Table 3.

Co-stimulation with EGF did not significantly affect the adenylyl cyclase and phospholipase C activities induced by agonists of GPCRs

		Drug-induced responses (fold induction)
GPCR	Response	Agonist	EGF	Agonist+EGF
D1R	cAMP level	12.8±0.8*	1.3±0.4	13.7±1.5*
	IP level	1.0±0.2	1.2±0.2	1.3±0.2
ORL1R	cAMP level	0.8±0.2	1.1±0.3	1.4±0.6
	IP level	1.0±0.2	1.2±0.1	1.3±0.2
GRPR	cAMP level	1.1±0.4	1.1±0.3	1.2±0.2
	IP level	9.7±0.5*	1.2±0.1	10.1±0.6*

Cos-7 cells were transfected with the cDNAs encoding G_s-coupled D₁R, G_i-coupled ORL₁R or G_q-coupled GRPR, and then labeled with [³H]adenine for cAMP assay, or [3 H]myo-inositol for IP assay. The cAMP and IP formation, which reflects the activity of adenylyl cyclases and phospholipase C, respectively, was determined at 30 min after individual or co-stimulation with specific agonists (10 μM Dopamine for D₁R, 100 nM OFQ for ORL₁R, 100 nM bombesin for GRPR and 100 ng ml⁻¹ EGF for EGFR). Data represent the mean±s.e. from three separate experiments, with the corresponding basal activities defined as one-fold of induction.

^*Agonist treatment significantly increased the cAMP or IP formation over basal levels (Bonferroni's corrected t-test, one-way ANOVA, P<0.05).