Effects of Neuropeptide Y on Neuron Spike Activity in the Rat Suprachiasmatic Nucleus in Vitro

Experiments on sagittal hippocampus slices from male Wistar rats addressed the effects of 10 nM neuropeptide Y on the level of electrical activity in neurons in the suprachiasmatic nucleus and parameters of spike-based information encoding. Application of neuropeptide Y led to a decrease in the action potential generation frequency in 35 of the 81 neurons recorded; eight cells showed increases in this parameter, and the remaining 38 neurons showed no change in the level of spike activity. The decrease in the spike generation frequency in suprachiasmatic nucleus neurons was accompanied by increases in the entropy of the distribution of interspike intervals and the mutual information between adjacent interspike intervals, which is evidence for increases in the degree of irregularity in these intervals and the patterning of spike information in response to neuropeptide Y. These results demonstrate the ability of neuropeptide Y to modulate the activity level and affect the spike code in the relatively numerous population of neurons in the circadian oscillator of the suprachiasmatic nucleus.