Dopaminergic regulation of ion uptake through the gills of the euryhaline crab Chasmagnathus granulatus. Possible interaction between D1-like and D2-like receptors.

1. GENOVESE, G; SENEK, M; ORTIZ, N; TOWLE, DW; URCOLA MR; LUQUET, CM.

JOURNAL OF EXPERIMENTAL BIOLOGY

The Company of Biologists

Lugar: Cambridge; Año: 2006 vol. 209 p. 2785 - 2793

0022-0949

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 (Vte) 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 hypoosmotic solution, or with the adenylyl cyclase activator forskolin, Vte was increased several-fold. DA applied under these stimulated conditions partially reversed theChasmagnathus granulatus. DA applied under steady state conditions perfusion with hemolymph-like saline) produced a transient increase of the transepithelial potential difference (Vte) 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 hypoosmotic solution, or with the adenylyl cyclase activator forskolin, Vte was increased several-fold. DA applied under these stimulated conditions partially reversed the. DA applied under steady state conditions perfusion with hemolymph-like saline) produced a transient increase of the transepithelial potential difference (Vte) 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 hypoosmotic solution, or with the adenylyl cyclase activator forskolin, Vte was increased several-fold. DA applied under these stimulated conditions partially reversed theVte) 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 hypoosmotic solution, or with the adenylyl cyclase activator forskolin, Vte was increased several-fold. DA applied under these stimulated conditions partially reversed theVte was increased several-fold. DA applied under these stimulated conditions partially reversed the Vte increase by 54% and 25%, respectively. Similarly, the D1-like agonist, fenoldopam, produced a 33% reduction in the stimulated Vte. 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.te increase by 54% and 25%, respectively. Similarly, the D1-like agonist, fenoldopam, produced a 33% reduction in the stimulated Vte. 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.Vte. 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.