[3H]aniracetam binds to specific recognition sites in brain membranes.
[3H]Aniracetam bound to specific and saturable recognition sites in membranes prepared from discrete regions of rat brain. In crude membrane preparation from rat cerebral cortex, specific binding was Na+ independent, was still largely detectable at low temperature (4 degrees C), and underwent rapid dissociation. Scatchard analysis of [3H]aniracetam binding revealed a single population of sites with an apparent KD value of approximately 70 nM and a maximal density of 3.5 pmol/mg of protein. Specifically bound [3H]aniracetam was not displaced by various metabolites of aniracetam, nor by other pyrrolidinone-containing nootropic drugs such as piracetam or oxiracetam. Subcellular distribution studies showed that a high percentage of specific [3H]aniracetam binding was present in purified synaptosomes or mitochondria, whereas specific binding was low in the myelin fraction. The possibility that at least some [3H]aniracetam binding sites are associated with glutamate receptors is supported by the evidence that specific binding was abolished when membranes were preincubated at 37 degrees C under fast shaking (a procedure that substantially reduced the amount of glutamate trapped in the membranes) and could be restored after addition of either glutamate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) but not kainate. The action of AMPA was antagonized by DNQX, which also reduced specific [3H]aniracetam binding in unwashed membranes. High levels of [3H]aniracetam binding were detected in hippocampal, cortical, or cerebellar membranes, which contain a high density of excitatory amino acid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Fallarino
F
F
Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Italy.
Genazzani
A A
AA
Silla
S
S
L'Episcopo
M R
MR
Camici
O
O
Corazzi
L
L
Nicoletti
F
F
Fioretti
M C
MC
D000818:Animals; D014151:Anti-Anxiety Agents; D001569:Benzodiazepines / Q000494:pharmacology; D001581:Benzothiadiazines / Q000494:pharmacology; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D018698:Glutamic Acid / Q000494:pharmacology; D008297:Male; D008566:Membranes / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D011760:Pyrrolidinones / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution; D014316:Tritium
D014151:Anti-Anxiety Agents; D001581:Benzothiadiazines; D011760:Pyrrolidinones; D014316:Tritium; C061950:GYKI 52466; D001569:Benzodiazepines; D015240:Phorbol 12,13-Dibutyrate; D018698:Glutamic Acid; C036466:aniracetam; C004639:cyclothiazide