Catecholamine Receptors Flashcards
D1 Receptors
Located in splanchnic arterioles
Causes vasodilation when agonized
D2 Receptors
Located in medulla and pituitary
Causes emesis in medulla (due to chemoreceptor trigger zone stimulation) and anxiety and fear in the midbrain-cortex
Alpha 1 Receptors
Located in pons, medulla, and blood vessels
Agonists in pons and medulla cause stimulation of RAS neurons to increase alertness and behavioral excitement
In blood vessels, causes vasoconstriction and splenic contraction leading to increased hematocrit
Alpha 2 receptors
Located in pons, medulla, spinal cord, blood vessels, pituitary, and pancreas
Causes decreased arousal in pons and medulla
Muscle relaxation and analgesia in spinal cord
Vasoconstriction hypertension and reflex bradycardia in high concentration in the blood vessels but all the opposite in low concentrations
And inhibits ADH (leads to diuresis and loss of water resorption) and insulin release in pituitary and pancreas
Opioid Receptor Cellular Actions
Diectly activate G-protein inwardly rectifying potassium channels (GIRK)
Directly inhibit voltage gated Ca channels and adenylyl cyclase
Indirectly activates calcium-activated big potassium channels (BK), phospholipase C, and mitogen activated protein kinase
Overall, causes neuronal hyperpolarization acting on Gprotein secondary messengers
Opioid Receptor Locations
Throughout CNS
Afferent nociceptive neurons and dorsal root ganglia
Opioid Effects
Analgesia on peropheral nociceptors, dorsal horn of spinal cord, and brain regions of medulla, pons, midbrain, and cortex
Sedation in most animals in brain receptors, euphoria in cats in small doses but excitation in high doses in cats and horses