Receptor-mediated activation of gastric vagal afferents by glucagon-like peptide-1 in the rat.

The vagus nerve plays a role in mediating effects of the two glucagon-like peptides GLP-1 and GLP-2 on gastrointestinal growth, functions and eating behaviour. To obtain electrophysiological and molecular evidence for the contribution of afferent pathways in chemoreception from the gastrointestinal tract, afferent mass activity in the ventral gastric branch of the vagus nerve and gene expression of GLP-1 receptors and GLP-2 receptors in the nodose ganglion were examined in Sprague-Dawley rats. Intravenous administration of GLP-1 (30-1000 pmol kg(-1)), reaching high physiological plasma concentrations, increased vagal afferent mass activity peaking (13-52% above basal level, P < 0.05) 3-5 min after injection. Repeated administration of GLP-1 (1000 pmol kg(-1); five times, 15 min intervals) elicited similar responses. Pretreatment with GLP-1 receptor antagonist exendin(9-39)amide (500 pmol kg(-1)) abolished the GLP-1 response to doses 30-300 pmol kg(-1) but had no effect on the vagal response to gastric distension. For comparison, GLP-2 (1000 pmol kg(-1)) had no effect on vagal afferent activity. Vagal chemoreception of GLP-1 is supported by expression of the GLP-1 receptor gene in the nodose ganglion. However, the GLP-2 receptor was also expressed. To conclude, our results show that peripherally administered GLP-1, differently from GLP-2, activates vagal afferents, with no evidence of desensitisation. The GLP-1 effect was blocked by exendin(9-39)amide, suggesting that GLP-1 receptors on vagal afferent nerves mediate sensory input from the gastrointestinal tract or pancreas; either directly or indirectly via the release of another mediator. GLP-2 receptors appear not be functionally expressed on vagal afferents.

Synthesis and anti-inflammatory activity of 1-acylaminoalkyl-3,4-dialkoxybenzene derivatives.

New 1-acylaminoalkyl-3,4-dialkoxybenzene derivatives 17-31 were synthesized by the acylation of amines 9-16 with acyl chlorides. Amines 9-16 were obtained from aryl ketones 1-8. Aryl ketones 1-8 were synthesized by the acylation of corresponding aromatic compounds. As it was preliminary predicted by PASS (Prediction of Activity Spectra for Substance) program, all 1-acylaminoalkyl-3,4-dimethoxy- and 3,4-diethoxybenzene derivatives possess anti-inflammatory activity. Activity of compounds 18, 19, 21, 24, 26, 27, 28, 29 was similar to that of acetylsalicylic acid or ibuprofen however their acute toxicity was less than that of mentioned anti-inflammatory drugs. A series of 1-acylaminoalkyl-3,4-dimethoxybenzene, 1-acylaminoalkyl-3,4-diethoxybenzene and 6-acylaminoalkyl-2,3-dihydro-1,4-benzodioxine derivatives have been synthesized. These compounds possess moderate or strong anti-inflammatory activity and low toxicity.

Cholecystokinin-8 (CCK-8) has no effect on heart rate in rats lacking CCK-A receptors.

Heart rate responses to i.v. administration of cholecystokinin-8 (CCK-8) were investigated in Otsuka Long-Evans Tokushima Fatty (OLETF) rats lacking CCK-A receptors and control Long-Evans Tokushima Otsuka (LETO) rats. The heart rate decreased after i.v. administration of 3 nmol.kg(-)(1) of CCK-8 in LETO rats, but not in OLETF rats. Bradycardia in the LETO rats disappeared after treatment with MK-329, but not after treatment with L-365,260. The expression of CCK-A receptor precursor mRNA was found exclusively in the atrium in LETO rats. These results suggest that CCK-8 decreases heart rate via CCK-A receptors located in the atrium of the rats.

Effects of systemic injection of interleukin-1beta on gastric vagal afferent activity in rats lacking type A cholecystokinin receptors.

We have shown that systemic administration of interleukin-1beta (IL-1beta) excites gastric vagal afferent activity in part via stimulation of type A cholecystokinin (CCK-A) receptors in rats. The present study was undertaken to determine whether the response of the gastric vagal afferent nerve to systemic IL-1beta is altered in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which lack CCK-A receptors. The response was compared with that of the control strain, Long-Evans Tokushima Otsuka (LETO) rats. All animals were anesthetized with pentobarbital and artificially ventilated. Intravenous administration of 4 microg/kg of IL-1beta increased gastric vagal afferent activity in both LETO and OLETF rats, whereas a smaller dose of 2 microg/kg of IL-1beta increased activity only in the OLETF rats. The present results demonstrate that the response of the gastric vagal afferent activity in CCK-A receptor deficient OLETF rats was more sensitive to intravenous administration of IL-1beta than was in control LETO rats.

Synthesis of 6,7-dialkoxy-2-arylmethylidene-2,3- dihydrobenzo[4,5]imidazo[2,1-b][1,3]thiazol-3-ones exhibiting anti-inflammatory activity.

