Slice preparation of rat medulla and pons maintained for five hours in vitro.

Slices of rat medulla and pons were incubated in bicarbonate-buffered medium and their electrical activity was monitored for five hours with microelectrodes. The morphology of these slices was compared with that of the same region of rats of the same age using prior perfusion or immersion in fixatives before incubation. Many neurons in incubated slices show shrinkage necrosis (apoptosis) but not dilatation of the endoplasmic reticulum seen in most neurons fixed immediately after slicing. In incubated slices, some processes but not somata of glia appeared swollen: to a lesser extent some dendritic and axonal processes were swollen. Glia showed no cytoplasmic reaction after five hours to indicate that they might phagocytose damaged tissue components. Synapses appeared morphologically normal after the period of incubation and there was an apparent increase in numbers of profiles resembling growth cones.