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Abstract

The brain is able to change the synaptic strength in response to stimuli that leave a memory trace. Long-term potentiation (LTP) and long-term depression (LTD) are forms of activity-dependent synaptic plasticity proposed to underlie memory. The induction of LTP appears mediated by glutamate acting on AMPA and then on NMDA receptors. Cholinergic muscarinic agonists facilitate learning and memory. Acetylcholine depolarizes pyramidal neurons, reduces inhibition, upregulates NMDA channels and activates the phosphoinositide cascade. Postsynaptic Ca2+ rises and stimulates Ca-dependent PK, promoting synaptic changes. Electroencephalographic desynchronization and hippocampal theta rhythm are related to learning and memory, are inducible by cholinergic agonists and elicited by hippocampal cholinergic terminals. Their loss results in memory deficits. Hence, cholinergic pathways may act synergically with glutamatergic transmission, regulating and leading to synaptic plasticity. The stimulation that induces plasticity in vivo has not been established. The patterns for LTP/LTD induction in vitro may be due to the loss of ascending cholinergic inputs. As a rat explores pyramidal cells fire bursts that could be relevant to plasticity.

Nontropic actions of neurotrophins: Subcortical nerve growth factor gene delivery reverses age-related degeneration of primate cortical cholinergic innervation

“…Cholinergic systems contribute only a small fraction to the total number of axons and synapses in the cortex (34), yet exert an important role in modulating neuronal excitability throughout the neocortex and hippocampus (35,36). Thus, alterations in this system can exert wide-ranging effects on various aspects of cognition, including attention and memory (37)(38)(39)(40). Although prior studies have reported age-related declines in some transmitter systems in the cortex (12)(13)(14)(15)(16)(17)(18)(19), structural alterations in neocortical systems have not been described previously.…”

Muscarinic Inhibition of Hippocampal and Striatal Adenylyl Cyclase is Mainly Due to the M4 Receptor

“…The modulation of excitatory transmission by muscarinic acetylcholine receptors (mAChRs) seems particularly relevant to learning and memory processing in the hippocampal formation, where the diversity and differential localization of the receptors are likely to account for the complex cholinergic modulation in this structure [1,2]. The non-selective muscarinic antagonist scopolamine causes amnesia for many behavioral tasks in rats when directly administered into the hippocampus immediately after training [3], supporting the idea of the involvement of hippocampal mAChRs in memory consolidation.…”

“…Taking into account the participation of the hippocampal cholinergic muscarinic transmission in learning and memory [1] and the reported effects of MTs on memory in rats [13,19,20], this work would also contribute to further understand the participation of mAChR subtypes in cognitive functions.…”

Neurobiology of Memory and Anxiety: From Genes to Behavior

“…Cholinergic synaptic transmission has long been implicated in learning, memory, and anxiety [36, 92]. Neuronal nicotinic (N) acetylcholine (ACh) receptors are hetero-oligomers (formed by five of 11 known α and β subunits) mediating anxiolytic-like effect of nicotine [35].…”