Comparison of serotonin and 5-methoxytryptamine immunoreactivity in rat raphe nuclei.

We studied the immunoreactivity of 5-methoxytryptamine (MT) and 5-hydroxytryptamine (HT) in the raphe region of rats using specific polyclonal antibodies and the peroxidase/anti-peroxidase (PAP) technique. Overall, the patterns of the specific staining for these two antibodies were found to be the same in this region of the rat brain. The staining reaction was considerably less intense for MT than for HT. Specificity tests were performed using HT, MT and tryptamine (T) conjugates at concentrations of 5 X 10(-8) M for antibodies to HT and 2.5 X 10(-9) M for antibodies to MT. Although the distribution of HT-like and MT-like immunoreactivity broadly overlapped, the results obtained from adsorption-specificity tests confirmed the presence of specific MT staining in the rat raphe.