Annular gap junctions in cuboidal ependymocytes of the median eminence of the rat after intraventricular administration of methysergide and thyrotropin releasing hormone.

The annular gap junctions in the cuboidal ependymocytes of the median eminence of rats were studied after intraventricular administration (3rd ventricle) of methysergide and thyrotropin releasing hormone. Isolated annular gap junctions were found in the ependymocytes of normal animals. In experimental rats an increase was observed in the number of annular gap junctions at 5 min after administration of the drugs; the increase was more apparent at 10 min postadministration. Likewise, the ependymocytes showed a clear development of the Golgi complex and an increase in the number of vesicles close to the lateral membranes. Accordingly, the increase observed in annular gap junctions could be interpreted as a sign of cellular activity indicative of a greater exchange of substances through the ependymocytes.