Flow cytometry and immunochemical methods are applied to embryonic rat spinal and supraspinal regions to study the development, differentiation and cellular distribution of transmitters and their corresponding receptor- coupled alterations in membrane excitability. At present this multidisciplinary investigation is focused on elucidation of a developmental calendar outlining the expression of specific transmitters and their functional receptors with a primary focus on the development of the GABA phenotype and a secondary focus on the glutamate phenotype. Principal observations this year include: 1) immunological detection of GAD-related proteins during embryonic development of the rat spinal cord with low molecular weight proteins apparent in many neurons before the advent of AB:,the product of GAD enzyme activity; 2) progressive appearance of GABA+ fibers, then GABA+ neurons during embryogenesis along rostrocaudal and ventrodorsal axes in the spinal cord coincident with the appearance of high molecular weight GAD proteins; 3) postnatal emergence of a second set of GAD-related proteins with a subcellular distribution and colchicine sensitivity characteristic of vesicular transport in neurons also immunoreactive for embryonic GAD proteins; 4) biochemical dejection of GABA transiently derived from ornithine and increasingly synthesized by GAD in embryonic rat cortex; 5) sizable secretion of GABA in vitro under resting conditions from embryonic cortical neurons; 6) early embryonic appearance of functional voltage-gated Na+ channels and depolarizing GABA-A progesterone metabolite receptors in rat cortex, cerebellum and thalamus; 7) in situ hybridization evidence of GABA-A receptor subunit beta receptor message preceding a subunit message throughout the embryonic rat CNS; 8) emergence of depolarizing GABA-A receptors along a rostrocaudal gradient throughout the early embryonic chick CNS; 9) critical requirement of GABA-A receptors for chick spinal cord neuron adherence in vitro and process formation; 10) arrival of spinothalamic tract projections in the thalamus about the time of birth in the rat.
Li, Y X; Schaffner, A E; Barker, J L (1999) Astrocytes regulate the developmental appearance of GABAergic and glutamatergic postsynaptic currents in cultured embryonic rat spinal neurons. Eur J Neurosci 11:2537-51 |
Zhang, L; Ma, W; Barker, J L et al. (1999) Sex differences in expression of serotonin receptors (subtypes 1A and 2A) in rat brain: a possible role of testosterone. Neuroscience 94:251-9 |
Chandross, K J; Cohen, R I; Paras Jr, P et al. (1999) Identification and characterization of early glial progenitors using a transgenic selection strategy. J Neurosci 19:759-74 |
Behar, T N; Scott, C A; Greene, C L et al. (1999) Glutamate acting at NMDA receptors stimulates embryonic cortical neuronal migration. J Neurosci 19:4449-61 |
Silverman, W F; Alfahel-Kakunda, A; Dori, A et al. (1999) Separation of dorsal and ventral dopaminergic neurons from embryonic rat mesencephalon by buoyant density fractionation: disassembling pattern in the ventral midbrain. J Neurosci Methods 89:1-8 |