ABSTRACT
Anabolic androgenic steroids (AAS), synthetic testosterone derivatives that are used for ergogenic purposes, alter neurotransmission and behaviors mediated by GABA(A) receptors. Some of these effects may reflect direct and rapid action of these synthetic steroids at the receptor. The ability of other natural allosteric steroid modulators to alter GABA(A) receptor-mediated currents is dependent upon the phosphorylation state of the receptor complex. Here we show that phosphorylation of the GABA(A) receptor complex immunoprecipitated by ß(2)/ß(3) subunit-specific antibodies from the medial preoptic area (mPOA) of the mouse varies across the estrous cycle; with levels being significantly lower in estrus. Acute exposure to the AAS, 17α-methyltestosterone (17α-MeT), had no effect on the amplitude or kinetics of inhibitory postsynaptic currents in the mPOA of estrous mice when phosphorylation was low, but increased the amplitude of these currents from mice in diestrus, when it was high. Inclusion of the protein kinase C (PKC) inhibitor, calphostin, in the recording pipette eliminated the ability of 17α-MeT to enhance currents from diestrous animals, suggesting that PKC-receptor phosphorylation is critical for the allosteric modulation elicited by AAS during this phase. In addition, a single injection of 17α-MeT was found to impair an mPOA-mediated behavior (nest building) in diestrus, but not in estrus. PKC is known to target specific serine residues in the ß(3) subunit of the GABA(A) receptor. Although phosphorylation of these ß(3) serine residues showed a similar profile across the cycle, as did phosphoserine in mPOA lysates immunoprecipitated with ß2/ß3 antibody (lower in estrus than in diestrus or proestrus), the differences were not significant. These data suggest that the phosphorylation state of the receptor complex regulates both the ability of AAS to modulate receptor function in the mPOA and the expression of a simple mPOA-dependent behavior through a PKC-dependent mechanism that involves the ß(3) subunit and other sites within the GABA(A) receptor complex.
Subject(s)
Anabolic Agents/pharmacology , Androgens/pharmacology , Estrous Cycle/physiology , Methyltestosterone/pharmacology , Preoptic Area/drug effects , Receptors, GABA-A/metabolism , Androstane-3,17-diol/pharmacology , Animals , Anxiety/psychology , Behavior, Animal/drug effects , Blotting, Western , Female , Immunoprecipitation , Male , Mice , Mice, Inbred C57BL , Nerve Tissue Proteins/isolation & purification , Nerve Tissue Proteins/metabolism , Nesting Behavior/drug effects , Phosphorylation , Phosphoserine/metabolism , Preoptic Area/metabolism , Protein Kinase C/metabolism , Real-Time Polymerase Chain Reaction , Sexual MaturationABSTRACT
Anabolic androgenic steroids (AAS) are synthetic derivatives of testosterone originally developed for clinical purposes but are now predominantly taken at suprapharmacological levels as drugs of abuse. To date, almost 100 different AAS compounds that vary in metabolic fate and physiological effects have been designed and synthesised. Although they are administered for their ability to enhance muscle mass and performance, untoward side effects of AAS use include changes in reproductive and sexual behaviours. Specifically, AAS, depending on the type of compound administered, can delay or advance pubertal onset, lead to irregular oestrous cyclicity, diminish male and female sexual behaviours, and accelerate reproductive senescence. Numerous brains regions and neurotransmitter signalling systems are involved in the generation of these behaviours, and are potential targets for both chronic and acute actions of the AAS. However, critical to all of these behaviours is neurotransmission mediated by GABA(A) receptors within a nexus of interconnected forebrain regions that includes the medial preoptic area, the anteroventral periventricular nucleus and the arcuate nucleus of the hypothalamus. We review how exposure to AAS alters GABAergic transmission and neural activity within these forebrain regions, taking advantage of in vitro systems and both wild-type and genetically altered mouse strains, aiming to better understand how these synthetic steroids affect the neural systems that underlie the regulation of reproduction and the expression of sexual behaviours.
