Figure 8.

Cocaine exposure alters vHPC-evoked excitation/inhibition balance. A, Schematic of cocaine sensitization experiments. Following habituation, animals received daily intraperitoneal injections of cocaine (15 mg/kg) or saline. After 5 treatment days, animals were either given a cocaine challenge to test for behavioral sensitization or used for in vitro recordings. B, Average postinjection locomotion across days for saline- and cocaine-treated animals, depicted as means ± SEM. C, Example of locomotion after the cocaine challenge on day 6 for cocaine- and saline-treated animals. D, Average vHPC-evoked EPSCs and disynaptic IPSCs in D1+ and D1− MSNs following saline (left) or cocaine (right) treatment, recorded at −70 or +20 mV in the presence of CPP. E, Left, Quantification of EPSC amplitudes, indicating a loss of bias after cocaine exposure. Connected data points are pairs of D1+ and D1− MSNs. Data represent means ± SEM. Right, Ratio of D1+ to D1− EPSC amplitudes, shown as geometric means with 95% confidence intervals. F, Similar to E for vHPC-evoked disynaptic IPSCs, showing lack of effect on relative inhibition of D1+ and D1− MSNs. G, Quantification of the E/I ratio, calculated from vHPC-evoked EPSC and IPSC amplitudes at D1+ and D1− MSNs, shown as geometric means with 95% confidence intervals. Connected data points represent pairs of neurons. Note the logarithmic axes in E–G. n.s., Not significant. *p < 0.05; **p < 0.01.