Actions of cholecystokinin on neurones in the central nervous system of the snail, Helix aspersa

Abstract

1. Intracellular recordings were made from identified neurons in the visceral and right parietal ganglia of the garden snail. Helix aspersa. Cholecystokinin (CCK) had a direct hyperpolarizing action on specific neurons and in some cases this was associated with an increase in membrane resistance. 2. CCK reduced the excitatory action of 5-hydroxytryptamine (5-HT) and acetylcholine while potentiating the inhibitory action of 5-HT. CCK also reduced the size of the inhibitory effect of acetylcholine and dopamine but potentiated the inhibitory effect of octopamine. 3. These results indicate that CCK can have both a direct effect on the membrane potential and also modulate the action of putative transmitters. 4. CCK-like immunoreactivity was demonstrated in cell bodies and axon terminals from unidentified neurons in the suboesophageal ganglia.