Glutamate-immunoreactive sensory neurons in quail neural crest cell culture

This study addresses the question of whether embryonic sensory neuroblasts of the quail are glutamate (Glu)-immunoreactive as a neurotransmitter in vivo and when grown in neural crest cell culture. Using a monoclonal antibody against carbodiimide-treated glutamate, we found a subset of neural crest-derived cells in culture. They were large, round and contained long pseudouni- or bipolar processes. There was Glu-immunoreactivity in the cytoplasm of the soma and more intense fluorescence within processes. Double-labeling experiments using a monoclonal antibody to Glu in conjunction with polyclonal antibodies to either neurofilament (NF), substance P (SP), or tyrosine hydroxylase (TH) revealed that: (1) the Glu-immunoreactive cells are a subpopulation of NF-positive sensory neuroblasts; (2) intensely Glu-immunoreactive cells were usually SP-negative. However, cells less intensely staining with both antibodies were observed as well; (3) the Glu-immunoreactive cells were TH-negative, whereas TH-positive adrenergic neuroblasts were Glu-negative; and (4) frozen sections of the spinal ganglia of 9- and 15-day-old quail embryos contained Glu-immunoreactive cells. These data combined indicate that the Glu-immunoreactive cells are a subpopulation of the sensory neuroblasts that were previously identified in neural crest cell cultures with antibodies against NF proteins and the stage-specific embryonic antigen 1 (SSEA-1). The results should prove valuable in future studies on the mechanisms that govern neural crest cell differentiation into autonomic and sensory neurons.