Distribution and developmental changes in GABA-like immunoreactive neuronsin the central nervous system of pond snail, Lymnaea stagnalis

We examined three-dimensionally the arrangement of gamma-aminobutyric acid; (GABA)-like immunoreactive neurons in the central nervous system (CNS) of the pond snail, Lymnaea stagnalis, by a combination of immunohistochemistry and confocal laser scanning microscopy on whole-mount preparations. GABA-l ike immunoreactivity was detected in all ganglia of the adult CNS. The foll owing distribution of immunoreactive cell bodies was noted in the adult sna il. Buccal ganglia: one cell body and five pairs of cell bodies, cerebral g anglia: one pair of cell bodies, pedal ganglia: two single cell bodies, two pairs of cell bodies, and three pairs of cell clusters, and pleural gangli a: one pair of cell bodies. In the asymmetrical parietal ganglia, three cel l bodies were located in the left parietal ganglion; three cell bodies and three cell clusters were located in the right parietal ganglion. In the sin gle visceral ganglion, a few scattered individual cell bodies and a cell cl uster were GABA-like immunoreactive. Our results showed that the occurrence of GABA is widely spread in the CNS of adult L. stagnalis. GABA-like immun oreactivity in the CNS was not detected in the embryo but; was observed aft er hatching, although the number of stained cells was less than in the adul t, with the exception of those in the cerebral ganglia where their number d ecreased with maturation. Our results provide detailed maps of the central GABA-like immunoreactive neurons in juveniles, immatures, and adults oft. s tagnalis. J. Comp. Neurol. 418:310-322, 2000. (C) 2000 Wiley-Liss, Inc.