[Generalized and signal-specific long-term nociceptive sensitization in the snail Helix lucorum]

Neurophysiological and behavioural correlates of the long-term sensitization were investigated in Helix lucorum small. Application of 10% quinine solution on the snail's head initiated a long-term (for more than 24 hours) facilitation of defensive reactions. The behavioural effects correlated with the changes in evoked and spontaneous activity of L-PP11 neurons, i.e., facilitation of synaptic components in responses to testing stimulation, increase in membrane excitability and depolarization. Efficacy of sensitization depended on the duration of the experimental procedure. After daily training site-specific and modality-specific effects dominated (i.e., more expressed facilitation of responses to testing stimulation of the sensitized body site than that of the other sites or to testing stimulation of the same modality as sensitizing stimulation). After 3 days of training the effects of general sensitization were predominantly observed, i.e., facilitation of neuronal responses to stimulation of different modalities and body sites, depolarization of the membrane and increase in its excitability.