“…In the female, the gonadal hormone estrogen modulates many behaviors and physiological processes besides those associated with reproduction (Segarra & Lee, 2004). One of these is the locomotor response to psychostimulants such as amphetamine and cocaine (Peris, Decambre, Coleman-Hardee, & Simpkins, 1991; Pittman & Fibiger, 1983; Sell, Scalzitti, Thomas, & Cunningham, 2000; Sircar & Kim, 1999). Repeated administration of psychostimulants results in a progressive increase in locomotion, referred to as sensitization.…”