title: Visual acuity is reduced in alpha 7 nicotinic receptor knockout mice.
abstract: OBJECTIVE
  Nicotinic receptors (nAChRs) are part of a heterogeneous family of pentameric ligand-gated ion channels that are widely expressed in the visual system. The impact of α7 homomeric nAChRs on visual function was investigated using mutant mice lacking the α7 nicotinic receptor subunit.
  
  
  METHODS
  The spatial resolution limit was measured in α7 knockout (α7 KO) and age-matched control mice using three independent methods: an operant behavioral visual task (Prusky maze), cortical visual evoked potentials (VEPs), and the pattern electroretinogram (PERG) evoked by alternating gratings of different spatial frequencies and contrasts.
  
  
  RESULTS
  Visual acuity measured by means of the visual water maze task was significantly decreased in the α7 KO mice and, concordantly, there was a reduction of the cortical spatial resolution limit measured by VEPs. However, the PERG was normal in α7 KO mice, compared with control mice. The use of fluorescently tagged cholera toxin showed that projections from the retina segregate normally in α7 KO mice and, in line with this, the visual cortical responses elicited by stimulating either eye were normally balanced in both visual cortices and showed no retinotopic anomalies.
  
  
  CONCLUSIONS
  These findings indicate that the absence of the α7 nicotinic subunit reduces visual acuity. Because the cortical output has an abnormal spatial resolution but retinal output is preserved, it can be concluded that the low visual acuity was due to a deficit specifically present in the visual cortex.
authors.affiliation: Neuroscience Institute (National Council of Research [CNR]), Pisa, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Origlia
authors.forename: Dario Riccardo
authors.initials: DR
authors.lastname: Valenzano
authors.forename: Milena
authors.initials: M
authors.lastname: Moretti
authors.forename: Cecilia
authors.initials: C
authors.lastname: Gotti
authors.forename: Luciano
authors.initials: L
authors.lastname: Domenici
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004596:Electroretinography; D005074:Evoked Potentials, Visual; D047468:Immunoprecipitation; D051379:Mice; D018345:Mice, Knockout; D011978:Receptors, Nicotinic / Q000172:deficiency*; D014792:Visual Acuity / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C579166:Chrna7 protein, mouse; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor