Monoamine transmitters and cAMP stimulation of Na transport in freshwater mussels

Abstract

The unionid mussels Ligumia subrostrata and Carunculina texasensis maintain a sodium steady state in artificial pond water. When the mussels were injected with serotonin, catecholamines, or phenylephrine (< 2 × 10 −5 M/L blood), the influx of Na was elevated 150–220% above controls and the animals accumulated Na from the medium. A similar response was observed with injections of dibutyryl cyclic AMP. Isolated gills of mussels accumulate Na from a pond-water bathing medium and the Na transport rate was stimulated by serotonin but not catecholamines. Serotonin was present in the gill tissue (2.26 ± 0.18 μg/g wet gill). Serotonergic neurons innervated by adrenergic fibers may be directly stimulating the Na transporting tissues in the gill of freshwater mussels.