Table 1

Blockade of dopamine agonist-mediated potentiation of isoproterenol-stimulated cyclic AMP accumulation

Cell type	Drug	Condition/pretreatment
Cell type	Drug	Vehicle	+ Spiperone (1 μm)	+ Staurosporine (1 μm)	+ Pertussis toxin (25 ng/ml)
		pmol/well
ACII/D2L	Control	9.92 ± 1.8	6.7 ± 1.3	7.9 ± 0.8	9.6 ± 2.0
	Dopamine	22.0 ± 3.3^*	5.7 ± 1.3	19.6 ± 1.7^*	5.8 ± 1.3
	Quinpirole	24.4 ± 4.9^*	8.0 ± 1.9	18.4 ± 2.1^*	8.5 ± 1.7
ACII/D4	Control	15.2 ± 2.3	6.7 ± 0.6	31.6 ± 3.3^**	9.8 ± 0.8
	Dopamine	37.1 ± 5.1^*	8.4 ± 2.6	62.3 ± 10.5^*	12.9 ± 1.4
	Quinpirole	36.0 ± 5.8^*	8.2 ± 1.9	68.4 ± 13.2^*	10.6 ± 2.1

cAMP accumulation was stimulated with 100 nm isoproterenol in the absence (control) and presence of dopamine (1 μm) or quinpirole (1 μm) for 15 min. As indicated, some experiments were carried out in the presence of spiperone (1 μm), staurosporine (1 μm), or following treatment with pertussis toxin (25 ng/ml, 18 hr). Data shown are the mean ± standard error for three or more independent experiments, each conducted with duplicate determinations. ^* p < 0.01 compared to control cells (Dunnett’s postrepeated measures ANOVA). ^** p < 0.01 compared to vehicle pretreatment (paired Student’s t test).