Colchicine delays the estrogen-induced copulatory response in the ovariectomized female rat

A study was made of the effect of colchicine on the lordotic response to estradiol benzoate (EB) plus progesterone in ovariectomized rats. Colchicine (0.5 + 0.25 mg/kg s.c.) given in connection with the EB treatment inhibited the response elicited by progesterone 24 or 48 h after administration of EB. In contrast, significantly more colchicine-treated animals responded when progesterone was given at 118 h. This increase in lordotic response occurred at a time when normally the response has declined. The response was not enhanced by the protein synthesis inhibitors anisomycin (50 mg/kg s.c.) or cycloheximide (1 mg/kg s.c.). The results suggest that an impairment of axonal transport by colchicine may lead to storage of lordosis-promoting products, which are released when the colchicine effect has worn off.