Basal forebrain cholinergic lesions reduce heat shock protein 72 response but not pathology induced by the NMDA antagonist MK-801 in the rat cingulate cortex.
Non-competitive N-methyl-D-aspartate (NMDA) antagonists, in addition to their neuroprotective potential, possess neurotoxic properties and induce seizures and psychosis. MK-801 induces cytoplasmic vacuoles and heat shock protein in pyramidal neurones in the rodent posterior cingulate and retrosplenial cortex. The mechanism of this neurotoxicity is unclear, involving many neurotransmitter systems. The aim of this study was to investigate the role of cholinergic pathways from the nucleus basalis of Meynert in mediating MK-801-induced neurotoxicity. Cholinergic projections from the nucleus basalis of Meynert were lesioned by focal injection of 192-IgG-saporin (80 ng), which after 7 days reduced the number of cholinergic cell bodies by 70% in the lesioned nucleus compared to the uninjected nucleus. Following a unilateral cholinergic lesion, MK-801 (5 mg/kg s.c.) induced expression of hsp72 mRNA (6 h) and HSP72 protein immunoreactivity (24 h) was reduced by 42 and 60%, respectively in the ipsilateral compared to the contralateral posterior cingulate. Despite this apparent protective effect, the unilateral cholinergic lesion did not affect the degree of neuronal vacuolation (6 h), necrosis (24 h) or the large and prolonged increase in cerebral blood flow which occurred over the first 9h following MK-801 administration. These results demonstrate that cholinergic neurones in the nucleus basalis of Meynert play an important role in the heat shock response to NMDA antagonist-induced neurotoxicity but also reveal an unexpected divergence between the heat shock response and the pathophysiological response. This suggests that other cholinergic pathways or non-cholinergic mechanisms are responsible for the pathological changes induced by MK-801.
Willis
Colin L
CL
MRC Applied Neuroscience Group, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK. colin.willis@nottingham.ac.uk
Ray
David E
DE
Marshall
Hilary
H
Elliot
Gill
G
Evans
John G
JG
Kind
Clive N
CN
D000818:Animals; D000911:Antibodies, Monoclonal / Q000633:toxicity; D020532:Basal Nucleus of Meynert / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000187:drug effects; D016291:Dizocilpine Maleate / Q000633:toxicity*; D018691:Excitatory Amino Acid Antagonists / Q000633:toxicity*; D005260:Female; D006179:Gyrus Cinguli / Q000098:blood supply / Q000473:pathology*; D050884:HSP72 Heat-Shock Proteins / Q000096:biosynthesis*; D000922:Immunotoxins / Q000633:toxicity; D009699:N-Glycosyl Hydrolases; D009336:Necrosis; D009474:Neurons / Q000473:pathology; D010275:Parasympathetic Nervous System / Q000098:blood supply / Q000473:pathology*; D016548:Prosencephalon / Q000098:blood supply / Q000473:pathology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D014617:Vacuoles / Q000473:pathology
C085696:192 IgG-saporin; D000911:Antibodies, Monoclonal; D018691:Excitatory Amino Acid Antagonists; D050884:HSP72 Heat-Shock Proteins; D000922:Immunotoxins; D012333:RNA, Messenger; D054789:Ribosome Inactivating Proteins, Type 1; D016291:Dizocilpine Maleate; D009699:N-Glycosyl Hydrolases; D000076985:Saporins