Phase IIa study of the CD19 antibody MOR208 in patients with relapsed or refractory B-cell non-Hodgkin's lymphoma.

Background: This two-stage, phase IIa study investigated the antitumor activity and safety of MOR208, an Fc-engineered, humanized, CD19 antibody, in patients with relapsed or refractory (R-R) B-cell non-Hodgkin's lymphoma (NHL). CD19 is broadly expressed across the B-lymphocyte lineage, including in B-cell malignancies, but not by hematological stem cells. Patients and methods: Patients aged ≥18 years, with R-R NHL progressing after ≥1 prior rituximab-containing regimen were enrolled into subtype-specific cohorts: diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), other indolent (i)NHL and mantle cell lymphoma (MCL). Treatment was MOR208, 12 mg/kg intravenously, weekly, for 8 weeks. Patients with at least stable disease could continue treatment for an additional 4 weeks. Those with a partial or complete response after 12 weeks could receive extended MOR208 treatment (12 mg/kg, either monthly or every second week) until progression. The primary end point was overall response rate. Results: Ninety-two patients were enrolled: DLBCL (n = 35), FL (n = 34), other iNHL (n = 11) and MCL (n = 12). Responses were observed in DLBCL, FL and other iNHL cohorts (26%, 29% and 27%, respectively). They lasted ≥12 months in 5/9 responding patients with DLBCL, 4/9 with FL and 2/3 with other iNHL. Responses in nine patients are ongoing (>26 months in five instances). Patients with rituximab refractory disease showed a similar response rate and progression-free survival time to patients with non-refractory disease. The most common adverse events (any grade) were infusion-related reactions (12%) and neutropenia (12%). One patient experienced a grade 4 infusion-related reaction and eight patients (9%) experienced grade 3/4 neutropenia. No treatment-related deaths were reported. Conclusions: MOR208 monotherapy demonstrated promising clinical activity in patients with R-R DLBCL and R-R FL, including in patients with rituximab refractory tumors. These efficacy data and the favorable safety profile support further investigation of MOR208 in phase II/III combination therapy trials in R-R DLBCL. ClinicalTrials.gov number: NCT01685008.

Endothelin receptor blockers protect against ischemia/reperfusion impairment of gastrointestinal motility in rats.

Intestinal ischemia/reperfusion (I/R) injury remains associated with high morbidity and mortality. The protective efficacy of the following endothelin (ET) receptor blockers: BQ-123 (ET(A) receptor), BQ-788 (ET(B)); tezosentan (dual ET blocker) was tested against the inhibition of gastrointestinal (GI) motility induced by intestinal I/R. Intestinal Evans blue transit was measured in untreated (UN) rats and animals subjected to skin incision (SI), I/R (1h superior mesenteric artery clamping followed by 2-24h reperfusion) or sham operation (SO). Surgical procedures were conducted under diethyl ether anesthesia. Anesthesia and SI did not affect the GI transit compared to UN rats. In contrast both SO and I/R significantly reduced GI motility, the latter evident at 2-24h of reperfusion. Tezosentan (1-10 mg/kg), BQ-123 and BQ-788 (0.1-1 mg/kg) protected against I/R-induced inhibition of intestinal motility in a time- and dose-dependent manner at the early and late stages of reperfusion. Furthermore tezosentan alleviated the I/R-induced decrease in the contractile response of the longitudinal jejunal smooth muscle strips to carbachol in vitro. The serum ET(1-21) level was increased at 2h but not 24h of reperfusion compared to SO animals and ET(1-21) was higher in tezosentan pretreated rats.

Salutary effects of tachykinin receptor antagonists in a rat model of postoperative ileus.

