Differential effects of dopamine on a potassium current in cultured rutabaga and wild-type Drosophila cells

The rutabaga mutation which has a low intracellular cyclic adenosine monophosphate (cAMP) concentration is defective in short-term memory. The aim of this study was to compare modulation effects of dopamine on the delayed-rectifier potassium current (IKDR) in rutabaga and wild-type Drosophila neurons. The conventional whole-cell patch-clamp technique was applied to cultured Drosophila neurons derived from embryonic neuroblasts. IKDR was measured from cultured (2 days) wild-type and rutabaga neurons. IKDR was smaller in rutabaga neurons (373 ± 38 pA) than in wild-type neurons (519 ± 40 pA) but there was no difference in IKDR activation in wild-type inactivation between the two genotypes. We examined the effects of dopamine on IKDR in wild-type and rutabaga neurons. IKDR was measured from neurons before and after addition of dopamine to the external solution. Dopamine application reduced IKDR in wild-type neurons but did not significantly affect IKDR in rutabaga neurons (single-cell studies). In the presence of dopamine there was no difference in IKDR between wild-type (344 ± 29 pA) and rutabaga (338 ± 27pA) neurons (population studies). These results indicate that dopamine differentially affects the delayed-rectifier channel in wild-type and rutabaga neurons. This can alter neuronal excitability in rutabaga and may affect the processing of neural signals necessary for learning and memory.