Cocaine-induced sensitization correlates with testosterone in male Japanese quail but not with estradiol in female Japanese quail

Abstract

Research has indicated that gonadal hormones may mediate behavioral and biological responses to cocaine. Estrogen, in particular, has been shown to increase behavioral responding to cocaine in female rats relative to male rats. The current study investigated the effect of cocaine on locomotor activity and hormonal correlates in male and female Japanese quail (Coturnix japonica). In Japanese quail, circulating hormone levels can be manipulated without surgical alterations via modifying the photoperiod. Male and female quail were housed on either an 8L:16D (light:dark) or 16L:8D (light:dark) cycle for 21 days. Blood samples were taken prior to the beginning of the experiment and assays were performed to determine levels of testosterone (T) and estradiol (E2). Quail were given injections of saline or cocaine (10 or 20 mg/kg) once a day for 10 days. Immediately after each injection, birds were placed in open field arenas and distance travelled was measured for 30 min. Results showed that male quail housed under long-light conditions exhibited cocaine-induced sensitization to 10 mg/kg cocaine which was correlated with high levels of plasma T. Female quail housed under short-light conditions demonstrated sensitization to 10 mg/kg cocaine, but this was not correlated with levels of plasma E2. The current findings suggest that cocaine-induced locomotor activity was associated with T in males but not with E2 in females.

Intramuscular Route of Administration Increases Potency in Eliciting Cocaine-Induced Behavioral Sensitization

“…Similar to rodent models, previous research in quail replicates the findings that IP administration of chronic cocaine dose-dependently enhances locomotor activity and induces cocaine sensitization [10, 11]. Specifically, cocaine sensitization is evident with IP administration of cocaine ranging from doses of 10 to 23 mg/kg in both rodents and quail using similar procedures [e.g., 13, 14, 15, 11].…”

“…In preclinical studies, the majority of cocaine sensitization studies utilize intraperitoneal (IP) injections as the primary route of administration in rodents [e.g., 5, 6, 7, 8] and quail [e.g., 9, 10, 11, 12]. Similar to rodent models, previous research in quail replicates the findings that IP administration of chronic cocaine dose-dependently enhances locomotor activity and induces cocaine sensitization [10, 11].…”

“…The results showed that all of the doses induced cocaine sensitization and cocaine dose-dependently decreased preening. Of particular interest, cocaine sensitization occurred at much lower doses (1 and 3 mg/kg) in pigeons using the IM route of administration compared to rodents and quail given IP administration of cocaine [e.g., 9–11, 23–27]. …”

“…Doses of 3 mg/kg and 10 mg/kg and were chosen based on previous research that demonstrated cocaine-enhanced locomotor activity in pigeons with IM injections [22] and quail with IP injections [10, 11], respectively.…”

“…Typically, in both rodents and quail, cocaine sensitization is measured during 30 min locomotor activity sessions with IP injections of cocaine [e.g., 14, 15, 11). Pinkston & Branch [22] gave 150 min cocaine locomotor activity sessions.…”