Neuroactive steroids

Apart from exerting effects on the genome via intracellular steroid receptors, neuroactive steroids (or neurosteroids) rapidly alter neuronal excitability through interaction with neurotransmitter-gated ion channels. Several of these steroids accumulate in the brain after local synthesis or after metabolism of adrenal steroids. The 3alpha-hydroxy ring A-reduced pregnane steroids allopregnanolone and tetrahydrodeoxycorticosterone have been surmised to enhance GABA-mediated chloride currents, whereas pregnenolone sulfate and dehydroepiandrosterone (DHEA) sulfate display functional antagonistic properties at GABA A receptors.

Neurosteroids are synthesized in the central and peripheral nervous system, especially in myelinating glial cells, from cholesterol or steroidal precursors imported from peripheral sources. They include 3 beta-hydroxy-delta 5-compounds, such as pregnenolone (PREG) and dehydroepiandrosterone (DHEA), their sulfates, and reduced metabolites such as the tetrahydroderivative of progesterone 3 alpha-hydroxy-5 alpha-pregnane-20-one (3 alpha,5 alpha-THPROG). These compounds can act as allosteric modulators of neurotransmitter receptors, such as GABA(A), NMDA, and sigma receptors. Progesterone (PROG) is also a neurosteroid, and a progesterone receptor (PROG-R) has been identified in peripheral and central glial cells.

Neurosteroids affect synaptic functioning, are neuroprotective, and affect myelinization.[1] They are investigated for their potential to improve memory and cognitive ability. Progesterone as a neuroprotectant affects regulation of apoptotic genes. Its effect as a neurosteroid works predominantly through the GSK-3 beta pathway, as an inhibitor. Other GSK-3 beta inhibitors include bipolar mood stabilizers, lithium and valproic acid. It also raises epidermal growth factor-1 levels, a factor often used to induce proliferation, and used to sustain cultures of stem cells.