RESUMO
In vitro experiments have shown that PGF2 alpha or indomethacin produces different effects on muscle strips isolated from different compartments of sheep complex stomach. PGF2 alpha (10(-6) - 10(-5) M) increases the tone of the ruminal preparations and exerts a negligible effect on the reticulum and omasum strips. Indomethacin (5 X 10(-6) M) inhibits the mechanical activity of the rumen and omasum and has no effect on that of the reticulum. More pronounced are the effects on the different parts of the abomasum: PGF2 alpha (10(-9) - 10(-6) M) markedly increases the tone of the proximal abomasum and decreased the amplitude and the phasic contractions of the antral abomasum; indomethacin (5 X 10(-6) M) inhibits the tone and the phasic contractions of the middle abomasum. PGF2 alpha (10(-9) - 10(-6) M) inhibits while indomethacin (5 X 10(-6) M) stimulates the contractile activity of the antral abomasum.
Assuntos
Indometacina/farmacologia , Contração Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Prostaglandinas F/farmacologia , Abomaso/efeitos dos fármacos , Acetilcolina/farmacologia , Animais , Dinoprosta , Galopamil/farmacologia , Cobaias , Técnicas In Vitro , Indometacina/antagonistas & inibidores , Omaso/efeitos dos fármacos , Prostaglandinas F/antagonistas & inibidores , Retículo/efeitos dos fármacos , Rúmen/efeitos dos fármacos , OvinosRESUMO
In the majority of experiments the ruminal preparations did not exhibit spontaneous electrical and contractile activity but showed a Ca-dependent spike-free myogenic tone. Ba2+ or Sr2+ evoked spike activity and phasic contractions and increased the muscle tonic tension. Tetraethylammonium (TEA) exerted no effect on the ruminal preparations but potentiated the effect of Ba2+. Acetylcholine (ACh) induced dose-dependent spike-free tonic contractions which were verapamil resistant and were suppressed by sodium nitroprusside. When applied to BaCl2- or TEA-pretreated preparations ACh caused spike activity and phasic contractions. The antral abomasum exhibited a spontaneous electrical activity--slow waves on which spike potentials were superimposed. ACh and TEA induced membrane depolarization and increased the spike activity and the phasic contraction amplitude.
Assuntos
Contração Muscular , Músculo Liso/fisiologia , Estômago de Ruminante/fisiologia , Abomaso/fisiologia , Acetilcolina/farmacologia , Animais , Cálcio/antagonistas & inibidores , Cálcio/fisiologia , Estimulação Elétrica , Técnicas In Vitro , Potenciais da Membrana/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Rúmen/fisiologia , Ovinos , Estômago de Ruminante/efeitos dos fármacosRESUMO
In vitro experiments were carried out on muscle strips from different compartments of sheep complex stomach. The following conclusions were drawn: 1. In Ca2+-free medium containing EDTA (0.5 mM) proximal and antral abomasum preparations are mechanically inactive. The addition of BaCl2 (0.2-1 mM) induces phasic contractions in the rumen and antrum strips. In contrast to the simple stomach Ba2+ causes a significant increase in the tone of the rumen and proximal abomasum preparations. This tonic contraction is verapamil resistant and is completely suppressed by sodium nitroprusside. 2. The Ba2+ effect is not mediated by cholinergic or adrenergic systems. Ba2+ can substitute Ca2+ in generating both phasic and tonic contractions in complex stomach smooth muscles. 3. Compared with the simple stomach Mn2+ (0.2-0.8 mM) influences neither the ACh-induced activity in normal nutrient medium nor the tone of the rumen and proximal abomasum preparations in Ca2+-free solution.