ENDOGENOUS OPIOIDS OF MODEL GASTROPODS - COORDINATION OF MOTOR PROGRAMS FOR FEEDING AND DEFENSIVE BEHAVIORS IN THE POND SNAIL LYMNAEA-STAGNALIS

Opioids are known to influence feeding behavior in land pulmonates [6, 7]. We found this to be the case in the pond snail L. stagnalis: morp hine increases, while naloxone decreases, food consumption. Evidence i n presented that the pond snail central pattern generator (CPG) for fe eding in influenced by opiates indirectly. The endogenous opioid syste m seems to directly control the CPG for a defensive fixed motor action accompanied with the arrest of feeding activity. Results of neurophys iological experiments on the isolated CNS indicate that target cells f or opioid control are situated outside the buccal ganglia where the CP G for feeding is located.