Stimulus-dependent modulation of [(3)H]norepinephrine release from rat neocortical slices by gabapentin and pregabalin.
Gabapentin (GBP; Neurontin) has proven efficacy in several neurological and psychiatric disorders yet its mechanism of action remains elusive. This drug, and the related compounds pregabalin [PGB; CI-1008, S-(+)-3-isobutylgaba] and its enantiomer R-(-)-3-isobutylgaba, were tested in an in vitro superfusion model of stimulation-evoked neurotransmitter release using rat neocortical slices prelabeled with [(3)H]norepinephrine ([(3)H]NE). The variables addressed were stimulus type (i.e., electrical, K(+), veratridine) and intensity, concentration dependence, onset and reversibility of action, and commonality of mechanism. Both GBP and PGB inhibited electrically and K(+)-evoked [(3)H]NE release, but not that induced by veratridine. Inhibition by these drugs was most pronounced with the K(+) stimulus, allowing determination of concentration-effect relationships (viz., 25 mM K(+) stimulus: GBP IC(50) = 8.9 microM, PGB IC(50) = 11.8 microM). R-(-)-3-Isobutylgaba was less effective than PGB to decrease stimulation-evoked [(3)H]NE release. Other experiments with GBP demonstrated the dependence of [(3)H]NE release inhibition on optimal stimulus intensity. The inhibitory effect of GBP increased with longer slice exposure time before stimulation, and reversed upon washout. Combination experiments with GBP and PGB indicated a similar mechanism of action to inhibit K(+)-evoked [(3)H]NE release. GBP and PGB are concluded to act in a comparable, if not identical, manner to preferentially attenuate [(3)H]NE release evoked by stimuli effecting mild and prolonged depolarizations. This type of modulation of neurotransmitter release may be integral to the clinical pharmacology of these drugs.
Dooley
D J
DJ
Department of Neuroscience Therapeutics, Pfizer Global Research & Development, Ann Arbor, Michigan 48105, USA. david.dooley@pfizer.com
Donovan
C M
CM
Pugsley
T A
TA
D000085:Acetates / Q000494:pharmacology*; D000588:Amines; D000818:Animals; D003509:Cyclohexanecarboxylic Acids; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D000077206:Gabapentin; D008297:Male; D019579:Neocortex / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D000069583:Pregabalin; D051381:Rats; D017207:Rats, Sprague-Dawley; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives* / Q000494:pharmacology
D000085:Acetates; D000588:Amines; D003509:Cyclohexanecarboxylic Acids; D000069583:Pregabalin; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D011188:Potassium; D009638:Norepinephrine