Synaptogenesis in the foetal and neonatal cerebellar system. 2. Pontine nuclei and cerebellar cortex.

Precise temporal and spatial sequences of synaptogenesis were demonstrated in 172 human foetuses and neonates post-mortem in transverse paraffin sections of pons and cerebellar vermis and hemispheres, using synaptophysin immunoreactivity of this protein of synaptic vesicular walls. The pontine nuclei exhibit a transitory patchy pattern not predicted from the uniform histology and reminiscent of the corpus striatum; synaptic vesicle reactivity appears at 20 weeks and is uniform by 34 weeks. In the cerebellar cortex, the vermis matures sooner than the cerebellar hemispheres and the paravermal portions earlier than the lateral folia. The earliest synapses occur around the somata of Purkinje neurons and later in the internal granular layer, but synaptic glomeruli are not well formed until after 26 weeks. The normal patterns here shown, together with earlier data of the Guillain-Mollaret triangle, provide controls for the interpretation of synaptic delay or precociousness and other pathological patterns in malformations, genetic/metabolic conditions and prenatal acquired insults affecting the human foetus.