fedotozine and norbinaltorphimine

The aim of this study was to characterize plasma membrane pathways involved in the intracellular calcium ([Ca(2+)](i)) response of small DRG neurons to mechanical stimulation and the modulation of these pathways by kappa-opioids. [Ca(2+)](i) responses were measured by fluorescence video microscopy of Fura-2 labeled lumbosacral DRG neurons obtained from adult rats in short-term primary culture. Transient focal mechanical stimulation of the soma, or brief superfusion with 300 nM capsaicin, resulted to [Ca(2+)](i) increases which were abolished in Ca(2+)-free solution, but unaffected by lanthanum (25 microM) or tetrodotoxin (10(-6) M). 156 out of 465 neurons tested (34%) showed mechanosensitivity while 55 out of 118 neurons (47%) were capsaicin-sensitive. Ninty percent of capsaicin-sensitive neurons were mechanosensitive. Gadolinium (Gd(3+); 250 microM) and amiloride (100 microM) abolished the [Ca(2+)](i) transient in response to mechanical stimulation, but had no effect on capsaicin-induced [Ca(2+)](i) transients. The kappa-opioid agonists U50,488 and fedotozine showed a dose-dependent inhibition of mechanically stimulated [Ca(2+)](i) transients but had little effect on capsaicin-induced [Ca(2+)](i) transients. The inhibitory effect of U50,488 was abolished by the kappa-opioid antagonist nor-Binaltorphimine dihydrochloride (nor-BNI; 100 nM), and by high concentrations of naloxone (30-100 nM), but not by low concentrations of naloxone (3 nM). We conclude that mechanically induced [Ca(2+)](i) transients in small diameter DRG somas are mediated by influx of Ca(2+) through a Gd(3+)- and amiloride-sensitive plasma membrane pathway that is co-expressed with capsaicin-sensitive channels. Mechanical-, but not capsaicin-mediated, Ca(2+) transients are sensitive to kappa-opioid agonists.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Amiloride; Animals; Benzyl Compounds; Calcium; Capsaicin; Cells, Cultured; Gadolinium; Ganglia, Spinal; In Vitro Techniques; Kinetics; Male; Naltrexone; Neurons; Physical Stimulation; Propylamines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa

Fedotozine, a kappa opioid agonist, reverses digestive ileus caused by acetic acid (AA)-induced visceral pain in rats. The aims of this study were: to map, in conscious rats, central pathways activated by AA using Fos as a marker of neuronal activation; to characterize primary afferent fibres involved in this activation; and to investigate the effect of fedotozine on AA-induced Fos expression. AA (0.6%; 10 mL kg-1) was injected i.p. in conscious rats either untreated; pretreated 14 days before with capsaicin; pretreated 20 min previously with fedotozine; or pretreated 2 h prior to fedotozine with the kappa-antagonist nor-binaltorphimine (nor-BNI). Controls received the vehicle alone. 60 min after injection of AA, rats were processed for Fos immunohistochemistry. Visceral pain was assessed by counting abdominal cramps. AA induced Fos in the thoraco-lumbar spinal cord (laminae I, V, VII and X) and numerous brain structures such as the nucleus tractus solitarius, and paraventricular nucleus (PVN) of the hypothalamus, whereas almost no Fos labelling was observed in controls. Capsaicin pretreatment blocked AA-induced Fos in all structures tested. Fedotozine significantly decreased AA-induced abdominal cramps and Fos immunoreactivity in the spinal cord and PVN, this effect being reversed by nor-BNI pretreatment. AA induces Fos in the spinal cord and numerous brain nucuei, some of which are involved in the control of digestive motility in rats. This effect is mediated through capsaicin-sensitive afferent fibres and prevented by fedotozine most likely through a peripheral action on visceral afferents.

Topics: Abdominal Pain; Acetic Acid; Afferent Pathways; Animals; Benzyl Compounds; Brain; Capsaicin; Gene Expression Regulation; Genes, fos; Injections, Intraperitoneal; Intestinal Obstruction; Male; Naltrexone; Paraventricular Hypothalamic Nucleus; Propylamines; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Solitary Nucleus; Spinal Cord; Supraoptic Nucleus

