Effects of physalaemin on some exocrine secretions of dogs and rats

1. Physalaemin, an endecapeptide recently found in the skin of the South American amphibian Physalaemus fuscumaculatus, possesses, besides a marked hypotensive action and a powerful sialogogic activity, also a stimulant activity on other exocrine secretions.2. Exocrine structures which were more potently stimulated by the peptide were lacrimal glands and exocrine pancreas. In the anaesthetized dog the threshold lacrimatory dose was 0.05-0.3 mug/kg; in the rat the threshold dose was 2.5-5 mug/kg. The minimum active dose on exocrine pancreas of the dog was 0.05-0.5 mug/kg.3. Physalaemin did not influence the gastric acid secretion of the dog at the maximum tolerated dose (40 mug/kg). Gastric acid secretion of the rat was stimulated very little if at all.4. In the dog the peptide caused some changes in the bile flow which were connected more with contracture of the gall-bladder than with a true secretory stimulant activity. In the rat the peptide was completely ineffective.5. The results obtained after administration of sympatholytic and parasympatholytic agents suggest that the action of the peptide is at least partly independent from the autonomic nervous system.

Intestinal chronic obstruction affects motor responsiveness of rat hypertrophic longitudinal and circular muscles

Extensive morphological and neurochemical changes have been experimentally and clinically documented in the hypertrophied intestine located orally to a chronic partial stenosis of the lumen. Functional studies revealed not only disruption of the interdigestive motor complex in vivo and decreased efficiency of contraction but also preservation of the peristaltic reflex in vitro. Given the critical role played in intestinal peristalsis by the coordinated activity of the longitudinal (LM) and circular muscle (CM), this work focuses on the motor responses of LM and CM isolated from rat hypertrophied ileum following mechanical obstruction. Maximal contractions to both receptor (acetylcholine and substance P) and non-receptor (K+) mediated stimuli were up to 10-fold increased in hypertrophic CM rings compared with control tissues, while a higher potency of substance P was revealed in both hypertrophied muscle layers. Relaxations to vasoactive intestinal polypeptide and 8-Br-cGMP were more intense on prostaglandin F(2alpha)-contracted hypertrophic LM strips compared with control tissues and a general tendency towards increased relaxation was shared also by hypertrophic CM basal tone. The present results collectively suggest that hypertrophic growth leads to hyperresponsiveness to contractile agents, particularly evident in the CM, and to increased sensitivity to relaxing mediators, especially exhibited by the LM. In this regard, the complementary role exerted by each muscle layer and the plasticity of the intestinal tissue could both come into play to preserve the intestinal functions in a changing environment.

Plasticity of rat small intestine after removal of a chronic mechanical obstruction

Chronic intestinal obstruction is associated with morphological changes and functional disorders clinically reported and experimentally documented in laboratory animals. In contrast, little is known about the properties of the hypertrophied intestine after removal of the obstruction. In the present study, we removed the ileal obstruction previously applied to the ileum of rats and, after 1 or 2 weeks, studied in vitro the motor responses of de-obstructed segments of intestine to pharmacological or electrical field stimulation (EFS). By 2 weeks after de-obstruction, maximal contractile responses to receptor (acetylcholine) and non-receptor (K(+)) mediated stimuli were comparable in operated and control tissues; furthermore, the loss of sensitivity to nitric oxide (NO) unmasked in obstructed tissues was, after de-obstruction, replaced by supersensitivity to exogenous NO and vasoactive intestinal polypeptide, probably acting through cyclic nucleotide-independent pathways. Despite the complete recovery of smooth muscle responses, neurogenic contractions remained impaired in de-obstructed tissue; however, the equal contribution of cholinergic/peptidergic components to EFS responses could represent a sign of gradual but delayed recovery of enteric neurotransmission.