BACKGROUND: Postoperative ileus (PI) is a common surgical complication treated mainly with supportive measures. Tachykinins control gastrointestinal motility and modulate somatic and visceral pain sensation; therefore, the effect of tachykinin receptor antagonists in a rat model of PI using NK(1-3) antagonists, SR140333, SR48968, and SR142801, was investigated. MATERIALS AND METHODS: Intestinal transit was measured as Evans blue migration after varied nociceptive stimuli: skin incision (SI), laparotomy (LAP), or laparotomy plus gut manipulation (L + M) in anesthetized rats. RESULTS: Diethyl ether anesthesia and SI did not influence the intestinal transit of the dye in comparison to untreated animals--UN: 61.17 +/- 5.47, 62.10 +/- 8.30, and 56.70 +/- 4.10 cm, respectively. In contrast LAP and L + M have significantly reduced intestinal motility to 26.40 +/- 2.07 and 9.70 +/- 1.15 cm, respectively. SR140333 (3-30 microg/kg), SR48968 (1-30 microg/kg), and SR142801 (3-10 microg/kg) reversed the additional inhibitory effects of gut manipulation subsequent to LAP dose-dependently, the dye transit returning with the use of the most effective antagonist doses up to 25.28 +/- 1.08, 21.70 +/- 0.19, and 25.0 +/- 1.34 cm. The combinations of submaximal doses of NK(1) and NK(3), NK(2) and NK(3) and NK(1), and NK(2) and NK(3) antagonists were not more effective than a single-agent regimen. On the other hand SR140333 and SR48968 (NK(1) + NK(2) antagonists) acted additively, the intestinal transit reaching 26.60 +/- 0.85 cm. SR140333, SR48968, and SR142801 have not affected the intestinal passage in UN rats or those undergoing SI or LAP. CONCLUSIONS: SR140333, SR48968, and SR142801 exert a salutary action on suppressed gut motility following surgical manipulation of the gut, the combination of NK(1) and NK(2) antagonists being most beneficial.

The contractile effects of several substituted short analogues of porcine galanin in isolated rat jejunal and colonic smooth muscle strips.

The activity of short porcine galanin (Gal) analogues was tested in vitro using rat jejunal and colonic smooth muscle strips. Peptides evoked concentration-dependent tissue contractions yielding typical response curves in concentration range from 0.3 nM to 300 microM, with a characteristic fall-down effect at the supramaximal concentrations. Gal(1-15) was less potent than Gal(1-29). Furthermore, [D-Trp(2)]Gal(1-15), [endo-Trp(2),Cle(4)]Gal(1-15), [D-Leu(4)]Gal(1-15), [des-Leu(4)]Gal(1-15), [Hse(6)]Gal(1-15), [Dab(14)]Gal(1-15), [Dpr(14)]Gal(1-15) or [Arg(14)]Gal(1-15) showed a considerable decrease in potency compared to Gal(1-15) in jejunal and/or colonic smooth muscle cells. Functional evidence confirmed that the integrity of both N- and C-terminals must be preserved in order to preserve a full excitatory myogenic potential of the peptide in rat jejunum and colon. Besides, amino acids located in positions 2, 4, 6 and 14 play a crucial role in recognition and activation of molecular domains responsible for Gal action in the intestinal smooth muscle.

The role and interactions of nitric oxide (NO), carbon monoxide (CO), and prostanoids in the pathogenesis of postoperative ileus in rats.

The effects of heme oxygenase (HO) inhibitors, zinc-protoporphyrin-IX (ZnPP-IX), and tin protoporphyrin-IX (SnPP-IX) and their interactions with L-arginine/nitric oxide synthase (NOS) and cyclooxygenase (COX) pathways were investigated in postoperative ileus in rats. Intestinal transit was measured as Evans blue migration after skin incision, laparotomy or laparotomy plus gut evisceration and handling. Laparotomy and small intestinal manipulations increased blood plasma nitrites/nitrates level 1.88-fold. N(omega)-nitro-L-arginine methyl ester, indomethacin, a selective COX-1 blocker (resveratrol) and COX-2 antagonists (nimesulide, DuP-697, NS-398) reversed the additional inhibitory effects of gut manipulation subsequent to laparotomy. In contrast, N-(3-(aminomethyl)benzyl)acetamidine or S-methylisothiourea, highly selective inducible NOS blockers, remained ineffective. ZnPP-IX and SnPP-IX overturned the effects of laparotomy on dye propulsion, but were only partially effective after laparotomy and gut handling attenuating the additional inhibitory influences of gut manipulation, the intestinal transit reaching 89.21%, 92.87%, 53.46%, and 48.56% of respective controls transit. Salutary effects of L-NAME, ZnPP-IX, and SnPP-IX were dose-dependent, L-arginine or hemin (HO substrate) sensitive. Administration of indomethacin and resveratrol subsequent to SnPP-IX reversed the inhibitory effects of laparotomy and manipulation, amounting to 93.91% and 87.43% of controls. On the other hand, L-NAME injected after SnPP-IX abolished the salutary effects of the latter, study dye migration reached 25.18% of control rat. Therefore we demonstrated that nitric oxide, carbon monoxide, and prostanoids play a role in the pathogenesis of postoperative ileus albeit in different mechanisms. Laparotomy stimulated HO activity, whereas gut manipulation led to an excessive constitutive NOS stimulation accompanied by augmented prostanoid synthesis by COX-1. Unaffected synthesis of either NO or CO enables a return of gastrointestinal transit during postoperative period, whereas a pharmacological blockade of two complementary metabolic pathways provides a most effective measure against postoperative ileus development.

