Premium
A positive allosteric modulator of α7 n AChR s augments neuroprotective effects of endogenous nicotinic agonists in cerebral ischaemia
Author(s) -
Kalappa Bopanna I,
Sun Fen,
Johnson Stephen R,
Jin Kunlin,
Uteshev Victor V
Publication year - 2013
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.12247
Subject(s) - methyllycaconitine , neuroprotection , nicotinic agonist , pharmacology , ex vivo , choline , neuroscience , chemistry , in vivo , anesthesia , medicine , nicotinic acetylcholine receptor , biology , receptor , biochemistry , microbiology and biotechnology
Background and Purpose Activation of α7 nicotinic acetylcholine receptors (n AChR s) can be neuroprotective. However, endogenous choline and ACh have not been regarded as potent neuroprotective agents because physiological levels of choline/ ACh do not produce neuroprotective levels of α7 activation. This limitation may be overcome by the use of type‐ II positive allosteric modulators ( PAMs ‐ II ) of α7 n AChR s, such as 1‐(5‐chloro‐2,4‐dimethoxyphenyl)‐3‐(5‐methylisoxazol‐3‐yl)‐urea ( PNU ‐120596). This proof‐of‐concept study presents a novel neuroprotective paradigm that converts endogenous choline/ ACh into potent neuroprotective agents in cerebral ischaemia by inhibiting α7 nAChR desensitization using PNU ‐120596. Experimental Approach An electrophysiological ex vivo cell injury assay (to quantify the susceptibility of hippocampal neurons to acute injury by complete oxygen and glucose deprivation; COGD ) and an in vivo middle cerebral artery occlusion model of ischaemia were used in rats. Key Results Choline (20–200 μM) in the presence, but not absence of 1 μM PNU ‐120596 significantly delayed anoxic depolarization/injury of hippocampal CA 1 pyramidal neurons, but not CA 1 stratum radiatum interneurons, subjected to COGD in acute hippocampal slices and these effects were blocked by 20 nM methyllycaconitine, a selective α7 antagonist, thus, activation of α7 nAChRs was required. PNU ‐120596 alone was ineffective ex vivo . In in vivo experiments, both pre‐ and post‐ischaemia treatments with PNU ‐120596 (30 mg·kg −1 , s.c. and 1 mg·kg −1 , i.v., respectively) significantly reduced the cortical/subcortical infarct volume caused by transient focal cerebral ischaemia. PNU ‐120596 (1 mg·kg −1 , i.v., 30 min post‐ischaemia) remained neuroprotective in rats subjected to a choline‐deficient diet for 14 days prior to experiments. Conclusions and Implications PNU‐120596 and possibly other PAMs ‐ II significantly improved neuronal survival in cerebral ischaemia by augmenting neuroprotective effects of endogenous choline/ ACh .