D-Cycloserine is an analog of the amino acid D-alanine.Target: AntibacterialD-Cycloserine selectively potentiated the duration of motor cortical excitability enhancements induced by anodal tDCS. D-Cycloserine alone did not modulate excitability [1]. Participants receiving d-cycloserine in addition to exposure therapy reported significantly less social anxiety compared with patients receiving exposure therapy plus placebo. Controlled effect sizes were in the medium to large range [2]. Chronic D-cycloserine significantly reduced nicotine self-administration selectively in rats with low baseline nicotine use, but was ineffective with the rats with higher levels of baseline nicotine self-administration [3].

References:
[1]. Nitsche, M.A., et al., Consolidation of human motor cortical neuroplasticity by D-cycloserine. Neuropsychopharmacology, 2004. 29(8): p. 1573-8.
[2]. Hofmann, S.G., et al., Augmentation of exposure therapy with D-cycloserine for social anxiety disorder. Arch Gen Psychiatry, 2006. 63(3): p. 298-304.
[3]. Levin, E.D., et al., D-cycloserine selectively decreases nicotine self-administration in rats with low baseline levels of response. Pharmacol Biochem Behav, 2011. 98(2): p. 210-4.