Changes in Acetylcholine Extracellular Levels During Cognitive Processes: Table 1.

Abstract

Measuring the changes in neurotransmitter extracellular levels in discrete brain areas is considered a tool for identifying the neuronal systems involved in specific behavioral responses or cognitive processes. Acetylcholine (ACh) is the first neurotransmitter whose diffusion from the central nervous system was investigated and whose extracellular levels variations were correlated to changes in neuronal activity. This was done initially by means of the cup technique and then by the microdialysis technique. The latter, notwithstanding some technical limitations, makes it possible to detect variations in extracellular levels of ACh in unrestrained, behaving animals. This review summarizes and discusses the results obtained investigating the changes in ACh release during performance of operant tasks, exposition to novel stimuli, locomotor activity, and the performance of spatial memory tasks, working memory, and place preference memory tasks. Activation of the forebrain cholinergic system has been demonstrated in many tasks and conditions in which the environment requires the animal to analyze novel stimuli that may represent a threat or offer a reward. The sustained cholinergic activation, demonstrated by high levels of extracellular ACh observed during the behavioral paradigms, indicates that many behaviors occur within or require the facilitation provided by the cholinergic system to the operation of pertinent neuronal pathways.Acetylcholine (ACh) is the first neurotransmitter whose diffusion from the central nervous system was investigated and whose extracellular levels variations were correlated to changes in neuronal activity. ACh outflow from the spinal cord was detected by Bulbring and Burn (1941) during nerve stimulation, and the first attempts to demonstrate ACh outflow from the intact cortex were made 50 years ago. The purpose was to demonstrate whether ACh had a role in the CNS, and the theoretical approach was the same used in the previous decade for demonstrating the neurotransmitter role of ACh in the peripheral nervous system (Burn 1968). Using the cup technique and the leech bioassay, MacIntosh and Oboring (1955) demonstrated in the dog that ACh release was related to the spontaneous electrical activity of the cortex. The cup was formed by a small cylinder exerting a slight pressure over the meninges, filled with Ringer solution containing a cholinesterase inhibitor. No ACh could be detected in the absence of the inhibitor. The method was perfected by Mitchell (1953), and a description of the procedure with an analysis of the early literature reporting the changes in ACh release induced by stimulation of peripheral nerves, specific brain areas, and drugs can be found in reviews by Pepeu (1973), and Moroni and Pepeu (1984).The first question asked was whether ACh diffusing from the brain into the cortical cup originated from cholinergic nerve endings and whether changes in its extracellular levels were expressions of changes in the activity of the cholinergic nerve endings under the cup. The answer ...

A review of neurotoxicity of microcystins

“…As one of the most important modulatory neurotransmitter systems, the cholinergic system plays critical roles in the controlling of locomotor activity, emotional behavior, and cognitive processes (Pepeu and Giovannini 2004;Martins-Silva et al 2011). AChE (acetylcholonesterase), with classical functions in terminating neurotransmission at cholinergic synapses and neuromuscular junctions, was increased in MC-LRexposed zebrafish brain (Kist et al 2012).…”

Combined administration of D-galactose and aluminium induces Alzheimerlike lesions in brain

“…This set of data strongly indicates that Al plays a significant role in AD. learning and memory, and can be increased in hippocampus and cortex by animal training [29] . ACh is synthesized by ChAT, and degraded by AChE, both of which have reduced activity in AD brain, resulting in an overall decrease of ACh concentration that may contribute to the decline in learning and memory.…”

The Role of Acetylcholine in Cocaine Addiction

“…This activation produces an aberrant engagement of the learning process (Hyman, 2005). Because of the effect of cholinergic systems on reward and drug selfadministration, the prevalence of acetylcholine (ACh) within the striatum (Butcher and Butcher, 1974;Pisani et al, 2001), and the involvement of ACh in higher order cognitive processes (Pepeu and Giovannini, 2004), ACh may play an important role in the addictive processes underlying cocaine dependence. To date, research has emphasized the role of ACh in neurocognitive disorders, such as Alzheimer's and Parkinson's disease (Bosboom et al, 2003;Mesulam, 1996), as well as nicotine dependence (Stolerman and Shoaib, 1991), with less attention devoted to the role of ACh in other addictive disorders.…”