Fig. 2.

VTA DA neurons were excited by theta stimulation of dorsal CA3, and non-DA neurons were inhibited. (A) Representative neuron excited (E-E) by theta stimulation. (Top) Spike train and mean frequency. Red bar indicates time of stimulation. Digitized waveform (bottom left), and expanded view (bottom right) of spike train from top. Red rectangle corresponds to the same time period as red bar in top graph. (B) Representative neuron inhibited (I-I) by theta stimulation. Descriptions are the same as in (A). Stimulation artifacts have been digitally removed from (A) and (B) for clarity. (C) Time course of excitatory and inhibitory responses in E-E and I-I neurons, respectively (Dunnett’s post hoc test, *P < 0.001, **P < 0.0001). Red bar indicates time of stimulation. (D) Photomicrographs of representative juxtacellularly labeled E-E and I-I neurons processed to reveal neurobiotin fills, and of tyrosine hydroxylase immunoreactivity to identify dopaminergic and nondopaminergic neurons. Midline is to the left for E-E photomicrographs and to the right for I-I photomicrographs. Dorsal is up for all images. Scale bars, 50 μm. Biotin, neurobiotin; TH, tyrosine hydroxylase.