Figure 2.
A, Frequency (Freq) of walking during 5 min samples after successive injections of saline and cocaine (10 mg/kg, i.p.) by rats exposed to 10 d of episodic stress (n = 24; light gray bar) and corresponding controls (n = 24; open bar) or to 36 d of continuous social stress (n = 22; dark gray bar) and corresponding controls (n = 22; open bar). B, Intravenous cocaine self-administration by rats exposed to 10 d of episodic stress (n = 14; light gray bars) and corresponding controls (n = 14; open bars) or exposed to 36 d of continuous social stress (n = 9; dark gray bars) and corresponding controls (n = 8; open bars). Left, Median number of ratios completed (break point) over three sessions of responding according to a PR schedule. Right, Total number of infusions accumulated during a 24 h unrestricted-access binge. All values are means ± SEM. Filled symbols and bars, Stressed animals; open symbols and bars, controls. **p < 0.01, compared with saline; #p < 0.05, ##p < 0.01, compared with the relevant control group.