Physiology Dapartment, Shaheed Beheshti University of Medical Sciences, Tehran, Iran
Introduction: In the present study the effect of nucleus basalis of Meynert (NBM) destruction on the temporal characteristics of response integration evoked by multiple whisker stimulations in rat barrel cortex was studied.
Material and Methods: Wistar male rats weighing 250-350 g were used. The animals were randomly distributed into two groups: In the first group bilateral NBM lesions was induced by 5µg ibotonic/5µl phosphate-buffered saline; rats in the other group were sham perated. Extracellular single-unit recording and controlled whisker stimuli were used to compare response properties of cells in barrel cortex between the two groups. Two neighboring principal and adjacent whisker in the same row were deflected alone or in paired combination in a condition-test paradigm, to assess excitatory and inhibitory receptive field (RF) characteristics.
Results: Results show that NBM lesion significantly decreased response magnitude (P<0.05) but did not affect response latencies. Units discharge to subsequent deflection of adjacent whisker were reduced in a time dependent fashion in both groups. But the magnitude of responses were significantly reduced at each inter-deflection interval in rats with NBM lesion (P<0.001). The excitatory FR of barrel units, which are the most tightly focused on the principal whisker, were the most greatly defocused by NBM lesion and NBM lesion increased surround inhibition.
Conclusion: Our results suggest that NBM has an important role in changing the balance of excitation and inhibition in the barrel cortex and can affect on the temporal integration of tactile inputs in the cortex.