Subject(s)
Anabolic Agents/pharmacology , Androgens/pharmacology , Prosencephalon/drug effects , Synapses/drug effects , gamma-Aminobutyric Acid/metabolism , Animals , Mice , Neurons/drug effects , Neurons/metabolism , Prosencephalon/metabolism , Synapses/metabolism , Synaptic Transmission/drug effects , Synaptic Transmission/physiologyABSTRACT
Anabolic androgenic steroids (AAS) are synthetic derivatives of testosterone that are illicitly self-administered for enhancement of performance and body image, but which also have significant effects on the brain and on behavior. While the stereotypical AAS user is an adult male, AAS abuse in women is rapidly increasing, yet few studies have examined AAS effects in female subjects. We have assessed the effects in female mice of a combination of commonly abused AAS on neuronal activity and neurotransmission mediated by GABA type A (GABA(A)) receptors in the medial preoptic nucleus (MPN); a nexus in the circuits of the hypothalamus and forebrain that are critical for the expression of social behaviors known to be altered in AAS abuse. Our data indicate that chronic exposure to AAS resulted in androgen receptor (AR)-dependent upregulation of alpha(5), beta(3) and delta subunit mRNAs. Acute application of the alpha(5) subunit-selective inverse agonist, L-655,708 (L6), indicated that a significant fraction of the synaptic current is carried by alpha(5)-containing receptors and that AAS treatment may enhance expression of alpha(5)-containing receptors contributing to synaptic, but not tonic, currents in the MPN. AAS treatment also resulted in a significant decrease in action potential frequency in MPN neurons that was also correlated with an increased sensitivity to L-655,708. Our data demonstrate that chronic exposure to multiple AAS elicits significant changes in GABAergic transmission and neuronal activity that are likely to reflect changes in the expression of alpha(5)-containing synaptic receptors within the MPN.
Subject(s)
Anabolic Agents/adverse effects , Androgens/adverse effects , Methyltestosterone/adverse effects , Nandrolone/analogs & derivatives , Testosterone/analogs & derivatives , Action Potentials , Anabolic Agents/administration & dosage , Androgens/administration & dosage , Animals , Drug Interactions , Female , GABA-A Receptor Agonists , Imidazoles/pharmacology , Methyltestosterone/administration & dosage , Mice , Mice, Inbred C57BL , Nandrolone/administration & dosage , Nandrolone/adverse effects , Nandrolone Decanoate , Neurons/drug effects , Neurons/physiology , Preoptic Area/cytology , Preoptic Area/drug effects , Preoptic Area/physiology , Protein Subunits/agonists , Protein Subunits/physiology , RNA, Messenger/biosynthesis , Receptors, Androgen/physiology , Receptors, GABA-A/biosynthesis , Receptors, GABA-A/physiology , Signal Transduction/drug effects , Synaptic Transmission , Testosterone/administration & dosage , Testosterone/adverse effectsABSTRACT
Anabolic androgenic steroids are synthetic derivatives of testosterone designed for therapeutic purposes, but now taken predominantly as drugs of abuse. The most common behavioral effects associated with anabolic androgenic steroid use are changes in anxiety, aggression and reproductive behaviors, including the onset of puberty and sexual receptivity. GABAergic circuits in the forebrain underlie these behaviors and are regulated by gonadal steroids. Work from our laboratories has shown that the expression and function of GABA(A) receptors in the rat and mouse forebrain varies between the sexes and across the estrous cycle. We have also shown that there are significant changes in GABA(A) receptor expression that occur with the progression through puberty to adulthood. Because GABAergic systems are both steroid-sensitive and critical for the expression of behaviors altered with anabolic androgenic steroid use, forebrain GABA(A) receptors are an attractive candidate to assess how molecular actions of anabolic androgenic steroids may be translated to known behavioral outcomes. Our studies demonstrate that anabolic androgenic steroids elicit both acute modulation of GABA(A) receptor-mediated currents, as well as chronic regulation of GABA(A) receptor expression and forebrain GABAergic transmission. Because anabolic androgenic steroid use has now become prevalent not only among adolescent boys, but in an increasing number of adolescent girls, we have also been particularly interested in determining age- and sex-specific effects of anabolic androgenic steroids. Our data show that the effects of chronic anabolic androgenic steroid exposure can be greater for adolescent than adult animals and are more marked in females than in males. These data have particularly important implications with respect to studies we have done demonstrating that chronic anabolic androgenic steroid exposure alters the onset of puberty, estrous cyclicity and sexual receptivity.
