gamma-Aminobutyric acid (GABA) is an important inhibitive neurotransmitter in central nervous system (CNS). Many studies have been made about the distribution of GABA-ergic neurons in the spinal cord (SC), but little is known about the morphology of GABA-ergic spinal cord neuron (SCN) in culture. Moreover, whether GA-BA-ergic neuron existed in dorsal root ganglion (DRG) or not is still under discussion. Considering together with the fact that the same neuron can synthesize different. kinds of neurotransmitter in different periods of development, we find that it is attractive to study the GABA immunoreactivity of cultured SCNs and DRG cells. The SC and DRG were dissected from 12-14 day old mouse (C57BL/6J) embryo and plated at a density of 1 x 10(6)-2 x 10(6) cells per dish. At 5 day in vitro (DIV), the cells reaggregate and form complicated neurite network. While SCNs varies in the morphology of cell body and neurite, DRG cells of different sizes can be easily discriminated by their round cell bodies and sharply defined nuclei and nucleoli, and their sizes do not undergo major change during the culture period. Immunoreaction was performed by using a polyclonal anti-GABA serum (rabbit) and PAP procedure. Two types of immunoreactive SCNs were observed: 1. SCNs with intensely positive reacted somata, nucleoli, and neurites. 2. SCNs with reactivity shown only on part or whole of neurites and cell membrane while the cell body is negative (to be considered as the result of GABA uptake).(ABSTRACT TRUNCATED AT 250 WORDS)