Meeting Abstract
P2.89 Tuesday, Jan. 5 Correlation of Membrane Potential and Ciliary Activity of Lateral Ciliated Cells of Gill of the Bivalve Crassostra virginica and the Neurotoxic Effects of Manganese NELSON, M.*; ADAMS, T.; CARROLL, M.A.; CATAPANE, E.J.; Medgar Evers College, Brooklyn catapane@mec.cuny.edu
Cilia of the lateral cells of gill of Crassostrea virginica are controlled by serotonin (HT) and dopamine (DA) nerves. HT is cilio-excitatory, DA cilio-inhibitory. The pharmacology of this system has been well studied but the fast movement of the cilia has prevented microelectrode studies of membrane potentials other then the elegant studies of Murakami and Takahashi in the 1970s. Voltage sensitive fluorescent probes are now available that change fluorescent intensity in relation to cell membrane potential. In this study we observed membrane potentials of lateral ciliated cells of gill of C. virginica while measuring beating rates. Applying HT to gill or a 5 Hz electrical stimulation (ES) to the branchial nerve (BN) caused prolonged membrane depolarizations, similar to plateau potentials, and increased beating rates. Applying DA to gill or a 20 Hz ES to the BN after exciting the cilia, repolarized the cell membrane and decreased beating rates. Manganese (Mn) is a neurotoxin causing Manganism in people exposed to high environmental levels. Previously we showed Mn disrupts the dopaminergic, cilio-inhibition in C. virginica. We now show Mn prevented the cilio-inhibitory response and corresponding repolarization when DA was applied to gill or the BN stimulated at 20 Hz. The effects of Mn were prevented by co-treating gills with p-Aminosalicylic Acid, a potential therapeutic drug for Manganism. This study shows a correlation between membrane potential and actions of HT and DA. It helps elucidate the neurotoxic mechanism of Mn by showing the site of action of Mn is postsynaptic. This information is helpful in understanding causes and potential treatments of the disease. This work was supported by grants 2R25GM06003-05 of NIGMS, 0516041071 of NYSDOE, 0622197 of NSF and P382A080040 of the USDE.
