A, Active lever presses for animals used in studying the behavioral effects of St-Ht31 peptide on reinstatement of cocaine seeking. B, Microinjection of St-Ht31 peptide significantly impaired reinstatement compared to microinjection of St-Ht31P. Active lever presses are shown as total presses over a 2 hr reinstatement trial. C, Lack of effect by St-Ht31 on distance traveled in response to an acute cocaine challenge (10 mg/kg, i.p.). *p≤ 0.05, comparing control to active peptide using a two-tailed Student's paired t-test.