Table 2

Reversal of chronic morphine-induced up-regulation of AC by an inversebeta-2 AR agonist

Condition	cAMP Accumulation (pmol/10 min/10⁶ cells)
Condition	Naive	Chronic Morphine (10 μM; 2 d)
Basal	0.82 ± 0.19	1.22 ± 0.10^2-a
ICI 118,551 (1 μM)	0.59 ± 0.09^2-b (−28%)	0.71 ± 0.11^2-c (−48%)
ICI 118,551
+ propranolol (1 μM)	0.80 ± 0.11	1.14 ± 0.09

Basal cAMP accumulation was determined in control and chronically morphine-pretreated A431/μ13 cells either in the absence or in the presence of ICI 118,551 or ICI 118,551 together with (−)-propranolol. Percentage reduction of basal AC activity by ICI 118,551 activity is given in brackets. All data are mean values ± S.D. from four or six experiments.

↵2-a Significantly different at P < .01 as compared with naive cells.
↵2-b Significantly different at P < .01 as compared with control values of naive cells.
↵2-c Significantly different at P < .001 as compared with control values of morphine-treated cells.