Co-localisation of nitric oxide synthase and endothelin in the rat supraoptic nucleus.

The co-localisation of neuronal nitric oxide synthase and endothelin-1 was studied in the rat supraoptic nucleus at the electron microscopy level. Double pre-embedding immunocytochemistry was performed using ExtrAvidin-horseradish peroxidase and immunogold-silver techniques. Immunoreactivities to neuronal nitric oxide synthase and endothelin-1 were co-localised in sub-populations of endocrine neurones (cell bodies) and dendrites. Double-labelled axon terminals making asymmetrical synapses on unlabelled dendrites were also observed. The findings are discussed in terms of the possible role and significance of nitric oxide and endothlin-1 in the hypothalamo-neurohypophysial system.