Neuroplastic effects of neonatal capsaicin on barrel cortex of adult rat. An electrophysiological and autoradiographic study

Farkas, Tamás and Rojik, I. and László, F. and Varga, Csaba and Toldi, József (1997) Neuroplastic effects of neonatal capsaicin on barrel cortex of adult rat. An electrophysiological and autoradiographic study. European Journal of Neurology, 4 (4). pp. 397-403. ISSN 1351-5101 (print), 1468-1331 (online)

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Abstract

Capsaicin (50 mg/kg s.c./25 mu l) was administered to rats on the 2nd and 5th days after birth. The animals were raised, and from the age of 3 months the properties of the evoked activity were tested in the contralateral barrelfield. This neonatal capsaicin treatment was found to induce profound changes in the responsiveness of the barrel cortex in the adult rats: (1) the receptive field of the neurons in the C1 barrel was expanded; units within a particular barrel were driven by a significantly larger number of vibrissae than in the controls. (2) The rate of discharge evoked by the related vibrissa deflection was enhanced, while (3) the angular sensitivity of the neurons was decreased. (4) The most prominent change in cortical activity was observed by autoradiography: capsaicin-treated rats exhibited an enhanced labelling of different types of neurons throughout the hemisphere (surpassing the cortical representation of stimulated vibrissae). The present observations indicate that neonatal capsaicin affects the functional activity of the rat somatosensory cortex. It is suggested that unmyelinated sensory afferents play a role in the development of the rat somatosensory system.

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