Synaptic Organization of Local Circuit Neurons in the Terminal Abdominal Ganglion of the Crayfish

Abstract

The synaptic organization of the local circuit generation uropod movements of the crayfish has been analyzed by using electrophysiological, pharmacological and immunocytochemical techniques. Sensory afferents innervating hairs on the tailfan contain the neurotransmitter acetylcholine and make direct excitatory synaptic connections with intersegmental ascending interneurones, spiking local interneurones and nonspiking local interneurones in the terminal (sixth) abdominal ganglion. Ascending interneurones, in turn, make excitatory connections with nonspiking interneurones while spiking local interneurones make direct inhibitory connection with nonspiking interneurones. Most nonspiking interneurones contain the inhibitory neurotransmitter, GABA, and play a prominent premotor role in organizing the motor patterns of the uropods.