BRAIN AND PITUITARY IMMUNOCYTOCHEMISTRY OF CARASSIN IN THE GOLDFISH, CARASSIUS-AURATUS - A NEW NEUROHORMONE PEPTIDE

Carassin is a 21-amino-acid tachykinin-related peptide originally isol ated from the goldfish brain. Carassin-immunoreactive (ir) perikarya w ere restricted to the nucleus preopticus periventricularis (NPP); immu noreactive perikarya were distributed sparsely in the rostral and caud al NPP, and were comparatively more in the lateral areas of the mid-NP P. Most perikarya showed thick axonal processes that extended into the rostral area of the organum vasculosum lamina terminalis (OVLT) and t erminated extensively in the vicinity of cells and blood capillaries i n its ventral area below the preoptic recess; the OVLT may play a role in release of the carassin-ir material into the general circulation. The axonal terminals diminished caudally and were almost absent in the posterior region of the OVLT. Most epithelial cells of the olfactory organ were carassin-ir positive. Several fibers showing carassin-ir we re also present in the olfactory bulb and are presumed to originate fr om the olfactory epithelium. Carassin-like ir granules were found in s ome cells of the proximal pars distalis (PPD) of the pituitary gland. Adjacent sections reacted with growth hormone (GH) and gonadotropin (G tH) antibodies, revealed that carassin coexists with GtH in a small pe rcentage of cells. Further, there is sexual dimorphism in the nature a nd distribution pattern of carassin-ir granules in the PPD. In males, GtH cells contained a few carassin-ir granules; whereas, in females, G tH cells frequently had clusters of carassin-ir granules. These carass in-containing granules may participate in auto- and/or paracrine regul ation of the pituitary. The ir-perikarya of the NPP may influence hypo physial function through a multisynaptic pathway. The functions of car assin in goldfish remain to be investigated.