Fig. 4.
Phasic DA neuron stimulation leads to transient DA release and place preference. (A and B) Effect of phasic (50 Hz) (A) and tonic (1 Hz) (B) stimulation on place preference. (Left) Time spent in each chamber during preference test. (Right) Comparison of preference scores; for A, n = 7, and for B, n = 6. *P < 0.05. (C) Relative effects of stimulation frequency examined by using the difference scores for phasic, tonic, and nonassociative control (same as No Stim in Fig. 3E) cohorts. (D) FSCV measurements of VTA stimulation–triggered transient DA release in NAc in anesthetized TH∷IRES-Cre mice. (Top) Representative voltammetry traces during phasic (25 flashes per 50 Hz) and tonic (16 flashes per 1 Hz) stimulation of VTA. (Insets) Background-subtracted voltammogram taken from the peak of stimulation, indicating that signal measured is DA on the basis of comparison to voltammograms of DA obtained in vitro. (Bottom) All background-subtracted voltammograms recorded over the 20-s interval. y axis is applied potential (Eapps versus Ag/AgCl reference electrode); x axis is the time at which each voltammogram was recorded. Current changes at the electrode are encoded in color. DA can be seen during stimulation at the feature ∼0.650 V (oxidation peak encoded as green) and between ∼−0.20 V and ∼−0.25 V at the end of the voltage scan. (E) Comparison of phasic and tonic light-evoked DA transients (n = 3).