IMMUNOHISTOCHEMICAL STUDIES OF GABA AND PARVALBUMIN IN THE DEVELOPINGHUMAN CEREBELLUM

The localization of GABA and parvalbumin was studied in the developing cerebellum of human fetuses from 16 to 28 weeks of gestation. The avi din-biotin complex immunohistochemical method combined with silver sta ining were used to reveal the presence of GABA- and parvalbumin-positi ve neurons and nerve fibres. As early as the 16th week of gestation, G ABA immunopositivity was observed in the cerebellar cortex and the dee p nuclei. GABA-positive neurons included Purkinje cells, stellate and basket cells of the cerebellar cortex and neurons in the deep nuclei. The gradient of immunoreactivity increased with the maturing cells, be ing weak at 16 weeks and becoming markedly pronounced at 28 weeks of g estation. GABA-immunopositive messy fibres were observed in the granul ar cell layer at 16 weeks, and by 28 weeks, a robust fibre network was present in the cortex and deep nuclei. Immunohistochemical localizati on for parvalbumin indicates that weak immunoreactivity was observed i n Purkinje cells, stellate and basket cells at 16 weeks of gestation, increasing in intensity with advancing age, notably in the Purkinje ce lls which had acquired an elaborate arbor of neurites at 28 weeks of g estation. In the deep nuclei, parvalbumin-positive cells and nerve fib res were observed throughout the 16 to 28 week period. These results i ndicate that GABA- and parvalbumin-positive neurons and fibres appeare d as early as 16 weeks of gestation, expressing a high degree of immun oreactivity by the 28 week of fetal age.