41. Tamsulosin is relatively selective for ? 1a-adrenergic receptors , which are mainly present in the prostate. 42. It activates both ? and ? adrenergic receptors . 43. Both mitragynine and 7-HMG are ? 2-adrenergic receptors . 44. Several drug companies are working on medicines, called beta-3 adrenergic receptor agonists, that stimulate the receptor. 45. One of the genes, an alpha-2 adrenergic receptor , controls the release of norepinephrine in the heart. 46. Beta-3 adrenergic receptors are found principally in brown fat, which is especially abundant in the abdomen. 47. It is an ? 1a adrenergic receptor antagonist. 48. Since ? 2 adrenergic receptors can cause vascular smooth muscle dilation beta-blockers may cause some vasoconstriction. 49. The other, a beta-1 adrenergic receptor , locks the norepinephrine onto heart muscle cells, causing them to contract. 50. It works by blocking the beta-2-adrenergic receptor .
