The suprachiasmatic nucleus generating biological circadian rhythms in mammals and humans, contains a high proportion of neurons, producing arginine-vasopressin. In in vitro experiments on hypothalamic slices of rats, the comparative analysis of the effect of 20 nM argininevasopressin on the spike activity parameters of neurons with regular (n =23) and irregular (n=28) activity in the suprachiasmatic nucleus was performed.