Evidence of a key-role for histamine from mast cells in the analgesic effect of clomipramine in rats.

OBJECTIVE AND DESIGN: We investigated the role of neuronal and mast cell histamine in the analgesic effect of clomipramine. SUBJECTS: Male Sprague-Dawley rats (4-6 weeks old) were used (n = 228). TREATMENT: Clomipramine (10, 20 or 40 mg/kg i.p.) was injected in rats pretreated with [a] saline i.cv. or i.p., [b] alpha-fluoromethylhistidine (alpha-FMH, 200 microg i.cv.), [c] compound 48/80 (C48/80, 1 mg/kg i.p.). Other rats were pretreated with clomipramine, before C48/80. METHODS: Antinociceptive responses were determined before and 30, 60, 90, 120 min after drug injection by tail-flick (TFT) and hot-plate (HPT) tests. Results for each treatment group are given as mean %MPE +/- SEM (Student's t-test, ANOVA). RESULTS: Clomipramine produced no significant changes in TFT and HPT in saline- or alpha-FMH-pretreated rats. Following C48/80, clomipramine (10 and 20 mg/kg) produced a dose-related significant increase in latencies, between 30 and 120 min: 28.5 +/- 5.7 vs 8 +/- 1.6 (p < 0.05), 56 +/- 5 vs 9.2 +/- 1.9 (p < 0.01) in TFT; 31 +/- 4.3 vs 12 +/- 2.5 (p < 0.05), 46.2 +/- 6 vs 11.5 +/- 1.9 (p < 0.01) in HPT. Clomipramine (40 mg/kg, after C48/80) produced marked and persistent increase in latencies 83.2 +/- 4.2 vs 10.5 +/- 3 (p < 0.01) in TFT and 91.2 +/- 4.6 vs 10.5 +/- 3 (p < 0.01) in HPT, followed by symptoms of toxicity and death of some animals. In rats pretreated with clomipramine, C48/80 was unable to show antinociceptive effects on TFT and HPT. CONCLUSIONS: Results suggest that the antinociceptive effect of clomipramine may depend on mast cell histamine levels.

Histaminergic mechanisms in clonidine induced analgesia in rat tail-flick test.

The role of neural histamine in clonidine-analgesia and in clonidine-induced potentiation of stress analgesia was studied. Pretreatment of rats with alpha-fluoromethylhistidine (FMH) (200 ug icv/rat; daily for five days) increased the analgesic effect of the alpha 2-agonist clonidine on the spinal reflex of the tail-flick test. Rats subjected to cold-restraint stress (30 min at 4 degrees C) showed increased latency compared to the unstressed rats. The analgesic efficacy of clonidine was significantly greater in rats subjected to cold-restraint with respect to unstressed rats. However, the inhibition of histamine biosynthesis by FMH significantly reduced cold-restraint analgesia in saline-controls, and consistently increased the analgesic efficacy of the alpha 2-agonist, showing a maximum latency. Yohimbine exhibited high affinity as an antagonist for alpha 2-receptors, inducing hyperalgesic effects and antagonizing clonidine analgesia and clonidine-induced potentiation of cold stress analgesia. In FMH-pretreated rats, yohimbine failed to reverse clonidine analgesia and did not block the increased analgesic efficacy of clonidine in cold-restrained FMH-pretreated rats. Results of this study suggest that inhibition of histamine release through alpha 2-adrenoceptors on histaminergic axons may contribute to the analgesic efficacy of systemically injected clonidine, also confirming that neural histaminergic pathways are implicated in the mediation of pain response in particular conditions of stress.

Synthesis of carboxyalkylthio-triazoles and bicyclic derivatives with antiinflammatory and analgesic activity.

3-Carboxyalkylthio derivatives of 5-alkoxyphenyl-1,2,4-triazole were prepared, performing some substitutions both on carboxyalkyl chain, by lengthening it or introducing substituents with increasing molecular weight in alpha- at the carboxy group, and on N-4 atom in the triazole ring, by introducing an amino or methyl group, so that to vary steric conformation along with the lipophilicity of molecules. The corresponding bicyclic thiazolo-triazolone and triazolo-thiazinone derivatives, which represent the rigid models of carboxymethylthio- and carboxyethylthio- open structures, were also obtained. All the compounds show "in vivo" antiinflammatory activity, while only carboxyalkylthio derivatives of 4-amino- and 4-methyltriazole display an appreciable analgesic one. From the relief of some data on substituent present in the synthesized compounds, a structure-activity relationship is also suggested.

Effect of indomethacin on opioid-induced gastric protection in cold-restrained stress.

Morphine and the synthetic opioid met-enkephalin analog [D-Ala2, MePhe4, Met(0)5ol] enkephalin (FK 33-824) injected intraperitoneally to rats at doses of 5-20 and 0.5-2 mg/kg respectively showed a protective effect on gastric lesion induced by cold-restraint stress. This protective effect was abolished by pretreatment with indomethacin. This suggests a role for prostaglandins in the protection, induced by opioids of the gastric mucosa against the development of stress-induced ulcers.

