Improved immunohistochemical visualization of central serotonin nerves after loading with 5,7-dihydroxytryptamine

5,7-Dihydroxytryptamine (5,7-DHT), which reacts with a monoclonal antibody raised against 5-hydroxytryptamine (5-HT), has been used to increase the sensitivity of the immunohistochemical detection by this antibody of central 5-HT nerves in the rat brain. Rats pretreated with tricyclic antidepressants were given a single intraventricular injection of 5,7-DHT and were sacrificed 30 min-3 h later. This treatment resulted in accumulation of 5,7-DHT by central 5-HT nerves and selectively enhanced the immunofluorescence reaction of these nerves, particularly the terminals and non-terminal fibres.