Pharmacology with Autonomic Nervous System- 8 Flashcards
(23 cards)
Pharmacology
the study of the histories, sources, chemical properties, biological actions, biological handling and therapeutic uses of drugs in living organisms.
Autonomic nervous system
maintains homeostasis of visceral tissues. Primarily regulates the functions of 3 primary cell types- smooth muscle, cardiac muscle, and secretory glands. Provides a means for the body to alter the functions of many tissues in response to external (5 senses) or internal (body temp, pain, BP, fear, disease) changes.
Uses of autonomic drugs
re-establish normal function in dysfunctional organs.
Cardiovascular imbalances, GI disturbances, Respiratory-pulmonary disorders, urinary tract disorders, miscellaneous. Offset visceral changes secondary to CNS disorders or treatments with CNS acting drugs. Treat poisoning and hypersensitivity reactions.
Autonomic reflexes
common response to a primary drug-evoked change in a visceral organ. Ex: phenylphrine- contracts vascular smooth muscle, increased peripheral resistance, activates baroreceptors.
Reflexes involve higher level “integration centers” that are present at distinct loci.
sites of drug action in the ANS
pic pg. 4
Autonomic ganglia
all ganglia (sympathetic and parasympathetic) use identical forms of chemical transmission. Ganglionic drugs produce pervasive wide-spread effects. Unintentional site of action for some drugs (anti-AChE, muscle relaxants). Acetylcholine from preganglionic neuron stimulates nicotinic receptors on postganlionic neurons- ganglionic blockers are nicotinic cholinergic antagonists. Secondary events have no proven function.
Neuroeffector junction
primarily intended site of action for ANS drugs. Nearly all visceral tissues receive dual innervation by sympathetic and parasympathetic neurons. Elicit opposite tissue/organ responses.
Pharmacological antagonism
blockade of an agonist by an antagonist.
Ex: phancuronium blockade of ACh at skeletal muscles nicotinic receptors
Physiological antagonism
opposing actions produced by two drugs via actions on different receptors or via distinct mechanisms.
Ex: histamine and epinephrine on bronchial smooth muscle. Histamine causes labored breathing while Epinephrine improves breathing.
Physiological antagonism within the autonomic nervous system
allows for different pharmacological approaches for management of numerous disorders. Allows for complimentary treatments that target both branches of the autonomic nervous system.
Chemical transmission in the ANS
the sympathetic and parasympathetic branches use different transmitters and receptors for chemical transmissions between postganglionic neurons and target organs. Provides the opportunity for selective intervention with drugs.
Sites of drug action at the neuroeffector junction
pic pg. 10
Ach synthesis
inhibition is lethal (toxins). Stimulation has unclear effects (lecithin in CNS neurons).
Ach release
inhibition can be lethal (botulinum toxin in motor neurons). Stimulation can be lethal (black widow venom in motor neurons).
Presynaptic receptors
muscarinic autoreceptors inhibit Ach release. No proven therapeutic relevance.
Postsynaptic receptors
represents a major target for therapeutic control of parasympathetic…
Receptors are muscarinic cholinergic receptors (mAChR) .
5 subtypes known, but have unproven therapeutic significance.
Bethanechol, atopine, gyycopyrrolate.
Ach elimination
entirely enzymatic (acetylcholinesterase or AChE). No uptake (transport) process. Edrophonium, physostigmine, parathion.
NE biosynthesis
formed from L-tyrosine via tyrosine hydroxylase. Not a target for therapeutic agents.
NE storage and release
storage vesicles can be destroyed and cause prolonged loss of sympathetic activity. Release is enhanced by many compounds.
presynaptic receptors
can control transmitter release from nerve terminals. Probably insignificant in autonomic neurons. Important in CNS (xylazine).
Postsynaptic receptors
represents a major target for therapeutic control of sympathetic functions. all are classified as adrenergic receptors (alpha and beta). Expression of receptor subtypes is cell specific.
NE&EP eliminiation
Eliminated by cellular uptake as well as enzymatic degradation. Uptake- most important elimination process. Enzymatic degradation- mediated by multiple enzymes.
mini review
pic pg 12