Increased potency of some substituted short peptide analogues in comparison to galanin(1-15)-NH(2)in rat fundus strips.

The activity of short porcine galanin (Gal) analogues was tested in vitro using rat gastric fundus strips. The peptides contracted longitudinal smooth muscle in a concentration-dependent manner with the following order of potency: Gal(1-29) >[Cit(14)]Gal(1- 15) >[Asp(14)]Gal(1- 15) >[Dab(14)]Gal(1- 15) >[Nle(14)] Gal(1-15) >[Dpr(14)]Gal(1- 15) >[Arg(14)]Gal(1- 15) >[Orn(14)]Gal(1- 15) >Gal(1-15). Only in the case of two peptides, namely [Cit(14)]Gal(1-15) and [Dab(14)]Gal(1-15) did the values of Hill coefficients, estimated from the appropriate concentration-contraction curves, differ significantly from unity. Our results indicate that both N- and C-terminals of Gal molecule contribute towards the affinity and activity of Gal in rat gastric smooth muscle cell receptors, indicating that their integrity is essential for its full excitatory myogenic action. The substitution of histidine with citruline, aspartic acid, norleucine or diaminobutyric acid in position 14 of the amino acid chain led to a considerable increase in potency, suggesting that amino acids located at this position might play a crucial role where the strength of short analogues is concerned.

Actions of several substituted short analogues of porcine galanin on isolated rat fundus strips: a structure-activity relationship.

The activity of porcine galanin (Gal) fragments and analogues were tested in vitro using rat gastric fundus strips. The peptides contracted longitudinal smooth muscle in a concentration-dependent manner with the following order of potency: [Nle4]Gal(1-15), Gal(-15), [Cle4]Gal(1-15), [Hse6]Gal(1-15), [Va14]Gal(1-15), [Ile4]Gal(1-15), [endoTrip2a, Cle4]Gal(1-15), [desThr3, Cle4]Gal(1-15), [D-Leu4] Gal(1-15), [desLeu4]Gal(1-15). On the contrary [desTrp2, Val4]Gal (1-15) remained inactive up to 10 microM. The values of Hill's coefficients estimated from the appropriate concentration-contraction curves for all analogues except for [Val4]Gal(1-15), [Hse6]Gal(1-15), [endoTrp2a,Cle4]Gal(1-15), [desLeu4]Gal(1-15) and [D-Leu4] Gal(1-15) did not significantly differ from unity. Our results indicate that the integrity of the first four N-terminal amino acids of Gal molecule is essential for the full excitatory myogenic action of the peptide in rat gastric fundus. Similarly, substitution, addition or deletion of amino acid residues in positions two, three, four and six can considerably influence the ability of Gal analogues to interact with Gal receptors. The data acquired in the course of our structure-activity study suggest that both N- and C-terminals of Gal molecule contribute towards the affinity and activity of Gal in rat gastric smooth muscle cell receptors.

Polaprezinc exerts a salutary effect on impaired healing of acute gastric lesions in diabetic rats.

