[Osmosensitive neurons in the retrochiasmatic area of the hypothalamus. An ultrastructural study].

An ultrastructural study has been conducted of the response of rat retrochiasmatic area neurons to an intraperitoneal injection of hypertonic sodium chloride. The formation of numerous communications between nuclear envelope and the granular endoplasmic reticulum (GER) is seen as a response of these neurons to the osmotic stimulus. Some of the GER cisterns may establish contact with the neuronal membrane. The quantity of polyribosomal rosettes increases, especially in the nuclear cytoplasmic infoldings. These results are interpreted as a change in the programmed activity of synthesis of these neurons. Previous electrophysiologic studies appear to demonstrate the possibility of these neurons being osmoreceptors. These ultrastructural observations seem to confirm this hypothesis.