Selectivity of action of

SECTION ASSIGNEMENT Neuropharmacology This article has not been copyedited and formatted. The final version may differ from this version. ABSTRACT The present study was planned to investigate the action of pregabalin on voltage-dependent Ca 2+ channels (VDCC) and on novel targets (fusion pore formed between the secretory vesicle and the plasma membrane, exocytotic machinery and mitochondria) that would further explain its inhibitory action on neurotransmitter release. Electrophysiological recordings in the perforated-patch configuration of the patch-clamp technique revealed that pregabalin inhibits by 33.4±2.4% and 39±4%, respectively, the Ca 2+ current charge density and exocytosis evoked by depolarizing pulses in mouse chromaffin cells. About half of the inhibitory action of pregabalin was rescued by L-isoleucine, showing the involvement of α2δ-dependent and  independent mechanisms. Ca 2+ channel blockers were used to inhibit Cav1.2, Cav2.1 and Cav2.2 channels in mouse chromaffin cells, which were unselectively blocked by the drug. Similar values of Ca 2+ current charge blockade were obtained when pregabalin was tested in human or bovine chromaffin cells, species that express very different percentage of VDCC types with respect to mouse chromaffin cells. These results demonstrate that the inhibitory action of pregabalin on VDCC and exocytosis does not depend on α1 Ca 2+ channel subunit types. Carbon fibre amperometric recordings of digitonin-permeabilized cells showed that neither the fusion pore nor the exocytotic machinery were targeted by pregabalin. Mitochondrial Ca 2+ measurements performed with mit-r-Pericam demonstrated that Ca 2+ uptake or release from mitochondria were not either affected by the drug. The selectivity of action of pregabalin might explain its safety, good tolerability and reduced adverse effects. In addition, the inhibition of the exocytotic process in chromaffin cells might have relevant clinical consequences. This article has not been copyedited and formatted. The final version may differ from this version.