Neurophysiological mechanisms responsible for generalized and signal-specific long-term (longer than 24 h) nociceptive sensitizations were studied in theHelix command neurons of defensive behavior. After a one-day acquisition, the manifestations of the signal-specific sensitization were predominant. These included the site and modal specificities. The former was manifested in a predominant synaptic facilitation of the responses to testing stimulation of the same body areas to which the sensitizing stimulation was applied, compared with stimulation of other body areas. The latter was manifested as a more expressed facilitation of the responses to testing stimulation of sensory modality similar to the sensitizing one, compared with the facilitation of the responses to testing stimulations of other sensory modalities. A three-day acquisition resulted in a predominance of the generalized sensitization signs: a clear non-selective facilitation of the responses to activation of all synaptic inputs, together with depolarization and increased excitability of the command neurons.