Neuropharm
The study of drugs that alter processes controlled by the nervous system. Effects are
equivalent of those produced by excitation or suppression of neuronal activity
● Neuropharm drugs work by influencing receptors activity on target cells
How neurons regulate other cells:
● Two basic steps in eliciting responses from other cells
● Post synaptic cell could be another neuron (increase/decrease firing rate), a muscle
cell (contract/relax), or a cell within a secretory gland (increase/decrease secretion)
1. Axonal conduction
a. action potential moves down the axon
b. drug is less selective = drug will activate many different receptor types
2. Synaptic transmission
a. Process by which the signal is carried across the gap (between neuron and
postsynaptic cell)
● Release of neurotransmitter from axon terminal, followed by binding to receptors on
postsynaptic cell
● Drug alters one of two basic neuronal activities (axonal conduction or synaptic
transmission)
○ Usually synaptic transmission -- much more selective
■ Synapses at different sites employ different transmitters
■ Body employs more than one receptor
○ Altering of axonal conduction = not selective
■ Ex: local anesthetics
● Want to be more selective for the receptor on target cell it is intended to activate
● Direct receptor binding - drug is key receptor
● The impact of a drug on a neuronally activated process is dependent on the ability
of that drug to directly or indirectly influence receptors activity on target cells
Synaptic Transmission
, ● Steps - neurotransmitters
○ Present in nerve terminal - synthesis
○ Stored until release - in vesicles
○ Released from the presynaptic cleft - triggered by arrival of action potential @
axon terminal
○ Go into synaptic cleft
○ Bind to receptors - reversible process
● Effects of drugs on synaptic transmission
○ Activation: an effect on receptor function equivalent to that produced by the
natural neurotransmitter at a particular synapse
○ A drug that mimics effects of natural transmitter = increase receptor activation
○ Drug that reduces amount of natural transmitter = decrease receptor activation
● Acetylcholine
○ Activated cholinergic receptors
● Ex: SSRI (selective serotonin reuptake inhibitor)
○ Inhibits uptake of serotonin and prevents from being reabsorbed into receptors
Selectivity
● Most desirable quality a drug can have
● Able to alter a disease process while leaving other physiologic processes unaffected
● The more selective = the more picky for receptors
● The more receptors = the more selective
Learning about the PNS
● Type of receptor → what is a normal response to activation of said receptor?
● To understand PNS drugs → 3 types of info
○ Type of receptor (for which the drug works)
○ Normal response from said receptor
○ What does the drug do to said receptor function
Peripheral Nervous System
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