Fig. 2.

Frequency distribution of mRNAs for neurotransmitter synthesizing enzymes, neuropeptides, and Ca²⁺-binding proteins in SN and VTA.A, Percentage of neurons coexpressing GAD and TH mRNA versus age; numbers at the base of histogram bars indicate the total number of neurons in each age group bin (2 d).B1, Percentage of neurons expressing the neuropeptides CCK and NT and the Ca²⁺-binding proteins CR, PV, and CB. B2, Percentage of DA and Gaba neurons that are CCK positive. CCK is preferentially expressed in DA neurons.B3, Percentage of CB-positive neurons in the SNc, SNr, and VTA. CB was found preferentially in the VTA (**p < 0.01).