Selective effects of antibodies to protein SMP-69 on the activity of defensive behavior command neurons in the common snail.

The effects of antibodies to the serotonin-modulated protein SMP-69 on the activity of defensive behavior command neurons LP11 and RP11 in semi-intact preparations from common snails were studied. Antibody to SMP-69 increased membrane excitability and facilitated neuron responses to chemical sensory stimulation by application of dilute quinine solution to the animal's head, these effects being seen at 1-1.5 h. The synaptic effects of the antibodies were specific, as they had no influence on responses induced by tactile stimulation of the head. The neuronal effects of antibody SMP-69 were similar to changes in the activity of cells LP11 and RP11 induced by serotonin and cAMP, and to changes seen when snails acquired nociceptive sensitization. It seems likely that a protein homologous to mammalian SMP-69 is involved in the mechanisms controlling excitability and long-term specific plasticity of the synaptic inputs to neurons LP11 and RP11 from chemoreceptors on the snail's head.