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

Using an indirect immunoperoxidase technique, we studied the location of be ta-endorphin (1-27) fibres and cell bodies in the cat brainstem. The highes t density of immunoreactive fibres was found in the lateral and medial para brachial nuclei and in the locus coeruleus; a moderate density was observed in the periaqueductal gray and the central reticular nucleus, and a low de nsity was observed in the interpeduncular nucleus, the nucleus incertus, th e raphe pallidus nucleus, the paralemniscal reticular nucleus! the laterodo rsal tegmental nucleus, the pericentral division of the dorsal tegmental nu cleus and the lateral reticular nucleus. Immunoreactive neurons were observ ed in the superior central nucleus, the pericentral division of the dorsal tegmental nucleus, the interpeduncular nucleus, the nucleus incertus and th e 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 ma mmals. The distribution of beta-endorphin (1-27)-immunoreactive fibres and perikarya is compared with the location of other neuropeptides in the cat b rainstem. Moreover, our findings reveal that beta-endorphin (1-27)immunorea ctive structures are widely distributed in the cat brainstem, suggesting th at the peptide might be involved in several physiological functions.