Background: Barrel cortex of rodents is responsible for sensory information processing via facial whiskers. Locus coeruleus (LC), main source of cortical norepinephrine (NE), influences tactile sensory processing. In this study, the effect of phasic electrical stimulation of LC and sensory deprivation following the deflection of adjacent whisker on response properties of principal whisker related-neurons in layer IV of rat barrel cortex was investigated.

Materials and Methods: Response properties of 18 neurons in controls and 22 neurons in sensory deprivation group (P4) were evaluated using extracellular single unit recording following the controlled deflection of adjacent whisker or before a combined deflection of principal and adjacent whiskers. All whiskers on the left muzzle, except for D2, were plucked every other day for two mounts in P4 group. In both groups, LC was stimulated at 0, 50, 100, 200, 400 and 800 ms before adjacent whisker deflection and its effect on response latency, response magnitude and CTR (Condition Test Ratio) index was assessed.

Results: The mechanical deflection of adjacent whisker with no electrical stimulation of LC in P4 group caused significant decrease and increase in neuronal response magnitude and CTR index, respectively. Almost in all times of LC stimulation and following combinations of whisker deflection, LC electrical stimulation before adjacent whisker deflection in P4 group caused a decrease in neuronal response magnitude and an increase in CTR index.

Conclusion: LC electrical stimulation following sensory deprivation modulates neuronal response properties and changes the response patterns.