Effect of N-methyl-d-aspartate receptor blockade on neuronal plasticity and gastrointestinal transit delay induced by ischemia/reperfusion in rats

Intestinal ischemia impairs gastrointestinal motility. The aims of this study were to investigate the effect of intestinal ischemia on gastrointestinal transit and on the expression of enteric transmitters in the rat, and whether the glutamate N-methyl-d-aspartate receptors influence these effects. Ischemia (1 h), induced by occluding the superior mesenteric artery, was followed by 0 or 24 h of reperfusion. Normal and sham-operated rats served as controls. Serosal blood flow was measured with laser Doppler flow meter. Gastrointestinal transit was measured as time of appearance of a marker in fecal pellets. Immunohistochemistry was used to evaluate the number of neurons immunoreactive for neuronal nitric oxide synthase (NOS) or vasoactive intestinal polypeptide and the density of substance P immunoreactive fibers in the myenteric plexus. The N-methyl-d-aspartate receptors antagonist, (+)-5-methyl-10,11-dihydro-5HT-[a,b] cyclohepten-5,10-imine (MK-801) (1 mg/kg i.v.) or the NOS inhibitor, N-nitro-l-arginine (10 mg/kg i.v.) was administered prior to ischemia. Serosal blood flow was decreased by 70% during ischemia, but it was not altered in sham-operated rats. Gastrointestinal transit was significantly prolonged in ischemic/reperfused rats compared with controls. There was a significant increase in the number of vasoactive intestinal polypeptide and neuronal nitric oxide synthase immunoreactive neurons, and a marked decrease of substance P immunoreactive fibers in ischemia followed by 24 h of reperfusion animals compared with controls. These alterations were not observed in ischemia without reperfusion. A significant delay of gastrointestinal transit and increase of vasoactive intestinal polypeptide neurons were also observed in sham-operated rats. The changes in transmitter expression and gastrointestinal transit in ischemic/reperfused rats were prevented by pre-treatment with the NOS inhibitor, N-nitro-l-arginine or the N-methyl-d-aspartate receptors antagonist, MK-801. This study suggests an involvement of the glutamatergic system and its interaction with nitric oxide in intestinal ischemia/reperfusion. Ischemia/reperfusion might induce local release of glutamate that activates N-methyl-d-aspartate receptors leading to increased production of nitric oxide and adaptive changes in enteric transmitters that might contribute to gastrointestinal dysmotility.

Comparative screening of plant essential oils: phenylpropanoid moiety as basic core for antiplatelet activity

Essential oils extracted from different plants (Anthemis nobilis L., Artemisia dracunculus L., Cannabis sativa L., Cupressus sempervirens L., Cymbopogon citratus (DC.) Stapf., Curcuma longa L., Foeniculum vulgare L., Hypericum perforatum L., Hyssopus officinalis L., Mentha spicata L., Monarda didyma L., Ocimum basilicum L., Ocotea quixos Kosterm., Origanum vulgare L., Pinus nigra J.F. Arnold, Pinus silvestris L., Piper crassinervium Kunth., Rosmarinus officinalis L., Salvia officinalis L., Salvia sclarea L., Santolina chamaecyparissus L., Thymus vulgaris L., Zingiber officinaie L.) were screened in guinea pig and rat plasma in order to assess antiplatelet activity and inhibition of clot retraction. The oils were chemically analysed and a relationship between components and ability to affect hemostasis was evidenced. O. quixos, F. vulgaris, and A. dracunculus showed the highest antiplatelet activity against ADP, Arachidonic Acid and the Thromboxane A2 agonist U46619 (IC50, 4-132 microg ml(-1)), and a good ability to destabilize clot retraction (IC50, 19-180 microg ml(-1)). For these oils a significant correlation between antiplatelet potency and phenylpropanoids content (54-86%) was evidenced thus suggesting a key role for this moiety in the prevention of clot formation. These findings provide the rationale to take in account the antiplatelet activity in the pharmacological screening of natural products containing phenylpropanoids.

Antinociceptive and gastroprotective effects of inhaled and orally administered Lavandula hybrida Reverchon “Grosso” essential oil

In this study the antinociceptive and the gastroprotective effects of orally administered or inhaled Lavandula hybrida Reverchon "Grosso" essential oil, and its principal constituents linalool and linalyl acetate were evaluated in rodents. Either when orally administered (100 mg/kg) or inhaled for 60 min lavender essential oil significantly reduced the acetic acid-writhing response in a naloxone-sensitive manner. In the hot plate test, analgesic activity observed after oil inhalation was inhibited by naloxone, atropine, mecamylamine pretreatment suggesting the involvement of opioidergic as well as cholinergic pathways. Regardless of the administration route and the experimental model used both linalool and linalyl acetate did not produce significant analgesic response. Oral or inhalatory treatment with analgesic doses of essential oil did not affect mice spontaneous locomotor activity. Concerning the gastric effects, lavender oil, linalool and linalyl acetate oral administration protected against acute ethanol-induced gastric ulcers but did not prevent indomethacin-induced lesions indicating no interference with arachidonic acid metabolic cascade. In conclusion, besides this gastroprotection, lavender oil reveals an interesting analgesic activity mainly relevant after inhalation, at doses devoid of sedative side effect, suggesting the interest for potential application of this oil in aromatherapy.

