Phospho-ERK and sex steroids in the mPOA: involvement in male mouse sexual behaviour

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   Figure 1

   Activation of ERK by testosterone and its metabolites. Brain slices including mPOA were incubated 30 min in aCSF + DMSO (control), testosterone (T, 100 nM), dihydrotestosterone (DHT, 100 nM), oestradiol (E2, 100 nM) or testosterone 3-(O-carboxymethyl)oxime-BSA (T-BSA, 100 nM). (A) Representative blot detecting pERK, ERK and GAPDH in the mPOA after 30 min of incubation. (B) Densitometric evaluation of the Western blots. Results (pERK/ERK) are presented as mean percentage of the control group ± s.e.m., n = 7 in each group analysed by one-way ANOVA followed by Dunnett’s multiple comparison test, *P < 0.05 when compared to control group.
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   Figure 2

   Mating-induced ERK phosphorylation in the mPOA and sexual experience. (A) Experimental design used to analyse the effect of mating and sexual experience on ERK phosphorylation in the mPOA. N: naive male staying in home cage, N + S: naive male with sex stimulus killed 5 min after the first intromission, E: experienced male staying in home cage, E + S: experienced male with sex stimulus killed 5 min after the first intromission. Sexual behaviour expressed as (B) total anogenital sniffing time before the first intromission, (C) latency to the first intromission and (D) number of mounts for N + S and E + S males. Results are presented as mean ± s.e.m. and analysed by Student’s t test, *P < 0.05, **P < 0.01 compared to N + S group. (E) Representative blot detecting pERK, ERK and GAPDH in the mPOA for N, N + S, E and E + S males and densitometric evaluation. Results (pERK/ERK) are presented as mean percentage of the N group ± s.e.m. (n = 7 in each group) and analysed by two-way ANOVA followed by Bonferroni post hoc tests, *P < 0.05, ***P < 0,001, ^#P < 0.05 when compared to N + S group.
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   Figure 3

   Involvement of ERK phosphorylation in the induction of male sexual experience. (A) Experimental design used to analyse the effect of a unique administration of the ERK phosphorylation inhibitor SL-327 administration (30 mg/kg, i.p.) on sexual behaviour improvement. SL-327- and vehicle-injected groups were compared during the first and the second mating (separated by 14 days) for (B) total anogenital sniffing time before the first intromission, (C) latency to the first intromission and (D) mating duration. Results are presented as mean ± s.e.m. (n = 15 for vehicle group and n = 17 for SL-327 group) and analysed by two-way repeated measures ANOVA followed by Bonferroni post hoc tests. ^#P < 0.05, ^###P < 0,001 for sexual experience effect and *P < 0.05, **P < 0.01 when compared to mating 1 of vehicle group.
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   Figure 4

   Involvement of ERK phosphorylation in sexual behaviour, locomotor activity and olfactory preference of sexually experienced males. (A) Experimental design used to analyse the effect of SL-327 administration (30 mg/kg, i.p.) on sexual behaviour, locomotor activity, olfactory preference and ERK phosphorylation in the mPOA of sexually experienced males. Sexual behaviour expressed as (B) total anogenital sniffing time before the first intromission and (C) latency to the first intromission (n = 8 in each group) presented as mean ± s.e.m. and analysed by Student’s t test, *P < 0.05 when compared to vehicle group. Olfactory preference in D and E. (D) Olfactory preference score defined as the time spent sniffing the female – time spent sniffing the male/total time sniffing, (E) percentage of entries in female arm analysed by Student’s t test (n = 11 in each group). Locomotor activity in F and G. (F) Locomotor activity during the 120-min test, assessed by counting the number of beam interruptions every 5-min intervals, analysed by two-way repeated-measures ANOVA followed by Bonferroni post hoc test, (G) total locomotor activity, defined as the total number of beam interruptions during the 120-min test analysed by Student’s test (n = 11 in each group). (H) Representative blot detecting pERK and ERK in the mPOA of experienced male mice kept in their home cage without a female (home cage) or injected either with SL-327 (SL-327) or vehicle (vehicle), put in the presence of a receptive female and killed 5 min after the first intromission. (I) Densitometric evaluation of the Western blot. Results (pERK/ERK) are expressed as mean percentage of the home cage group ± s.e.m. and analysed by one-way ANOVA followed by Tukey post hoc test (n = 8 for vehicle and SL-327 groups, n = 5 for home cage group). *P < 0.05, **P < 0.01 compared to home cage group.

• © 2017 Society for Endocrinology