The classification of alpha and beta subtypes of the adrenergic receptor results from the diverse responses towards adrenergic stimulation. Epinephrine and norepinephrine are the primary adrenergic neurotransmitters. The receptors are part of the super family of metabotropic G-protein coupled receptors (GPCR-A17), and are often referred to as being responsible for the ‘flight or fight response’. Activation of the alpha subtype generally results in vasoconstriction, whereas activation of the beta subtype leads to vasodilatation. While beta blockers are generally known for their management of cardiac arrhythmias, cardioprotection after myocardial infarction (heart attack), angina and hypertension (e.g. Axon 1159 (Celiprolol hydrochloride), and Axon 1518 (Timolol maleate)), in contrast, drugs interacting at the alpha adrenergic receptors are often used for a variety of medical disorders; e.g. for the treatment of hemorrhagic shock (Axon 1154, B-HT 933 dihydrochloride), as an antidepressant, antidiabetic, or to prevent central neurodegenerative disorders (e.g. Axon 1155, Efaroxan hydrochloride), or for the treatment of narcolepsy and sleep disorders (e.g. Axon 1296, Modafinil).