The paper characterizes melatonin receptors 1A in the neurons of the leading pacemaker of circadian rhythms in the brain of mammalians — suprachiasmatic nuclei of the hypothalamus. It has been established that the density of the receptors in question is subject to accurate circadian organization with the maximum value at 02.00 a. m. and 8.00 p. m., whereas at 08.00 a. m. and at 2 p. m. it decreases sufficiently.