We examined the influence of diabetes mellitus (DM) on the healing of HCl-induced gastric lesions and the healing promoting effect of polaprezinc [N-(3-aminopropionyl)-L-histidinato zinc] on these lesions. Studies were performed on rats injected intraperitoneally with streptozotocin (STZ, 70 mg/kg) five weeks prior to experiments. Diabetic rats had blood glucose levels (BGLs) higher than 350 mg/100 ml. Randomly chosen animals were treated subcutaneously with insulin (4 IU/day/rat) starting 1 week after STZ. Animals were given 1 ml of 0.6 N HCl by oral gavage (per os) following 18 hr of fasting; they were fed normally from 1 hr later and killed at various time points after HCl administration. Polaprezinc (3-30 mg/kg) or its components ZnSO4/7H2O and L-carnosine were given orally, twice daily for four days following HCl treatment. Gastric lesions induced by HCl healed macroscopically to quiescence within 10 days. DM and insulin did not affect the development of HCl-invoked gastric lesions, but the healing of such lesions was markedly impaired in animals with DM. Daily administration of insulin returned high BGLs to significantly lower ranges (190-208 mg/100 ml) and markedly antagonized the healing impairment. Polaprezinc (>10 mg/kg) significantly reversed the delay observed in diabetic rats without any notable effects on BGLs or acid secretion. Similar trends were observed with ZnSO4/7H2O or a mixture of ZnSO4/7H2O and L-carnosine, but not by L-carnosine alone. The mucosal expression of insulin-like growth factor-1 (IGF-I) mRNA was significantly lower in diabetic rats, a dysregulation partially corrected by insulin and polaprezinc. In addition, the delayed healing in diabetic rats was also significantly promoted by the repeated subcutaneous administration of rhIGF-I (>10 microg/kg, twice daily) without any notable effect on BGLs or acid secretion. These results suggest that DM exerted a deleterious influence on the healing of acute gastric lesions in both insulin- and zinc-sensitive manner. The salutary effects of polaprezinc on the impaired healing of gastric lesion in STZ-diabetic animals may at least be partly explained by enhancement of mucosal IGF-I mRNA expression in the stomach.

The inhibitory effects of terikalant on the contractile activity of galanin in isolated rat fundus strips.

The maximal responses (E(max)s) of isolated rat gastric fundus strips to 300 n m porcine galanin (Gal) were decreased in a concentration-dependent manner by terikalant (RP 62719). EC(50)of the agent equalled 4.39 microm (2.35-8.22). On the contrary the action of 30 n m of carbachol were not affected by the modulator in concentrations up to 30 microm. It is concluded that potassium currents may contribute to the modulation of Gal myotropic activity in the gut.

Exogenous insulin-like growth factor (IGF)-1 improves the impaired healing of gastric mucosal lesions in diabetic rats.

BACKGROUND: We examined the influence of diabetes mellitus (DM) on the healing of HCl-induced gastric lesions and the healing promoting effect of IGF-1 on these lesions. METHODS: Experiments were performed on rats injected with streptozotocin (STZ, 70 mg kg(-1), i.p.) 5 weeks prior to the experimental session. Diabetic animals had blood glucose levels (BGLs) higher than 350 mg dl(-1). Randomly chosen rats were treated with insulin (4 IU day(-1) rat(-1)) starting 1 week after STZ. Animals were given 1 ml of 0.6 m HCl by gavage following 18 h of fasting. Normal feeding was started 1 h later. Animals were killed at various time points after HCl. Recombinant human IGF-1 (rhIGF-1) at doses 10-400 microg kg(-1) was injected subcutaneously twice daily for 4 days following HCl treatment. RESULTS: Gastric lesions induced by HCl healed macroscopically within 10 days. DM and insulin regimen did not affect the development of HCl-invoked gastric lesions. However, DM significantly delayed the healing of such lesions. Daily administration of insulin returned the high BGLs to significantly lower ranges (190-210 mg dl(-1)) and markedly antagonized the delayed healing. Likewise, the repeated administration of rhIGF-1 (>/=10 microg kg(-1)) significantly enhanced the healing of gastric lesions in diabetic rats, without any notable effect on BGLs or gastric acid secretion. The mucosal expression of IGF-1 mRNA was lower in diabetic rat stomachs as compared to normal rats, although the expression was apparently restored after insulin treatment. CONCLUSION: These results suggest that DM has a deleterious influence on the healing of acute gastric lesions in both insulin- and IGF-1-sensitive manner. The systemic administration of rhIGF enhanced the rate of healing of gastric lesions observed in the healing-impaired STZ-diabetic animals.

Sources of activator Ca2+ for galanin-induced contractions of rat gastric fundus, jejunum and colon.

