The Combined Inhibitory Effect of the Adenosine A₁ and Cannabinoid CB₁ Receptors on cAMP Accumulation in the Hippocampus Is Additive and Independent of A₁ Receptor Desensitization

Figure 2

Reversal of the inhibitory effects of CPA (a) and WIN55212-2 (b) on forskolin-stimulated cAMP accumulation, by selective A₁ receptor and CB₁ receptor antagonists, respectively. (a) Slices were incubated for 30 min in the presence of rolipram (50 M), adenosine deaminase (2 U/mL) and in the absence or in the presence of DPCPX (50 nM). After this period, incubation continued for 15 min in the absence or in the presence of CPA (100 nM). Finally incubation proceeded in the presence of forskolin (10 M) for a further 15 min period. The solid bars represent the % inhibition of control cAMP accumulation produced by (from left to right) CPA, DPCPX, and CPA plus DPCPX. For CPA and for DPCPX the control corresponded to the cAMP accumulation obtained in the absence of both CPA and DPCPX, while for CPA plus DPCPX the control corresponded to the cAMP accumulation obtained in the absence of CPA but in presence of DPCPX. (b) Slices were incubated for 30 min in the absence or in the presence of AM251 (10 M). After this period, the incubation continued for 45 min in the presence of rolipram (50 M) and in the absence or in the presence of WIN55212-2 (10 M). Finally incubation proceeded in the presence of forskolin (10 M) for a further 35 min period. The solid bars represent the % inhibition of control cAMP accumulation produced by (from left to right) WIN55212-2, AM251, and WIN55212-2 plus AM251. For WIN55212-2 and for AM251 the control corresponded to the cAMP accumulation obtained in the absence of both WIN55212-2 and AM251, while for WIN55212-2 plus AM251 the control corresponded to the cAMP accumulation obtained in the absence of WIN55212-2 but in the presence of AM251. Data are mean ± SEM from 3–8 independent experiments run at least in triplicate. and when compared with zero (Student’s -test). when compared with the effect obtained in the absence of antagonist (One-way ANOVA, followed by LSD test). Statistically significant () when comparing the cAMP accumulation obtained in the presence of CPA or WIN55212-2 with control cAMP accumulation (One-way ANOVA, followed by LSD test). The number of experiments performed in each situation is indicated in brackets above the bars.

(a)

(b)