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Ion channels are vital components of plasma membranes. This article presents an evolutionary view of the biochemical mechanism of controlling activity of ion channels by rigid lipids, such as steroids or biophysically similar molecules, which were instrumental in formation and control of ion channels in cell membranes at the very origin of life. Such regulatory mechanisms exist in all cellular forms of life from ancient bacteria to humans and participate in a diversity of biological functions, from the most basic, such as maintenance of cell shape, homeostasis, feeding, cell fusion, and reproduction to the most intricate, such as the mind. Learning about the regulation of membrane ion channels by steroids and like molecules is important for understanding the evolution of life and various aspects of cell and organism physiology, for unraveling the mysteries of mind, and for practical purposes such as developing new pharmacotherapies.
The neurosteroids, dehydroepiandrosterone sulfate (DHEAS) and androsterone, are implicated in drug addictions. We examined their influence on locomotor activity and reward in male Wistar rats, and on steroid and monoamine metabolism in the hippocampus and striatum. In the open field test, DHEAS injections (10, 40, 80 mg/kg, i.p.) 30 min prior the test had no significant effect on ambulation, but androsterone (10 mg/kg) increased general locomotion and at doses 1-10 mg/kg, increased central field activity, suggestive of an anxiolytic action. In the conditioned place preference test, both steroids had a biphasic effect: DHEAS was rewarding at doses of 10 and 40 mg/kg, but not at 80 mg/kg, while androsterone was rewarding at doses of 1 and 10 mg/kg, but aversive at 40 mg/kg. Monoamine and steroid concentrations were analyzed in homogenates from the hippocampus and striatum of DHEAS and androsterone injected rats. DHEAS reduced the hippocampal dopamine level, increased striatal homovanilic acid (HVA) and decreased the striatal serotonin concentrations. Androsterone did not affect dopamine levels or turnover, but increased noradrenaline concentration and serotonin turnover in the hippocampus. DHEAS administration augmented concentrations of DHEA, pregnenolone, androstendiol and androstentriol in both brain structures, while androsterone injections increased brain levels of androsterone, epiandrosterone, 5a-dihydrotestosterone, and androstandiol. Present data document that although psychobehavioral and neurochemical effects of DHEAS and androsterone differ in several aspects; both neurosteroids have rewarding properties at certain dose ranges, suggesting their likely involvement in addictions, which entail different mechanisms.
An association between autism and early life exposure to mercury is a hotly debated issue. In this study, 91 autistic Polish children, male and female, 3-4 and 7-9 years old, were compared to 75 age- and sex-matched healthy children with respect to: demographic, perinatal, clinical and developmental measures, parental age, birth order, morphometric measures, vaccination history, and hair mercury content. In demographic and perinatal measures there were no consistent differences between the autistic and control groups. Autistic children had a significantly greater prevalence of adverse reactions after vaccinations and abnormal development than controls. Between 45 and 80% of autistic children experienced developmental regress. Autistic children significantly differed from healthy peers in the concentrations of mercury in hair: younger autistics had lower levels, while older – higher levels than their respective controls. The results suggest that autistic children differ from healthy children in metabolism of mercury, which seems to change with age.
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