Daily changes of neuropeptide Y-like immunoreactivity in the suprachiasmatic nucleus of the rat

Changes in neuropeptide Y immunoreactivity and transcript levels in circadian system structures of the diurnal rodent, the thirteen-lined ground squirrel

“…An increase in NPY-ir levels in the SCN began at ZT12, and reached maximal levels at ZT18. The data at these times do not agree with prior reports in rats (Calzá et al, 1990;Shinohara et al, 1993b), which state that NPY content in the rat SCN peaks just before the onset of darkness. Additionally, our results demonstrate that the density of NPYir is somewhat diminished at ZT22 and continues to decrease to ZT0.…”

“…Although NPY-ir levels are higher at ZT's 22 and 0, compared to trough, it is apparent that levels are on the decline. This differs from previous reports in rat that demonstrate a second peak in NPY content in the rat SCN at the onset of lights (Jhanwar-Uniyal et al, 1990) or two hours after the onset of lights (Calzá et al, 1990;Shinohara et al, 1993b). The stability of the background measurements across sections from different animals and the lack of any daily variation in NPY-ir measurements in the supraoptic nucleus lend strong support to our conclusions.…”

“…Increases in NPY content in the SCN of rats near or at the times of photic transitions have led to the conclusion that NPY serves to convey information on photic transitions to the pacemaker (Calzá et al, 1990;Jhanwar-Uniyal et al, 1990;Shinohara et al, 1993b). Furthermore, rats presented with a 5 min light pulse at ZT0, to mimic the sudden dusk to dawn transition, exhibit increases in NPY content in the SCN (Shinohara et al, 1993a).…”

“…All reports have shown increases in NPY levels both at the beginning and at the end of the light portion of the daily photoperiod (Calzá et al, 1990;Jhanwar-Uniyal et al, 1990) and suggest that NPY in the SCN is under photic regulation. Thus far, none have addressed the question whether the increases in NPY levels in the SCN are the result of increased peptide synthesis in NPY-producing cells of the IGL or the result of selective turnover in the SCN.…”

Novel analogues of neuropeptide Y with a preference for the Y1‐receptor

“…Profound effects on stimulation of food intake, secretion of luteinizing and growth hormone, and insulin release suggest an important role for NPY in the pathophysiology of obesity and diabetes [2±5]. A wide range of other effects of NPY have been reported, such as potent vasoconstriction [6], facilitation of learning and memory [7], modulation of locomotor behaviours [8], induction of hypothermia [9,10], inhibition of sexual behaviour [11], shifts in circadian rhythms [12], modulation of cardiorespiratory parameters[13], anxiolytic potency [14] and inhibition of alcohol consumption and resistance [15].NPY is a 36-amino acid peptide amide belonging to the family of pancreatic polypeptides that includes also pancreatic polypeptide (PP) and peptide YY; it was first isolated from pig brain in 1982 [16].NPY is widely distributed within the central nervous system and in the periphery. [25,26].…”