ABSTRACT
Capsaicin-sensitive primary afferent fibers (CSPA) in the small intestine regulate many functions through the release of peptides and neurotransmitters. This study was undertaken to assess the role of CSPA in the regulation of jejunal alanine absorption in the rat. In a series of in vivo experiments, the effects of the sensory neurotoxin capsaicin on small intestinal alanine absorption were evaluated. In vitro experiments were also done to study its effects on alanine uptake by isolated jejunal strips and mucosal scrapings. Jejunal alanine absorption was reduced by 27% when capsaicin (160 and 800 microM) was perfused intraluminally and by 21% when it was applied topically to the cervical vagi. On the other hand, bilateral cervical vagotomy and reversible block of vagal CSPA increased alanine absorption by 29 and 41%, respectively. In vitro, capsaicin reduced alanine uptake by intestinal strips in a dose-dependent manner. Maximal inhibition (36.5%) occurred at 400 microM with the mean ineffective concentration at 87 microM. Alanine uptake by jejunal mucosal scrapings, however, was decreased only by 6.7% when incubated with 1,600 microM capsaicin. These data suggest that vagal CSPA exerts a tonic inhibitory effect on alanine absorption and that capsaicin's inhibitory effect on alanine absorption is mediated largely by the capsaicin-sensitive afferent fibers.
Subject(s)
Alanine/metabolism , Capsaicin/pharmacology , Jejunum/innervation , Jejunum/metabolism , Absorption/drug effects , Afferent Pathways/drug effects , Afferent Pathways/physiology , Animals , Female , In Vitro Techniques , Male , Nerve Fibers/drug effects , Nerve Fibers/physiology , Nervous System Physiological Phenomena , Rats , Rats, Sprague-Dawley , Vagus Nerve/drug effects , Vagus Nerve/physiologyABSTRACT
The effects of intracerebral injections of VIP on jejunal alanine absorption and gastric acid secretion, and its association with vagal outflow were examined in Sprague-Dawley rats. Intracerebroventricular injection of VIP (2 ng) decreased significantly (P < 0.05) alanine absorption across the jejunum, whereas similar injections in vagotomized rats did not show further decrease in absorption beyond that noticed by vagotomy only. Moreover, VIP injected in the Nucleus Tractus Solitarius-Dorsal Motor Nucleus (NTS-DMN) complex (1 ng) produced also a significant inhibition of Ala absorption which was reduced but remained significant (P < 0.05) after vagotomy. Water movement was not affected by VIP injection in the lateral ventricle, while VIP injections in the NTS-DMN inhibited significantly (P < 0.05) jejunal water absorption by 10-12%. Vagotomy increased water absorption by 15-20% above control (P < 0.05) which was not altered by injecting VIP in the NTS-DMN complex. On the other hand, VIP injection in the NTS-DMN produced a 25.7% increase in gastric acid output in the first hour of the experiment followed by a non-significant decrease (P > 0.05) in the second hour. Same injections done in vagotomized animals produced similar effects to those elicited by vagotomy only. It can be suggested that NTS-DMN complex could be a site of action of VIP since injection of VIP in it produced a more pronounced inhibitory effect on water and Ala absorption than that produced by VIP injection in the LV. These effects were reduced or abolished by vagotomy.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Alanine/metabolism , Gastric Acid/metabolism , Intestinal Absorption/drug effects , Vasoactive Intestinal Peptide/pharmacology , Animals , Body Water/metabolism , Female , Injections, Intraventricular , Jejunum/metabolism , Kinetics , Male , Rats , Rats, Sprague-Dawley , Solitary Nucleus/drug effects , Vagotomy , Vagus Nerve/drug effects , Vasoactive Intestinal Peptide/administration & dosageABSTRACT
The effect of intravenous vasoactive intestinal polypeptide (VIP) injection on jejunal L-alanine absorption and gastric acid secretion in the rat was investigated. Continuous intravenous VIP infusion (11.2 ng/kg per min) throughout the experimental period (160 min) produced 60% decrease in alanine absorption and 40% decrease in gastric acid secretion during the second hour of the experiment. Subdiaphragmatic vagotomy reduced alanine absorption to 91% (P > 0.05) and 71.3% (P < 0.05) of control value during the first and second hours of perfusion, respectively. VIP infusion following vagotomy elicited a reduced effect when compared to that produced by similar injections in normal rats. Gastric secretion in vagotomized rats was reduced by 40% (P < 0.05) below control. VIP infusion in vagotomized rats exerted a significant decrease (P < 0.05) of gastric acid secretion. Moreover, water absorption was decreased by almost 10% (P < 0.05) after i.v. injection of VIP and was increased by 20-24% above control value following vagotomy. However, i.v. administration of VIP following vagotomy did not elicit any further change in water absorption. It can be concluded that VIP inhibits alanine absorption and gastric acid secretion in the rat and that these inhibitory effects might be partially mediated by the vagus nerve.
