Fig. 1. (A) Effects of acute injections of estradiol (E₂; 500 μg/kg) on the four components of male sexual behavior (NG: neck grab, MA: mount attempt, M: mount and CCM: cloacal contact movements) measured after 5, 15 and 30 min during experiment 1 where all subjects were used as their own control. Data were analyzed by one-way ANOVAs with repeated measures. (B) Time–response curve for the effect of acute injections of estradiol on male sexual behavior. All results are expressed as a function of the percentage of the control values in each test. Data were analyzed by two-way ANOVA with time and treatment as repeated factors; ^*p < 0.05; n = 8 for all data.

Fig. 2. Effects of an acute injection of testosterone (T) on the mount attempt (MA) and cloacal contact movement (CCM) frequencies measured 15, 30, 45 or 60 min later. No significant change could be detected. All results are expressed as a function of the percentage of the control values in each test (see Fig. 1B). All results are expressed as means ± S.E.M. The black bars represent the vehicle treatment (Veh), while the white bars represent the effect of testosterone (T). Numbers in the bars refer to the number of subjects tested.

Fig. 3. Effects of an acute injection of estradiol (E₂) on the mount attempt (MA) and cloacal contact movement (CCM) frequencies measured 15 min later during experiment 2. The black bars represent the vehicle treatment (Veh; n = 9), while the white bars represent the effect of estradiol (E₂; n = 9).

Fig. 4. Interactions between the effects of an acute injection of estradiol (E₂) and the performance of sexual behavior on the serotonergic and dopaminergic activity measured in the preoptic area (HPOA) or cerebellum. Each panel represents the results of one ANCOVA that identified significant effects of the covariate (B) or significant interactions between the covariate and the group effect (A, C–F). A plot of all individual data is found in each panel together with the regression line reflecting the relationship between the amine level (or ratio) and the behavioural frequencies (vehicle: white circles; E₂: black circles).

Levels of monoamines measured in the four brain areas after vehicle or E₂ injection

F-ratios and probabilities obtained by one-way analysis of variance of these data with the treatment as independent factor are also presented. Significant probabilities (p < 0.05) are in bold while statistical trends (0.10 > p > 0.05) are underlined. All results are expressed as means ± S.E.M.

Analysis of the covariance (ANCOVA) of monoamines’ levels and ratios in the four brain areas with the treatment as independent factor and the frequencies of mount attempts (MA) or cloacal contact movements (CCM) as covariate

The table presents the probabilities associated with the effects of the main factor (E₂ vs. control injection), of the covariate (behavior frequencies) and of their interaction. All probabilities are associated with degrees of freedom of 1 and 16. Significant probabilities (p < 0.05) are in bold while trends (0.10 > p > 0.05) are underlined.