Suppression of synaptic input of defense behavior command neurons by stimulation of neurons of the mesocerebrum in a preparation of the isolated CNS of the common snail.

The intestinal nerve was stimulated in combination and uncombined with extracellular stimulation of the mesocerebral region of the brain, as well as with stimulation of serotoninergic neurons, in experiments on a preparation of the isolated CNS of the common snail, with preservation of the nerve connections with the sexual system. Responses were recorded in command neurons of defense behavior. The data were obtained indicating that, in the case of combinations with extracellular stimulation of the mesocerebrum, an analog of a conditioned reaction of diminution of EPSP in the command neurons of defense behavior was developed. When stimulation of the same nerve was reinforced by stimulation of the serotoninergic neurons, sensitization appears, both in the case of combined and uncombined presentation of the stimuli.