Zhang, H., Rodgers, E. W., Krenz, W.-D. C., Clark, M. C., Baro, D. J.
Dopamine (DA) modifies the motor pattern generated by the pyloric network in the stomatogastric ganglion (STG) of the spiny lobster, Panulirus interruptus, by directly acting on each of the circuit neurons. The 14 pyloric neurons fall into six cell types, and DA actions are cell type specific. The transient potassium current mediated by shal channels (IA) is a common target of DA modulation in most cell types. DA shifts the voltage dependence of IA in opposing directions in pyloric dilator (PD) versus lateral pyloric (LP) neurons. The mechanism(s) underpinning cell-type specific DA modulation of IA is unknown. DA receptors (DARs) can be classified as type 1 (D1R) or type 2 (D2R). D1Rs and D2Rs are known to increase and decrease intracellular cAMP concentrations, respectively. We hypothesized that the opposing DA effects on PD and LP IA were due to differences in DAR expression patterns. In the present study, we found that LP expressed somatodendritic D1Rs that were concentrated near synapses but did not express D2Rs. Consistently, DA modulation of LP IA was mediated by a Gs-adenylyl cyclase-cAMP-protein kinase A pathway. Additionally, we defined antagonists for lobster D1Rs (flupenthixol) and D2Rs (metoclopramide) in a heterologous expression system and showed that DA modulation of LP IA was blocked by flupenthixol but not by metoclopramide. We previously showed that PD neurons express D2Rs, but not D1Rs, thus supporting the idea that cell specific effects of DA on IA are due to differences in receptor expression.