Peripheral and central opioid activity in the analgesic potency of morphine.

The role of neural histamine in morphine-analgesia and in morphine-induced potentiation of stress analgesia was studied. Pretreatment of rats with alpha-fluoromethylhistidine (alpha-FMH) (200 micrograms i.c.v./rat; daily for five days) increased the analgesic potency of morphine, centrally or peripherally injected, in the tail-flick assay. This increase was significantly blocked by i.c.v. or i.p. beta-funaltrexamine (beta-FNA) a mu selective irreversible opioid receptor antagonist, whereas i.c.v. injected naltrexone did not block the increased analgesic potency of the i.c.v. morphine. Rats subjected to cold-restrained stress (60 min at 4 degrees C) showed increased tail-flick latency, compared to the unstressed group. The analgesic potency of morphine was significantly greater in rats subjected to restraint with respect to unstressed rats. However, the inhibition of histamine biosynthesis by alpha-FMH significantly reduced cold-restraint analgesia in controls, and also inhibited the analgesic efficacy of the opiate. These results indicate that neural histamine may be responsible for pain response modifications observed in rats subjected to cold-restraint conditions, and of morphine-potentiation of stress analgesia. The data also suggest a close association between increased analgesic potency of morphine and inhibition of histaminergic effects, possibly implying a functional supersensitivity and an increase in opioid receptors.

Modification of rat thermal responses to morphine by alpha-FMH suggests a role for neural histamine in morphine tolerance.

In rats, morphine may either raise or lower body temperature depending on the dose. A morphine dose of 50 mg/kg, i.p., consistently produced a nearly maximal hypothermic response in non tolerant rats, whereas this dosage induced an elevation of body temperature in tolerant rats. In rats pretreated with alpha-fluoromethylhistidine (alpha-FMH), an irreversible inhibitor of histidine decarboxylase which induces a reduction in brain histamine synthesis, this morphine dose of 50 mg/kg, i.p. produced an elevation of rectal temperature resembling that observed in morphine-tolerant rats. To confirm the suggestion that hyperthermic effects of the higher dose of morphine in morphine-tolerant rats or in alpha-FMH-pretreated rats could be related to a possible involvement of mediators of fever, e.g. prostaglandins, animals were pretreated with acetylsalicylic acid (aspirin, Bayer) 30 mg/kg, i.p., 60 min before morphine. Results showed that acetylsalicylic acid prevented the hyperthermic response of morphine, resulting in a fall in body temperature. Since morphine releases histamine and alpha-FMH inhibits histamine synthesis, our data demonstrating that an inhibitor of prostaglandin-synthetase showed efficacy only in animals responding with fever to the higher dose of the opiate, suggests a physiological antagonism between histamine and prostaglandins on mechanisms underlying hyper/hypothermic responses to morphine.

Correlations between histamine and opioid peptides on the modulation of inflammatory processes in rats exposed to stress.

The role of mast cell histamine in body reactivity of rats under experimental stressful conditions was studied. Animals submitted to chronic anaphylactoid reactions (by injecting compound 48/80 at the dose of 1 mg/kg, i.p., twice daily, for five days), when exposed to cold-restraint stress, exhibited a fully evident inflammatory response in the carrageenin-oedema test, whereas saline-treated rats, under the same experimental conditions, showed reduced paw oedema. Interestingly, a single injection of compound 48/80 increased the pituitary content of Beta-endorphin(ir), but chronic administration failed to produce this effect suggesting that some adaptation of the organism to repeated anaphylactoid reactions may occur. These results support the hypothesis of correlations between pituitary Beta-endorphin and mast cell histamine in the reactivity of the organism to stressful stimuli.

Evidence of correlations between mast-cell histamine and beta-endorphin (ir) from NIL-pituitary in the homeostasis.

This study was designed to characterize physiological events related to a single or repeated experimental anaphylactoid reactions (by Compound 48/80) in non-stressed or cold-restrained rats. Acute treatment with Compound 48/80 (1 mg/kg, i.p.) increases Beta-endorphin(ir) content in the neurointermediate lobe (NIL) of rat pituitary. Moreover, repeated treatment with Compound 48/80 showed tolerance effects. These animals, exposed to stressful conditions, exhibited a fully evident paw oedema following carrageenin oedema-test, whereas saline-pretreated rats, under the same experimental conditions, showed reduced local inflammation. Since Compound 48/80 produces characteristic, systemic, anaphylactoid reaction in the rat, with a very high degree of selectivity in its action, our results suggest that mast-cell histamine and Beta-endorphin from NIL pituitary are involved in the body's reactivity to stressful stimuli.

