Nefiracetam facilitates hippocampal neurotransmission by a mechanism independent of the piracetam and aniracetam action.
Nefiracetam, a nootropic (cognition-enhancing) agent, facilitated neurotransmission in the dentate gyrus of rat hippocampal slices in a dose-dependent manner at concentrations ranged from 1 nM to 1 microM, being evident at 60-min washing-out of the drug. The facilitatory action was blocked by the nicotinic acetylcholine (ACh) receptor antagonists, alpha-bungarotoxin and mecamylamine. A similar facilitation was induced by the other nootropic agents, piracetam and aniracetam, but the facilitation was not inhibited by nicotinic ACh receptor antagonists and it did not occlude the potentiation induced by nefiracetam. In the Xenopus oocyte expression systems, nefiracetam potentiated currents through a variety of neuronal nicotinic ACh receptors (alpha 3beta 2, alpha 3beta 4, alpha 4 beta 2, alpha 4 beta 4, and alpha 7) to a different extent. In contrast, neither piracetam nor aniracetam had any potentiating action on alpha 7 receptor currents. While aniracetam delayed the decay time of currents through the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor, GluR1, -2, -3, expressed in oocytes, nefiracetam or piracetam had no effect on the currents. Nefiracetam, thus, appears to facilitate hippocampal neurotransmission by functionally targeting nicotinic ACh receptors, independently of the action of piracetam and aniracetam.
Nomura
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Department of Physiology, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, 650-0017, Kobe, Japan.
Nishizaki
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D000818:Animals; D002038:Bungarotoxins / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D006624:Hippocampus / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000737:chemistry / Q000502:physiology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018697:Nootropic Agents / Q000494:pharmacology*; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D010889:Piracetam / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects*; D014981:Xenopus
D002038:Bungarotoxins; D018733:Nicotinic Antagonists; D018697:Nootropic Agents; D011760:Pyrrolidinones; D011978:Receptors, Nicotinic; C058876:nefiracetam; C036466:aniracetam; D008464:Mecamylamine; D010889:Piracetam