PLASTICITY OF CEREBRAL METABOLIC WHISKER MAPS IN ADULT MICE AFTER WHISKER FOLLICLE REMOVAL -I - MODIFICATIONS IN BARREL CORTEX COINCIDE WITH REORGANIZATION OF FOLLICULAR INNERVATION

We investigated alterations of the metabolic whisker map of barrel cor tex after the removal of the follicles of left whiskers C1, C2 and C3 in adult albino mice. The quantitative autoradiographic [C-14]deoxyglu cose method was used to measure local cerebral metabolic rates for glu cose in barrel cortex of mice two, four, eight, 64, 160 and 250 days a fter the lesion. Metabolic rates were measured in three groups of anim als: (i) mice with lesions that had all whiskers clipped; (ii) mice wi th lesions that had left whiskers B1-3 and D1-3 stimulated; and (iii) unoperated mice that had left whiskers B1-3 and D1-3 stimulated. Compa red with the metabolic rates in barrels C1-3 of stimulated unoperated mice, barrels C1-3 of stimulated mice with lesions showed the first di scernible increase in metabolic rate four days after the lesion. The i ncrease became distinct at 64 days, but attained statistical significa nce only similar to 160 days after the lesion. The lesion pei se, i.e. without whisker stimulation, caused only a small increase in metaboli c rate in barrels C1-3 accounting for not more than one fourth of the increase in metabolic rate measured after whisker deflection. The remo val of whisker follicles C1-3 led, therefore, to an enlargement of the metabolic representations of the adjacent whiskers into the barrels d eprived by the lesion. The gradual consolidation of the alterations of the metabolic whisker map coincided with the regeneration of follicul ar nerves in the whiskerpad. We detected anomalous deep nerves innerva ting follicles surrounding the lesion at similar to 64 days, and the n umber of myelinated nerve fibres in the deep nerves of these follicles was increasing with increasing time after the lesion. The coincidence of peripheral and central change suggests that the reorganization of the innervation of the sensory periphery plays an important role in th e persistent alterations of the cortical somatotopy in adults followin g a lesion in the sensory periphery. (C) 1997 IBRO. Published by Elsev ier Science Ltd.