اثر تحریک الکتریکی هسته رافه خلفی بر پاسخ برانگیخته نورون‌های لایه IV و V‌‌‌ قشر بارل (بشکه‌ای) در موش صحرایی

Effect of the Dorsal Raphe Nucleus Electrical Stimulation on Evoked Response of the IV Layers and V Barrel Cortical Neurons in Rat M.R Afarinesh MSc , V. Sheibani PhD , R. Farazifard MSc 1, M. Abasnegad PhD , A. Shamsi zadeh MSc Received: 17/09/06 Sent for Revision: 13/03/07 Received Revised Manuscript: 13/06/07 Accepted: 27/06/07 Background and Objective: Seretonergic pathway is one of the neuromodulatory mechanisms which mainly originates from dorsal raphe nucleus (DRN). In order to explore the role of serotonin on sensory processing, we investigated the effect of DRN stimulation on response properties of the IV layer and V neurons of whisker related area of rat somatosensory cortex. Materials and Methods: In this study twenty adult male Wistar rats (250-350gr) were used. DRN was stimulated at 0, 50, 100, 200 and 400ms before principal or adjacent whiskers deflection individually or in a condition test paradigm. For assessing the effect of DRN stimulation on inhibitory receptive field of barrel neurons, adjacent whisker was also deflected 20ms before principal whisker deflection. Results: DRN stimulation decreased the On response magnitude of layer V neurons to principal whisker deflection (p<0.05). The On response latency of the layer IV of neurons increased when DRN was stimulated 200 or 400ms before principal whisker deflection (p<0.05 and p<0.01 respectively). DRN stimulation had no effect on both the On response magnitude and latency of neurons to adjacent whisker deflection. We observed a decrease in inhibitory effect of adjacent whisker deflection on the magnitude of neuronal response to principal whisker deflection on the IV layer when DRN was stimulated 200ms before principal whisker deflection (p<0.05). Conclusion: Our results suggest that DRN have a modulatory effect on information processing in somatosensory cortex of rats. Key words: Barrel cortex, Dorsal Raphe Nucleus, Rat, Electrical stimulation