DISTRIBUTION OF SUBSTANCE P-LIKE IMMUNOREACTIVITY IN THE BRAIN OF THEELASMOBRANCH SCYLIORHINUS-CANICULA

Immunohistochemical methods were used to study the distribution of sub stance P in the brain of the small-spotted dogfish (Scyliorhinus canic ula). Substance P-like immunoreactive (SP-IR) cell bodies and fibers w ere widely distributed. In the telencephalon, sparse populations of SP -IR neurons are present in the olfactory bulbs, pallium, and subpalliu m. In the subpallium numerous SP-IR boutons form unusual coats (''peri cellular appositions'') on SP-immunonegative neurons. In the diencepha lon numerous SP-IR cerebrospinal fluid-contacting neurons are present in the preoptic recess organ and organon vasculosum hypothalami. Numer ous SP-IR fibers also run in the hypothalamus, although no immunoreact ivity was observed in the habenulo-interpeduncular system. A terminal field of SP-IR fibers is present in the median eminence. In the mesenc ephalic tegmentum, SP-IR neurons were observed in the Edinger-Westphal nucleus. SP-IR fibers are present at high density in the basal tegmen tum, forming a conspicuous tract. In the hindbrain, numerous SP-IR fib ers were observed in the isthmal region, the trigeminal descending roo t, the visceral sensory area and commissural nucleus, and the viscerom otor column. SP-IR fibers occur at high density in the substantia gela tinosa of the rostral spinal cord. (C) 1993 Wiley-Liss, Inc.