Synaptic Potentials

Abstract

Until the beginning of the 1950s, studies of the central nervous system were restricted to the analysis of potentials which could be recorded from the brain or the spinal cord by relatively coarse extracellular electrodes. Such recordings provided valuable information of the activity in groups of cells or bundles of nerve fibres, but not of the activity of individual cells. It was therefore a crucial advance when Eccles (Fig. 7.1) and his collaborators in 1951 succeeded in recording intracellularly from single motoneurons in the spinal cord. Their studies mark the beginning of a new era in neurophysiology and have greatly deepened our insight into the mechanisms of synaptic transmission in the central nervous system. Intrinsic to the technique developed by Eccles and collaborators is that a fine glass capillary filled with KC1 is introduced into the spinal cord aiming at the motoneurons in the anterior horn (Fig. 7.2). The tip of the electrode has a diameter less than 1 jiim and can therefore penetrate the cell membrane without seriously damaging the cell.