CHANGES IN GLUTAMATE IMMUNOREACTIVITY IN THE SOMATIC SENSORY CORTEX OF ADULT MONKEYS INDUCED BY NERVE CUTS

Antibodies to glutamate (Glu) were used to study the effects of reduce d afferent input on excitatory neurons in the somatic sensory cortex o f adult monkeys. In each monkey, immunocytochemical staining was compa red to thionin and cytochrome oxidase (GO) staining in adjacent sectio ns. In the cervical spinal cord, dorsal column nuclei, ventroposterior thalamus, and primary somatic sensory cortex (SI), Glu immunoreactivi ty (Glu-ir) was analogous to that described in normal animals; regions with reduced or absent Glu-ir were never observed and no appreciable differences were noted between the experimental and normal side. There were also no differences in CO or thionin-stained sections from the a ffected hemisphere. In the insuloparietal operculum, sections in the h emisphere contralateral to the nerve cut showed that most cortical fie lds had a normal pattern of Glu-ir (pattern a), some exhibited a reduc tion of Glu-ir (pattern b), and that in the central portion of the upp er bank of the central sulcus, which corresponds to the general locati on of the hand representation of the second somatic sensory cortex (SI I), Glu-ir had virtually disappeared (pattern c). Adjacent sections pr ocessed for CO or stained with thionin showed that in the regions corr esponding to those characterized by pattern c, CO was slightly decreas ed and that glial cells had increased in number. In the regions of SII characterized by pattern c, small intensely stained glial cells displ ayed Glu-ir. These findings indicate that Glu-ir is regulated by affer ent activity and suggest that changes in Glu levels in neurons as well as in glial cells may trigger the biochemical processes underlying th e functional and structural changes occurring during a slow phase of r eorganizational plasticity in the cerebral cortex of adult monkeys. (C ) 1996 Wiley-Liss, Inc.