Neonatal rat cerebellar granule and Purkinje neurons in culture express different GABAA receptors.

We have established a culture system for microexplants of rat cerebellar cortical tissue in which cells develop morphologically, express type-A receptors for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and form GABAergic synaptic connections. Criteria of cell size and shape allow reliable identification of granule and Purkinje neurons, criteria confirmed by studies of the binding of antibodies to calbindin D28K and GABA. Both granule and Purkinje neurons express GABAA receptors, but granule neurons fall into two classes in terms of their sensitivity. Granule neurons which do not show spontaneous synaptic currents are relatively insensitive to GABA, while granule neurons with synaptic currents are much more sensitive. The responses of Purkinje neurons to application of 1 microM GABA are relatively insensitive to Zn2+ ion (10 microM), and are potentiated by chlordiazepoxide (100 microM) and La3+ ions (100 microM). 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 innervated cells which express distinct types of GABAA receptors.