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Introduction: Neuroactive steroids represent a class of both synthetic and naturally occurring steroids that have an effect on neural function. In addition to classical genomic mechanism by the hormones progesterone, deoxycorticosterone and testosterone 3α-OH metabolites of these hormones enhance GABAA receptor through rapid non-genomic mechanism. The site(s) of action of these neuroactive steroids namely 3α-OH-5α-pregnan-20 one, (3α,5α)-3,21-deoxycorticosterone(3α5α-THDOC) and 5α androstane-3α,17β-diol on GABAA receptor are distinct from that of benzodiazepines and barbiturate binding sites. The modulation site(s) has a well-defined structure activity relationship with a 3α-hydroxy and a 20-ketone configuration in the pregnane molecule required for agonistic action. Pregnenolone sulfate is a noncompetitive GABAA receptor antagonist and inhibit GABA activated Cl- current in an activation dependant manner. 3β-hydroxy A-ring reduced pregnane steroids are also GABAA receptor antagonist and inhibit GABAA receptor function and its potentiation induced by their 3α-diesteromers in a noncompetitive manner. Aim: The aim was to investigate if the effect of GABA, pentobarbital antagonism by bicuculline and if the effect of GABA-agonist and antagonist neuroactive steroids including pregnenolone sulfate is dependant on the α-subunits of GABAA receptor. Furthermore, the studies aimed at investigating the binding site of pregnenolone sulfate and if its effect is dependent on γ-subunit. In addition, the inhibitory effect of pregnenolone sulfate and 3β-hydroxy steroids has been characterized. We also wanted to investigate if the neuroactive steroids effect vary between the human and rat recombinant α1β2γ2L receptors and between the long (L) and short (S) variants of γ2-subunit. Method: Experiments were performed by the two electrodes voltage-clamp technique using oocytes of Xenopus laevis expressed with recombinant GABAA receptors containing α1, α4 or α5, β2, γ2L and γ2S-subunits. Results: There was no difference between the α1, α4 and α5-containing subunits regarding GABA and pentobarbital inhibition by bicuculline. GABA-activated current in the binary αβ was potent than that of ternary αβγ receptor. Unlike Zn2+ effect, inhibition by pregnenolone sulfate on the GABAA receptor is not dependant on the γ-subunit. It is likely that the 2’ residue closest to the N-terminus of the protein at M2 helix on both α1 and β2 subunit are critical to the inhibitory actions of PS and the function of Cl- channels. Point mutation at M2 helix of the β2-subunit (b2A252S) can dramatically reduce the inhibitory effect of PS on the GABAA receptors without affecting the inhibitory properties of 3β-hydroxysteroids. Agonist and antagonist steroids also varied in their efficacy between the human and rat α1β2γ2L receptor. Neuroactive steroids also showed difference between human γ2L and γ2S-containing receptor. Conclusions: GABA and pentobarbital antagonism by bicuculline is not dependant on α-subunit. Pregnenolone sulfate binding site is different from that of Zn2+. 3β-hydroxysteroids and pregnenolone sulfate inhibit GABAA receptor through different mechanisms. Neuroactive steroids also differ between species and between the long and short variant of γ- subunit.

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Neuroactive steroids are a group of steroid hormones which act non-genomically to influence the neuron excitability of neuronal synapses. Addictive substances can interfere with the synthesis of neuroactive steroids through many mechanisms, affecting their levels and changing their functionality. At the same time, neuroactive steroids play a role in the development of addiction, since their levels change during attempts to quit and therefore affect the success of treatments for addiction. This study focuses on the relationships between individual addictive substances and neuroactive steroids, the individual functional mechanisms and how they influence each other. It is generally known that addictive substances result in the release of anxiolytics that act on neuroactive steroids. This plays a role in the development of addiction. We also describe in detail the effect of smoking on steroid hormones and the endocrine system in general. Using tobacco addition as a model, we studied the relationship between addiction and neuroactive steroids. As part of my doctoral studies we performed a prospective study that followed changes in the steroid spectra induced by smoking as well as when quitting smoking. We also developed a predictive model to predict the likelihood of success in treating tobacco...

