Gene expression of neuropeptide Y in the nucleus of the solitary tract is activated in rats under restricted daily feeding but not under 48-h food deprivation

The two neuropeptide Y (NPY) systems innervating the hypothalamic paraventrivular nucleus were examined regarding their roles in the prefeeding corticosterone peak developed under restricted daily feeding (RF). Protein and mRNA levels of NPY were measured in the arcuate nucleus (ARC) and the nucleus of the solitary tract (NST) in rats under 48-h food deprivation (48-hFD), RF, and 72-h food deprivation imposed after RF (post-RF 72-hFD) with 7 days of ad libitum feeding in between. NPY protein and mRNA levels in the ARC significantly increased with 48-hFD and decreased with re-feeding, whereas those in the NST were not changed by 48-hFD. When rats had RF imposed with free access to food from 10.00 to 12.00 h (lights on from 06.00 to 18.00 h) for 3 weeks, NPY concentrations in the ARC increased at 10.00 h, just prior to the daily meal, but those in the NST did not change significantly throughout the period examined. On the other hand, NPY mRNA levels in both the ARC and NST increased before the meal supply and remained high for 4 h after feeding. Under post-RF 72-hFD, the prefeeding peak of NPY mRNA was detected in the NST, but NPY mRNA levels in the ARC were continuously high throughout the 24-h period. These findings indicate that the NPY neurons from the NST are specifically activated by RF, whereas those from the ARC are generally stimulated by an increased food demand.