Central and peripheral β-adrenergic control of gastrointestinal motility in sheep

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Central and peripheral β-adrenergic control of

gastrointestinal motility in sheep

P Brikas, Jean Fioramonti, L Buéno

To cite this version:

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Central

and

_{peripheral β-adrenergic}

control of

_{gastrointestinal motility}

in

_sheep

P _Brikas,J Fioramonti L Buéno

Department of _{Pharmacology,}INRA, 180, chemin de Tournefeuille, 31300 Toulouse, France

Introduction - Some effects

of

13-adrenoceptor agonists on _{gastrointestinal}

motility have been _investigatedin mono-gastric species (Burks, 1987). Several side effects of _/3-blockersare mediated _through the central nervous _systemwhich is

in-volved in the control of _{gastrointestinal}

mo-tility. This _studywas undertaken to deter-mine the central and _peripheralactions of

/3!- and _P2-_agonistson forestomach, ab-omasal and intestinal myoelectrical activity

in _sheep.

Materials and Methods &horbar; Four ewes were

chronically fitted with an intracerebroventricular

(icv) cannula and _{intraparietal}electrodes in the reticulum, the caudodorsal and ventral blind

sacs of the rumen, the _greatcurvature of the

ab-omasum, the duodenal bulb and the proximal je-junum.

Results and Discussion - Intravenous (iv) infusion of the _/3₁_-agonistdobutamine

(Lilly France, St Cloud; 30 _!g/kg/min,15

min) decreased the _frequencyof reticular, ruminal and abomasal contractions,

in-creased the number of contractions on the

duodenal bulb _{(fig 1),} and induced a

phase of intense _{spiking activity}_{(phase 3)}

on the _jejunum.These effects were repro-duced _byan icv administration of

dobuta-mine ₍₁₀_,ug/kg)and were blocked _by

ace-butolol, a _{specific P1-antagonist, given}iv

(1 mg/kg) or icv _{(0.1 mg/kg).}Ritodrine

(Duphar, Weesp, NL) a _/3z-agonist, in-fused iv _{(10 P}_g/kg/min,15 _min),did not modify forestomach and _{jejunal motility}

but _stronglyreduced the _frequencyof abomasal contractions _{(fig 1}_Thiseffect

was blocked _{by propranolol given}iv _(0.5

mg/kg) but not icv _(0.05_mg/kg)and was

not modified _byacebutolol ₍₁ _{mg/kg, iv).} Ritodrine icv _{(15 !g/kg)}did not _modifythe

motility of all the sites _{investigated.}It is

concluded that _P1-agonistsact at the level of the central nervous _systemto inhibit the

motility of the forestomach and

aboma-sum and to stimulate the intestine, while

P2-agonists selectively inhibit abomasal

motility through peripheral receptors.