Novel antiplatelet and antithrombotic activities of essential oil from Lavandula hybrida Reverchon "grosso"

Lavender extracts are known to produce several mild effects at central and peripheral level. However, no studies are so far available about the potential effects of lavender essential oil on the hemostatic system. In this work, we demonstrated antiplatelet properties of lavender oil towards platelet aggregation induced by arachidonic acid, U46619, collagen and ADP (IC50 = 51, 84, 191 and 640 microg/ml, respectively) on guinea-pig platelet rich plasma (PRP) and its ability to destabilize clot retraction (IC50 = 149 microg/ml) induced by thrombin on rat PRP. Furthermore, antithrombotic properties were studied in an in vivo model of pulmonary thromboembolism induced by intravenous injection of a collagen-epinephrine mixture in mice subacutely treated with lavender oil. In this model, lavender oil (100 mg/kg/day os for 5 days) significantly reduced thrombotic events without inducing prohemorrhagic complications at variance with acetylsalicylic acid used as reference drug. Finally, main components of the oil were studied in vitro in order to assess their antiplatelet effects, but none of them possessed an activity comparable to the oil itself. These results provide the first experimental evidence of lavender oil's antiplatelet/antithrombotic properties which could be due to a synergistic effect of its components.

Motor responses of rat hypertrophic intestine following chronic obstruction

The present work aims at investigating the changes in motor responsiveness of rat intestine hypertrophied by chronic mechanical obstruction. Motor responses to pharmacological agents and electrical field stimulation (EFS) were studied in hypertrophic ileal segments excised from rats subjected to experimental stenosis (n = 20) and compared with responses of control tissues from sham-operated animals (n = 20). Spontaneous motility and contractile responses to exogenous agents (KCl, acetylcholine and substance P) and EFS (10-s trains every minute, 120 mA, 0.5 ms, 1-10 Hz) were increased in hypertrophic longitudinal segments; however, normalization of motor responses to tissue wet weight revealed a remarkable reduction of contractile efficiency in hypertrophied tissues coupled with a loss of sensitivity to nitric oxide-mediated relaxation. Furthermore, EFS under non-adrenergic non-cholinergic (NANC) conditions unveiled a major role of the cholinergic component over the peptidergic one in the neurogenic contraction of hypertrophic intestine. On the whole, hypertrophic intestinal growth emerges as a dynamic process entailing adaptation of smooth muscle and neuronal structures to the increased functional load imposed by lumen obstruction.

Different role of the histamine H3-receptor in vagal-, betanechol-, pentagastrin-induced gastric acid secretion in anaesthetized rats

BACKGROUND

To date, involvement of the histamine H3-receptor in the control of gastric acid secretion in rats is not conclusively defined because of the variability of experimental results. This study was therefore aimed at investigating the role of H3-receptors in acid secretion produced by nervous or pharmacological stimulation in anaesthetized rats.

METHODS

Gastric acid output was measured by flushing the rat stomach lumen with 5 ml saline and titrating the flushed perfusate. Hypersecretory responses were evoked through direct vagal stimulation (0.5 msec, 10 Hz, 50 V for 30 min every 30 min) or by stimulation with pentagastrin (20, 40, 100, 250 microg/kg/h i.v.) or betanechol (100, 250, 500 microg/kg/h i.v.). The selective H3 ligands (R)-alpha-methylhistamine and thioperamide (100 microg/kg i.v.) were tested alone or in combination on both basal and electrically/pharmacologically induced secretion.

RESULTS

Vagally-induced response was significantly reduced by the agonist R-alpha-methylhistamine and this effect was antagonized by the antagonist thioperamide at a dose unable by itself to modify vagal response. Thioperamide significantly increased acid response only on pentagastrin low dose (20 microg/kg/h) and this effect was counteracted by R-alpha-methylhistamine, which was ineffective when administered alone. Betanechol-induced hypersecretion was substantially unaffected by the H3 ligands, which were also inactive on basal acid output.

