RESPONSE-SPECIFIC INHIBITION DURING GENERAL FACILITATION OF DEFENSIVERESPONSES IN APLYSIA

Siphon responses of Aplysia have been used to examine the neural basis of nociceptive behavioral inhibition. The authors tested the response specificity and functional significance of this inhibition. Video ana lysis showed that strong tail-nerve shock decreased the duration of si phon constriction evoked by weak siphon shock. Tail-nerve shock also c aused the appearance of a novel flaring response to the test stimulus, which resembled the siphon response to tail-nerve shock. Novel flarin g responses were expressed to both mechanical and electrical siphon st imuli. Tailshock facilitated another defensive response, inking, durin g the period of inhibited siphon constriction. Tailshock also facilita ted tail contractions evoked by weak contralateral tail stimulation du ring this period. These results indicate that inhibition is not genera lized across defensive responses and is specific to siphon responses t hat interfere with directed ink ejection toward an injured site.