New 6,7-dialkoxy-2-arylmethylidene-2,3- dihydrobenzo[4,5]imidazo[2,1-b][1,3]thiazol-3-ones (3a-h, 4b, c, e, g) were synthesized from 2-(5,6-dialkoxy-1H-benzo[d]imidazol-2-ylsulfanyl)acetic acids (1, 2) and corresponding aromatic aldehydes in acetic anhydride. The compounds 3e, f and 4b, g were also synthesized from corresponding aromatic aldehydes and 6,7-dialkoxy-2,3-dihydrobenzo[4,5]imidazo[2,1-b][1,3]thiazol -3-ones (5, 6) obtained by the cyclization of the acids 1 and 2 in acetic anhydride. The synthesized compounds 3a-h and 4b, c, e, g exhibit anti-inflammatory activity.

Exogenous cholecystokinin-8 reduces vagal efferent nerve activity in rats through CCK(A) receptors.

It has been proposed that the vagus nerve plays a role in mediating cholecystokinin-8 (CCK-8) effect on such gastric functions as motility, emptying and gastric acid secretion. To examine the contribution of the efferent pathways in realizing these effects, efferent mass activity in the ventral gastric vagal nerve in Sprague-Dawley rats was recorded. Intravenous infusion of CCK-8 (0.1-1 nmol) suppressed the efferent activity. The effect of CCK-8 was significantly reduced in animals with total subdiaphragmatic vagotomy in comparison to those with partial vagotomy. Intravenous infusion of CCK(A) receptor antagonist L-364,718 (1-100x10(-6) g) blocked the response of vagal efferent activity to 0.1 nmol CCK-8, but the CCK(B) receptor antagonist L-365,260 (1-100x10(-6) g) did not in the conditions of either partial or total vagotomy. Intracisternal infusion of L-364,718 (1x10(-6) g) blocked the response of vagal efferent activity to 0.1 nmol CCK-8 i.v. Infusion of exogenous CCK-8 did not affect the activity of supradiaphragmatic vagal afferents. The results suggest that the effect of systemically administered CCK-8 on vagal efferent activity is mediated by both peripherally (subdiaphragmatically) and centrally localized CCK(A) receptors.

Effect of interleukin-1beta on subdiaphragmatic vagal efferents in the rat.

Interleukin-1beta (IL-1beta) is an important mediator of fever and illness. Recent studies have demonstrated that IL-1beta (2 microg kg(-1)) increases gastric vagal afferent activity. The peripheral mechanisms of the action of lower doses were studied by recording the mass efferent and afferent activity of the gastric branch of the ventral vagal nerve in anesthetized rats. Twenty min after i.v. administration of IL-1beta (1 microg kg(-1)) the efferent activity of the vagal nerve was decreased to 62+/-6% in totally but not in partly vagotomized rats. Preadministration of indomethacin (5 mg kg(-1)) 30 min before IL-1beta blocked this reduction. Administration of 1 microg kg(-1) of IL-1beta had no effect on the afferent activity of the gastric branch of the vagal nerve. The present results suggest that the subdiaphragmatic vagal afferents modulate the parasympathetic efferent outflow in response to IL-1beta partly through prostaglandin dependent mechanisms and that supradiaphragmatic afferents or central sites are more sensitive to the low doses of IL-1beta which becomes evident after elimination of the subdiaphragmatic vagal input.

Response of the gastric vagal afferent activity to cholecystokinin in rats lacking type A cholecystokinin receptors.

A systemic administration of cholecystokinin (CCK) increases gastric vagal afferent activity via type A CCK receptors (CCKAR). In the present study, the response of gastric vagal afferent activity to an intravenous administration of CCK was investigated in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which lack CCKAR, and compared with its control strain, Long-Evans Tokushima Otsuka (LETO) rats. The intravenous administration of 300 pmol kg(-1) and 3 nmol kg(-1) of CCK elicited dose-dependent increases in the gastric vagal afferent activity in LETO rats. The responses were not influenced by the pretreatment with L-365,260, a type B CCK receptor (CCKBR) antagonist, while they were significantly diminished by pretreatment with MK-329, a CCKAR antagonist. After pretreatment with MK-329, 3 nmol kg(-1) (but not 300 pmol kg(-1)) of CCK still elicited a small but significant increase in the activity. In the OLETF rats, both 300 pmol kg(-1) and 3 nmol kg(-1) of CCK produced small increases in the vagal afferent activity, and the responses were not influenced by pretreatment with either L-365,260 or MK-329. In addition, the systemic administration of CCK did not change gastric motility in the OLETF rats, indicating that the response of the vagal afferent activity in OLETF rats was independent of the gastric motility change. These results demonstrate that neither CCKAR nor CCKBR contributes to the response of the afferent activity of the gastric vagal nerve to a systemic administration of CCK in OLETF rats, suggesting an involvement of novel (non-A, non-B) CCK receptors.

Physical exercise increases survival after an experimental myocardial infarction in rats.

To directly evaluate the effect of physical exercise on survival, 80 rats were randomly assigned to either sedentary life (n = 40) or physical exercise 7 days/week during 6 weeks (n = 40), starting 2 weeks after coronary ligation. All animals were followed daily for 183 days. Size of myocardial infarction was determined by planimetry of serial histologic sections of the left ventricle. Physical exercise had no effect on survival in the total treatment group. However, rats with large myocardial infarctions, randomized to physical exercise, had significantly (p = 0.03) better survival (50%) after 6 months than control rats (17%) with large infarctions.

