Figure 5. Estrous phase did not affect acquisition, post-abstinence, or reinstatement preference scores.

Estrous phase in female mice was measured at key points in the CPP procedure and its relationship to CPP behaviors was examined. (a) Estrous phase was measured at the midpoint of conditioning, the morning prior to conditioning day 4 of 6, and was found to have no influence on CPP acquisition in either control or nicotine (0.75 mg/kg, s.c.) conditioning groups. (b) Similarly, estrous phase on acquisition test day also did not affect CPP preference scores. (c) Estrous phase was also measured after 2 weeks of abstinence, and did not have a significant effect on post-abstinence CPP preference scores. (d) Finally, estrous phase as measured on reinstatement test day did not have a significant effect on stress-induced reinstatement of nicotine CPP. There was also no effect of saline vs. guanfacine pre-treatment on the relationship between estrous phase and reinstatement scores. p&e = proestrous and estrous, d&m = diestrous and metestrous, S = saline, G = guanfacine. *p < 0.05