The NOP receptor involvement in both withdrawal- and CCk-8-induced contracture responses of guinea pig isolated ileum after acute activation of κ-opioid receptor.

In isolated guinea-pig ileum (GPI), the κ-opioid acute withdrawal response is under the control of several neuronal signaling systems, including the μ-opioid, the A(1)-adenosine and the CB(1) receptors, which are involved in the inhibitory control of the κ-withdrawal response. After κ-opioid system stimulation, indirect activation of μ-opioid, A(1)-adenosine and CB(1) systems is prevented by the peptide cholecystokinin-8 (CCk-8). In the present study, we have investigated whether the NOP system is also involved in the regulation of the acute κ-withdrawal response.

Biphasic regulation of the acute μ-withdrawal and CCk-8 contracture responses by the ORL-1 system in guinea pig ileum.

The cloning of the opioid-receptor-like receptor (ORL-1) and the identification of the orphaninFQ/nociceptin (OFQ/N) as its endogenous agonist has revealed a new G-protein-coupled receptor signalling system. The structural and functional homology of ORL-1 to the opioid receptor systems has posed a number of challenges in the understanding the often competing physiological responses elicited by these G-protein-coupled receptors. We had previously shown that in guinea pig ileum (GPI), the acute μ-withdrawal response is under the inhibitory control of several systems.

Acute withdrawal induced by adenosine A-receptor activation in isolated guinea-pig ileum: role of opioid receptors and effect of cholecystokinin.

Objectives: In isolated guinea-pig ileum, the mu-opioid acute withdrawal response is under control of several neuronal systems, including the kappa-opioid and the A(1)-adenosine systems, which are involved in the mu-withdrawal response inhibitory control. After mu-opioid system stimulation, indirect activation of both kappa-opioid and A(1)-adenosine systems is prevented by the peptide cholecystokinin-8 (CCk-8). Guinea-pig ileum exposed to A(1)-adenosine agonist (CPA), shows a withdrawal contracture precipitated by the A(1)-adenosine antagonist (CPT).

Involvement of the cannabinoid CB1 receptor in the opioid inhibition of the response to cholecystokinin and acute withdrawal response.

Numerous recent studies have reported major functional interactions between cannabinoid and opioid systems. These interactions can be studied in the myenteric plexus-longitudinal muscle isolated preparations. We had previously shown that in the guinea-pig ileum (GPI), the opioid acute withdrawal response is under the inhibitory control of several systems; mu-opioid agonist exposure indirectly activates the kappa-opioid system; conversely, exposure to a kappa-opioid agonist indirectly activates the mu-system; the indirectly activated opioid system inhibits the withdrawal response.

Inhibitory control of the acute mu-withdrawal response by indirectly activated adenosine A1 and kappa-opioid systems in the Guinea-pig ileum; reversal by cholecystokinin.

In the isolated guinea-pig ileum (GPI), the acute mu-opioid withdrawal response is inhibited by the kappa-opioid system, indirectly activated by the opioid agonist; yet, other inhibitory mechanisms are probably operating. On the other hand, cholecystokinin (CCK-8) strongly enhances the withdrawal response. In this study, we have shown that the adenosine A1 antagonist 8-cyclopenthyl-1,3-dimethylxantine (CPT) increased the withdrawal response in dermorphin/naloxone (NLX) tests but lacked any effect if the withdrawal tests were carried out in presence of CCK-8.

Biologic activity of the tachykinins on lamb and sheep gallbladder.

In this study, we examined the activity of the tachykinins (TKs) on lamb and sheep isolated gallbladder and whether the TKs are involved in the capsaicin-induced activity in these tissues. Substance P (SP) and physalaemin (PHYS) contracted lamb gallbladder, PHYS-induced striking tachyphylaxis. This tissue was nearly insensitive to neurokinin A (NKA), neurokinin B (NKB), septide, and capsaicin.

Intestinal motility disorder induced by free radicals: a new model mimicking oxidative stress in gut.

Literature data suggest that the inflamed intestine may be subjected to a considerable oxidative stress. Therefore, the aim of the present study was to simulate the oxidative stress in the gastrointestinal tract and to explore its effect on intestinal motility. This was attained by treating isolated segments from the rabbit jejunum and from the guinea pig ileum with 2,2'-Azobis (2-amidinopropane) dihydrochloride (ABAP), which generates peroxyl radicals by thermal decomposition.

Dissociation in the effects of the D2/D3 dopaminergic agonist quinpirole on drinking and on vasopressin levels in the rat.

In the present study, we investigated the role of vasopressin in the development of quinpirole-induced hyperdipsia in the rat. We report that: (1), an acute intraperitoneal (i.p.