MORPHOLOGY OF IDENTIFIED NEURONS IN ABDOMINAL-GANGLION OF APLYSIA-CALIFORNICA

The morphology of identified neurons and of 1 multiaction interneuron (L 10) of the abdominal ganglion of Aplysia was studied using cobalt chloride injected intracellularly. Cells with little synaptic input, R3-R14, had a relatively poorly developed dendritic tree, whereas the dendritic tree of cells L7 and L10, with extensive synaptic input, was highly complex. Cells L1-L6 and the RB cell cluster had intermediate complexity of synaptic inputs and dendritic morphology. Within cell clusters individual cells were often morphologically distinct. Identified cells had both invariant and variant axonal branches. Variant axons often projected down other than their customary nerve trunks or were supernumerary. Three features of neuropil architecture were encountered: when cells from the same cluster sent their axons down the same nerve they often ran in fascicles; although an identified cell''s dendritic geometry varied from preparation to preparation, its dendrites always occupied approximately the same position in the neuropil; and the postsynaptic follower cells of L10 sent their main axons through the axonal arborization of L10.