MODULAR DISTRIBUTION OF VASOACTIVE INTESTINAL POLYPEPTIDE IN THE RAT BARREL CORTEX - CHANGES INDUCED BY NEONATAL REMOVAL OF VIBRISSAE

The distribution of vasoactive intestinal polypeptide-immunoreactive n euronal structures in the barrel cortex (posteromedial barrel subfield ) of adult rats was analysed after unilateral removal of the vibrissal follicles of row C in neonatal rats. The hypothesis was tested whethe r the distribution of vasoactive intestinal polypeptide-immunoreactive structures depends on the normal anatomical organization of the speci fic sensory input. After three months survival the distribution of the vasoactive intestinal polypeptide-immunoreactive structures was morph ometrically evaluated. This approach revealed alterations in the contr alateral posteromedial barrel subfield, where the disappearance of bar rel row C and a substantial increase in size mainly of barrel row D, b ut also of other rows could be detected. Increase in row D included bo th barrels and the interspace (septal segments between barrels in one row). As vasoactive intestinal polypeptide immunoreactivity of the bar rel field was found previously to be localized in synaptic boutons inv olved in symmetric synapses, our present findings suggest that (i) the interspace is enriched in inhibitory vasoactive intestinal polypeptid e-immunoreactive synapses as opposed to the excitatory thalamocortical input reaching the barrel hollow, (ii) the spatial distribution of th e vasoactive intestinal polypeptide system in the barrel cortex is clo sely associated with the neuronal organization of the sensory input an d reacts with a considerable plasticity to lesion-induced changes of t he input, and (iii) the compensatory barrel hypertrophy in a row neigh bouring the deafferented row involves an increasing number of vasoacti ve intestinal polypeptide-immunoreactive synapses per barrel. (C) 1998 IBRO. Published by Elsevier Science Ltd.