SOME OF THE TRANSMITTER SUBSTANCES FOUND IN AUTONOMIC NERVOUS SYSTEM, ENTERIC NERVOUS SYSTEM, AND NONADRENERGIC, NONCHOLINERGIC NEURONS.

Question 1

• primary transmitter at ANS ganglia
• primary excitatory transmitter to smooth muscle and secretory cells in the ENS.
• major neuron-to-neuron (“ganglionic”) transmitter in the ENS.

Answer 1

Acetylcholine (ACh)

Question 2

• Acts as a transmitter or cotransmitter at many ANS-effector synapses.

Answer 2

Adenosine triphosphate (ATP)

Question 3

• Found with substance P in cardiovascular sensory nerve fibers.
• Present in some secretomotor ENS neurons and interneurons.
• A cardiac stimulant.

Answer 3

Calcitonin gene-related peptide (CGRP)

Question 4

• May act as a cotransmitter in some excitatory neuromuscular ENS neurons

Answer 4

Cholecystokinin (CCK)

Question 5

• A modulatory transmitter in some ganglia and the ENS.
• Possibly a postganglionic sympathetic transmitter in renal blood vessels.

Answer 5

Dopamine

Question 6

• Present in some secretomotor and interneurons in the ENS.
• Appear to inhibit ACh release and thereby inhibit peristalsis.
• May stimulate secretion.

Answer 6

Enkephalin and related opioid peptides

Question 7

• Present in secretomotor neurons
• may play a role in appetite-satiety mechanisms.

Answer 7

Galanin

Question 8

• May have presynaptic effects on excitatory ENS nerve terminals.
• Has some relaxant effect on the gut.
• Probably not a major transmitter in the ENS.

Answer 8

GABA (γ-aminobutyric acid)

Question 9

• Extremely potent excitatory transmitter to gastrin cells.
• Also known as mammalian bombesin.

Answer 9

Gastrin-releasing peptide (GRP)

Question 10

• Found in many noradrenergic neurons.
• Present in some secretomotor neurons in the ENS
• May inhibit secretion of water and electrolytes by the gut.
• Causes long-lasting vasoconstriction.
• It is also a cotransmitter in some parasympathetic postganglionic neurons.

Answer 10

Neuropeptide Y (NPY)

Question 11

• A cotransmitter at inhibitory ENS and other neuromuscular junctions;
• may be especially important at sphincters. - Cholinergic nerves innervating blood vessels appear to activate the synthesis of – by vascular endothelium.
• not stored, it is synthesized on demand by nitric oxide synthase, NOS;

Answer 11

Nitric oxide (NO)

Question 12

• primary transmitter at most sympathetic postganglionic nerve endings.

Answer 12

Norepinephrine (NE)

Question 13

• An important transmitter or cotransmitter at excitatory neuron-to-neuron junctions in the ENS.

Answer 13

Serotonin (5-HT)

Question 14

• an important sensory neurotransmitter in the ENS and elsewhere.
• vasodilator
• Found with CGRP in cardiovascular sensory neurons.

Answer 14

Substance P

Question 15

appear to be excitatory cotransmitters with ACh at ENS neuromuscular junctions.

Answer 15

Tachykinins

Question 16

• Excitatory secretomotor transmitter in the ENS;
• may also be an inhibitory ENS neuromuscular cotransmitter.
• A probable cotransmitter in many cholinergic neurons.
• A vasodilator (found in many perivascular neurons) and cardiac stimulant.

Answer 16

Vasoactive intestinal peptide (VIP)