Localization of corticotropin-releasing factor-immunoreactive nervous tissue and colocalization with neuropeptide Y-like substance in the optic lobe and peduncle complex of the octopus (Octopus vulgaris).

Abstract

The distribution of corticotropin-releasing factor (CRF)-like immunoreactivity and its colocalization with neuropeptide Y (NPY)-like substances were investigated in the optic lobe and peduncle complex of the octopus (Octopus vulgaris) using immunohistochemical techniques. In the optic lobe cortex, CRF-immunoreactive (CRF-IR) and NPY-immunonegative varicose fibers were observed in the plexiform layer. In the medulla, CRF-IR somata were seen in the cell islands, and CRF-IR varicose fibers were observed in the neuropil. About half of the CRF-IR structures in the medulla showed NPY-like immunoreactivity. In the peduncle lobe, no CRF-IR somata but abundant CRF-IR varicose fibers were observed, and about half of them showed NPY-like immunoreactivity. In the olfactory lobe, CRF-IR somata and abundant CRF-IR varicose fibers were observed. Almost all the CRF-IR somata located in the posterior olfactory lobule showed NPY-like immunoreactivity, whereas those seen in the median olfactory lobule were immunonegative for NPY. About half of the CRF-IR fibers in the anterior lobule neuropil were immunopositive for NPY, but those in the median and posterior lobule neuropils were immunonegative for NPY. In the optic gland, almost all the CRF-IR varicose fibers were immunoreactive for NPY. Western blot analysis of the optic lobe and peduncle complex indicated that anti-CRF antiserum labeled approximate 16.4- and 14.6-kDa bands and that anti-NPY antiserum labeled an approximate 16.2-kDa band. CRF-IR and NPY-immunoreactive neurons in the optic lobe may participate in the modulation of visual information and those in the optic gland may be involved in the regulation of endocrine function.