Anatomical distribution of beta-endorphin (1-27) in the cat brainstem: an immunocytochemical study

Using an indirect immunoperoxidase technique, we studied the location of beta-endorphin (1-27) fibres and cell bodies in the cat brainstem. The highest density of immunoreactive fibres was found in the lateral and medial parabrachial nuclei and in the locus coeruleus; a moderate density was observed in the periaqueductal gray and the central reticular nucleus, and a low density was observed in the interpeduncular nucleus, the nucleus incertus, the raphe pallidus nucleus, the paralemniscal reticular nucleus, the laterodorsal tegmental nucleus, the pericentral division of the dorsal tegmental nucleus and the lateral reticular nucleus. Immunoreactive neurons were observed in the superior central nucleus, the pericentral division of the dorsal tegmental nucleus, the interpeduncular nucleus, the nucleus incertus and the dorsal raphe nucleus. Our results point to a more widespread distribution of beta-endorphin (1-27)-immunoreactive perikarya in the cat brainstem in comparison with previous studies carried out in the same region of other mammals. The distribution of beta-endorphin (1-27)-immunoreactive fibres and perikarya is compared with the location of other neuropeptides in the cat brainstem. Moreover, our findings reveal that beta-endorphin (1-27)-immunoreactive structures are widely distributed in the cat brainstem, suggesting that the peptide might be involved in several physiological functions.