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First published online June 29, 2006
Journal of Experimental Biology 209, 2785-2793 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02308

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Dopaminergic regulation of ion transport in gills of the euryhaline semiterrestrial crab Chasmagnathus granulatus: interaction between D1- and D2-like receptors

Griselda Genovese^1,2,*, Mihaela Senek³, Nicolás Ortiz^1,, Mariana Regueira¹, David W. Towle³, Martín Tresguerres^1, and Carlos M. Luquet^1,2,

¹ Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria (C1428EHA) Buenos Aires, Argentina
² CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) Rivadavia 1917 (C1033AAJ) Buenos Aires, Argentina and
³ Mount Desert Island Biological Laboratory, Salisbury Cove ME (04672), USA

^* Author for correspondence at address 1 (e-mail: genovese{at}bg.fcen.uba.ar)

Accepted 3 May 2006

The effects of dopamine (DA) and dopaminergic agonists and antagonists on ion transport were studied in isolated perfused gills of the crab Chasmagnathus granulatus. DA applied under steady state conditions (perfusion with hemolymph-like saline) produced a transient increase of the transepithelial potential difference (V_te) from 2.2±0.2 to 4.8±0.3 mV, describing an initial cAMP-dependent stimulating phase followed by an inhibitory phase. Spiperone and domperidone (antagonists of D2-like DA receptors in vertebrates) completely blocked the response to DA, while the D1-like antagonist SCH23390 blocked only the inhibitory phase. Theophylline (phosphodiesterase inhibitor) and okadaic acid (protein phosphatases PP1 and PP2A inhibitor) were also able to block the inhibitory phase, suggesting that it depends on adenylyl cyclase inhibition and on protein phosphatases. When the gills were perfused with hypo-osmotic solution, or with the adenylyl cyclase activator forskolin, V_te was increased several-fold. DA applied under these stimulated conditions partially reversed the V_te increase by 54% and 25%, respectively. Similarly, the D1-like agonist, fenoldopam, produced a 33% reduction in the stimulated V_te. We propose that, in C. granulatus gills, DA stimulates adenylyl cyclase and therefore ion transport through D1-like receptors linked to a Gs protein, although they respond to antagonists that interact with D2-like receptors in vertebrates. The inhibitory phase seems to be mediated by D2-like receptors linked to a Gi/o protein, which inhibits adenylyl cyclase, although these receptors can be activated or blocked by agonists or antagonists that interact with D1-like receptors in vertebrates and insects.

Key words: dopamine receptor dopamine agonist, dopamine antagonist, cAMP, Na⁺/K⁺-ATPase, okadaic acid, transepithelial potential differences, crab, Chasmagnathus granulatus

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