Aim: 

Some fishes are known to have elaborate, specialized taste systems, as Cyprinus Carpio. The Cyprinidae have a large pair of barbels, exstending downward from their lower jaw and use this barbels to probe the loose substrate materials in search of food. The barbels are quite rigid and are moved rapidly to both probe and stir the substrate and are studded with numerous taste booth. In order to study the olfactory pattern of innervation of taste booth, the fluorescent carbocyanide dye Dil, was applied into barbels. Immunocytochemistry tecnhique was used to demonstrate the presence of glutamate and tyrosine hydroxylase (TH) into olfactory encephalic zones projecting to barbels.

Methods: 

The fishes were deeply anesthetized with MS222. Dil was injected by Hamilton syringe into barbels bilaterally. After four days, the animals were re-anesthetized and perfused by 4% paraformaldheyde in 0.1 M phosphate buffer. The brain was dissected out and two series of coronal sections of olfactory bulbs, all brain and a longitudinal sections of olfactory tract were cut by cryostate. One series was mounted onto gelatine-coated slides for Dil fluorescente microscopy. An adjacent series of section was processed for TH and glutamate immunocytochemistry procedure. Retrogradely labeled and immunoreactive projections were analyzed by a fluorescent Nikon Eclipse i80.

Results: 

Injection of Dil into the barbels resulted in large number of retrogradly labeled neurons throughout these olfactory areas; the olfactory bulbs, the olfactory tract, the dorsal thelencephalic areas and the habenula.

Conclusion: 

In this study, we demonstrated the existence of direct olfactory projections from barbels to different olfactive encephalic areas.