AROMATIC L-AMINO-ACID DECARBOXYLASE IMMUNOHISTOCHEMISTRY IN THE SUPRACHIASMATIC NUCLEUS OF THE SHEEP - COMPARISON WITH TYROSINE-HYDROXYLASEIMMUNOHISTOCHEMISTRY

Using antisera against tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC), we have demonstrated the presence of numero us AADC immunoreactive neurons and a few TH immunoreactive neurons, ho mogeneously distributed throughout the suprachiasmatic nucleus. Simila r results have been described in other species. These observations sho w that this nucleus is able to synthesize trace amines (such as phenyl ethylamine or tyramine) in addition to dopamine. It is hypothesized th at these trace amines are possibly involved in the integration of day length variation in sheep, a species whose reproduction is closely rel ated to photoperiod.