Neuroscience Letters, 45 (1984) 187-192 187 Elsevier Scientific Publishers Ireland Ltd. NSL 02630 PLATEAU POTENTIALS EVOKED BY CLIMBING-FIBRE STIMULATION ARE RESTRICTED TO THE PURKINJE CELL DENDRITES OF THE CAT NORMA C. CAMPBELL* and GERMUND HESSLOW** Institute of Physiology, University of Lund, S61vegatan 19, S 223 62 Lund (Sweden) (Received December 5th, 1983; Accepted January 9th, 1984) Key words: cerebellum - climbing fibres - plateau potentials - Purkinje cells - cat The present study investigated the duration of afterdepolarizations in Purkinje cell somata following climbing-fibre activation. Intracellular recordings revealed that, in cells with membrane potentials more negative than - 50 mV and with normal spike-generating capabilities, climbing-fibre activation resulted in somatic responses with short afterdepolarizations. As the cell deteriorated and the resting membrane potential became more positive, the duration and form of the climbing-fibre response resembled the plateau potentials recorded from proximal dendrites. The absence of plateau potentials in undamaged Purkinje cell somata was confirmed by extracellular recording of test spike amplitudes following evoked climbing-fibre responses. The responses evoked in cerebellar Purkinje cells by impulses in the climbing fibres have received much attention from neurophysiologists. It has recently been shown, both in vivo [6] and in vitro [7], that stimulation of the climbing fibres results in depolarizing plateau potentials with durations up to several hundred milliseconds in Purkinje cell dendrites. Earlier descriptions of climbing-fibre evoked responses (CFRs) have been concerned mainly with intracellular recordings from Purkinje cell somata, where it is reported that climbing-fibre activation results in a large initial spike followed by a series of smaller spikes which are superimposed on a 12-25 ms long afterdepolarization (ADP) [1, 8]. The ADP is sometimes follow- ed by a hyperpolarization [8]. Recently, however, plateau potentials lasting up to 150 ms have also been reported to occur in Purkinje cell somata in in vitro prepara- tions [7]. In view of the probable importance of climbing-fibre evoked plateaus in cerebellar function, it was considered timely to re-examine the duration of the ADP in CFRs in the Purkinje cell soma in vivo. The results of the present study suggest that, under normal conditions, long-lasting plateau potentials do not occur in the Purkinje cell soma. *Present address: Department of Physiology, University of Bristol Medical School, Bristol, BS8 1TD, U.K. **Author for correspondence. 0304-3940/84/$ 03.00 © 1984 Elsevier Scientific Publishers Ireland Ltd.