NEONATAL RAT CEREBELLAR GRANULE AND PURKINJE NEURONS IN CULTURE EXPRESS DIFFERENT GABA(A) RECEPTORS

We have established a culture system for microexplants of rat cerebell ar cortical tissue in which cells develop morphologically, express typ e-A receptors for the inhibitory neurotransmitter gamma-aminobutyric a cid (GABA) and form GABAergic synaptic connections. Criteria of cell s ize and shape allow reliable identification of granule and Purkinje ne urons, criteria confirmed by studies of the binding of antibodies to c albindin D28K and GABA. Both granule and Purkinje neurons express GABA (A) receptors, but granule neurons fall into two classes in terms of t heir sensitivity. Granule neurons which do not show spontaneous synapt ic currents are relatively insensitive to GABA, while granule neurons with synaptic currents are much more sensitive. The responses of Purki nje neurons to applications of 1 mu M GABA are relatively insensitive to Zn2+ ions (10 mu M), and are potentiated by chlordiazepoxide (100 m u M) and La3+ ions (100 mu M). Responses of innervated granule neurons , on the other hand, are blocked more Strongly by Zn2+ ions, are less affected by,chlordiazepoxide and are equally potentiated by La3+ ions. Hence these cultures provide a source of identifiable, functionally i nnervated cells which express distinct types of GABA(A) receptors.