Neuro Lecture # 5

Front 1

Types of Synaptic Connections Between Neurons

Back 1

1. Axodendritic
2. Axosomatic
3. Axoaxonic

Front 2

Axoaxonic

Back 2

Axoaxonic is widely used: Neuron A targeting the nerve terminal of neuron B to influence release
Effect can be either inhibitory or stimulatory
Inhibitory: Often seen with opiates, cannabinoids, and GABA at GABAB receptors
Excitatory: Often seen with acetylcholine at nicotinic receptors

Front 3

Clicker Question #1
Which type of synaptic connection would not influence the firing rate of the target neuron?

Back 3

A. Axosomatic
B. Axodendritic
C. Axoaxonic
D. All of the above

Front 4

Classical Neurotransmitters

Back 4

1. Amino Acids
a. Glutamate
b. GABA
c. Glycine
2. Monoamines
a. Dopamine
b. Norepinephrine
c. Serotonin
3. Acetylcholine

Front 5

Non-classical Neurotransmitters

Back 5

1. Neuropeptides
a. Endorphins and enkephalins
b. Corticotropin-releasing factor
2. Lipids
a. Anandamide
3. Gases
a. Nitric Oxide

Front 6

Clicker Question #2
Which type of transmitter category offers the possibility of having the greatest number of members?

Back 6

A. Amino Acids
B. Biogenic Amines (Monoamines)
C. Gases
D. Neuropeptides

Front 7

Co-Localization

Back 7

Having more than one neurotransmitter (NT) in the same nerve terminal
Could be two “classical” NTs or a classical NT + a peptide
The peptide could be a NT or a “neuromodulator”
Neuromodulator: Isn’t a signal by itself, but modulates the effect of the NT

Front 8

Neuromodulation

Back 8

Example: Calcitonin gene-related peptide (CGRP)
Released from motor terminals at the neuromuscular junction in response to high frequency stimulation
 cAMP which  protein kinase A activity which  phosphorylation of the nicotinic receptor
This produces a desensitization, so this is a form of modulatory regulation to tone down the effect of high levels of stimulation

Front 9

Clicker Question #3
True or False. One difference between neuropeptide transmitters and biogenic amine transmitters is that the release of biogenic amine transmitters is calcium-dependent.

Back 9

A. True
B. False

Front 10

Types of Receptors

Back 10

Ionotropic (Ligand-Gated, Transmitter-Gated). Examples: Nicotinic, GABAA
Metabotropic (G Protein-coupled). Examples: Muscarinic, Catecholamine
Tyrosine Kinase. Examples: Insulin, Nerve Growth Factor (NGF)
Internal. Example: Steroids

Front 11

Clicker Question #4
An example of a transmitter that targets both ionotropic and metabotropic receptors:

Back 11

A. Acetylcholine
B. Dopamine
C. Norepinephrine
D. A and B
E. A, B and C

Front 12

Cyclic AMP As A 2nd Messenger

Back 12

Discovered in the liver
Investigations on the mechanism of epinephrine-induced glucose production in the liver
A small molecule was discovered that could mimic the effect of epinephrine: cyclic AMP (cAMP)
Found that epinephrine could produce an activation of cAMP synthesis via activation of adenylyl cyclase
Enzyme assays revealed high level in the brain, with the prediction that this system would prove important in the central nervous system: Definitely Verified!!

Front 13

NO Target

Back 13

Guanylyl Cyclase, the enzyme that makes cyclic GMP (cGMP)
In vascular smooth muscle, cGMP helps promote relaxation (vasodilation: increase in blood flow)
cGMP normally broken down by a phosphodiesterase enzyme
This enzyme is the target for Viagra inhibition increases blood flow and is used as a treatment for erectile dysfunction (1st oral drug to do this)

Front 14

One Possible Role For Endocannabinoids:

Back 14

Retrograde Signaling
This could
reduce the
Input from
another
neuron

Front 15

Clicker Question #5
The agent that signals the smooth ER to release calcium into the cytoplasm:

Back 15

A. Cyclic AMP
B. Cyclic GMP
C. IP3
D. PIP2
E. DAG

Front 16

SUMMARY

Back 16

Axoaxonic connections allow for one neuron to directly influence transmitter release from the terminal of a target neuron
Release can also be influenced by presynaptic autoreceptors
Co-localization of 2 transmitters or a transmitter + a modulator is common

Front 17

SUMMARY (Cont.)

Back 17

Two common receptor types are ionotropic (ligand-gated) and metabotropic
Two important signaling systems are mediated via (1) cyclic AMP and (2) PIP2 metabolism
Signaling can also occur hormonally, as with the hypothalamic-pituitary axis (HPA)