After the administration of 11 mg/kg of sodium nitrite (NO of the generating drug) the motor disinhibition and increase in the myogram amplitude were observed in reaction of rabbits to non-reinforced flashes at the background of continuous light which served as a conditioned inhibitory signal (CIS). The disinhibition appeared within 1-1.5 h from he moment of NO administration and continued during the whole recording period (4 h). Under the NO dose of 5.5 mg/kg only the tendency was observed to motor disinhibition after the CIS presentation. The results obtained can be possibly explained by the NO ability to inhibit the functions of the GABA-ergic receptors, since it is known that elaboration of the internal inhibition is accompanied by an enhancement of the inhibitory hyperpolarizing processes realized with participation of the GABA-ergic transmitter system. Under the action on NO both in the small and doubled doses the myogram amplitude did not increase in response to combined presentation of the light flashes with pain reinforcement, in contrast to the repeated presentations of these paired stimuli in the control experiments. This phenomenon is probably determined by the inhibitory influence of NO on the NMDA receptors.