Pharmacological characterization of β 2 ‐adrenoceptor in PGT‐β mouse pineal gland tumour cells

The adrenoceptor in a mouse pineal gland tumour cell line (PGT‐β) was identified and characterized using pharmacological and physiological approaches. Adrenaline and noradrenaline, adrenoceptor agonists, stimulated cyclic AMP generation in a concentration‐dependent manner, but had no effect on inositol 1,4,5‐trisphosphate production. Adrenaline was a more potent activator of cyclic AMP generation than noradrenaline, with half maximal‐effective concentrations (EC 50 ) seen at 175±22 n M and 18±2 μ M for adrenaline and noradrenaline, respectively. The addition of forskolin synergistically stimulated the adrenaline‐mediated cyclic AMP generation in a concentration‐dependent manner. The pA 2 value for the specific β 2 ‐adrenoceptor antagonist ICI‐118,551 (8.7±0.4) as an antagonist of the adrenaline‐stimulated cyclic AMP generation were ∼3 units higher than the value for the β I ‐adrenoceptor antagonist atenolol (5.6±0.3). Treatment of the cells with adrenaline and forskolin evoked a ∼3 fold increase in the activity of serotonin N‐acetyltransferase with the peak occurring 6 h after stimulation. These results suggest the presence of β 2 ‐adrenoceptors in mouse pineal cells and a functional relationship between the adenylyl cyclase system and the regulation of N‐acetyltransferase expression.British Journal of Pharmacology (1999) 126 , 399–406; doi: 10.1038/sj.bjp.0702248