CONCLUSIONS

Although this functional study confirms the presence of histamine H3-receptors in the rat stomach, they appear to have minor weight in regulation of the acid secretion in this species.

Synthesis and pharmacological evaluation of 2,5-cycloamino-5H-[1]benzopyrano[4,3-d]pyrimidines endowed with in vitro antiplatelet activity

A series of new 2,5-cycloamino-5H-[1]benzopyrano[4,3-d]pyrimidines 3a-i have been synthesized and tested in vivo for the anti-inflammatory/analgesic/antipyretic effects and in vitro to evaluate the antiplatelet activity on guinea-pig platelet-rich plasma aggregated by collagen, adenosine-5'-diphosphate (ADP) and arachidonic acid (AA). Title compounds were ineffective in vivo; however, the pyrrolidino derivatives 3a and 3c exhibited an antiplatelet activity against all the aggregants differing from that of acetylsalicylic acid (ASA) while the 5-morpholino derivatives 3g-i showed the most potent ASA-like antiplatelet activity.

Evidence for specific analgesic activity of a muscarinic agonist selected among a new series of acetylenic derivatives

The central and peripheral effects of a series of Oxotremorine/Oxotremorine-M derivatives, previously characterized as muscarinic agonists in isolated preparations, were investigated in in vivo experiments. The molecules were tested for their antinociceptive activity (formalin licking and acetic acid writhing tests) and for their ability to induce tremor in mice. Peripheral cholinergic effects such as salivation, bradycardia, hypotension and intestinal hypermotility were studied in anaesthetized rats. All of the acetylenic compounds acted as muscarinic analgesics displaying the same order of potency shown in in vitro studies. The Oxotremorine-like subset showed a clearer distinction between doses producing antinociception and doses exerting undesirable central/peripheral side effects compared to the Oxotremorine-M derivatives. The most promising profile was displayed by the isoxazolin-3-one Oxotremorine-like derivative (compound 1a), which was characterized by a wider therapeutic window than that of the parent molecule Oxotremorine. Indeed, it produced atropine-sensitive analgesia (ID50 about 0.1 mg/kg i.p.) in the absence of tremorogenic (EC50 2.73 mg/kg i.p.) and cardiovascular effects while lethality occurred only at higher doses (LD50 19 mg/kg i.p.). These results suggest that such a derivative could be a candidate for further development of selective muscarinic analgesics.

New polycyclic pyrimidine derivatives with antiplatelet in vitro activity: synthesis and pharmacological screening

The preparation and the pharmacological screening of novel anti-aggregatory/antiphlogistic polycyclic pyrimidine derivatives are described. The compounds were developed starting from bioactive 2-aminobenzopyranopyrimidine derivatives in order to assess the importance of the benzopyrano[4,3-d]pyrimidine structure and the role of an amino basic moiety in position 2. Antiplatelet activity was assessed in vitro against ADP and arachidonic acid-induced aggregation in guinea-pig plasma. Anti-inflammatory/analgesic/antipyretic activities were studied in rat paw oedema, mouse writhing test and E. coli-induced rat fever. Ulcerogenic and gastroprotective effects were also investigated in vivo on rat gastric mucosa. Among the tested compounds, the 5-substituted benzopyranopyrimidine derivatives 3d and 4d proved to be the most active antiplatelet agents as potent as acetylsalicylic acid against arachidonic acid-stimulated aggregation. Furthermore the 2-methylthio derivative 4d was endowed with greater efficacy against ADP aggregation suggesting that additional non-TXA2 dependent mechanisms are involved in its biological activity. Orally administered at 100 mg kg(-1) in rats this latter compound displayed antiphlogistic acitivity comparable to indomethacin (10 mg kg(-1)) coupled with an unusual gastroprotective effect on ethanol-induced ulcers. In conclusion, these findings indicate that the 5-pyrrolidino-2-methylthiobenzopyrano[4,3-d]pyrimidine 4d fulfils the chemical requirements to exhibit antiplatelet activity associated with gastroprotective effect.

New analogues of oxotremorine and oxotremorine-M: estimation of their in vitro affinity and efficacy at muscarinic receptor subtypes

Two subsets of tertiary amines (1a-6a) and methiodides (1b-6b) with a structural resemblance to oxotremorine and oxotremorine-M were tested at rabbit vas deferens (M1), guinea pig left atrium (M2), guinea pig ileum and urinary bladder (M3) muscarinic receptor subtypes. The pharmacological profile of the derivatives under study has been discussed by evaluating their potency, affinity and efficacy as well as the regional differences in muscarinic receptor occupancy.

