SODIUM, CALCIUM AND LATE POTASSIUM CURRENTS ARE REDUCED IN CEREBELLAR GRANULE CELLS CULTURED IN THE PRESENCE OF A PROTEIN COMPLEX CONFERRING RESISTANCE TO EXCITATORY AMINO-ACIDS

Whole-cell, patch-clamp recordings were used to study voltage-gated currents generated by cerebellar granule cells that were cultured in medium containing either 10% fetal calf serum (hereafter termed S+ granules) or neurite outgrowth and adhesion complex (NOAC, hereafter called NOAC granules). NOAC is a protein complex found in rabbit serum that renders granules resistant to the excitotoxic action of excitatory amino acids. During depolarizing commands both S+ and NOAC granules generated Na+ and Ca2+ inward currents and an early and a late K+ outward currents. However, Na+ and Ca2+ inward currents and late outward K+ currents recorded in NOAC granules were smaller than those seen in S+ granules. Furthermore, although of similar amplitude, early K+ currents displayed different kinetics in the two types of neurons. Thus, these data demonstrate that the electrophysiological properties of cerebellar granules, and probably of other neuronal populations, depend upon serum components and raise the possibility that an analogous modulation might be operative in vivo, and play a role in development, synaptic plasticity or neuropathological processes.