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Nicotinic modulation of the early visual system and its underlying neuronal and metabolic changes

MPS-Authors
http://pubman.mpdl.mpg.de/cone/persons/resource/persons84059

Li,  J
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84324

Zaldivar,  D
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84289

von Pföstl,  V
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84210

Serr,  N
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84329

Zhang,  X
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84063

Logothetis,  NK
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84158

Rauch,  A
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Li, J., Zaldivar, D., von Pföstl, V., Serr, N., Zhang, X., Logothetis, N., et al. (2011). Nicotinic modulation of the early visual system and its underlying neuronal and metabolic changes. Poster presented at 41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011), Washington, DC, USA.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-B93E-1
Abstract
In macaques, cholinergic subreceptors of nicotine (nAChRs) are predominantly found in the excitatory afferents of the primary visual cortex (V1, layer 4c) originating from the lateral geniculate nucleus (LGN). This strategic termination pattern allows nicotine to up regulate thalamocortical activity, while in parallel activity outside layer 4c can be down regulated by nicotinic effects on GABAergic inhibition. In addition to this gain-modulating role, nicotine has also distinct neuroprotective effects. Here, we have examined whether such neuroprotective effects could be at least partially explained by the gain modulation itself which tunes neuronal networks to a most efficient input-output mode with little other interferences. We investigated nicotinic effects (systemic: 0.2mg/kg) in V1 by neurophysiological recordings using multi-laminar probes and sampling of intracortical glutamate, GABA and glutamine by microdialysis in anesthetized non-human primates. Multi unit activity (MUA: 900-3200 Hz) and gamma (65-120 Hz) activity showed an improved signal-to-noise ratio (SNR) while theta activity (4-8Hz) was significantly reduced (p<0.5). The neurochemical analysis on the other hand showed increased concentrations of GABA (+40) while glutamate (-60) and glutamine levels (-50) were reduced. Taken together nicotine shifts the ratio between glutamate and GABA clearly to GABA inducing inhibitory effects which reduce excitation and result in low glutamate levels. The decrease in excitatory neuronal activity is reflected in the reduced theta activity and the improved SNR in MUA and the gamma band resulting in an efficient input-output relation due to little excitatory interferences. The low levels of glutamine are most likely caused by the increased synthesis of GABA for which glutamine is a metabolic precursor. The neuroprotective effects of nicotine can be explained by the reduction of glutamate sparing neuronal networks from abundant excitatory activity resulting in excitotoxic effects by glutamate itself and other potentially toxic metabolites.