Synthesis and biological assays of new H3-antagonists with imidazole and imidazoline polar groups

New histamine H3-receptor antagonists were synthesised and tested on rat brain membranes and on electrically stimulated guinea-pig ileum. The new compounds have a central polar group represented by a 2-alkylimidazole or a 2-thioimidazoline nucleus. The effect of the polar group basicity on the optimal length of the alkyl chain, connecting this group to a 4(5)-imidazolyl ring, was investigated. The best affinity values, obtained by displacement of [3H]-RAMHA from rat brain, were obtained for the 2-alkylimidazole derivatives (2a-f) with tetramethylene chain (pKi 8.03-8.97), having an intermediate basicity between that of the previously reported 2-thioimidazoles (1a-i) and that of 2-alkylthioimidazolines (3a-h). In contrast, a general lowering of affinity (pKi 5.90-7.63) was observed for compounds of the last series (3a-h), with a complex dependence on the terminal lipophilic group and chain length.

Synthesis and functional characterization of novel derivatives related to oxotremorine and oxotremorine-M

Two subseries of nonquaternized (5a-10a) and quaternized derivatives (5b-10b) related to oxotremorine and oxotremorine-M were synthesized and tested. The agonist potency at the muscarinic receptor subtypes of the new compounds was estimated in three classical in vitro functional assays: M1 rabbit vas deferens, M2 guinea pig left atrium and M3 guinea pig ileum. In addition, the occurrence of central muscarinic effects was evaluated as tremorigenic activity after intraperitoneal administration in mice. In in vitro tests a nonselective muscarinic activity was exhibited by all the derivatives with potencies values that, in some instances, surpassed those of the reference compounds (i.e. 8b). Functional selectivity was evidenced only for the oxotremorine-like derivative 9a, which behaved as a mixed M3-agonist/M1-antagonist (pD2 = 5.85; pA2 = 4.76, respectively). In in vivo tests non-quaternary compounds were able to evoke central muscarinic effects, with a potency order parallel to that observed in vitro.

Characterization of antisecretory and antiulcer activity of CR 2945, a new potent and selective gastrin/CCK(B) receptor antagonist

The antigastrinic, antisecretory and antiulcer activities of CR 2945, (R)-1-naphthalenepropanoic acid,beta-[2-[[2-(8-azaspiro[4.5]dec-8-yl-carbonyl)-4,6-dimethylph enyl] amino]-2-oxoethyl], were investigated in vitro and in vivo in rats and cats. Its activities were compared with those of two gastrin/CCK(B) receptor antagonists, L-365,260 (3R(+)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepin -3-yl)-N'-(3-methylphenyl)urea and CAM-1028 (4-[[2-[[3-(1H-indol-3-yl)-2-methyl-1-oxo-2-[[[1,7,7-trimethylbicyclo [2.2.1]hept-2-yl)oxy]carbonyl]amino]propyl]amino]-1-phenylethyl]amino -4-oxo-[1S-1alpha,2beta[S'(S')4alpha]]-butanoate -N-methyl-D-glucamine), of the histamine H2 receptor antagonist, ranitidine, and the proton pump inhibitor, omeprazole. Cytosolic Ca2+ elevation in rabbit parietal cells induced by gastrin (50 nM) was blocked by CR 2945 with an IC50 value of 5.9 nM. CAM-1028 and L-365,260 showed similar activity. CR 2945 antagonized pentagastrin-stimulated gastric acid secretion in rats (ED50 = 1.3 mg kg(-1) i.v. and 2.7 mg kg(-1) i.d.) and cats (1.6 mg kg(-1) i.v.). CR 2945 was slightly less potent than the reference compounds after i.v. administration, whereas after intraduodenal (i.d.) administration, it was more potent than both ranitidine and omeprazole. In the rat, the gastrin antagonism exhibited by CR 2945 was reversible and competitive, with a pA2 value of 7.33. CR 2945 had specific antigastrin activity, as it was unable to antagonize the gastric acid secretion stimulated by histamine or carbachol in rats up to the dose of 30 mg kg(-1). CR 2945 was about as efficacious as ranitidine against the indomethacin- and ethanol-induced gastric ulcers and the cysteamine-induced duodenal ulcer in rats. On the contrary, L-365,260 was only slightly effective. These results suggest that CR 2945 might be a promising compound for the therapy of acid-related disorders, and that its clinical use could help clarify the therapeutic potential of gastrin/CCK(B) receptor antagonists in the gut.

