MORPHOLOGICAL AND FUNCTIONAL PROPERTIES OF IDENTIFIED NEURONS IN THE ABDOMINAL GANGLION OF APLYSIA CALIFORNICAl

THE ABDOMINAL GANGLION of the marine gastropod, ApZysia, is a valuable preparation for cellular electrophysiological studies. In large animals, most small nerve cells in this ganglion are comparable in size to the largest neurons in the vertebrate brain ganglion occasionally reach 1 (So-100 p), whereas the largest cells in the mm in diameter. Furthermore, the majority of the cells are located near the surfaces of the ganglion and can readily be visualized under the dissecting microscope. In a given preparation it is therefore possible to directly visualize and penetrate many cells with microelectrodes. The cells within the ganglion tional properties. Because of the vary greatly difficulty in in appearance and in funcrecognizing individual cells or homogeneous cell clusters from preparation to preparation, a great number of studies of this ganglion have been carried out on unidentified cells (7, 34, 41, 42)) with exceptions generally limited to the two or three most obvious and constant cells (3, 5, 27, 39, 46). Although this limitation has not restricted biophysical and pharmacological studies on these neurons (18, 44, 47), it has been a major deterrent to studying the organizational and plastic properties of the ganglion. To overcome this difficulty, we have tried to identify all the prominent cells and cell clusters in the ganglion and have tried to relate them to the functional organization of the ganglion as a whole. The possibility of identifying individual cells in the abdominal ganglion