Seguindo como um dos transtornos mais desafiadores, apesar dos avanços dos estudos que tentam elucidar sua fisiopatologia, a esquizofrenia continua sendo objeto de estudo de pesquisa na busca de novas opções de tratamento. Explicações que vão além da teoria dopaminérgica da esquizofrenia têm estimulado pesquisas, em particular as relacionadas a neurotransmissão glutamatérgica (com foco nos receptores N-metil-D-Aspartato - NMDA), receptor influenciado por diversas substâncias além do glutamato, como por exemplo, os aminoácidos D-serina e glicina, assim como os esteroides neuroativos, como a pregnenolona. Com a existência de estudos clínicos já sugerindo efeitos positivos da D-serina e da pregnenolona, como tratamento adjuvante aos antipsicóticos, tem-se acumulado interesse pelo estudo do papel desta na fisiopatologia da esquizofrenia. Ao mesmo tempo, pergunta-se se os antipsicóticos não influenciariam de alguma maneira a neurotransmissão gabaérgica e glutamatérgica, através de alteração nos níveis da pregnenolona e/ou de aminoácidos neuroativos, como a D-serina. Assim, este estudo objetivou a avaliação dos efeitos dos antipsicóticos atípicos clozapina e ziprasidona sobre os níveis cerebrais de aminoácidos neuroativos, como a D-serina, assim como da pregnenolona. Os testes foram feitos em cérebros de ratos após o tratamento com as medicações ou o placebo, após uso agudo (1, 3 e 24 horas) e subagudo (7 e 21 dias). Com grupos de 4 a 5 ratos, as medições dos aminoácidos e dos esteroides nos cérebros foram feitas através de cromatografia líquida de alta performance (CLAP) para os aminoácidos e de cromatografia gasosa/espectroscopia de massa para os esteroides neuroativos. Os dados foram analisados com software SPSS 17, através dos testes ANOVA e pós teste Student Newman Keuls. Como resultados, não observamos alterações dos níveis dos aminoácidos após o uso das medicações quando comparadas ao placebo. Já em relação a pregnenolona, esta se mostrou aumentada após o uso dos antipsicóticos, mas este aumento não manteve sua significância após análises pós teste. Apesar de estudos já terem demonstrado diferenças nos níveis de aminoácidos após uso de antipsicóticos, em regiões cerebrais de ratos, nosso estudo não evidenciou tal influência nas concentrações globais deaminoácidos nos cérebros estudados, assim como não demonstrou mudanças nos níveis de pregnenolona após o uso agudo e subagudo dos antipsicóticos. Considerando dados prévios, que apontavam para alterações de esteroides neuroativos após uso de psicotrópicos, inclusive com estudos demonstrando previamente efeitos da clozapina nos níveis de pregnenolona, nosso estudo obteve dados discordantes, que podem ser explicados pelo desenho de uso agudo das medicações. As observações feitas no presente estudo trazem novos dados em relação ao que já existia na literatura, quanto ao potencial de alterações dos níveis cerebrais de aminoácidos e esteroides neuroativos. Assim, esperamos contribuir de alguma forma, para um melhor entendimento do mecanismo de ação das medicações antipsicóticas, apesar de ressaltar a necessidade de estudos mais amplos que avaliem as alterações nos níveis das moléculas aqui estudadas, mas que considerem mensurações em regiões específicas cerebrais. / It is considered one of the most challenging disorders, despite advances in studies that attempt to elucidate its pathophysiology, schizophrenia continues to be the subject of research in the search for new treatment options. Explanations that go beyond the dopaminergic theory of schizophrenia, have stimulated research, in particular, those related to glutamatergic neurotransmission (focusing on N-methyl-D-Aspartate - NMDA receptors), a receptor influenced by several substances besides glutamate, , amino acids D-serine and glycine, as well as neuroactive steroids, such as pregnenolone. With the existence of clinical studies already suggesting positive effects of D-serine and pregnenolone, as an adjunctive treatment to antipsychotics, interest has been accumulated in the study of its role in the pathophysiology of schizophrenia. At the same time, it is questioned whether antipsychotics would not, in some way, influence gabaergic and glutamatergic neurotransmission, through changes in the levels of pregnenolone and / or neuroactive amino acids, such as D-serine. Thus, this study aimed to evaluate the effects of atypical antipsychotics clozapine and ziprasidone on brain levels of neuroactive amino acids, such as D-serine, as well as pregnenolone. Tests were performed on rat brains after treatment with the medications or placebo, after acute (1, 3 and 24 hours) and subacute (7 and 21 days) use. With groups of 4 to 5 mice, measurements of amino acids and pregnenolone in the brains were made by high performance liquid chromatography (CLAP) for amino acids and gas chromatography / mass spectroscopy for pregnenolone. Data were analyzed using SPSS 17 software, using ANOVA and Student Newman Keuls post hoc test. As a result, we did not observe changes in amino acid levels after the use of the medications when compared to placebo. Regarding pregnenolone, it was shown to be increased after the use of antipsychotics, but this increase did not maintain its significance after post-test analysis. Although studies have shown differences in amino acid levels after antipsychotic use in rat brain regions, our study failed to demonstrate such an influence on overall amino acid concentrations in the brains studied, as well as to demonstrate changes in pregnenolone levels after use acute and subacute antipsychotics. Considering previous data, which pointed to neuroactive steroid alterations after the use of psychotropic drugs, including studies showingpreviously effects of clozapine on pregnenolone levels, our study obtained discordant data, which can be explained by the design of acute use of medications. The observations made in the present study bring new data in relation to what already existed in the literature, regarding the potential of alterations of the cerebral levels of aminoacids and neuroactive steroids. Thus, we hope to contribute in some way to a better understanding of the mechanism of action of antipsychotic medications, although it emphasizes the need for broader studies that assess changes in the levels of the molecules studied here, but that consider measures in specific regions of the brain.