Interactions of new and conventional H3-antagonists with non-histaminergic receptors involved in neurogenic and myogenic contractile responses of guinea-pig ileum

1. Possible effects of new and conventional H3-receptor antagonists towards various non-histaminergic receptors (alpha2-adrenergic, 5-HT3-serotonin, mu-opiate, A1-adenosine, M1-and M3-muscarinic) involved in neurogenic and myogenic contractile responses of guinea-pig ileum are investigated. 2. When the isolated ileum was contracted by the 5-HT3 receptor agonist, 2-methyl-5-HT (5 x 10(-7)-8 x 10(-6) M), acetylcholine (1 x 10(-9)-1 x 10(-7) M), KCl (3 x 10(-2) M) or electrical stimulation some of the drugs, included thioperamide and clobenpropit, reduced the contractile response when tested at micromolar concentrations (1-3 x 10(-5) M) (only compound IV exhibited an M3 competitive antagonism with a pK(B) = 5.49 +/- 0.18). 3. Ileal twitch responses to electrical stimulation were dose-dependently inhibited by the selective agonists clonidine (3 x 10(-10)-1 x 10(-7) M), dermorphin (1 x 10(-11)-1 x 10(-8) M), R-N6-(2-phenylisopropyl)-adenosine (1 x 10(-9)-3 x 10(-8) M) and McN-A-343 (1 x 10(-7)-1 x 10(-5) M) with different potencies and comparable efficacy (spike amplitude reduction > 85%). All the H3 antagonists under study (up to 1 x 10(-5) M) showed no or minor interactions at the neuronal sites except the compound V which behaved as a weak competitive antagonist at alpha2-adrenoreceptors (pK(B) = 5.96 +/- 0.06). 4. In conclusion, both new and conventional H3-blockers interacted at the enteric neuronal sites here studied with a 1000-30,000 fold lower antagonistic potency than that previously reported for the ileal H3 histamine receptors. Their spasmolytic activity precludes firm conclusions about the non-competitive interaction with 5-HT3 ileal receptor which requires further investigations.

[Bisphosphonates stimulate the production of basic fibroblast growth factor and the formation of bone marrow precursors of osteoblasts. New findings about their mechanism of action]

BACKGROUND

It has been recently shown that bisphosphonates may affect bone resorption either directly on osteoclast activity or through the mediation of osteoblasts activity. In this experimental study the potential effects of etidronate and alendronate on osteoblastic bone formation are investigated.

METHODS

The number of fibroblastic colony forming units (CFU-F) and mineralized nodules (CFU-OB) in murine and human bone marrow cultures, assessed. In addition, the basic-FGF production by human osteoblastic cells MG-63 measured.

RESULTS

In murine bone marrow cultures etidronate and alendronate stimulate CFU-F formation with a mean increases vs control of 106 +/- 17% at 10(-5) M and 78 +/- 5% at 10(-7) M respectively (p < 0.001). The formation of bone nodules is inhibited by bisphosphonates at high concentrations (> 10(-6) M) and stimulated at lower concentrations (from 10(-7) M to 10(-9) M for etidronate and from 10(-7) M to 10(-10) M for alendronate; p < 0.001). Similarly, in human bone marrow cultures alendronate increases CFU-F formation with a maximal effect at 10(-10) M (+161 +/- 12% vs control; p < 0.01) and the formation of CFU-OB with a maximal effect at 10(-10) M (+133 +/- 34%; p < 0.001). Finally, etidronate (from 10(-9) to 10(-11) M) and alendronate (from 10(-9) to 10(-12) M) stimulate the b-FGF production by human osteoblastic cells (p < 0.01).

CONCLUSIONS

In line with previous histomorphometric and clinical observations, the results obtained indicate that bisphosphonates directly affect osteoblastic cells with a positive effect on bone formation, probably via the stimulation of growth factors.

