Cetylcholine Release Is Elicited in the Visual Cortex, Ut Not in the Prefrontal Cortex, by Patterned Visual Timulation: a Dual in Vivo Microdialysis Study with Unctional Correlates in the Rat Brain

bstract—By its projections to the primary visual and the refrontal cortices, the basal forebrain cholinergic system is nvolved in cognitive processing of sensory stimuli. It has een suggested that visual stimulus-induced cholinergic acivation of the visual cortex may exert a permissive role on halamocortical inputs. However, it is not known if visual timulation elicits cholinergic activation of high-order brain reas in the absence of attentional need. In the present study, e measured the effects of patterned visual stimulation (horzontal grating) on the release of acetylcholine with dualrobe in vivo microdialysis in the visual and the prefrontal ortices of anesthetized rats. We also used retrograde tracing o determine the anatomical relationships of cholinergic neuons with neurons of the visual system and the prefrontal ortex. Finally, we evaluated a functional correlate of this timulation, namely c-fos immunolabeling. Patterned visual timulation elicited significant increases in acetylcholine reease in the visual cortex, accompanied by an increased umber of c-fos immunoreactive neurons in this brain area. n contrast, in the prefrontal cortex, neither the level of aceylcholine release nor the number of c-fos immunoreactive eurons was significantly changed because of the stimulaion. Cholinergic basal forebrain neurons projecting to the isual or the prefrontal cortices were both localized within the orizontal limb of the diagonal band of Broca but were not mmunoreactive for c-fos during visual stimulation. No parts f the visual system were found to directly project to these asal forebrain neurons. These results suggest the differenial involvement of cholinergic projections in the integration f sensory stimuli, depending on the level of activity of the argeted cortical area. © 2005 IBRO. Published by Elsevier td. All rights reserved.