1992 Volume 4 Issue 2 Pages 115-123
The innervation of vasopressin (VP) -containing neurons by brain natriuretic peptide (BNP) -containing neurons was examined by electron microscopy using a pre-embedding double immunostaining technique based on the consecutive use of silver-gold intensified peroxidase-antiperoxidase complex-3, 3'-diaminobenzidine (SGI-PAP-DAB) and the traditional PAP-DAB method in the same tissue sections. BNP-like immunoreactive (BNP-LI) nerve fibers and terminals were distributed in the ventral and dorsal parts of the supraoptic nucleus (SON) . Ultrastructural observation revealed that BNP-LI terminals that contained immunoreactive granular vesicles (90-120 nm diameter) formed synapse-like contacts with cell bodies and processes of magnocellular neurosecretory neurons in the SON. On observation of double-immunostained sections of the rat hypothalamic SON, BNP-LI terminals were found to make synapse-like contacts with VP-like immunoreactive nerve cell bodies and processes. These findings suggest direct synaptic influence of BNP neurons on the secretory activity of VP-containing neurons in the rat hypothalamic SON.
