Nigrostriatal dopaminergic neurons exhibit tonic and phasic patterns of neuronal firing activity. HTT also facilitates vesicular transport and synaptic transmission and controls neuronal gene transcription. Neurons fired in a pattern resembling human neuronal patterns. Calcium granules are seen within the cytoplasm of neuronal and glial cells. Glutamate transporters, EAAT and VGLUT, are found in neuronal and glial membranes. Apoptotic death is crucial for the correct population size of neuronal and glial cells. Cells called guidepost cells assist in the guidance of neuronal axon growth. Endothelial proliferation, hyperplasia of capillaries, demyelination and neuronal loss can also occur. Actin is predominately found at the tips of axons and dendrites during neuronal development. These proteins play key roles in neuronal function. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. These depolarization events have shown to be key in neuronal development. Grey matter contains most of the brain's neuronal cell bodies. Later ligand-binding studies provided direct evidence of binding sites for baclofen on central neuronal membranes. The latter also decreases reelin expression in neuronal culture.