drugs that bind to physiological receptors make them do the same things as would the endogonous things that would bind to said receptors
agonists, his def
drugs that bind to a receptor and interfere with whatever the endogonous things that bind there would like to make happen
partial agonists or antagonists
drugs that are only partly effective as ant/agonists
capacity to stimulate or produce an effect for a given receptor occupancy
DOSE required to produce a given effect
if a drug acts on a receptor that serves functions common to most cells, its effects ...
will be widespread
if a drugs's function is pretty vital, what else do you know about the drug?
it's pretty difficult or dangerous to use
what do you know about a drug that interacts with unique receptors?
its effects are pretty specific
histamine or histamine-like agents (2-methylhistamine) -- how do the affect the cardiovascular system via H1 receptors?
vasodilation -- reduction of peripheral resistance & decrease in BP
increased capillary permeability & formation of edema
histamine or histamine-like agents (2-methylhistamine) -- how do the affect the extravascular smooth muscle via H1 receptors?
bronchospasm in pts w bronchial asthma (less pronounced affect in normal pts)
where are histamine H1 receptors found
many tissues (vascular, respiratory)
where are histamine H2 receptors found
parietal cells of stomach mucosa
activation of H2 receptors by histamine or agonist 4-methylhistamine may cause...
increased gastric acid secretion
(to a lesser extent) secretion in small and large intestine
where are histamine H3 receptors? _ _ _
predominantly presynaptic - located in the brain, plexus myentericus, and other neurons
what can activate H3 receptors?
histamine, norepinephrine, serotonin, acetylcholine (possibly by a decrease in Ca influx)
3 ways to limit the effects of histamine
physiologic antagonists: (they act at diff receptors and have smooth muscle actions opp to histamine. important in systemic anaphylaxis induced by histamine -- epinephrine)
release inhibitors: reduce degranulation of mast cells (degran would release histamine into body) that result from IgE binding to mast cells during allergic responses .. cromolyn - reduces bronchospasm
receptor antagonists: H1,2,3 antagonists
a release inhibitor that reduces degranulation of mast cells