Pregnenolone as a nootropic?

http://www.ncbi.nlm.nih.gov/pubmed/1654510

Pregnenolone sulfate, a neurosteroid, specifically enhances NMDA-gated currents in spinal cord neurons, while inhibiting receptors for the inhibitory amino acids glycine and gamma-aminobutyric acid, as well as non-NMDA glutamate receptors.

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http://www.sciencedirect.com/science/article/pii/S0301008203001680

these data suggest that neurosteroids can influence cognitive processes, particularly in senescent subjects, through a modulation of ACh neurotransmission associated with paradoxical sleep modifications; furthermore, our recent data suggest a critical role for neurosteroids in the modulation of cerebral plasticity, mainly on hippocampal neurogenesis.

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http://www.nature.com/npp/journal/v34/n8/abs/npp200926a.html

Patients receiving pregnenolone demonstrated significantly greater improvements in SANS scores (mean change=10.38) compared with patients receiving placebo

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http://europepmc.org/abstract/MED/11744095

Studies in animals demonstrated that the neurosteroids pregnenolone (PREG) and dehydroepiandrosterone (DHEA), as sulfate derivatives (PREGS and DHEAS, respectively), display memory-enhancing properties in aged rodents. Moreover, it was recently shown that memory performance was correlated with PREGS levels in the hippocampus of 24-month-old rats. Human studies, however, have reported contradictory results. First, improvement of learning and memory dysfunction was found after DHEA administration to individuals with low DHEAS levels, but other studies failed to detect significant cognitive effects after DHEA administration.

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So it looks like a possibility, but there may be conflicting results in humans. There is most likely a balance that needs to be reached.