Distribution of parvalbumin immunoreactivity in the brain of the tench (Tinca tinca L., 1758)

The distribution of parvalbumin (PV) immunoreactivity in the tench brain wa s examined by using the avidin-biotin-peroxidase immunocytochemical method. This protein was detected in neuronal populations throughout all main divi sions of the tench brain. In the telencephalic hemispheres, PV-immunopositi ve neurons were distributed in both the dorsal and ventral areas, being mor e abundant in the area ventralis telencephali, nucleus ventralis. In the di encephalon, the scarce distribution of PV-containing cells followed a rostr ocaudal gradient, and the most evident staining was observed in the nucleus periventricularis tuberculi posterioris and in a few nuclei of the area pr aetectalis. In the mesencephalon, abundant PV-immunoreactive elements were found in the tectum opticum, torus semicircularis, and tegmentum. In the te ctum opticum, PV-immunoreactivity presented a laminar distribution. Three P V-containing neuronal populations were described in the torus semicirculari s, whereas in the tegmentum, the PV staining was mainly located in the nucl eus tegmentalis rostralis and in the nucleus nervi oculomotorii. In the met encephalon, Purkinje cells were PV-immunopositive in the valvula cerebelli, lobus caudalis cerebelli, and in the corpus cerebelli. In the myelencephal on, PV immunoreactivity was abundant in the nucleus lateralis valvulae, in the nucleus nervi trochlearis, nucleus nervi trigemini, nucleus nervi abduc entis, nucleus nervi glossopharyngei, and in the formatio reticularis. Maut hner cells were also PV immunostained. By contrast to other vertebrate grou ps, only a restricted population of PV-containing neurons was GABA-immunore active in the tench, demonstrating that this calcium-binding protein cannot be considered a marker for GABAergic elements in the teleost brain. This s tudy demonstrates a low phylogenetic conservation of the distribution of PV comparing teleosts and tetrapods. (C) 1999 Wiley-Liss, Inc.