Leukemia inhibitory factor induces nociceptin mRNA in cultured rat cortical neurons

The effects of leukemia inhibitory factor (LIF) on the expression of neurotransmitter synthetase and neuropeptide mRNAs in cultured rat cortical neurons were examined by reverse transcription-polymerase chain reaction. Nociceptin mRNA expression was increased by treatment with 20 or 80 ng/ml LIF for 24 h, but choline acetyl transferase, glutamic acid decarboxylase, enkephalin, dynorphin, substance P, somatostatin and galanin mRNA expression were not altered by LIF. These observations indicated a specific effect of LIF on nociceptin gene regulation in cultured cortical neurons.

Probable involvement of the 5-hydroxytryptamine(4) receptor in methotrexate-induced delayed emesis in dogs

Delayed emesis in cancer patients undergoing chemotherapy remains a significant problem. The pathogenesis of delayed emesis is still obscure. It was recently demonstrated that methotrexate (MTX), an anticancer drug, evoked delayed emesis in dogs in a manner similar to its actions in humans. We evaluated the antiemetic activity of FK1052, a potent antagonist for both the 5-hydroxytryptamine (HT)(3) and 5-HT(4) receptors, on delayed emesis induced by MTX in beagle dogs. Animal behavior was recorded for 3 days using a video camera. Delayed emesis lasting up to 72 h was observed in dogs treated with MTX (2.5 mg/kg i.v.), but acute emesis did not occur. The following antiemetics, at the dose that prevents cisplatin-induced acute emesis in dogs, were administered i.v. as multiple injections every 12 h during days 2 to 3. FK1052 (1 and 3.2 mg/kg) significantly reduced the emetic episodes caused by MTX, whereas ondansetron (1 mg/kg), a selective 5-HT(3) receptor antagonist, was not effective. The emetic episodes induced by MTX were also inhibited by another 5-HT(3/4) receptor antagonist, tropisetron (1 mg/kg). CP-122,721 (0. 1 mg/kg), a potent selective tachykinin NK(1) receptor antagonist, significantly reduced the emetic responses to MTX. Copper sulfate-induced emesis in dogs was also prevented by FK1052, tropisetron, and CP-122,721 but not by ondansetron. FK1052, tropisetron, and ondansetron had negligible affinity for the NK(1) receptor at 1 microM. These results suggest that the 5-HT(4) receptor may be in part involved in the production of delayed emesis induced by MTX in dogs and that FK1052 may be a useful drug against both acute and delayed emesis induced by cancer chemotherapy.

Effects of cyclooxygenase-2 selective and nitric oxide-releasing nonsteroidal antiinflammatory drugs on mucosal ulcerogenic and healing responses of the stomach

Effects of selective cyclooxygenase-2 (COX-2) inhibitors (NS-398) and nitric oxide (NO) -releasing aspirin (NO-ASA) on gastric ulcerogenic and healing responses were examined in comparison with nonselective COX inhibitors such as indomethacin and aspirin (ASA). Hypothermic stress (28-30 degrees C, 4 hr) induced gastric lesions in anesthetized rats with an increase of acid secretion. The lesions induced by hypothermic stress were markedly worsened by subcutaneous administration of both indomethacin and ASA but were not affected by either NS-398 or NO-ASA, although the increased acid secretion during hypothermia was not affected by any of the drugs. On the other hand, the healing of gastric ulcers induced in mice by thermal cauterization (70 degrees C, 15 sec) was significantly delayed by daily subcutaneous administration of indomethacin and ASA as well as NS-398, but not by NO-ASA. COX-2 mRNA was not detected in the intact mucosa but was positively expressed in the ulcerated mucosa, most potently on day 3 after ulceration. Prostaglandin contents in the intact mouse stomach were reduced by indomethacin, ASA, and NO-ASA, while the increased prostaglandin generation in the ulcerated mucosa was inhibited by all drugs including NS-398. After subcutaneous administration of NO-ASA to pylorus-ligated rats and mice, high amounts of NOx were detected in both the gastric contents and serum. In addition, both NS-398 and NO-ASA showed an equipotent antiinflammatory effect against carrageenan-induced paw edema in rats as compared with indomethacin and ASA. These results suggest that both indomethacin and ASA not only increased the mucosal ulcerogenic response to stress but impaired the healing response of gastric ulcers as well. The former action was due to inhibition of COX-1, while the latter effect was accounted for by inhibition of COX-2 and was mimicked by the COX-2-selective inhibitor NS-398. NO-ASA, although it inhibited both COX-1 and COX-2 activity, had no deleterious effects on gastric ulcerogenic and healing responses.