Bisphosphonates stimulate formation of osteoblast precursors and mineralized nodules in murine and human bone marrow cultures in vitro and promote early osteoblastogenesis in young and aged mice in vivo

Recent in vitro findings suggest that bisphosphonates, potent inhibitors of osteoclastic bone resorption, may also have a direct action on osteoblasts. The purpose of this study was to search for potential effects of etidronate and alendronate on the formation of early and late osteoblastic cell precursors by measuring the number of colony-forming units for fibroblasts (CFU-F) and colony-forming units for osteoblasts (CFU-OB) in murine and human bone marrow cultures. In murine marrow cultures, etidronate (10(-5) to 10(-9) mol/L) significantly stimulated the formation of CFU-F with a maximal effect at 10(-5) mol/L (mean increase over control values+/-SD: 106+/-17%;p < 0.001), whereas alendronate had a biphasic effect, being stimulatory at concentrations below 10(-7) mol/L (78+/-5%; p < 0.001), and inhibitory at higher doses. The formation of CFU-OB was also inhibited by both bisphosphonates at the highest concentrations (10(-5) mol/L and 10(-6) mol/L), but it was significantly stimulated at lower concentrations (from 10(-7) to 10(-9) mol/L for etidronate and 10(-7) to 10(-10) mol/I, for alendronate; p < 0.001). In human bone marrow cultures, alendronate (10(-8) to 10-(12) mol/L) increased CFU-F formation with a maximal effect at 10(-10) mol/L (161+/-12 %; p < 0.01). CFU-OB formation, observed only in the presence of dexamethasone (10(-8) mol/L), was markedly stimulated by alendronate at the above concentrations with a maximal increase at 10(-10) mol/L (133+/-34%; p < 0.001). The in vivo short-term effects of bisphosphonates on the formation of early osteoblast precursors were also studied in bone marrow cultures from young female mice treated with weekly subcutaneous injections of etidronate (0.3, 3, and 30 mg/kg) or alendronate (0.3, 3, and 30 microg/kg) and from aging female mice treated with the two lowest doses of both drugs. After 1 month of treatment, etidronate (0.3 and 3 mg/kg) and alendronate (0.3 and 3 microg/kg) significantly increased the number of CFU-F colonies in the bone marrow from young and old animals, whereas the highest dose of both drugs had no effect in young mice. Our results, together with previously reported observations of bone-forming effects in osteoporosis, suggest that bisphosphonates may have, in vivo, a potentially relevant influence on cells of the osteoblastic lineage, distinct from their inhibitory action on osteoclasts.

H3-receptor antagonists: synthesis and structure-activity relationships of para- and meta-substituted 4(5)-phenyl-2-[[2-[4(5)-imidazolyl]ethyl]thio]imidazoles

We report the synthesis, octanol/water partition coefficient (log P), dissociation constants (pKa), H3-receptor affinity (pKi in rat brain membranes, [3H]-N alpha-methylhistamine), and H3-antagonist potency (pA2 in guinea ileum, (R)-alpha-methylhistamine) of novel H3-receptor antagonists obtained by introducing a para or meta substituent on the phenyl ring of the lead compound 4(5)-phenyl-2-[[2-[4(5)-imidazolyl]ethyl]thio]imidazole (3a). The substituents were chosen to obtain broad and uncorrelated variation in their lipophilic, electronic, and steric properties. The log P values of the neutral species cover almost 3 orders of magnitude (from 1.40 to 4.11). The pKa,2 values (protonation of the 2-thioimidazole fragment) vary from 3.13 to 4.34, indicating that this fragment, which incorporates the so-called polar group common to many H3-receptor antagonists, is neutral at physiological pH. The compounds had pKi values in a range too narrow (from 7.28 to 8.03) to derive QSAR equations. In one case (3g), a biphasic displacement curve was observed (pKi,1 = 8.53; pKi,2 = 6.90). The pA2 values ranged 2 orders of magnitude (from 6.83 to 8.87) and yielded a QSAR model (PLS) indicating that antagonist potency depends parabolically on lipophilicity and is decreased by bulky para substituents. The compounds of this series, therefore, maintain a fair-to-good affinity for rat brain H3-receptor and a fair-to-good H3-antagonist potency on guinea pig ileum, although varying markedly in their lipophilicity. The series thus appears as a good candidate for pharmacokinetic optimization leading to brain-penetrating H3-receptor antagonists.

