Neuroscience
Online
Section I:
Cellular and Molecular Neurobiology

12. Biogenic Amine Neurotransmitters
Part 2 of 11

Jack C. Waymire, Ph.D.


Anatomy
Cell Biology
Physiology and Behavior
Clinical

Anatomy of Catecholamines

Catecholamines are neurotransmitters in a sympathetic limb of the autonomic nervous system and in the CNS.

Autonomic Nervous Systems

As shown in Figure 12.2, norepinephrine is a neurotransmitter in postganglionic sympathetic neurons where it acts on smooth muscle to cause either contraction or relaxation, depending on the types of receptors present (see below). DA is a neurotransmitter in autonomic ganglia where it modulates cholinergic transmission and in the kidney, where it produces renal vasodilation and inhibits Na+ and H2O reabsorption. Epinephrine and norepinephrine are neurohumoral agents released into the circulation by the adrenal medulla. The ratio of E to NE released is 4 to 1.
Figure 12.2

Location of NE and Epi at sympathetic nerve endings and in the adrenal medulla.

Central Nervous System

Generally, the cell bodies of catecholamine neurons are found in clusters in the brain stem or midbrain and project to other regions of the brain and spinal cord. NE, for example, projects to almost every area of the brain. In contrast, DA has a more restricted projection. Epinephrine, which will not be covered in this chapter, has the most restricted distribution.

Contact the author(s) at: nba_course@uth.tmc.edu
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