Cyclo-oxygenase isozymes in mucosal ulcergenic and functional responses following barrier disruption in rat stomachs

1. We examined the effects of selective and nonselective cyclo-oxygenase (COX) inhibitors on various functional changes in the rat stomach induced by topical application of taurocholate (TC) and investigated the preferential role of COX isozymes in these responses. 2. Rat stomachs mounted in ex vivo chambers were perfused with 50 mM HCl and transmucosal potential difference (p.d.), mucosal blood flow (GMBF), luminal acid loss and luminal levels of prostaglandin E2 (PGE2) were measured before, during and after exposure to 20 mM TC. 3. Mucosal application of TC in control rats caused a reduction in p.d., followed by an increase of luminal acid loss and GMBF, and produced only minimal damage in the mucosa 2 h later. Pretreatment with indomethacin (10 mg kg[-1], s.c.), a nonselective COX-1 and COX-2 inhibitor, attenuated the gastric hyperaemic response caused by TC without affecting p.d. and acid loss, resulting in haemorrhagic lesions in the mucosa. In contrast, selective COX-2 inhibitors, such as NS-398 and nimesulide (10 mg kg[-1], s.c.), had no effect on any of the responses induced by TC and did not cause gross damage in the mucosa. 4. Luminal PGE2 levels were markedly increased during and after exposure to TC and this response was significantly inhibited by indomethacin but not by either NS-398 or nimesulide. The expression of COX-1-mRNA was consistently detected in the gastric mucosa before and after TC treatment, while a faint expression of COX-2-mRNA was detected only 2 h after TC treatment. 5. Both NS-398 and nimesulide significantly suppressed carrageenan-induced rat paw oedema, similar to indomethacin. 6. These results confirmed a mediator role for prostaglandins in the gastric hyperaemic response following TC-induced barrier disruption, and suggest that COX-1 but not COX-2 is a key enzyme in maintaining 'housekeeping' functions in the gastric mucosa under both normal and adverse conditions.

Localization of mRNA for leukemia inhibitory factor receptor in the adult rat brain

The distribution of leukemia inhibitory factor receptor (LIFR) mRNA in the adult rat brain was examined by in situ hybridization technique. The intense signals of LIFR mRNA were restricted to specific brain regions relevant to the motor and sensory systems. The moderate expression of LIFR mRNA was observed in several brain regions, including the cerebral cortex, hippocampus, thalamus, hypothalamus and cerebellum. Most of the signals of LIFR mRNA were detected on likely neuronal cells. These findings suggest the possibility that LIF has potential actions on the neuronal cells in the central nervous system of the adult rat.

New 5-HT3 (serotonin-3) receptor antagonists. V. Synthesis and structure-activity relationships of pyrrolo[2,1-c][1,4]benzoxazine-6-carboxamides

This paper describes the discovery of structurally novel heterocyclic carboxamides which are highly potent 5-HT3 (serotonin-3) receptor antagonists. Pyrrolo[2,1-c][1,4]benzoxazine-6-carboxamides (12 and 20) were found to possess potent 5-HT3 receptor antagonist activity on the von Bezold-Jarisch reflex in anesthetized rats. Structure-activity studies showed that compounds with small and lipophilic substituents such as chloro and methyl at the 8-position of the aromatic ring portion retained high potency, whereas those with bulky substituents showed essentially no activity. A dimethyl group at the 4-position slightly decreased the potency. 1-Azabicyclo[2.2.2]octan-3-amine as the amine part afforded the most potent activity. From this series, 20a was found to be the most potent 5-HT3 receptor antagonist, being 40-fold more potent than ondansetron (1).

