Impaired functional organization in the visual cortex of muscarinic receptor knock-out mice.
Acetylcholine modulates maturation and neuronal activity through muscarinic and nicotinic receptors in the primary visual cortex. However, the specific contribution of different muscarinic receptor subtypes in these neuromodulatory mechanisms is not fully understood. The present study evaluates in vivo the functional organization and the properties of the visual cortex of different groups of muscarinic receptor knock-out (KO) mice. Optical imaging of intrinsic signals coupled to continuous and episodic visual stimulation paradigms was used. Retinotopic maps along elevation and azimuth were preserved among the different groups of mice. However, compared to their wild-type counterparts, the apparent visual field along elevation was larger in M2/M4-KO mice but smaller in M1-KO. There was a reduction in the estimated relative receptive field size of V1 neurons in M1/M3-KO and M1-KO mice. Spatial frequency and contrast selectivity of V1 neuronal populations were affected only in M1/M3-KO and M1-KO mice. Finally, the neuronal connectivity was altered by the absence of M2/M4 muscarinic receptors. All these effects suggest the distinct roles of different subtypes of muscarinic receptors in the intrinsic organization of V1 and a strong involvement of the muscarinic transmission in the detectability of visual stimuli.
Laboratoire de Neurobiologie de la Cognition Visuelle, École d'optométrie, Université de Montréal, Montréal, Québec, Canada; Laboratoire des Neurosciences de la Vision, École d'optométrie, Université de Montréal, Montréal, Québec, Canada.
Marianne
M
Groleau
Laboratoire de Neurobiologie de la Cognition Visuelle, École d'optométrie, Université de Montréal, Montréal, Québec, Canada.
Hoang Nam
HN
Nguyen
Laboratoire des Neurosciences de la Vision, École d'optométrie, Université de Montréal, Montréal, Québec, Canada.
Matthieu P
MP
Vanni
Laboratoire de Neurobiologie de la Cognition Visuelle, École d'optométrie, Université de Montréal, Montréal, Québec, Canada.
Frédéric
F
Huppé-Gourgues
Laboratoire des Neurosciences de la Vision, École d'optométrie, Université de Montréal, Montréal, Québec, Canada.
Christian
C
Casanova
Laboratoire de Neurobiologie de la Cognition Visuelle, École d'optométrie, Université de Montréal, Montréal, Québec, Canada.
Elvire
E
Vaucher
D000818:Animals; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010775:Photic Stimulation; D043643:Receptor, Muscarinic M1 / Q000235:genetics / Q000502:physiology; D043585:Receptor, Muscarinic M2 / Q000235:genetics / Q000502:physiology; D043587:Receptor, Muscarinic M3 / Q000235:genetics / Q000502:physiology; D043588:Receptor, Muscarinic M4 / Q000235:genetics / Q000502:physiology; D011976:Receptors, Muscarinic / Q000235:genetics / Q000502:physiology*; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*
D043643:Receptor, Muscarinic M1; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D043588:Receptor, Muscarinic M4; D011976:Receptors, Muscarinic
Cartography; Cortical activity; Muscarinic receptors; Visual cortex