Effects of hormone-releasing stimuli on the area of the perivascular space in the neural lobe of the rat.

Neural lobes from rats subjected to neurohypophysial hormone-releasing stimuli were examined electron microscopically following fixation in 4% tannic acid in 2.5% glutaraldehyde. This fixation allowed the delineation of the perivascular space in the neural lobe tissue. Measurement of the area of the perivascular space showed that it was significantly increased in the rats subjected to vagal stimulation and intraarterial calcium ions compared to the control rats. The rats which had been subjected to haemorrhage as a hormone-releasing stimulus did not show any significant change in the area of the perivascular space. The significance of these findings in relation to hormone release is discussed.