New 5-HT3 (serotonin-3) receptor antagonists. IV. Synthesis and structure-activity relationships of azabicycloalkaneacetamide derivatives

The synthesis and structure-activity relationships of a series of new azabicycloalkanes as 5-HT3 (serotonin-3) receptor antagonists are described. Our study on the azabicycloalkaneacetamide derivatives showed that 2,3-dihydroindole as the aromatic ring moiety afforded potent 5-HT3 receptor antagonist activity, as judged by blockade of bradycardia induced by i.v. injection of 2-methylserotonin in anesthetized rats. 7-Azaindole as the aromatic moiety afforded weak 5-HT3 receptor antagonists activity. The best 5-HT3 antagonists in this study were endo-3,3-diethyl- (9k) and 3,3-dimethyl-2,3-dihydro-1-[(8-methyl-8-azabicyclo[3.2.1]oct-3-yl) acetyl-1H-indole (9d), being approximately 10-fold more potent than ondansetron (1). This study shows that the azabicycloalkaneacetyl group is a new pharmacophoric element as a basic nitrogen and a linking carbonyl moiety.

New 5-HT3 (serotonin-3) receptor antagonists. I. Synthesis and structure-activity relationships of pyrido[1,2-a]indoles

A series of pyrido[1,2-alpha]indol-6(7-H)-ones was prepared and evaluated for 5-HT3 receptor antagonist activity. The structural requirements for the 5-HT3 receptor antagonist have been defined as an aromatic moiety, a basic nitrogen, and a linking acyl group. The (5-methylimidazol-4-yl)methyl group as a basic nitrogen moiety was an important element for high potency. The highest potency was observed for compounds which have 7- and 10-methyl substituents on the pyrido[1,2-alpha]indol-6(7H)-one ring. From this series, (+)-11b (FK 1052) was selected for further evaluation. FK 1052 was a potent 5-HT3 receptor antagonist in the Bezold-Jarisch reflex test in rats (ED50 0.9 microgram/kg, i.v.) and a very effective antiemetic agent against cisplatin-induced emesis in dogs (ED50 1.2 x 2 micrograms/kg, i.v. and 2.7 x 2 micrograms/kg, p.o.).

New 5-HT3 (serotonin-3) receptor antagonists, II. Synthesis and structure-activity relationships of pyrimido[1,6-a]indoles

A series of pyrimido[1,6-alpha]indol-1(2H)-ones was prepared and evaluated for 5-HT3 receptor antagonist activity. The compounds in this series were regarded as bioisosters of the pyrido[1,2-alpha]indol-6(7H)-ones previously reported. High potency was found for compounds having 5-methyl substituents on both the pyrimido[1,6-alpha]indole ring and the imidazole ring. Optimized members of this series, 8b and (+)-26a, were potent 5-HT3 receptor antagonists as determined by measuring inhibition of the Bezold-Jarisch reflex in anesthetized rats (ED50 0.6 and 0.8 microgram/kg i.v., respectively), being equipotent to or more potent than FK 1052 (1) in the previous paper and 20- to 30-fold more potent than ondansetron (2).

Functional and morphological alterations in the rat stomach following exposure to hypertonic NaCl solution

We examined the effects of 1 M NaCl as a mild irritant on gastric potential difference (PD), acid secretion, mucosal blood flow (MBF), and DNA synthetic activity in anesthetized rat stomachs and compared these effects with those of 4 M NaCl as a strong irritant. Both 1 M and 4 M NaCl produced a PD reduction (mucosal injury), but the reduced PD recovered faster in the mucosa exposed to 1 M NaCl as compared to 4 M NaCl. Acid secretion ceased after exposure to these hypertonic NaCl solutions, but histamine infusion (8 mg/kg/hr) stimulated acid secretion only in the mucosa exposed to 1 M NaCl. The MBF was significantly increased in response to 1 M NaCl, while exposure to 4 M NaCl had no effect on the MBF. These changes in acid secretion and MBF induced by 1 M NaCl were significantly antagonized by pretreatment with indomethacin (5 mg/kg, s.c.). The levels of PGE2 and 6-keto PGF1 alpha in the corpus mucosa were significantly increased in the stomach exposed to both 1 M and 4 M NaCl, and these increases disappeared in the presence of indomethacin. The rate of [3H]-thymidine incorporation was significantly reduced in the mucosa after exposure to 4 M NaCl, but remained unaltered in the stomach exposed to 1 M NaCl. These results suggest that although both 1 M and 4 M NaCl produced mucosal injury (PD reduction) and enhanced PGs formation, a variety of functional alterations mediated by PGs occurred in response to injury in the stomach exposed to 1 M NaCl. The presence or absence of these functional responses may be associated with the biphasic actions on the gastric mucosa of these hypertonic NaCl solutions as mild and strong irritants.