are a class of G-protein coupled receptors (GPCRs) that mediate the actions of catecholamines like norepinephrine and epinephrine in the sympathetic nervous system. They are broadly divided into two families, α1alpha sub 1 α2alpha sub 2
-Adrenoceptors : Often found presynaptically, where they act as "autoreceptors" to inhibit further neurotransmitter release. : α2Aalpha sub 2 cap A end-sub α2Balpha sub 2 cap B end-sub α2Calpha sub 2 cap C end-sub Species Variation : The rat α2Dalpha sub 2 cap D end-sub is the functional equivalent of the human α2Aalpha sub 2 cap A end-sub 2. Signaling Pathways alpha-adrenoceptor
Hypertension, Benign Prostatic Hyperplasia (BPH) , nasal congestion α2alpha sub 2 CNS (brainstem), presynaptic terminals Decreased sympathetic outflow, sedation, analgesia Hypertension, sedation (Dexmedetomidine), ADHD 💡 : α1alpha sub 1 activation is generally stimulatory (constriction), while α2alpha sub 2 are a class of G-protein coupled receptors (GPCRs)
receptors in the prefrontal cortex may improve spatial working memory and offer neuroprotective benefits in dementia. : Cardiac α1alpha sub 1 Signaling Pathways Hypertension
Recent studies highlight complex roles for alpha receptors beyond simple muscle contraction: : α1Aalpha sub 1 cap A end-sub
: Hyperpolarization and inhibition of neurotransmitter release (sympatholytic effect). 3. Physiological Roles and Therapeutic Applications
: Increased intracellular calcium leads to smooth muscle contraction (e.g., vasoconstriction). α2alpha sub 2 Mechanism: The Gicap G sub i α2alpha sub 2 -receptors are coupled to proteins , which inhibit Adenylyl Cyclase . cAMP Reduction : Lowers intracellular cyclic AMP levels. Ion Channel Modulation : Opens K+cap K raised to the positive power channels or inhibits Ca2+cap C a raised to the 2 plus power