Assay of Convulsants Using Single Unit Activity

THE ABDOMINAL ganglion of Aplysia was introduced as a neurophysiological preparation by Cardot and Arvanataki1in 1941. Since the pioneering work of Tauc2(1955) it has found increasing application for the intracellular recording of single unit activity. Among the advantages of this excellent preparation are neurones of immense size (to 0.8 mm diameter in some species), continued functioning for hours in vitro in a sea water bath, absence of pulsation or other movement of the preparation, and several connecting nerves permitting both orthodromic and antidromic stimulation. Neurone somata are readily penetrated under direct vision with a micropipette which may then record intracellular activity for hours. Aplysiaare molluscs related to the snail which have undergone detorsion and loss of the calcified shell during evolution.3The ganglia of these and other invertebrates have been characterized as miniature brains and indeed do represent the highest integrative centers of