GABAergic neurons in cultures derived from three-, six- or eight-day-old chick embryo: a biochemical and immunocytochemical study.

Cultures were prepared from 3-, 6- and 8-day-old chick embryos. Whole chick embryos were dissociated by sieving through a nylon mesh for E3 cultures and cerebral hemispheres for E6 and E8 cultures. The dispersed cells were plated onto poly-L-lysine coated culture dishes in Dulbecco's modified Eagle's medium, containing 10% fetal bovine calf serum. Growth patterns in these cultures have been previously described. Biochemical and immunocytochemical markers were used to identify GABAergic neurons in culture. Neurons exhibiting GABA-like immunoreactivity were present in all 3 types of cultures as early as 4-6 days in culture. The developmental profile of glutamic acid decarboxylase (GAD) derived from 3-day-old whole chick embryo cultures showed low activities whereas the enzyme activity markedly rose in cultures derived from 6- or 8-day-old chick embryo cerebral hemispheres during the first two weeks. The changes in GAD activity observed in these cultures are interpreted to reflect the maturational state of GABAergic neurons and also their responsiveness to microenvironmental factors.