Summary Stahl's Essential Psychopharmacology - PMHNP

Chapter 1: Chemical Neurotransmission
Dendrite
Anatomical versus Chemical Basis of Neurotransmission s



 Anatomical basis of neurotransmission
o Neurons and the connections between them Cell
Dendritic
body
(synapses) (Soma) spines

o Synapses
 Asymmetric: communication is in one direction
(axon  dendrite, soma, another axon)
 Presynaptic and postsynaptic elements
that differ
 Neurons are designed to send information to En
other neurons via an axon that passes by passant
presynapt
Axo
(en passant) or ends (presynaptic axon n
c axon
terminals
terminal)
Principles of Chemical Neurotransmission
 Neurotransmitters
o Six neurotransmitters are targeted by psychotropic drugs Presynapti
 Serotonin c axon
terminals
 Norepinephrine
 Dopamine
 Acetylcholine
 Glutamate
 GABA
o To effectively treat psychiatric disorders it may be necessary to target neurons in
specific circuits
 Necessary to treat with multiple drugs because monotherapy is not effective
at relieving symptoms
 Especially if more than one neurotransmitter defect is present in the
illness
Neurotransmission: Classic, Retrograde and Volume
 Classic Neurotransmission
o Electrical process by which
neurons send electrical signals
from one part of the cell to
another part of the same cell
via their axons
 One neuron is sending
neurotransmitters
towards the receptor of a
second neuron
 Excitation-
secretion
coupling:
Electrical signal is
converted to a
chemical signal at
the synapse
o First stage of chemical neurotransmission

, o From the presynaptic axon terminal to the second postsynaptic
neuron

 Retrograde Neurotransmission
o Postsynaptic neurons can “talk back” to their presynaptic elements
o Endocannabinoids
 Produced specifically as retrograde neurotransmitters
 Synthesized in the
postsynaptic neuron
and then released and
diffuse to presynaptic
receptors

o Nitric Oxide (NO)
 Synthesized by
postsynaptic neuron
and then released to
interact with
presynaptic cGMP
sensitive targets

o Nerve Growth Factor (NGF)
 Diffuses to presynaptic neuron where it is taken up by vesicles
 Transported back to the cell nucleus via retrograde transport systems

 Volume Neurotransmission

o Transmission that does NOT require a synapse
 Non-synaptic diffusion neurotransmission
 Neurotransmission can occur at any
compatible receptor within the diffusion
radius of the neurotransmitter
 Modifying volume transmission may
be a way in which several
psychotropics work in the brain
 Dopamine action in the prefrontal cortex
 There are very few dopamine transporters (DATs) to terminate the
action of dopamine during neurotransmission
o Dopamine is free to spill over to neighboring dopamine receptor
sites and activate them
 Dopamine in the striatum
 Presence of multiple dopamine reuptake pumps

 Autoreceptors
 Inhibit the release of
neurotransmitters from the axonal
end of the neuron
 Somatodendritic autoreceptors
o Receive neurotransmitters
from dendritic release
o No synaptic vessels