Increased concentrations of calcitonin gene-related peptide-like immunoreactivity in rat brain and peripheral tissue after ischaemia: correlation to flap survival.

The effects of experimentally induced ischaemia after free-flap surgery on concentrations of neuropeptide Y (NPY), neurokinin A (NKA), substance P (SP) and calcitonin gene-related peptide (CGRP)-like immunoreactivity (-LI) were studied in flap tissue and in different regions of the rat brain (striatum, hippocampus, pituitary, hypothalamus, frontal and occipital cortex). Ten days after the operation, CGRP-LI and NKA-LI were decreased in the ischaemic tissue but increased in the surrounding tissue. In the brain, CGRP-LI was increased in five of six regions analysed, with the exception of the striatum. SP-LI and NKA-LI were increased in the pituitary and hippocampus, but decreased in other brain regions. Changes of CGRP-LI in the brain correlated positively with the CGRP-LI concentrations in the surrounding flap tissue and the CGRP-LI concentrations in the ischaemic flap tissue with the extent of flap survival. The results of the present study suggest that higher concentrations of CGRP-LI are related to tissue survival and that endogenous CGRP has a regulatory effect in ischaemia.

Interleukin-1beta sensitizes the response of the gastric vagal afferent to cholecystokinin in rat.

Interleukin-1beta (IL-1beta) and cholecystokinin (CCK) are important mediators in the development of anorexic response during disease. The role of IL-1beta and CCK in the peripheral mechanisms of anorexia was studied by recording the mass afferent activity of the gastric vagal nerve in anesthetized rats. The i.v. administration of CCK (1 nmol) increased the activity of the vagal nerve, and this response was raised by 55-72% 2 h after i.v. injection of IL-1beta. It is proposed that IL-1beta-induced anorexia is mediated via the sensitization of type A CCK receptors in the periphery.

Effects of repeated sensory stimulation (electro-acupuncture) and physical exercise (running) on open-field behaviour and concentrations of neuropeptides in the hippocampus in WKY and SHR rats.

The effects of repeated sensory stimulation (electro-acupuncture) and physical exercise (running) on open-field behaviour and on hippocampal concentrations of neuropeptide Y, neurokinin A, substance P, galanin and vasoactive intestinal peptide (VIP)-like immunoreactivities were studied in WKY (wistar-Kyoto) and SHR (spontaneously hypertensive) rats. Significantly higher concentrations of substance P-like immunoreactivity, neurokinin A-like immunoreactivity and neuropeptide Y-like immunoreactivity were found in the hippocampus immediately after 3 weeks of treatment (electro-acupuncture and running), but not 1 week after the last (tenth) changes in neuropeptide concentrations were similar in the two rat strains. Open-field behaviour was significantly reduced during the treatment period in both strains. There were significant negative correlations between behaviour and neuropeptide concentrations in SHR rats, suggesting interdependency with sympathetic activity. It is proposed that the effects of electro-acupuncture and physical exercise in rats are related to increases in neuropeptide Y, neurokinin A and substance P in the hippocampus.

Changes of neuropeptide concentrations in the brain following experimentally induced mononeuropathy in Wistar Kyoto and spontaneously hypertensive rats.

The effect of unilateral, experimentally induced, mononeuropathy on concentrations of neuropeptide Y (NPY), neurokinin A (NKA), substance P (SP), calcitonin gene-related peptide CGRP) and galanin- (GAL-) like immunoreactivities (-LI) was studied in Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rat brains. Two weeks following ligation of the sciatic nerve, significantly higher concentrations of NPY-LI were found in the hippocampus, striatum and occipital cortex of both rat strains. CGRP-LI and GAL-LI were increased in the hippocampus of WKY rats. NKA-LI and SP-LI were decreased to different degrees in the pituitary of the WKY and SHR rats, indicating that the changes of the tachykinins, CGRP and GAL were selectively associated with the basal level of sympathetic tone. The increased concentrations of NPY-LI in the brain, not influenced by sympathetic tone, may be part of a general defense reaction in response to trauma.

Effects of electro-acupuncture and physical exercise on regional concentrations of neuropeptides in rat brain.

The effects of single or repeated treatments with manual acupuncture (ACU), electro-acupuncture (ELACU) or physical exercise on neuropeptide Y (NPY), neurokinin A (NKA), substance P (SP), galanin (GAL) and vasoactive intestinal peptide (VIP)-like immunoreactivity (-LI) in different regions of the rat brain were studied. Initially the effect of microwave irradiation (MWI) was compared to decapitation on the recovery of neuropeptides, and significantly higher concentrations of SP-LI, NKA-LI and NPY-LI were found in the hippocampus, occipital cortex, pituitary and striatum following MWI. Repeated ELACU treatments significantly increased SP-LI, NKA-LI and NPY-LI in the hippocampus and NPY-LI in the occipital cortex. No changes were found in animals receiving ACU or performing physical exercise.