Post-ischemic recovery of acetylcholine release in vitro: influence of different excitatory amino acid receptor subtype antagonists.
The release of endogenous acetylcholine was measured in electrically (5-20 Hz) stimulated guinea pig cerebral cortex and caudate nucleus slices under ischemic (hypoxic and glucose-free) conditions. Ischemia reduced acetylcholine release by 40-90%; the inhibition depended on the duration of ischemia (10-30 min) while the extent of post-ischemic recovery was inversely related to it. Caudate nucleus slices displayed a higher sensitivity to ischemia than did cortical slices. To test the effects of excitatory amino acid receptor antagonists on the ischemia-induced reduction of acetylcoline release and on its post-ischemic recovery, the following drugs were used: 5-methyl-10,11-dihydro-5-H-dibenzo-[a,b]-cyclohepten-5,10-imine (MK-801,-a blocker of the N-methyl-D-aspartate [NMDA] receptor-linked channel), 7-chloro-kynurenic acid (7-Cl-KYN) and (E)-3-[2(phenylcarbamoyl)ethenyl]-4,6-dichloroindole-2-carboxylic acid sodium salt (GV150526A, blockers of the glycine site of the NMDA receptor), eliprodil, (an antagonist at the polyamine site of the NMDA receptor), and 6-cyano- 7-nitro-quinoxalin-2,3-dione (CNQX, a D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid [AMPA] receptor antagonist). These did not modify the time-course and the extent of ischemia-induced inhibition but improved post-ischemic recovery in a concentration dependent manner. GV 150526A and CNQX appeared to be more effective in the cerebral cortex. Only eliprodil was devoid of any effect in both areas. The evaluation of acetylcholine release from brain slices represents a suitable in vitro model to quantify the effectiveness of drugs in favouring recovery from the cholinergic presynaptic failure induced by ischemic conditions. The different effects of the excitatory amino acid receptor antagonists cited above, depending on the brain areas considered and the receptor subtypes involved, may be of interest in view of their therapeutic potential.
Badini
I
I
Department of Clinical and Experimental Medicine, University of Ferrara, Italy.
Beani
L
L
Bianchi
C
C
Marzola
G
G
Siniscalchi
A
A
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002545:Brain Ischemia / Q000188:drug therapy* / Q000378:metabolism; D002421:Caudate Nucleus / Q000098:blood supply*; D002540:Cerebral Cortex / Q000098:blood supply*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D008297:Male
C105319:3-(2-((phenylamino)carbonyl)ethenyl)-4,6-dichloroindole-2-carboxylic acid; D018691:Excitatory Amino Acid Antagonists; D007211:Indoles; D000109:Acetylcholine