Chronic exposure to anabolic androgenic steroids alters neuronal function in the mammalian forebrain via androgen receptor- and estrogen receptor-mediated mechanisms - PubMed (original) (raw)

Chronic exposure to anabolic androgenic steroids alters neuronal function in the mammalian forebrain via androgen receptor- and estrogen receptor-mediated mechanisms

Carlos A A Penatti et al. J Neurosci. 2009.

Abstract

Anabolic androgenic steroids (AAS) can promote detrimental effects on social behaviors for which GABA type A (GABA(A)) receptor-mediated circuits in the forebrain play a critical role. While all AAS bind to androgen receptors (AR), they may also be aromatized to estrogens and thus potentially impart effects via estrogen receptors (ER). Chronic exposure of wild-type male mice to a combination of chemically distinct AAS increased action potential (AP) frequency, selective GABA(A) receptor subunit mRNAs, and GABAergic synaptic current decay in the medial preoptic area (mPOA). Experiments performed with pharmacological agents and in AR-deficient Tfm mutant mice suggest that the AAS-dependent enhancement of GABAergic transmission in wild-type mice is AR-mediated. In AR-deficient mice, the AAS elicited dramatically different effects, decreasing AP frequency, spontaneous IPSC amplitude and frequency and the expression of selective GABA(A) receptor subunit mRNAs. Surprisingly, in the absence of AR signaling, the data indicate that the AAS do not act as ER agonists, but rather suggest a novel in vivo action in which the AAS inhibit aromatase and impair endogenous ER signaling. These results show that the AAS have the capacity to alter neuronal function in the forebrain via multiple steroid signaling mechanisms and suggest that effects of these steroids in the brain will depend not only on the balance of AR- versus ER-mediated regulation for different target genes, but also on the ability of these drugs to alter steroid metabolism and thus the endogenous steroid milieu.

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Figures

Figure 1.

Effects of chronic AAS treatment on AP frequency and patterning in wild-type and AR-deficient male mice. A, Average AP frequency under control (black) and AAS treatment (gray) conditions from wild-type (left) and AR-deficient (right) mice. Asterisks indicate values from AAS-treated subjects were significantly different from their age-matched oil-injected controls in the same genotype. B, Representative examples of action potentials (top) and autocorrelograms (bottom) corresponding to irregular, bursty, and regular firing patterns. C, The percentage of neurons displaying irregular, bursty or regular firing patterns as assessed by autocorrelational analyses of MPN neurons from control or AAS-treated wild-type (left) or AR-deficient (right) mice. Recordings were made from 8 mice for each treatment condition and each genotype.

Figure 2.

Effects of chronic AAS treatment on GABAA receptor expression and function in the mPOA of wild-type male mice. A, Data indicating average levels of subunit mRNAs in tissue isolated from the mPOA from 8 wild-type mice treated with the AAS mixture for 6 weeks. The mRNA levels for each subunit normalized to 18S rRNA from 8 oil-injected control animals were analyzed and relative subunit mRNA levels for controls were set to 1.00 for each subunit mRNA (horizontal line). Values (2−ΔΔCT) for treated animals were plotted relative to this control value of 1.00. B, Averaged sIPSCs recorded from MPN neurons in slices isolated from control (black line) and AAS-treated (gray line) wild-type mice. C, D, Average _I_peak (left), τw (center) and charge transfer (_Q_tot; right) (C) and frequency for sIPSCs from these MPN neurons of control (black bars) and AAS-treated (gray bars) mice (D). Asterisks indicate values from AAS-treated subjects that were significantly different from their age-matched oil-injected controls. Recordings were made from 16 mice for each treatment condition.

Figure 3.

GABAA receptor subunit mRNA levels in the mPOA of wild-type and AR-deficient mice. A, Data are presented as the 2−ΔCT values indicating the relative levels of GABAA receptor subunit expression in the mPOA of control wild-type (black) and control AR-deficient (white) mice. B, Data indicating average levels of subunit mRNAs in tissue isolated from the mPOA from AR-deficient mice treated with the AAS mixture for 6 weeks. For data shown in B, values from oil-injected control animals were analyzed and relative subunit mRNA levels for controls were set to 1.00 for each subunit mRNA (horizontal line). The 2−ΔΔCT values for AAS-treated animals were plotted relative to this control value of 1.00. Analyses were made from 8 control and 8 treated animals of each genotype.

Figure 4.

Effects of chronic AAS treatment on GABAA receptor function in the MPN of AR-deficient mice. A, Averaged sIPSCs recorded from MPN neurons in slices isolated from control and AAS-treated AR-deficient mice. B, C, Average _I_peak (left), τw (center) and charge transfer (_Q_tot; right) (B) and frequency for sIPSCs from these MPN neurons of control and AAS-treated mice (C). D, Average mIPSCs recorded from MPN neurons of control and AAS-treated AR-deficient mice. E, F, Average _I_peak (left), τw (center), and charge transfer (_Q_tot; right) (E) and frequency for mIPSCs from these MPN neurons (F). Black lines and bars, Control; gray lines and bars, AAS-treated. Asterisks indicate values from AAS-treated subjects that were significantly different from their age-matched oil-injected controls. Recordings were made from 12 to 16 mice for each treatment condition.

Figure 5.

Effects of pharmacological manipulation of estrogens on AAS-dependent modulation of GABAergic sIPSC amplitudes in the MPN of the AR-deficient Tfm mouse. Graphical representation of averaged _I_peak from AR-deficient Tfm mice chronically treated with oil alone (Control), the AAS mixture in oil (AAS), tamoxifen (Tx), the AAS mixture and tamoxifen (Tx+AAS), formestane (Frm), or the AAS mixture and formestane (Frm+AAS). Data for Control and AAS are the same as shown in Figure 5. Identical letters (among the a–d designations) indicate means that were not statistically different from one another as assessed by two-way ANOVA followed by the means comparison by least significant means. In a separate cohort of AR-deficient Tfm mice, experiments were later performed to determine the effects of concurrent treatment with 17β-estradiol and the AAS mixture (E2+AAS) or 17β-estradiol (E2) alone versus control. The identical letter (a') indicates that when concurrently treated with 17β-estradiol and AAS, the AAS did not significantly diminish _I_peak. For both sets of data, numbers in parentheses indicate numbers of cells. Recordings were made from 8 to 12 mice for each treatment condition.

Figure 6.

AAS-dependent changes in Aromatase mRNA in the mPOA. Data are presented as the 2−ΔCT values indicating the relative levels of aromatase (Cyp19) mRNA in tissue isolated from the mPOA from wild-type (left) and AR-deficient Tfm (right) adult male mice injected with oil (control) or treated with the AAS mixture (AAS) for 6 weeks. Identical letters indicate means that were not statistically different from one another as assessed by two-way ANOVA followed by the means comparison by least significant means. Analyses were made from 8 control and 8 treated animals of each genotype.

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Chronic exposure to anabolic androgenic steroids alters neuronal function in the mammalian forebrain via androgen receptor- and estrogen receptor-mediated mechanisms - PubMed (original) (raw)