Quantitative neurophysiological studies have identified the presence of at least 2 spinal neuronal populations (abrupt and sustained) that are excited by the noxious visceral stimulus colorectal distention. This study examined the effects of the kappa opioid receptor agonists fedotozine and U50488H on the activity of these neurons.. In decerebrate, cervical spinal cord-transected male rats, the lumbosacral spinal cord was exposed by a laminectomy. Dorsal horn neurons showing excitatory responses to colorectal distention (80 mm Hg, 20 seconds) were identified using microelectrodes. Cumulative doses of fedotozine and U50488H were administered intravenously or intrathecally, and antagonists were used.. Intravenous fedotozine and U50488H dose-dependently inhibited the evoked activity of sustained neurons. This inhibition was partially reversed by the kappa opioid antagonist norbinaltorphimine. The same agents had insignificant effects on the evoked activity of abrupt neurons. Fedotozine inhibited spontaneous activity of both abrupt and sustained neurons. Intrathecally administered U50488H had no effect on abrupt or sustained neurons, but intrathecally administered fedotozine inhibited the evoked and spontaneous activity of both groups.. Kappa opioid receptor agonists acting peripherally had differential effects on 2 spinal neuronal populations responsive to colorectal distention. Fedotozine had additional inhibitory effects acting within the spinal cord.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzyl Compounds; Colon; Male; Naltrexone; Propylamines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Rectum; Spinal Cord

Fedotozine has been shown to act on gastrointestinal sensitivity through peripheral kappa-opioid receptors. The present study investigated the action of fedotozine and reference compounds, morphine and (+/-)-U-50,488H, on duodenal pain in anesthetized rats. The noxious stimulus was produced by duodenal distension (100 mm Hg; 30 s). Fedotozine (1-5 mg/kg i.v.) produced a dose-dependent inhibition of the cardiovascular reflex induced by duodenal distension (ED50 = 1.87 mg/kg) but had no effect at doses up to 300 micrograms/rat by either intracerebroventricular (i.c.v.) or intrathecal routes (i.t.). The mu-opioid receptor agonist, morphine, was active by both i.v. (ED50 = 0.62 mg/kg) and i.c.v. routes (ED50 = 2.17 micrograms/rat) as was the kappa-opioid receptor agonist, (+/-)-U-50,488H (trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1- pyrrolidinyl]cyclohexyl)benzeneacetamide) (ED50 = 0.25 mg/kg and 149 micrograms/rat for i.v. and i.c.v. routes, respectively). The selective kappa-opioid receptor antagonist, nor-binaltorphimine (10 mg/kg s.c.), abolished the response to fedotozine (5 mg/kg i.v.) and (+/-)-U-50,488H (2 mg/kg i.v.) but not that to morphine (1 mg/kg i.v.). In contrast, naloxone (30 micrograms/kg i.v.) blocked the response to morphine (1 mg/kg i.v.) but not that to fedotozine (5 mg/kg i.v.) or (+/-)-U-50,488H (2 mg/kg i.v.). It is concluded that the antinociceptive effects of fedotozine on duodenal pain are mediated by peripheral kappa-opioid receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzyl Compounds; Blood Pressure; Dose-Response Relationship, Drug; Duodenum; Injections, Intravenous; Injections, Intraventricular; Male; Morphine; Naloxone; Naltrexone; Pain; Propylamines; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Reflex

Gastric motor disturbances, associated with a delay in gastric emptying, occur in patients with the irritable bowel syndrome. The influence of fedotozine and kappa agonists on the cologastric reflex produced by nonpainful colonic distention was evaluated in conscious dogs.. Colonic distention was applied in dogs fitted with either strain gauges or gastric cannula to assess its influence on gastrointestinal motility and gastric emptying, respectively.. Colonic distention delayed the occurrence of gastric migrating motor complex by 141%, an effect blocked by intravenous fedotozine, U 50,488 (25 and 50 micrograms/kg), and hexamethonium (0.5 mg/kg) but not by D-Ala2, N-methyl, Phe4, Gly5-ol enkephalin (1, 5, and 10 micrograms/kg), granisetron (50 and 100 micrograms/kg), or bretylium tosylate (5 mg/kg). Nor-binaltorphimine hydrochloride (1 mg/kg intravenously) eliminated the suppressive action of fedotozine. Colonic distention reduced the 1-hour gastric emptying of solids by 40.1%, an effect blocked by fedotozine and U 50,488 (50 and 100 micrograms/kg); nor-binaltorphimine hydrochloride (1 mg/kg) antagonized the blocking effect of fedotozine.. Fedotozine acts through kappa receptors to block the colonic distention-induced delay on gastric motility and emptying. The cologastric reflex involves nicotinic ganglionic receptors but not adrenergic pathway and 5-hydroxytryptamine 3 receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Benzyl Compounds; Bretylium Compounds; Catheterization; Colon; Dogs; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Gastric Emptying; Gastrointestinal Motility; Granisetron; Hexamethonium; Male; Naltrexone; Narcotic Antagonists; Propylamines; Pyrrolidines; Receptors, Opioid, kappa; Receptors, Opioid, mu; Reflex; Stomach