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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

View larger version (13K): [in a new window]   Fig. 1. Effect of the addition of 10 µmol l-1 dopamine (DA) to 30 saline solution in isolated perfused posterior gills of Chasmagnathus granulatus. (A) Time course of a representative experiment. (B) Means plot. Dopamine significantly induces transepithelial potential differences (Vte) (*P<0.01; N=5). After 40-60 min of dopamine application, Vte becomes not significantly different from the control value.

View larger version (36K): [in a new window]   Fig. 2. Transepithelial potential differences (Vte) of posterior gills of Chasmagnathus granulatus. Gills were initially perfused with 30 saline and then perfused with 20 saline (hypo-osmotic shock), means were calculated 30 and 90-100 min after the beginning of the experiment. Then, 50 µmol l-1 dopamine (DA) was added to the perfusion saline and reversibly reduced the stimulatory effect of hypo-osmotic perfusion. In these cases means were calculated 150-160 and 210-230 min after the beginning of the experiment. Significant differences are noted by different letters (a and b) (P<0.05; N=7).

View larger version (14K): [in a new window]   Fig. 3. Effect of DA on posterior gills previously stimulated with the adenylyl cyclase activator forskolin (10 µmol l-1); mean was calculated 40-60 min after the beginning of the experiment. Perfusion with 10 µmol l-1 DA did not produce consistent effects; 50 µmol l-1 partially reversed the stimulating effect of forskolin on Vte (P<0.05; N=7, mean was obtained 80-100 min after the beginning of the experiment). Dotted line represents mean control value obtained after 20 min of perfusion with 30 saline. Asterisk, significantly different from -DA values.

View larger version (11K): [in a new window]   Fig. 4. Effects of 10 µmol l-1 dopamine (DA) on transepithelial potential differences (Vte) of posterior gills of Chasmagnathus granulatus, after pretreatment with the protein phosphatase inhibitor, okadaic acid (60 nmol l-1). Vte is strongly and permanently stimulated. (*P<0.001; N=5).

View larger version (13K): [in a new window]   Fig. 5. Effects of 10 µmol l-1 dopamine (DA) on transepithelial potential differences (Vte), of posterior gills of Chasmagnathus granulatus previously perfused with the phosphodiesterase inhibitor theophylline (T), as a percentage of control values (30 saline perfusate). Gills were perfused with 30 saline solution plus 2.5 mmol l-1 T, then 10 µmol l-1 DA was added. After stabilization, DA was withdrawn. Finally DA was applied alone (*P<0.05; N=6).

View larger version (15K): [in a new window]   Fig. 6. Effects of D1-like dopamine (DA) receptor agonists and antagonists on transepithelial potential differences (Vte) of posterior gills of Chasmagnathus granulatus. (A) 10 µmol l-1 DA applied after pretreatment with the D1 antagonist, SCH23390 (10 µmol l-1) produced the typical stimulatory phase, increasing Vte (*P<0.05; N=5), but not the subsequent inhibitory phase observed in control conditions. (B) Addition of the D1 agonist fenoldopam (15 µmol l-1) to posterior gills previously stimulated with the adenylyl cyclase activator forskolin (Forsk; 10 µmol l-1) produced a partial reversion of the forskolin-induced increase of Vte (*P<0.05; N=6; mean was obtained 100-120 min after the beginning of the experiment). Dotted line represents mean control value obtained after 20 min of perfusion with 30 saline.

View larger version (12K): [in a new window]   Fig. 7. Effects of D2-like dopamine (DA) antagonists, spiperone (A) (10 µmol l-1; N=6) and domperidone (B) (50 µmol l-1; N=6) on transepithelial potential differences (Vte) of posterior gills of Chasmagnathus granulatus. Mean control values (antagonist alone), were obtained 40-50 min after the beginning of the experiment. Both antagonists completely blocked the DA (10 µmol l-1) stimulating effect; means were calculated 60-80 min after the beginning of the experiment. Only when domperidone was used was the blockade reversible.