title: Muscarinic and nicotinic receptor modulation of object and spatial n-back working memory in humans.
abstract: Working memory impairments in the n-back task in schizophrenia have been linked to sustained deficiency in mesocortical dopamine function. More recently, abnormalities in the cholinergic system have also been documented in schizophrenia, with cortical reductions in both nicotinic and muscarinic receptors. While the cholinergic hypothesis of memory is well established, the role of cholinergic receptors in modulating n-back working memory is not known. We investigated the effects of selective and simultaneous muscarinic and nicotinic antagonism on spatial and object n-back working memory performance. The study was a double-blind, placebo-controlled repeated-measures design in which 12 healthy subjects were tested under four acute treatment conditions; placebo (P), mecamylamine (M), scopolamine (S) and mecamylamine+scopolamine (MS). Muscarinic antagonism with scopolamine significantly impaired both object and spatial n-back working memory, whereas nicotinic antagonism with mecamylamine had little effect. Simultaneous antagonism of both muscarinic and nicotinic receptors produced greater impairments in both object and spatial n-back working memory performance than muscarinic or nicotinic antagonism alone. These results suggest that: (1) both muscarinic and nicotinic receptors may functionally interact to synergistically modulate n-back working memory, and (2) that n-back working memory impairments in schizophrenia may in part be due to reductions in both muscarinic and nicotinic receptors.
authors.affiliation: Behavioural Neuroscience Laboratory, Department of Physiology, Monash Centre for Brain and Behaviour, PO Box 13F, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: Amity
authors.initials: A
authors.lastname: Green
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Ellis
authors.forename: Julia
authors.initials: J
authors.lastname: Ellis
authors.forename: Cali F
authors.initials: CF
authors.lastname: Bartholomeusz
authors.forename: Susan
authors.initials: S
authors.lastname: Ilic
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Croft
authors.forename: K Luan
authors.initials: KL
authors.lastname: Phan
authors.forename: Pradeep J
authors.initials: PJ
authors.lastname: Nathan
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003071:Cognition / Q000187:drug effects; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology*; D008570:Memory, Short-Term / Q000187:drug effects*; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009483:Neuropsychological Tests / Q000592:standards; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D010919:Placebos; D011976:Receptors, Muscarinic / Q000502:physiology; D011978:Receptors, Nicotinic / Q000502:physiology; D015203:Reproducibility of Results; D012601:Scopolamine / Q000494:pharmacology*
chemical_list: D018727:Muscarinic Antagonists; D018733:Nicotinic Antagonists; D010919:Placebos; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; D008464:Mecamylamine; D012601:Scopolamine