Journal of neurophysiology
-
Animal survival in the forest, and human success on the sports field, often depend on the ability to seize a target on the fly. All bodies fall at the same rate in the gravitational field, but the corresponding retinal motion varies with apparent viewing distance. ⋯ Functional magnetic resonance imaging (fMRI) revealed blood-oxygen-level-dependent correlates of these visual context effects on gravitational motion processing in the vestibular nuclei and posterior cerebellar vermis. Our results suggest an early stage of integration of high-level visual analysis with gravity-related motion information, which may represent the substrate for perceptual constancy of ubiquitous gravitational motion.
-
The tetrodotoxin (TTX)-resistant Na(+) current arising from Na(V)1.8-containing channels participates in nociceptive pathways but is difficult to functionally express in traditional heterologous systems. Here, we show that injection of cDNA encoding mouse Na(V)1.8 into the nuclei of rat superior cervical ganglion (SCG) neurons results in TTX-resistant Na(+) currents with amplitudes equal to or exceeding the currents arising from natively expressing channels of mouse dorsal root ganglion (DRG) neurons. The activation and inactivation properties of the heterologously expressed Na(V)1.8 Na(+) channels were similar but not identical to native TTX-resistant channels. ⋯ In contrast, expression of tagged Na(V)1.8 in HeLa cells revealed a fluorescence pattern consistent with sequestration in the endoplasmic reticulum, thus providing a basis for poor functional expression in clonal cell lines. Our results establish SCG neurons as a favorable surrogate for the expression and study of molecularly defined Na(V)1.8-containing channels. The data also indicate that unidentified factors may be required for the efficient functional expression of Na(V)1.8 with a biophysical phenotype identical to that found in sensory neurons.