Depolarizing stimuli induce high levels of dopamine synthesis in fetal rat sensory neurons.

To investigate the role of activity-dependent mechanisms in sensory transmitter 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 are normally detectable in only 10-20% of ganglion neurones, exposure to depolarizing concentrations of potassium chloride (40 mM) or veratridine (10 microM) in culture induced tyrosine hydroxylase expression in 100% of petrosal neurons and a 10-fold increase in dopamine content. Tyrosine hydroxylase expression remained elevated in a subset of neurons following return to control conditions, suggesting that chronic depolarization elicits a phenotypic switch in some cells. These data show for the first time that transmitter expression in developing sensory neurons can be regulated by activity-related cues.