Anaerobic cilio-excitation and metabolic stimulation by 5-hydroxytryptamine in bivalve gill

Abstract

1. 1. 5-Hydroxytryptamine (5-HT) exerts a cilio-excitatory effect in the gills of Modiolus demissus and Mytilus edulis under the anaerobic conditions described. 2. 2. The anaerobic cilio-excitation can be blocked by the metabolic inhibitors of glycolysis, iodoacetate and fluoride. 3. 3. Anaerobic glycolytic rates, determined by standard manometric techniques, are markedly stimulated by 5-HT in Modiolus gill, and to a lesser extent in Mytilus gill. 4. 4. The addition of dextrose or adenosine triphosphate (ATP) and, to a greater extent, dextrose plus ATP produced increased rates of glycolysis in the gills of both species. 5. 5. 5-HT stimulated the dextrose- or the ATP-enhanced rates, but it had no stimulatory effect in the presence of dextrose plus ATP. 6. 6. Glycolytic rates of gill homogenates were also studied, and the effects of nicotinamide adenine dinucleotide (NAD), fructose-6-phosphate (F-6-P), and fructose-1,6-diphosphate (FDP) are reported. 7. 7. It is suggested, on the basis of indirect evidence, that 5-HT exerts its effect in this system by activating phosphoglucomutase.