Function and pharmacology of multiple GABAA receptor subunits.

LYl7l555. SinLe forskolin activates adenylyl cyclase, effects of Dr receptors on Na'/X+-ATPase would then be mediated via protein phosphorylation and CAMP-dependent protein kinase. There are reports that Na+/K+-ATPase may be regulated by phosphoryl-ation, and CAMP has been reported to inhibit the enzyme via a cAMP-&pendent protein kinase7, consistent with the scheme outlined above. However, it will be necessary to provide a mechanism for the synergy between Dr and 9 receptors. A permissive effect of Dr receptors on high-affinity dop-amine binding to 9 receptors has been ~xW&'*~ and this interaction could contribute to the synergism. Alternatively, the synergism could occur at the level of a second messenger, but this is unlikely since Dr receptors reduce adenylyl cyclase activity, providing opposition to D1 receptor effects. At present, therefore, the mechanism of the synergistic interaction described here is obscure .