Abstract
Serotonin is crucial in gastrointestinal functions, including motility, sensitivity, secretion, and the inflammatory response. The serotonin transporter (SERT), responsible for serotonin reuptake and signaling termination, plays a prominent role in gastrointestinal physiology, representing a promising therapeutic target in digestive disorders. Serotonin transporter expression has been poorly investigated in veterinary medicine, under both healthy and pathological conditions, including canine chronic enteropathy, in which the serotonin metabolism seems to be altered. The aim of the present study was to determine the distribution of SERT immunoreactivity (SERT-IR) in the dog intestine and to compare the findings with those obtained in the rat and human intestines. Serotonin transporter-IR was observed in canine enterocytes, enteric neurons, lamina propria cells and the tunica muscularis. Data obtained in dogs were consistent with those obtained in rats and humans. Since the majority of the serotonin produced by the body is synthesized in the gastrointestinal tract, SERT-expressing cells may exert a role in the mechanism of serotonin reuptake.
Highlights
Serotonin (5-hydroxytryptamine [5-HT]) is one of the most important monoamine neurotransmitters in the central (CNS) and peripheral nervous systems [1]
5-HT exerts a crucial role in the CNS, only 5% of the endogenous 5-HT is localized in the brain neurons [2]; 95% is present in the gut where 5-HT is synthesized by the enterochromaffin cells (ECs)
serotonin transporter (SERT)-IR was visible in the intracellular compartments, close to the basolateral membrane
Summary
Serotonin (5-hydroxytryptamine [5-HT]) is one of the most important monoamine neurotransmitters in the central (CNS) and peripheral nervous systems [1]. Once released by the ECs, 5-HT binds to specific 5-HT receptors located on the enteric neurons and nerve fibers, immune cells, smooth muscle cells, epithelial cells and blood vessels, and induces different responses, SERT in the Dog Intestine modulating GIT functions, such as motility, sensitivity, secretion and inflammation [1, 11, 14, 15]. The multiplicity of enteric 5-HT targets and 5-HT receptors complicates ascertaining the physiological roles of 5-HT [9] It is well-known that exogenous serotonin potently stimulates gastrointestinal motility, the role of the endogenous serotonin released from the ECs is unclear, and is still the subject of debate. The most recent literature has indicated that serotonin is released from the ECs in response to contraction of the GIT [23], and that this subsequently modulates the frequency of contractile events by means of interaction with nerve processes of the myenteric plexus (MP) neurons [24, 25]
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