The Journal of neuroscience : the official journal of the Society for Neuroscience
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The striatum is important in basal ganglia motor control and movement disorders. In this study we demonstrate the existence of two distinct sensorimotor cortical input systems to the striatum of the squirrel monkey. The first is a group of discrete zones in the extrastriosomal matrix of the putamen ("matrisomes") that receive somatotopically organized projections from both the body map in ipsilateral primary motor cortex (MI) and maps in ipsilateral primary somatosensory cortex (SI). ⋯ Thus, with the exception of the face representation, inputs from contralateral and ipsilateral body representations may alternate in the primate striatal matrix, an arrangement reminiscent of the alternating ocular dominance columns in visual cortex. Ipsilateral SI and MI and contralateral MI all innervated matrisomes intermingled with striosomes and with matrisomes not receiving sensorimotor cortical input. The patchiness of these maps is thus unlike the smoother somatotopic maps of sensorimotor cortex, and is also unlike the fractured somatotopy reported for the cerebellum.
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The aim of these experiments was to analyze how depolarization influences neurite outgrowth in leech neurons and what role the substrate and Ca2+ play in this response. Neurons in culture were exposed to 60 mM extracellular K+ for 30 min, which induced retraction of a subset of neurites growing on extracellular matrix substrate (ECM), a response comparable to that observed after electrical stimulation (Grumbacher-Reinert and Nicholls, 1992). After normal medium had been restored, the neurites continued to retract for about 1 hr to approximately 80% of the total starting neurite length. ⋯ The growth cones of cells grown on ECM and exposed to high K+ revealed retraction of lamellipodial and filopodial structures. On ConA, however, no differences were observed between growth cones of cells exposed to high K+ and those of control cells. These results demonstrate the importance of substrate molecules in the responses of growth cones to depolarization and therefore in the differentiation of neurons.