PSYB64H3 Lecture Notes - Lecture 4: Astrocyte, Acetylcholine Receptor, Fetus
Chapter 4: Psychopharmacology
Neurotransmitters, neuromodulators and neurohormones !
1. 3 general categories!
I) Neurotransmitters: participate in directed synapses by acting on neurons in their own
immediate vicinity (@ synaptic gap)!
II) Neuromodulators: chemical messenger that communicates with target cells more distant
than the synapse by diffusing away from the point of release!
III) Neurohormones: chemical messenger that communicates with target cells at great
distance, often by traveling through the circulation.!
2. Neuromodulators!
I) Volume transmission: Diffusing from site of release and influencing a diverse population
of neurone !
II) Remain in CSF for extended period of time—> Influencing CNS !
3. Neurohormones!
I) Travel in the blood supply but only interacts with cells w/ specialized receptor sites !
!
A. Identifying neurochemicals!
1. Immunohistochemistry: uses antibodies for particular neurochemicals, makes the
identification of function !
2. Criteria !
I) The substance must be present within a presynaptic cell.!
II) The substance is released in response to presynaptic depolarization.!
III) The substance interacts with specific receptors on a postsynaptic cell!
!
Connecting to research: Otto Loewi and “Vagus stuff”!
1. Otto wanted to prove that there was chemical communication along with electrical !
2. Experiment !
I) Stimulated vagus nerve—> HR slowed !
II) Removed liquid from cannula in heart and applied it to the second heart—> HR slowed !
III) Conclusion: Substance released by vagus nerve is responsible for slowing of the heart !
IV) Substance is known today as acetylcholine !
!
B. Types of neurochemcials !
1. 3 classes of neurochemicals!
I) Small molecules: includes amino acids and amines.!
II) Neuropeptides: peptide that acts as a neurotransmitter, a neuromodulator, or a
neurohormone !
III) Gasotransmitters: gas such as nitric oxide (NO) that performs a signaling function.!
2. Small molecules vs. neuropeptides!
Chapter 4: Psychopharmacology
3. Motor neurons!
I) release ACh onto muscle fibres and spinal cord!
II) Release glutamate only into spinal cord !
!
I. Small molecules !
1. ACh: Choline is obtained from dietary fats and acetyl CoA is from mitochondria !
I) ChAt (enzyme) produce ACh !
II) Marker for ChAt identifies ACh neurons !
2. AChE (enzyme): breaks down ACh in the
synaptic gap—> ACh is recaptured by
presynpatic neuron to make more ACh !
3. Role of ACh/ cholinergic neurone!
I) Primary neurotransmitter between
neuron and muscle fibre !
II) Essential to ANS, PNS!
III) Brain: Basal forebrain, septal area,
and brainstem influences the cerebral
cortex, hippocampus, and amygdala !
IV) Alzheimers: Cholinergic neurons
deteriorate—> memory loss !
V) Neurons participate in attention,
wakefulness, learning and memory !
4. Major subtype of cholinergic receptors (in
NS) !
I) Nicotinic receptor: postsynaptic
receptor that responds to nicotine and
acetylcholine (ACh)—> Fast iontropic
receptors (Found in neuromuscular
junction)!
II) Muscarinic receptor: postsynaptic
receptor that responds to both
acetylcholine (ACh) and muscarine—> Slow metabotropic receptors
(Found in heart muscle and smooth muscles) !
5. Abundance of receptors!
I) CNS: Both nicotinic and muscarinic receptors but muscarinic are
most common !
II) ANS: Both are found !
6. 6 Monoamines:!
I) Catecholamines (dopamine, norepinephrine, epinephrine):!
II) Indoleamines (serotonin, melatonin) !
III) Histamine !
7. Characteristics!
I) Subjected to reuptake from the synaptic gap following release!
II) Within axon terminal—> Not encased vesicles are broken down by
MAO (monoamine oxidase) !
III) Outside neurons—> Catcholamines are broken down by COMT !
8. Catecholamines share a common synthesis pathway—> !
!
!
Chapter 4: Psychopharmacology
9. Dopaminergic systems in the brain !
I) Role: Motivated behaviours & processing
of rewards !
II) Involved in addiction to drugs & addiction
(gambling) !
III) Disruptions—> schizophrenia, attention
deficit hyperactivity disorder !
IV) Origin: Midbrain!
10. Pathway #1: Mesostriatal pathway/
Nigrostriatal pathway !
I) Dopaminergic pathway originating in the
substantia nigra and projecting to the
basal ganglia!
II) Midbrain/ substantia nigra—>basal
ganglia !
III) Dorsal direction by the caudate nucleus,
putamen, globus pallidua of the basal
ganglia —> Role: Voluntary motor activity
(parkinson disease)!
IV) Ventral direction by the nucleus
accumbens, olfactory cortex, caudate nucleus, putamen —> Role: Reward and incentive !
11. Pathway #2: Mesolimbocortical system!
I) Ventral tamentum (midbrain)—> limbic system/ cortex (hippocampus, amygdala,
olfactory cortex, septal area; cingulate cortex + parahippocampal cortex)!
II) midbrain-limbic system—> influence motivated behaviour !
III) midbrain-cortex—> Higher level cognitive functioning (planning of behaviour) !
IV) Disruption—> schizophrenia !
12. 2 other dopaminergic pathway !
I) Originate @ hypothalamus !
II) Paraventricular dopamine system: Hypothalamus + thalamus + Sympathetic neurons
(spinal cord)—> appetite, sex and thirst !
III) Hypothalamus + Pituitary gland—> Control milk production !
13. Receptors for dopamine (D1 to D5)!
I) Class 1 : D1 & D5 —> Produce excitation (Hippocampus, hypothalamus)!
II) Class 2: D2, D3, D4—> Produce inhibition (frontal lobes of the cortex, thalamus,
brainstem)!
III) All are slow metabotropic variety !
IV) Origin: Basal ganglia, olfactory cortex !
14. Epinephrine!
I) Role: CNS neurochemical for eating
and regulation of BP !
II) Found in: 2 areas in medulla release
epinephrine !
III) Adrenalin rush: Epinephrine released
from adrenal glands—> blood supply !
15. Norepinephrine !
I) Found in: Pons, medulla, hypothalamus
but mostly in the locus coeruleus of the
pons !
Document Summary
Neurotransmitters, neuromodulators and neurohormones : 3 general categories, neurotransmitters: participate in directed synapses by acting on neurons in their own immediate vicinity (@ synaptic gap)! Ii) neuromodulators: chemical messenger that communicates with target cells more distant than the synapse by diffusing away from the point of release! Iii) neurohormones: chemical messenger that communicates with target cells at great distance, often by traveling through the circulation: neuromodulators, volume transmission: diffusing from site of release and in uencing a diverse population of neurone ! Ii) remain in csf for extended period of time > in uencing cns : neurohormones! 1: travel in the blood supply but only interacts with cells w/ specialized receptor sites ! Immunohistochemistry: uses antibodies for particular neurochemicals, makes the identi cation of function : criteria , the substance must be present within a presynaptic cell. Ii) the substance is released in response to presynaptic depolarization. Iii) the substance interacts with speci c receptors on a postsynaptic cell!
