The Journal of neuroscience : the official journal of the Society for Neuroscience
-
The functions of neurotrophins in relation to axon growth and branching during development of the nervous system are unknown. In order to address this question, we have investigated the influences of systemically administered mouse nerve growth factor (mNGF) and human recombinant neurotrophin-3 (hrNT-3) on dorsal root axon growth in the spinal cord of embryonic rats. As anticipated, mNGF has a marked influence on growth of dorsal root axons. ⋯ We conclude that the ability of mNGF to stimulate axon growth in both white and gray matter is consistent with the idea that mNGF regulates the developing axonal projections of DRG neurons in vivo. In contrast, systemically administered hrNT-3 inhibits the axon collateralizations of DRG neurons in gray matter at early developmental stages. We hypothesize that this inhibitory effect may be related to disruption of a chemotropic gradient of NT-3, or to the widespread expression of the NT-3 receptor trkC, on non-neuronal cells.
-
Severe tissue acidosis has been viewed traditionally as a damaging component of cerebral hypoxia. However, a neuroprotective action of low pH during hypoxia has been described in primary neuronal cultures. To identify and characterize this effect in mature brain tissue, adult rat hippocampal slices were made hypoxic after adjusting pHo with HCl or NaOH. ⋯ For each of these parameters, mild alkalinity (bath pH = 7.7) had the opposite effect. Acid treatment did not affect the decrease in [Ca2+]o during HSD but accelerated its recovery after reoxygenation. These results suggest that mild acidosis may limit hypoxic neuronal injury in vitro by delaying HSD onset and by additional mechanisms unrelated to the degree of calcium influx during neuronal depolarization.