Electron microscopic studies on the pars intermedia of the rat under stress.

Using electron microscopy, we have studied the pars intermedia (PI) of the pituitary gland of Wistar rat under psychogenic stress, finding a considerable increase in dark cells. The cells of the PI present striking vacuoles in all their cytoplasms, increasing up to a phase of total cellular disintegration. We have also observed a cell type, not found in the animal control group, of regular size and electrondense matrix of medium contrast.