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Types of serotonergic receptors involved in the control of reticulo‐ruminal myoelectric activity in sheep
Author(s) -
BRIKAS P.,
FIORAMONTI J.,
BUENO L.
Publication year - 1994
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.1994.tb00257.x
Subject(s) - ritanserin , agonist , endocrinology , medicine , serotonergic , chemistry , receptor , antagonist , serotonin , receptor antagonist , 5 ht receptor , reticulum , pharmacology , biology , endoplasmic reticulum , biochemistry
The effects of peripheral (intravenous, i.v.) and central (intracerebroventricular, ICV) administrations of agonists of 5‐HT 1A , 5‐HT 2 , 5‐HT 3 and 5‐HT 4 receptors were investigated in conscious sheep chronically fitted with intraparietal electrodes on the reticulum and the dorsal, ventral and caudo‐ventral rumen. The 5‐HT 1A agonist 8‐hydroxydipropylaminotetralin increased reticular and decreased ruminal spike burst frequency when given i.v. (80 μg/kg) and ICV (8 μg/kg). The 5‐HT 2 and 5‐HT 3 agonists, α‐methylserotonin and 2‐methylserotonin, induced a moderate inhibition of rumino‐reticular contractions when given i.v. at 100 and 150 μg/kg, respectively, while marked inhibition was observed after ICV administration at doses of 10 and 5 μg/kg, respectively. The 5‐HT 4 agonist 5‐methoxytryptamine strongly stimulated rumino‐reticular motility by the ICV (10 μg/kg) route, whereas it induced a moderate inhibition when administered i.v. (200 μg/kg). The selective antagonist of 5‐HT 1A , 5‐HT 2 , 5‐HT 3 and 5‐HT 4 receptors, spiroxatrine, ritanserin, granisetron and DAU 6285, respectively, blocked the responses of the respective agonists given by the same route. Moreover, the antagonists given ICV blocked the effects of the agonists given i.v. except for DAU 6285 ICV, which did not antagonize the inhibition induced by 5‐methoxytryptamine i.v. It is concluded that the four types of serotonergic receptors investigated control rumino‐reticular motility at the central level. However, according to the receptor type and the forestomach area (reticulum or rumen) this control may be stimulatory or inhibitory, demonstrating a pleiotropic role of serotonin in the control of rumino‐reticular motility in sheep.