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. Author manuscript; available in PMC: 2010 Aug 2.
Published in final edited form as: Eur J Neurosci. 2008 Nov;28(10):2028–2040. doi: 10.1111/j.1460-9568.2008.06479.x

Fig. 2.

Fig. 2

Cocaine inhibition of VTA GABA neuron ICPSDs in vivo: time course and comparison to dopamine agonists, VSSC blockers and DAT inhibitors. (A) The inset shows a 1.0-s trace of a representative VTA GABA neuron spike in association with brief (50 ms), high frequency (200 Hz) stimulation of the IC. The horizontal bar above the stimulus artifacts indicates the time of the stimulus train. VTA GABA neurons evince multiple spike discharges for hundreds of ms following IC stimulation. These are termed IC-induced poststimulus spike discharges, or ICPSDs. The peristimulus spike histogram (PSH) below the trace shows the average of 12 IC stimulation trials on ICPSDs obtained from this representative VTA GABA neuron following i.v. saline. The stimulus artifacts in the PSH are omitted to illustrate spikes only. The bottom PSH trace shows the effects of 1.0 mg/kg i.v. cocaine on ICPSDs in this same neuron 1.0 min after cocaine injection. Note that cocaine markedly decreased VTA GABA neuron ICPSDs at this dose level. (B) This graph summarizes the time course of cocaine inhibition of VTA GABA neuron ICPSDs at the 1.0 mg/kg dose level. Note the marked and pronounced inhibition of ICPSDs at 1 min with recovery in 30 min (n = 5). (C) Cocaine significantly reduced ICPSDs at all dose levels tested, cocaine methiodide did not significantly alter them at any dose level, lidocaine, similar to cocaine, significantly reduced them at all dose levels tested, and methamphetamine did not significantly alter them at any dose level. *P < 0.005 and **P < 0.0005. (D) This graph summarizes the effects of DA receptor antagonists on i.v. cocaine inhibition of VTA GABA neuron ICPSDs at 1.0 min after injection. The ability of 1.0 mg/kg cocaine to reduce ICPSDs was not affected by a dose of saline administered 10 min prior to cocaine. Intravenous administration of the D1/D5 receptor antagonist SCH23390 had no effect on ICPSDs, nor on the ability of 1.0 mg/kg cocaine to reduce them when administered 10 min prior to cocaine (n = 5). Similarly, i.v. administration of the D2/D3 receptor antagonist eticlopride had no effect on ICPSDs, nor on the ability of 1.0 mg/kg cocaine to reduce them when administered 10 min prior to cocaine (n = 5). *P < 0.005.