EFFECTS OF MET-ENKEPHALIN ON ELECTRICAL COUPLING BETWEEN IDENTIFIED NEURONS IN THE PULMONATE SNAILS, HELIX AND LYMNAEA

1. The effects of met-enkephalin on electrical coupling between mollus can neurons have been investigated using the isolated brains of Helix Pomatia and Lymnaea stagnalis. 2. In the presence of both serotonin an d met-enkephalin, non-rectifying electrical coupling is strongly facil itated between identified respiratory neurons in Helix, whilst couplin g between putative, serotonin-containing, ciliomotoneurons in Lymnaea is facilitated by met-enkephalin alone. 3. Facilitation of coupling by met-enkephalin is weaker in the strongly coupled neurons, VD1/RPaD2 o f Lymnaea. 4. These data suggest that met-enkephalin can modulate diff erent groups of electrically coupled cells and may be involved in coor dination of motor patterns.