Subject(s)
Alanine/metabolism , Gastric Acid/metabolism , Intestinal Absorption/drug effects , Vasoactive Intestinal Peptide/pharmacology , Animals , Female , Infusions, Intravenous , Jejunum/metabolism , Male , Rats , Rats, Sprague-Dawley , Vagotomy , Vasoactive Intestinal Peptide/administration & dosageABSTRACT
The effects of motilin on proline absorption and gastric and biliary secretions were examined in the rat. Prolonged intravenous administration of motilin (50 pmol/kg/min) significantly inhibited (P < 0.05) proline transport across the jejunum and reduced basal acid secretion to 40% of control value. The same concentration of motilin induced choleresis and increased bile output by 32%. Incubation of intestinal strips with different concentrations of motilin produced a dose-dependent inhibitory pattern of proline accumulation in the intestinal cells.
Subject(s)
Bile/metabolism , Gastric Acid/metabolism , Intestinal Absorption/drug effects , Motilin/pharmacology , Proline/pharmacokinetics , Animals , Bile/drug effects , Biological Transport/drug effects , Female , Gastric Mucosa/drug effects , In Vitro Techniques , Infusions, Intravenous , Jejunum/drug effects , Jejunum/physiology , Male , Motilin/administration & dosage , Rats , Rats, Sprague-Dawley , Time FactorsABSTRACT
The effect of chlorpromazine on proline absorption across jejunum in anaesthetized rats was investigated. Intravenous infusion of chlorpromazine reduced significantly (P less than 0.01) proline absorption across the jejunum. Intraluminal perfusion of chlorpromazine into the jejunal segment reversed net absorption of proline to net secretion. Net water absorption was increased significantly (P less than 0.01) when chlorpromazine was infused intravenously or perfused intraluminally. Unidirectional influx of proline across the mucosal surface was significantly inhibited (P less than 0.01) after preincubation with 1 mM chlorpromazine.
Subject(s)
Chlorpromazine/pharmacology , Intestinal Absorption/drug effects , Proline/pharmacokinetics , Animals , Chlorpromazine/administration & dosage , Infusions, Intravenous , Intestinal Mucosa/drug effects , Intestinal Mucosa/metabolism , Jejunum/drug effects , Jejunum/metabolism , Male , Rats , Rats, Inbred StrainsABSTRACT
1. The effect of colchicine on calcium absorption across rat duodenum has been investigated using the single-pass continuous perfusion technique and the two-compartment system model. 2. Perfusing the rat duodenum with 0.1 and 0.5 mM colchicine produced a dose-dependent inhibiting pattern of calcium transport with no effect noted for water transport. 3. Colchicine at 0.5 mM caused a significant decrease in the rate of calcium uptake and in the accumulation capacity of the duodenal cells. 4. Accumulation of calcium in the duodenal strips displayed saturation kinetics with increasing concentration of calcium in the incubation medium. Colchicine at 0.5 mM showed a lower saturation level and decreased the average maximal flux around 46%.