Effects of morphine and met-enkephalin analogue on gastric lesions induced by indomethacin.

The effects of morphine HCl and a synthetic met-enkephalin analogue [D-Ala2,MePhe4,Met(O)5ol]enkephalin (FK 33-824) on gastric damage produced by the intraperitoneal administration of indomethacin (10 mg/kg i.p.) have been investigated. Rats intraperitoneally pretreated with morphine HCl (10 mg/kg i.p.) and FK 33-824 (1 mg/kg i.p.) showed a statistically significant reduction both of the number and intensity of lesions induced by indomethacin. This protection was reversed by naloxone HCl (2 mg/kg i.p.). The protective effect was not related to a reduction of gastric secretion since the antisecretory drug cimetidine (25 mg/kg i.p.) and methscopolamine bromide (10 mg/kg i.p.) did not significantly prevent mucosal damage under the same experimental conditions.

[2,5-diaryl-substituted 1,3,4-oxadiazoles: synthesis and preliminary pharmacological investigation]. / 1,3,4-ossadiazoli 2,5-diarilsostituiti: sintesi e ricerca farmacologica preliminare.

Seven 2,5-diarylalkyloxysubstituted 1,3,4-oxadiazoles were synthesized. They showed pronounced antiphlogistic action together with central activity (sedative, analgesic) that principally seems to be connected with the presence in the molecule of the 3,4-dioxymethylenephenyl radical.

[Alkyl and aryl derivatives of isoquinoline. II. Synthesis and pharmacologic activity of dialkylaminoalkyl esters of 1-chloro-3-carboxy-4-methylisoquinoline and the corresponding 4-phenyl derivative]. / Ricerche su derivati alchilici ed arilici della isochinolina. Nota II. Sintesi ed attività farmacologica di dialchilamminoalchilesteri della 1-cloro-3-carbossi-4-metilisochinolina e corrispondenti 4-fenilderivati.

The synthesis of a series of dialkylaminoalkylic esters of 1-chloro-3-carboxy-4-methylisoquinoline and of 1-chloro-3-carboxy-4-phenylisoquinoline is described. The pharmacological activity of some of these compounds was studied. The morpholinoethylester of 1-chloro-3-carboxy-4-methylisoquinoline (VIIa), dimethylaminoethylester (VIIb) and diethylaminoethylester (VIIc) showed a good antispasmodic activity. 4-Phenyl-derivatives (XVa), (XVb), (XVc) were more active than analogous 4-methyl derivatives; particularly the diethylaminoethylester of 1-chloro-3-carboxy-4-phenylisoquinoline (XVc) showed an antagonist effect against spasmogens similar to that of papaverine.

Central and peripheral sites of action for the protective effect of opioids of the rat stomach.

Rats exposed to combined cold and restraint exhibited a reduced intensity of gastric damage when pre-treated intraperitoneally with morphine HCl or with the synthetic enkephalin analog [D-Ala2, MePhe4, Met(0)5ol]enkephalin (FK 33-824). Morphine HCl and FK 33-824 prevented some of the indices of the lesion also when injected intracerebroventricularly; morphine methyliodide, quaternary derivative of morphine with does not cross the blood brain barrier, was fully effective, by intraperitoneal route, in preventing the gastric damage. Both peripheral and central mechanisms seem, therefore, involved in the protective effect of opioids on rat gastric mucosa. Morphine HCl and FK 33-824 reduced significantly gastric acid secretion when administered intracerebroventricularly or intraperitoneally; in addition, a concomitant increase of prostaglandin production was observed in rat gastric mucosa after i.p. administration of both opioids. Both these events might contribute to the protective action of opioids on the stomach.

[Synthesis of 1-aroyl-4H(R)-thiosemicarbazides, the corresponding 5-aryl 4H(R)-1,2,4-triazolin-3-thiones and some derivatives of pharmaceutical interest]. / Sintesi di 1-aroil-4H(R)-tiosemicarbazidi, dei corrispondenti 5-aril-4H(R)-1,2,4-triazolin-3-tioni e di alcuni derivati di interesse farmaceutico.

A series of 1-aroyl-4H(R)-thiosemicarbazides (IV-XVIII) and the corresponding 5-phenyl-4H(R)-1,2,4-triazolin-3-thiones (XIX-XXXIII) were synthesized: biological assay demonstrated their in vitro antibacterial and antimycotic activities. The preparation of same hydrazinoaroylthiazoles (XXXIV-XXXVI) was reported also, obtained by condensation of 1-aroyl-4H-thiosemicarbazides with phenacyl bromide and the synthesis of thiazole[3,2-b]-s-triazol-3(2H)-ones (XLIX-LI) prepared by cyclodehydration of carboxymethylthiotriazoles (XLVI-XLVIII). The results of pharmacological testing for both series of derivatives (XLIX-LI) and (XLVI-XLVIII) showed good antiinflammatory and antipyretic activities.