Galanin (Gal) evoked reproducible contractions of isolated rat gastric fundus, colon and jejunum longitudinal strips in concentrations ranging from 1 nM to 3 microM. EC50 of Gal equalled 12.63, 23.27 and 56.02 nM, respectively. Hill's coefficients were not different from unity in any of the tissues examined. Experiments have been performed in the presence of protease and peptidase inhibitors, a variety of specific antagonists and tetrodotoxin (TTX) to exclude the non-specific stimulatory or inhibitory action of Gal. Gal-evoked contractions were attenuated by diminished extracellular Ca2+ concentration and by diltiazem. Gal activity in gastric fundus and colon, but not in jejunum was inhibited by depleting intracellular Ca2+ stores, thapsigargin, dantrolene, ryanodine, TMB-8, neomycin and U-73122. Our data confirmed that Gal contracts rat fundus, jejunum and colon by stimulating specific receptors, which are coupled both to Ca2+ influx through the voltage-dependent calcium channels and intracellular Ca2+ release from ryanodine- and IP3-sensitive stores (stomach and colon) or the extracellular Ca2+ influx only (jejunum). Phosphatidylinositol-specific phospholipase C (PI-PLC) plays a crucial role in the former but not in the latter signal transduction cascade.

Increased susceptibility of diabetic rat gastric mucosa to food deprivation during cold stress.

BACKGROUND: We investigated the mechanisms responsible for the increased susceptibility of diabetic rat gastric mucosa to damage inflicted by overnight food deprivation (18 h) and its worsening by the cold restraint stress (4 degrees C, 3 h). METHODS: Gastric damage was measured in fasted animals, some of which were rendered diabetic by a single intraperitoneal injection of streptozotocin (STZ; 70 mg/kg) 5 weeks before experiments (STZ 5W). RESULTS: STZ 5W rodents showed a number of hemorrhagic lesions in corpus mucosa (26. 8 +/- 5.2 mm(2)) which could be prevented by insulin or nitric oxide synthase (NOS) inhibitors: aminoguanidine or L-NAME (N(omega)-nitro-L-arginine methyl ester). Mucosal injury was further aggravated by low temperature (51.1 +/- 7.8 mm(2)), the damage ameliorated by insulin, aminoguanidine, or L-NAME. The salutary actions of L-NAME were L-arginine sensitive. Low temperature and L-NAME did not significantly influence the gastric secretory parameters in normal rats. On the other hand, L-NAME and aminoguanidine counteracted the attenuation of gastric juice acidity and acid output in STZ 5W rodents. Blood plasma nitrite and nitrate levels and outputs in gastric juice were augmented in STZ 5W animals in comparison to controls. The total activities of NOS including inducible NOS but not constitutive NOS were markedly enhanced by fasting and cold restraint in gastric mucosa of STZ 5W animals (2.2- and 3.7- or 2.4- and 17.9-fold respectively). CONCLUSIONS: Stressful stimuli, such as food bereavement and cold challenge contribute to the elevated susceptibility of diabetic gastric mucosa to damage, even though the main aggressive factor, i.e., gastric acid secretion, is attenuated. The enhanced production of nitric oxide by inducible NOS during food deprivation and cold exposure seems to play an important role in gastric mucosal integrity disturbances during diabetes.

Roles of enterobacteria, nitric oxide and neutrophil in pathogenesis of indomethacin-induced small intestinal lesions in rats.

Roles of enterobacteria, nitric oxide (NO) and neutrophil in indomethacin-induced small intestinal lesions were examined in rats. Indomethacin (10 mg kg-1), administered s.c. as a single injection, caused haemorrhagic lesions in the small intestine, mostly in the jejunum and ileum. The lesions were first observed 6 h after administration of indomethacin, the severity increasing progressively with time up to 24 h later. Following indomethacin, the enterobacterial numbers, inducible NO synthase (iNOS) activity and NO production in the intestinal mucosa were also increased with time, and changes in the former preceded those in the latter two as well as the occurrence of intestinal damage. Treatment of the animals with both NG-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine prevented intestinal lesions induced by indomethacin, with suppression of NO production. Both dexamethasone and FR167653 (an inhibitor of interleukin-1 beta/tumour necrosis factor-alpha production) also reduced the severity of intestinal lesions as well as the increase in iNOS activity following administration of indomethacin. Likewise, the occurrence of intestinal lesions was attenuated by pretreatment of the animals with anti-neutrophil serum (ANS). None of these treatments, however, affect the translocation of enterobacteria in the mucosa. By contrast, ampicillin (an anti-bacterial agent) suppressed the increase in mucosal iNOS activity as well as the enterobacterial numbers invaded in the mucosa and inhibited the occurrence of intestinal lesions after administration of indomethacin. These results strongly suggest that enterobacterial translocation in the mucosa is the first step required for activation of various factors such as iNOS/NO and neutrophils, all involved in the pathogenesis of indomethacin-induced intestinal lesions.

