Development of catecholaminergic neurons in the pond snail, Lymnaea stagnalis: II. Postembryonic development of central and peripheral cells

Catecholamines have long been thought to play important roles in different mollusc neural functions. The present study used glyoxylate- and aldehyde-i nduced histofluorescence to identify central and peripheral catecholaminerg ic neurons in the snail Lymnaea stagnalis. The majority of these cells were also found to react to antibodies raised against tyrosine hydroxylase. A m inority of the catecholaminergic neurons, however, exhibited no such immuno reactivity. The number of central catecholaminergic neurons nearly doubled (from about 45 to about 80 cells) during the first 2-3 days of postembryoni c development. Thereafter, catecholaminergic neurons again doubled in numbe r and generally grew by about 100-200% in soma diameter as the snails grew by 1,000% in overall linear measurements. In contrast to the relatively mea ger addition of central catecholaminergic neurons, several thousand catecho laminergic somata were added to different peripheral tissues during postemb ryonic development. These small, centrally projecting neurons were particul arly concentrated in the lips, esophagus, anterior margin of the foot, and different regions of the male and female reproductive tracts. Chromatograph ic analyses indicated that dopamine was the major catecholamine present in the central ganglia, foot, and esophagus, although detectable levels of nor epinephrine (approximately 20% of dopamine levels) were also found in the g anglia. The total content but not the concentration of dopamine increased w ithin the tissue samples during postembryonic development. The companion st udy (Voronezhskaya et al. [1999] J. Comp. Neurol. 404:285-296) and the pres ent study furnish a complete description of central and peripheral catechol aminergic neurons from their first appearance in early embryonic developmen t to adulthood. (C) 1999 Wiley-Liss, Inc.