Adrenoceptors in the Gall bladder

Effects of sympathomimetics and sympatholytics were studied on cat gall bladderin vivoand on cat and human gall bladder stripsin vitro.Isoprenaline 0.1‐1 μg/kg and terbutaline 1‐10 μg/kg consistently decreased the intraluminal gall bladder pressurein vivo.Propranolol 1 mg/kg prevented this response. Noradrenaline 1‐10 μg/kg also decreased the gall bladder pressure. Isoprenaline (0.08‐0.24 μg/ml), terbutaline (0.26‐4.4 μg/ml), noradrenaline (0.04‐3.2 μg/ml), adrenaline (0.04‐1.6 μg/ml) and tyramine (0.08‐4 μg/ml) produced the same maximum relaxation in isolated strips from the cat gall bladder. The relaxation was abolished by propranolol 0.1‐1 μg/ml but not by practolol 160 μg/ml. Tyramine 2‐32 μg/ml was without effect on strips from reserpine‐treated cats. After propranolol, noradrenaline and adrenaline consistently produced contraction which was blocked by phenoxybenzamine 0.1 μg/ml. This contraction was much weaker than that produced by acetylcholine 0.08‐0.2 μg/ml and chole‐cystokinin 0.02‐0.3 i.u./ml. Different parts of the gall bladder reacted similarly to α‐ and β‐receptor stimulation. About half of the human gall bladders were relaxed by isoprenaline 0.4‐1 μg/ml and terbutaline 4‐16 μg/ml. Propranolol 5 μg/ml prevented the relaxation. Cat gall bladder contains relaxation mediating β‐receptors possibly of the β2‐type and a small population of contraction mediating α‐receptors. The adrenergic function may be to counteract cholecystokinin. Human gall bladder preparations can also be relaxed by β‐receptor stimulation.