TRANSMITTER SUBSTANCES Flashcards
What is Acetylcholine (ACh)?
The primary transmitter at ANS ganglia, at the somatic neuromuscular junction, and at parasympathetic postganglionic nerve endings. A primary excitatory transmitter to smooth muscle and secretory cells in the ENS. Probably also the major neuron-to-neuron (‘ganglionic’) transmitter in the ENS.
What is the function of Adenosine triphosphate (ATP)?
Acts as a transmitter or cotransmitter at many ANS-effector synapses.
What is Calcitonin gene-related peptide (CGRP)?
Found with substance P in cardiovascular sensory nerve fibers. Present in some secretomotor ENS neurons and interneurons. A cardiac stimulant.
What is the role of Cholecystokinin (CCK)?
May act as a cotransmitter in some excitatory neuromuscular ENS neurons.
What is Dopamine’s function?
A modulatory transmitter in some ganglia and the ENS. Possibly a postganglionic sympathetic transmitter in renal blood vessels.
What is the function of Enkephalin and related opioid peptides?
Present in some secretomotor and interneurons in the ENS. Appear to inhibit ACh release and thereby inhibit peristalsis. May stimulate secretion.
What is Galanin?
Present in secretomotor neurons; may play a role in appetite-satiety mechanisms.
What is GABA (y-aminobutyric acid)?
May have presynaptic effects on excitatory ENS nerve terminals. Has some relaxant effect on the gut. Probably not a major transmitter in the ENS.
What is Gastrin-releasing peptide (GRP)?
Extremely potent excitatory transmitter to gastrin cells. Also known as mammalian bombesin.
What is Neuropeptide Y (NPY)?
Found in many noradrenergic neurons. Present in some secretomotor neurons in the ENS and may inhibit secretion of water and electrolytes by the gut. Causes long-lasting vasoconstriction. It is also a cotransmitter in some parasympathetic postganglionic neurons.
What is Nitric oxide (NO)?
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 NO by vascular endothelium. NO is not stored, it is synthesized on demand by nitric oxide synthase, NOS.
What is Norepinephrine (NE)?
The primary transmitter at most sympathetic postganglionic nerve endings.
What is Serotonin (5-HT)?
An important transmitter or cotransmitter at excitatory neuron-to-neuron junctions in the ENS.
What is Substance P?
An important sensory neurotransmitter in the ENS and elsewhere. Tachykinins appear to be excitatory cotransmitters with ACh at ENS neuromuscular junctions. Found with CGRP in cardiovascular sensory neurons. Substance P is a vasodilator (probably via release of nitric oxide).
What is Vasoactive intestinal peptide (VIP)?
Excitatory secretomotor transmitter in the ENS; may also be an inhibitory ENS neuromuscular cotransmitter.
