Neuronal response properties of somatosensory cortex (layer IV) are modulated following experience dependent plasticity in c-fiber depleted rats

Introduction: Previous studies have shown that the receptive field properties, spontaneous activity and spatio-temporal interactions of low-threshold mechanical somatosensory cells in the barrel cortex are influenced by C-fibers. In this study, we examined the effect of C-fiber depletion on response properties of barrel cortex neurons following experience dependent plasticity. Methods: In this study, exteracellular single unit recording was performed on 154 barrel cortex neurons in 70 male Wistar rats (38-41days old). For depleting of C-fibers, neonatal rats received an intra-peritoneal injection of capsaicin solution (50 mg/kg) on the first neonatal day. For induction of experience dependent plasticity, all whiskers but D2 on the left muzzle, were plucked from first neonatal day. Neuronal ON and OFF responses were recorded in right barrel cortex following principal whisker (PW) and its caudal adjacent whisker (AW) deflection. Results: Whisker plucking increased PW–evoked ON responses both in capsaicin and vehicle treated rats (all P<0.05). In vehicle treated rats, AW-evoked ON responses were decreased in plucked animals (P< 0.05). Of particular interest, in capsaicin treated rats, AW-evoked ON responses were not decreased in plucked animals. Analyzing OFF responses showed similar result to ON responses. Conclusion: These findings indicate that c-fibers can modulate neuronal response properties following experience dependent plasticity in layer IV of barrel cortex.