Peptides

How brain injections of neuropeptide Y affect feeding based on daily eating rhythms

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Abstract

Neuropeptide Y (NPY) effectively stimulated eating in satiated rats across all tested time points in the light-dark cycle.

The perifornical hypothalamus (PFH) is the primary site for NPY's effect on eating behavior.
A modest daily cycle of sensitivity to NPY was observed in the PFH, affecting eating responses.
NPY increased food intake in a dose-dependent manner during both the early light and early dark phases.
The magnitude of NPY's effects on food intake was similar across doses during these phases.
The peptide's effects were primarily additive to the natural patterns of spontaneous intake.

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Hypothalamic injection of neuropeptide Y (NPY) can elicit eating in satiated rats, and the perifornical hypothalamus (PFH) is the site where this effect is most pronounced (48). Additionally, there is a well-documented circadian rhythm of spontaneous eating behavior. Our objective was to determine whether there are daily rhythms of sensitivity to NPY in the PFH that might contribute to this behavioral rhythm. To accomplish this, the effectiveness in eliciting eating of PFH injection of NPY was examined at six different time points in the light-dark cycle. Neuropeptide Y (78 pmol/10 nl) or vehicle (10 nl) were injected through chronically implanted guide cannulas into the PFH of satiated adult male rats and food intake was measured 1, 2, and 4 h later. In animals on 12-12 h light-dark cycles, these injections were given 1 h before and after the onset of the light and dark phases, and in the middle of these phases. Additionally, dose-response effects of NPY were examined at two points: the first hour of both the dark and the light phases. The results show that NPY was effective at every time tested, and that the magnitude of the peptide-elicited intakes was primarily additive to the underlying patterns of spontaneous intake, with only a modest daily cycle of sensitivity to NPY. Consistent with this, NPY dose-dependently increased intake in the early light and in the early dark, and the magnitude of these effects across doses was similar at these times. This suggests that the sensitivity of the PFH system mediating NPY eating exhibits only a modest daily cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

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Feeding responses to perifornical hypothalamic injection of neuropeptide Y in relation to circadian rhythms of eating behavior

Abstract

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