Background and objectives: Neonatal single whisker experience can modulate inhibitory interactions in layer IV of spared barrels. Also C-fiber depletion results in expansion of low threshold somatosensory mechanoreceptive fields. In this study, we examine the effect of c-fibres depletion on inhibitory interactions in D2 spared barrel.
Methods: C-fibres depletion was induced by neonatal treatment with capsaicin (50 mg/kg I.P). Plucking of all whiskers but D2 started at 0 (P0), 5 (P5) and 8 (P8) post partum days. To assess inhibitory receptive field characteristics principal whisker (PW) and adjacent whisker (AW) were moved serially at different inter-stimulus intervals (10, 20, 30, 50 and 100 ms). Neuronal ON and OFF responses were recorded in D2 spared barrel in layer IV. We quantified inhibitory interaction with a condition-test ratio (CTR).
Finding: In vehicle treated groups whisker plucking from P0, P5 and P8 increased CTR value (all P<0.05). The most increase in CTR was observed in P5 plucked animals. In capsaicin treated animals whisker plucking at different postnatal ages had a significant effect on the CTR index (all P<0.004). The greatest increase in CTR value was observed in P0 plucked animals (compared to unpluck rats, all P<0.002).
Conclusion: These findings indicate that in spared barrels, the observed changes in inhibitory interactions may be influenced by c-fibers.