DEPOLARIZING STIMULI INDUCE HIGH-LEVELS OF DOPAMINE SYNTHESIS IN FETAL-RAT SENSORY NEURONS

To investigate the role of activity-dependent mechanisms in sensory tr ansmitter development, we examined the effect of depolarizing stimuli on tyrosine hydroxylase expression and dopamine synthesis in cells of the fetal rat petrosal ganglion, a model of catecholaminergic sensory neurons. Although dopaminergic traits detectable in only 10-20% of gan glion exposure to depolarizing concentrations of potassium chloride (4 0 mM) or veratridine (10 mu M) in culture induced tyrosine hydroxylase expression in 100% of petrosal neurons and a 10-fold increase in dopa mine content. Tyrosine hydroxylase expression remained elevated in a s ubset of neurons following return to control conditions, suggesting th at chronic depolarization elicits a phenotypic switch in some cells. T hese data show for the first time that transmitter expression in devel oping sensory neurons can be regulated by activity-related cues.