Increased susceptibility of gastric mucosa to ulcerogenic stimulation in diabetic rats--role of capsaicin-sensitive sensory neurons.

1. We examined the gastric mucosal blood flow (GMBF) and ulcerogenic responses following barrier disruption induced by sodium taurocholate (TC) in diabetic rats and investigated the role of capsaicin-sensitive sensory neurons in these responses. 2. Animals were injected streptozotocin (STZ: 70 mg kg(-1), i.p.) and used after 5, 10 and 15 weeks of diabetes with blood glucose levels of > 350 mg dl(-1). The stomach was mounted on an ex-vivo chamber under urethane anaesthesia and exposed to 20 mM TC plus 50 mM HCl for 30 min in the presence of omeprazole. Gastric transmucosal potential difference (PD), GMBF, and luminal acid loss (H+ back-diffusion) were measured before and after exposure to 20 mM TC, and the mucosa was examined for lesions 90 min after TC treatment. 3. Mucosal application of TC caused PD reduction in all groups; the degree of PD reduction was similar between normal and diabetic rats, although basal PD values were lower in diabetic rats. In normal rats, TC treatment caused luminal acid loss, followed by an increase of GMBF, resulting in minimal damage in the mucosa. 4. The increased GMBF responses associated with H+ back-diffusion were mitigated in STZ-treated rats, depending on the duration of diabetes, and severe haemorrhagic lesions occurred in the stomach after 10 weeks of diabetes. 5. Intragastric application of capsaicin increased GMBF in normal rats, but such responses were mitigated in STZ diabetic rats. The amount of CGRP released in the isolated stomach in response to capsaicin was significantly lower in diabetic rats when compared to controls. 6. The deleterious influences on GMBF and mucosal ulcerogenic responses in STZ-diabetic rats were partially but significantly antagonized by daily insulin (4 units rat(-1)) treatment. 7. These results suggest that the gastric mucosa of diabetic rats is more vulnerable to acid injury following barrier disruption, and this change is insulin-sensitive and may be partly accounted for by the impairment of GMBF response associated with acid back-diffusion and mediated by capsaicin-sensitive sensory neurons.

Effects of diabetes mellitus on the contractile activity of carbachol and galanin in isolated gastric fundus strips of rats.

The role of the cholinergic and peptidergic pathways in the impairment of gastric motility associated with diabetic gastroparesis was assessed at the postsynaptic level using isolated fundus smooth muscle strips. Maximal contractile responses to carbachol and galanin were significantly decreased in fundus strips isolated from rats rendered diabetic by a single intraperitoneal injection of streptozotocin (STZ, 70 mg/kg) 1, 4 and 8 weeks before experiments. We also observed notable decrements in the slopes and Hill's coefficients without conspicuous changes in the EC50 of the respective galanin concentration-response curves measured in strips obtained from STZ animals after 4 and 8 weeks. L-NAME reversed the above-mentioned alterations in an L-arginine-sensitive manner in STZ rats after 4 weeks but not in STZ rats after 8 weeks. The blood plasma nitrite/nitrate levels in STZ animals after 4 and 8 weeks were increased by 44.6 and 61.9%, respectively. Ca2+-independent nitric oxide synthase activity in gastric fundus strips and stomach corpus mucosa from STZ rats after 4 weeks was markedly enhanced by 37.4 and 31.9%, respectively, suggesting an enhanced nitric oxide production. In vivo insulin treatment prevented diabetes-induced alterations in smooth muscle contractility. We conclude that the smooth muscle dysfunction evoked by experimental diabetes causing diminished contractions of fundus strips to carbachol and galanin is at least partly due to the increased nitric oxide synthesis.

Influence of intracerebroventricular administration of tetanus toxin on experimental seizures and protection afforded by some antiepileptic drugs in mice.

