BRS

Pathways 21

Neurotransmitters and

chapter

Objectives ■ List the various types of pathways as characterized by their neurotransmitter. ■ Describe the major pathways, function, and characteristics of acetylcholine, dopamine, nor epinephrine, serotonin, opioid and nonopioid peptides, and amino acids. ■ Describe endogenous pain control pathways.

I. OVERVIEW

A. Neurotransmitters ■ substances released on excitation, typically from presynaptic neurons (can be reversed, eg, ni tric oxide). They produce the effects of nerve stimulation in postsynaptic neurons or in receptor cells.

B. Neurochemical pathways and loci ■ classified based on the chemical composition of their neurotransmitters. 1. Monoaminergic pathways

■ make use of monoamines as neurotransmitters; they contain one amine group. Monoamines include dopamine , norepinephrine , epinephrine , and serotonin . a. Catecholaminergic pathways (Figure 21.1) ■ make use of a monoamine that contains a catechol nucleus. Catecholamines include dopamine , norepinephrine , and epinephrine . ■ include dopaminergic, noradrenergic (norepinephrinergic), and adrenergic (epinephrinergic) pathways. b. Indolaminergic pathways ■ make use of a monoamine that contains an indole nucleus. Serotonin is an indolamine. ■ include serotonergic pathways. 2. Cholinergic pathways : use acetylcholine (ACh) as a neurotransmitter 3. Peptidergic pathways : use peptides as neurotransmitters 4. Gamma-aminobutyric acid (GABA)-ergic pathways : use GABA as a neurotransmitter 5. Glutamatergic pathway s : use glutamate as a neurotransmitter 6. Glycinergic pathways : use glycine as a neurotransmitter 7. l -Arginine-nitric oxide pathway : use the gaseous neurotransmitter nitric oxide

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