Lack of change in high affinity glutamate uptake in nucleus tractus solitarius following removal of the nodose ganglion.

High affinity glutamate uptake in the intermediate portion of the nucleus tractus solitarius (NTS) was not altered by prior removal of one nodose ganglion or by prior midline transection at the level of the NTS. In contrast, glutamate uptake in a tissue punch of the septal nucleus was significantly reduced by prior transection of the fornix. Studies also compared septal glutamate uptake in crude homogenate, supernatant resulting from centrifugation at 3000 X g, and the pellet resulting from centrifugation at 17,000 X g. The results show quantitative differences between measures of glutamate uptake in these different fractions, but qualitatively the results were similar. (These results, do, however, suggest that glutamate uptake might be most appropriately measured in the pellet resulting from centrifugation at 17,000 X g.) The observation that removal of the nodose ganglion did not effect glutamate uptake in the NTS is therefore not due to the method by which glutamate uptake was assessed. These studies fail to replicate the previous observation that glutamate uptake in the NTS decreases following removal of the nodose ganglion, and thus question the hypothesis that glutamate is the neurotransmitter of vagal afferent fibers.