Dopaminergic cells in the caudal A13 cell group express somatostatin-like immunoreactivity.

The caudal extension of the hypothalamic A13 dopamine cell group (A13c) was studied in the rat brain with immunohistochemical techniques using antibodies raised against the dopamine synthesizing enzymes tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC). Adjacent sections revealed that the TH- and AADC-staining patterns exhibited a clear overlap with that for somatostatin (SOM). Employing a double-labelling method with SOM- and AADC-antisera and subsequent elution and restaining of the same section with TH-antiserum, it was found that all immunoreactivities occurred in the same cell bodies. This study gives the first evidence for the presence of SOM-immunoreactivity in dopamine neurons.