Magnetic resonance diffusion tensor microimaging reveals a role for Bcl-x in brain development and homeostasis

A new technique based on diffusion tensor imaging and computational neuroanatomy was developed to efficiently and quantitatively characterize the three- dimensional morphology of the developing brains. The technique was used to analyze the phenotype of conditional Bcl-x knock-out mice, in which the bcl-x gene was deleted specifically in neurons of the cerebral cortex and hippocampus beginning at embryonic day 13.5 as cells became postmitotic. Affected brain regions and associated axonal tracts showed severe atrophy in adult Bcl-x-deficient mice. Longitudinal studies revealed that these phenotypes are established by regressive processes that occur primarily during the first postnatal week, whereas neurogenesis and migration showed no obvious abnormality during embryonic stages. Specific families of white matter tracts that once formed normally during the embryonic stages underwent dramatic degeneration postnatally. Thus, this technique serves as a powerful tool to efficiently localize temporal and spatial manifestation of morphological phenotype

Facilitation, augmentation, and potentiation of synaptic transmission at the superior cervical ganglion of the rabbit.J

ABSTRACT The effect of repetitive stimulation on synaptic transmission was studied in the isolated superior cervical ganglion of the rabbit under conditions of reduced quantal content. Excitatory postsynaptic potentials (EPSP) were recorded with the sucrose gap technique to obtain estimates of transmitter release. Four components of increased transmitter release, with time constants of decay similar to those observed at the frog neuromuscular junction at 20~ were found in the ganglion at 34 ~ a first component of facilitation, which decayed with a time constant of.59-+ _ 14 ms (mean + SD); a second component of facilitation, which decayed with a time constant of 388 + 97 ms; augmentation, which decayed with a time constant of 7.2 +- 1 s; and potentiation, which decayed with a time constant of 88 __. 25 s. The addition of 0.1-0.2 mM Ba 2+ to the Locke solution increased the magnitude but not the time constant of decay of augmentation. Ba 2 § had little effect on potentiation. The addition of 0.2-0.8 mM Sr 2 § to the Locke solution appeared to increase the magnitude of the second component of facilitation. Sr 2 § had little effect on augmentation o