Neurosteroids, also known as neuroactive steroids, are endogenous or exogenous steroids that rapidly alter neuronal excitability through interaction with ligand-gated ion channels and other cell surface receptors.
Inhibitory neurosteroids
These neurosteroids exert inhibitory actions on neurotransmission. They act as positive allosteric modulators of the GABAA receptor (especially δ subunit-containing isoforms), and possess, in no particular order, antidepressant, anxiolytic, stress-reducing, rewarding, prosocial, antiaggressive, prosexual, sedative, pro-sleep, cognitive and memory-impairing, analgesic, anesthetic, anticonvulsant, neuroprotective, and neurogenic effects.
Major examples include tetrahydrodeoxycorticosterone (THDOC; from 5osb), the androstane 3α-androstanediol, the cholestane cholesterol and the pregnanes pregnanolone (eltanolone), allopregnanolone (3α,5α-THP).
Excitatory neurosteroids
These neurosteroids have excitatory effects on neurotransmission. They act as potent negative allosteric modulators of the GABAA receptor, weak positive allosteric modulators of the NMDA receptor, and/or agonists of the σ1 receptor, and mostly have antidepressant, anxiogenic, cognitive and memory-enhancing, convulsant, neuroprotective, and neurogenic effects. Major examples include the pregnanes pregnenolone sulfate (PS), epipregnanolone, and isopregnanolone (sepranolone), the androstanes dehydroepiandrosterone (DHEA; prasterone), and dehydroepiandrosterone sulfate (DHEA-S; prasterone sulfate), and the cholestane 24(S)-hydroxycholesterol (NMDA receptor-selective; very potent).
Mixed
Cholesterol: cholest-5-en-3β-ol – NMDA receptor positive allosteric modulator, possible GABAA receptor positive allosteric modulator, many other actions.
Epipregnanolone sulfate: 5β-pregnan-3β-ol-20-one 3β-sulfate – GABAA and NMDA receptor negative allosteric modulator, Transient receptor potential cation channel subfamily M member 3 (TRPM3) agonist.
Pheromones
Pheromones are neurosteroids that influence brain activity, notably hypothalamic function, via activation of vomeronasal receptor cells.
They include the androstanes androstadienol, androstadienone, androstenol (1xnx), and androstenone and the estrane estratetraenol.