The dose to the intracerebroventricularly administered (i.c.v.) tetanus toxin (Tetx) evoking the death of 50% of experimental mice (LD50) was estimated to be 18.0 (11.5-28.2) times the minimal lethal dose (MLD). MLD is defined as the lowest does of Tetx necessary to kill a 20-g albino mouse within 96 h after intraperitoneal treatment. Tetx (0.25 and 0.5 LD50) increased the convulsive threshold of electric current from 24 to 96 and 120 h, respectively, following i.c.v. administration. Both doses of Tetx diminished convulsant potencies of pentylenetetrazole, bicuculline, aminophylline and pilocarpine 24 h after application. At the same time Tetx (0.5 LD50) increased the protection afforded by carbamazepine, valproate, phenobarbital and diazepam in maximal electroshock (MES) by approximately 36, 11, 21 and 26%, respectively, without affecting total blood plasma levels of antiepileptic drugs. No marked changes in gamma-aminobutyric acid (GABA) concentration and total activity of L-glutamic acid decarboxylase (GAD) assessed in the whole-brain homogenates resulted from Tetx treatment. Our results seem to indicate that low doses (< LD50) of i.c.v. administered Tetx may lead to a relative prevalence of inhibitory over excitatory processes in the central nervous system suggesting a complex action of Tetx at the neuronal level.

Inhibition of gastric acid secretion by galanin in rats. Relation to endogenous histamine release.

Inhibitory effect of galanin on basal and secretagogs-stimulated gastric acid secretion was investigated in urethane-anesthetized rats. A rat stomach was mounted in an ex-vivo chamber, perfused with saline, and either gastric acid or alkaline secretion was determined by titrating the perfusate. Gastric mucosal blood flow (GMBF) was measured by a laser Doppler flowmeter. Intravenous infusion of galanin dose-dependently inhibited the increase of acid secretion induced by pentagastrin and carbachol but not by histamine, without any influence on the GMBF response. Galanin also reduced basal acid secretion while increasing GMBF, but did not evoke any change in basal gastric alkaline secretion. M15, which is a galanin receptor antagonist in the central nervous system but acts as a full agonist in the gastrointestinal smooth muscle, also suppressed pentagastrin-induced acid secretion, similar to galanin. In addition, pentagastrin increased the release of histamine into the gastric lumen, and this response was significantly inhibited by galanin. These results suggest that the inhibitory effect of galanin on acid secretion is mediated by suppression of endogenous histamine release from enterochromaffin-like cells and that the process may be related to the activation of the same subtype of galanin receptors as in the central nervous system and pancreatic beta-cells.

Role of nitric oxide in regulation of gastric acid secretion in rats: effects of NO donors and NO synthase inhibitor.

1. The role of nitric oxide (NO) in the regulation of acid secretion was examined in the anaesthetized rat. 2. A rat stomach was mounted in an ex vivo chamber, instilled with 2 ml of saline every 15 min, and the recovered sample was titrated at pH 7.0 against 0.1 N NaOH by use of an automatic titrator for acid secretion. Gastric mucosal blood flow (GMBF) was measured simultaneously by laser Doppler flowmeter. 3. Intragastric application of NO donors such as FK409 (3 and 6 mg ml[-1]) and sodium nitroprusside (SNP; 6 and 12 mg ml[-1]) as well as i.p. administration of cimetidine (60 mg kg[-1]), a histamine H2-receptor antagonist, significantly inhibited the increase in acid secretion in response to pentagastrin (60 microg kg(-1) h(-1), i.v.), in doses that increased gastric mucosal blood flow (GMBF). 4. Intragastric application of FK409 (6 mg ml[-1]) increased both basal and stimulated acid secretion induced by YM-14673 (0.3 mg kg(-1), i.v.), an analogue of thyrotropin-releasing hormone (TRH), but had no effect on the acid secretory response induced by histamine (4 mg kg(-1) h(-1), i.v.). 5. Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME; 10 mg kg(-1), i.v.) did not affect basal acid secretion, but significantly potentiated the increase in acid secretion induced by YM-14673 and slightly augmented the acid secretory response to pentagastrin. 6. Both pentagastrin and YM-14673 increased the release of nitrite plus nitrate (NOx), stable NO metabolites, into the gastric lumen, and these changes were completely inhibited by prior administration of L-NAME (10 mg kg(-1), i.v.). 7. Pentagastrin caused an increase in luminal release of histamine and this response was significantly suppressed by intragastric application of FK409 (6 mg ml[-1]). 8. These results suggest that either exogenous or endogenous NO has an inhibitory action on gastric acid secretion through suppression of histamine release from enterochromaffin-like (ECL) cells.