In vitro activity: Gabapentin produces concentration-dependent inhibitions of the K(+)-induced [Ca(2+)](i) increase in fura-2-loaded human neocortical synaptosomes with IC50 of 17 mM and maximal inhibition of 37%. Gabapentin may bind to the Ca(2+) channel alpha 2 delta subunit to selectively attenuate depolarization-induced Ca(2+) influx of presynaptic P/Q-type Ca(2+) channels; this results in decreased glutamate/aspartate release from excitatory amino acid nerve terminals leading to a reduced activation of AMPA heteroreceptors on noradrenergic nerve terminals. Gabapentin produces alterations in the cytosolic and extracellular concentrations of several amino acids, including L-leucine, L-valine and L-phenylalanine, in rat cortical astrocytes and synaptosomes, effects that are postulated to be of pharmacological significance. Gabapentin reduces potassium-evoked calcium influx via voltage-gated calcium channels in a mouse pituitary cell line that constitutively expresses GABAB receptors comprising the functional gb1a–gb2 subunit heterodimer. Gabapentin can increase N-methyl-d-aspartate (NMDA)-evoked currents in GABA-positive rat dorsal horn neurones in the presence of protein kinase C, possibly by increasing the glycine sensitivity of the NMDA receptor complex. Gabapentin produces a delayed allosteric enhancement of an unspecified voltage-activated potassium current in rat dorsal root ganglion neurons.

Neuropharmacology. 2002 Feb;42(2):229-36; Curr Opin Pharmacol. 2006 Feb;6(1):108-13.