Ch 4: NT and Drug Action

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Slide 1: 

How Neurons Send and Receive Signals Chapter 4 Neural Conduction and Synaptic Transmission

Small-Molecule Neurotransmitters : 

Small-Molecule Neurotransmitters Amino acids – the building blocks of proteins Monoamines – all synthesized from a single amino acid Acetylcholine (Ach) – activity terminated by enzymatic degradation Unconventional neurotransmitters – soluble gases and endacannabinoids

Amino Acid Neurotransmitters : 

Amino Acid Neurotransmitters Usually found at fast-acting directed synapses in the CNS Glutamate – Most prevalent excitatory neurotransmitter in the CNS GABA Synthesized from glutamate Most prevalent inhibitory NT in the CNS Aspartate and glycine

Monoamines : 

Monoamines Effects tend to be diffuse Catecholamines – synthesized from tyrosine Dopamine Norepinephrine Epinephrine Indolamines – synthesized from tryptophan Serotonin

Soluble Gases and Ach : 

Soluble Gases and Ach Soluble gases – exist only briefly Nitric oxide and carbon monoxide Retrograde transmission – backwards communication Acetylcholine (Ach) Acetyl group + choline Neuromuscular junction

Neuropeptides : 

Neuropeptides Large molecules Example – endorphins “Endogenous opioids” Produce analgesia (pain suppression) Receptors were identified before the natural ligand was

Pharmacology of Synaptic Transmission : 

Pharmacology of Synaptic Transmission Many drugs act to alter neurotransmitter activity Agonists – increase or facilitate activity Antagonists – decrease or inhibit activity A drug may act to alter neurotransmitter activity at any point in its “life cycle”

Agonists – Two examples : 

Agonists – Two examples Cocaine – catecholamine agonist Blocks reuptake – preventing the activity of the neurotransmitter from being “turned off” Benzodiazepines – GABA agonists Binds to the GABA molecule and increases the binding of GABA

Antagonists – Two examples (continued) : 

Antagonists – Two examples (continued) Atropine – Ach antagonist Binds and blocks muscarinic receptors Many of these metabotropic receptors are in the brain High doses disrupt memory Curare – Ach antagonist Bind and blocks nicotinic receptors, the ionotropic receptors at the neuromuscular junction Causes paralysis

Daily Quiz 4 : 

Daily Quiz 4 Explain how neural communication occurs. Include a diagram that contains the major steps of an action potential and a description of how synaptic transmission occurs.

Daily Quiz 4 : 

Daily Quiz 4 50% for drawing a diagram that illustrates the mechanisms of an action potential 50% for explaining the steps of synaptic transmission