Subject(s)
Anabolic Agents/pharmacology , Androgens/pharmacology , Prosencephalon/physiology , Synaptic Transmission/physiology , gamma-Aminobutyric Acid/physiology , Adolescent , Animals , Female , Gene Expression Regulation , Humans , Male , Prosencephalon/drug effects , Receptors, GABA-A/drug effects , Receptors, GABA-A/genetics , Synaptic Transmission/drug effectsABSTRACT
Anabolic androgenic steroids are synthetic derivatives of testosterone designed for therapeutic uses, but now taken as drugs of abuse. Potential health risks associated with anabolic androgenic steroid abuse are believed to be higher in adolescents than in adults, but few studies have tested anabolic androgenic steroid effects in adolescent subjects or determined if effects of these steroids differ between females and males. We have studied GABA(A) receptor expression and function in the medial preoptic nucleus of mice chronically treated during adolescence with the anabolic androgenic steroid, 17alpha-methyltestosterone. Three-week treatment did not elicit significant differences the expression of alpha1, alpha2 or alpha5 subunit mRNAs in animals of either sex, although there was a trend toward decreases in all three subunit mRNAs in female mice, which was augmented and attained significance for the alpha2 subunit mRNA in females treated for six weeks. Immunocytochemical analysis revealed that treatment with 17alpha-methyltestosterone for 6 weeks also elicited a significant decrease in the number of alpha2-immunopositive neurons in female subjects. To test if anabolic androgenic steroid treatment also promoted changes in GABA(A) receptor function, spontaneous inhibitory synaptic currents were analyzed in adolescent animals treated for 3-4 weeks. This treatment regimen promoted a significant decrease in spontaneous inhibitory synaptic current frequency in female, but not male mice. Finally, anabolic androgenic steroid treatment was found to have no effect on the numbers of interneurons within the medial preoptic nucleus, as assessed by immunoreactivity for calcium binding proteins, suggesting that the decrease in the frequency of spontaneous inhibitory synaptic currents in female mice does not arise from an anabolic androgenic steroid-induced loss of interneurons. Taken together, our results indicate that chronic exposure to 17alpha-methyltestosterone elicits significant changes in GABAergic transmission in the medial preoptic nucleus of female, but not male, mice effectively enhancing the sexually dimorphic nature of GABAergic transmission in a forebrain region crucial for the expression of aggression and sexual behaviors.
Subject(s)
Anabolic Agents/administration & dosage , Gene Expression/drug effects , Methyltestosterone/administration & dosage , Neurons/physiology , Receptors, GABA-A/metabolism , Sex Characteristics , Animals , Animals, Newborn , Blotting, Western/methods , Calbindin 2 , Calbindins , Cell Count/methods , Dose-Response Relationship, Radiation , Electric Stimulation/methods , Female , Immunohistochemistry/methods , In Vitro Techniques , Indoles/metabolism , Male , Membrane Potentials/drug effects , Membrane Potentials/physiology , Membrane Potentials/radiation effects , Mice , Mice, Inbred C57BL , Neural Inhibition/drug effects , Neural Inhibition/physiology , Neural Inhibition/radiation effects , Neurons/drug effects , Patch-Clamp Techniques/methods , Prosencephalon/cytology , Prosencephalon/physiology , Protein Subunits/genetics , Protein Subunits/metabolism , RNA, Messenger/biosynthesis , Receptors, GABA-A/genetics , Reverse Transcriptase Polymerase Chain Reaction/methods , S100 Calcium Binding Protein G/metabolismABSTRACT
Many physical agents cause neuropathies. The most common are chronic pressure, vibration and temperature. In general, these lesions occur at work, as a result of accidents or through chronic exposure to the physical agent. Radiation leading to peripheral neuropathy is also related to radiotherapy in cancer treatment, as an undesirable side-effect. We present here a case report of short, intense UV radiation exposure at work, leading to delayed-onset ocular neuropathy. A clear cause-effect relationship is shown, demonstrated using magnetic resonance imaging scans. We suggest that the mechanism was thermal and ischaemic.
