Intrinsic activation/inactivation parameters of CaV2.1 calcium channels are shifted by Pregabalin, modulating neurotransmitter release

DI GUILMI MARIANO N.; F. J. URBANO; C. GONZALEZ INCHAUSPE,; O. D. UCHITEL

Placencia, Belize

Conferencia; Second International Calcium Channel Conference - Placencia, Belize; 2010

Drs. Terrance P. Snutch & Gerald W. Zamponi

Mechanisms by which Pregabalin (PGB) might act as an anticonvulsant are unknown. The α2-δtype 1 auxiliary subunit of voltage-gated calcium channels is the primary high-affinity bindingsite for PGB. Here we studied PGB effects on both postsynaptic excitatory transmitter responsesof principal neurons from Medial Nucleus of the Trapezoid Body and presynaptic calciumcurrents (IpCa) present on the afferent called Calyx of Held in brainstem slices from mice, usingwhole cell patch clamp recordings.We found that a dose-response relationship showed a maximum drug effect at 500 μM. At thisconcentration, PGB reduced the amplitude of EPSCs by a 30%. No differences were observed inthe depression rate using high frequency trains. Faster rate of recovery from synaptic depressionat 100 Hz was observed in the presence of PGB (p=0.043). We found no differences in the meanamplitude of miniature EPSCs while observing greater minis frequencies -PGB versus +PGBconditions (1.71±0.35 Hz and 0.49±0.06 Hz, respectively; p=0.004). On the other hand, multipleeffects of PGB on the IpCa intrinsic properties were observed. PGB blocked CaV2.1 channelsmediatedcurrents and decrease their facilitation during 100Hz train, without changing theirvoltage-dependence of activation. However, two-pulse inactivation protocol showed a largerrescue of the inactivation. Additionally, the inactivation curve observed with PGB showed aclear change on the kinetic but not on the half-activation voltage using a long conditioning pulseprotocol. Supported by: UBACYT X-223; FONCYT (ANPCyT) PICT 2005-32113; 2006-199,Wellcome Trust (to ODU); FONCYT (ANPCyT) PICT 2007-01009 & PIDRI-PRH 2007 (to FU)