Indenopyridazinone derivatives as potential antisecretory and antiulcer agents

A series of substituted indenopyridazinones (4b-h) has been synthesized and tested for their antisecretory and antiulcer activity, in comparison with ranitidine, as reference drug. While the monomethoxy (4b-d), as well as the benzyloxy (4f) and the 6,9-dimethoxy (4g) derivatives were found to be devoid of overt antisecretory properties, the 9-methoxy (4e) was weakly active. The most interesting compound of this class was the 7,8-dimethoxy substituted (4h), which at an oral dose of 30 mg/kg still retains a significant activity. The dihydroderivatives of 4g,h (compounds 1g,h) were more active (1g) or comparable (1h) to the parent compounds, thus proving that the 4, 4a-double bond, which was an essential requirement in the analogues 2 and 3, is not necessary in this new series. The disubstituted derivatives (1g,h; 4g,h) were also tested as antiulcer agents, in two different models. All compounds were able to prevent haemorragic lesions induced in rats by 90% ethanol in a dose dependent manner. In the indomethacin model they still showed a significant activity, though lower than in the previous test. Attempts have been made to elucidate their mechanism of action.

In vitro characterization of potency, affinity and selectivity of H3-antagonists: from thioperamide to thioperamide unrelated imidazole derivatives

This paper summarizes the findings obtained for three different series of original compounds designed as potential H3-antagonists starting from thioperamide structure. The compounds were tested in functional and binding assays to estimate their potency, affinity and selectivity for histamine H3 receptors. Among them, many non-thiourea/isothiourea derivatives acted as selective H3 competitive antagonists and, particularly, 4(5)-[2-[4(5)-cyclohexylimidazol-2-ylthio]ethyl] imidazole (dIII) proved to be the most potent H3 blocker vs (R)-alpha-methylhistamine in electrically-stimulated ileum. This imidazole derivative, devoid of thiourea dependent toxic effects, with high affinity displaced biphasically [3H]-N alpha-methylhistamine bound to rat brain H3 sites. Thus, such compound could be proposed as the prototype molecule for the development of new non-thiourea/isothiourea H3-antagonists and as experimental tool to explore the intriguing question of H3 receptor heterogeneity.

Study of the antisecretory and antiulcer mechanisms of a new indenopirydazinone derivative in rats

The present study investigates the antisecretory and antiulcer mechanisms of a new indenopyridazinone derivative previously reported to inhibit gastric acid secretion in pylorus-ligated rats and to prevent gastric ulcerations induced by indomethacin or ethanol in the same animal species. The new compound was tested on the acid hypersecretion induced by histamine, pentagastrin and bethanechol in in vivo and in vitro experimental models. Furthermore, its influence on the mucosal layer adhering the gastric wall in indomethacin-treated rats was considered. Ranitidine was selected as a reference drug. The results obtained demonstrated that the new molecule, at variance with ranitidine, exerts antiulcer activity mainly enhancing the gastric mucosal integrity and simultaneously inhibiting the gastric acid hypersecretion evoked exclusively by cholinergic pulses. Therefore, an involvement of a neuronal rather than an effectorial mechanism has been suggested. Due to these mechanisms of action it clearly differentiates from ranitidine and its possible application in the peptic disease resistant to H2-blockers could be speculated.

Ligands of the histamine H3-receptor: new potent antagonists of the 2-thioimidazole type

An overview of H3-receptor ligands is presented, with particular attention to antagonists. The protein binding of the classical H3-receptor antagonist thioperamide and its effect on in vivo distribution are discussed. A series of H3-receptor antagonists characterised by the presence of an imidazole ring, a spacer (ethylthio-, ethylamino-, propylthio- or propylamino-chain), a second heterocycle nucleus and a lipophilic group is described. Their H3-receptor antagonist potency has been measured on electrically stimulated guinea-pig intestine, and their affinity for central H3-receptor has been determined by competitive inhibition of [3H]N alpha-methylhistamine binding to rat cortex. Biphasic inhibition curves have been observed in some cases. Compounds endowed with interesting activity belong mostly to the class of 2-[[2-[4(5)-imidazolyl]ethyl]thio]imidazole, having a phenyl or a cyclohexyl group.

R-alpha-methylhistamine-induced inhibition of gastric acid secretion in pylorus-ligated rats via central histamine H3 receptors

1. The effect of central H3 histamine receptor activation on gastric acid and pepsin production has been investigated in pylorus-ligated rats. 2. Intracerebroventricular injections (i.c.v.) of the selective H3 agonist, R-alpha-methylhistamine (0.5-50 nmol per rat) caused a dose-dependent inhibition of gastric acid secretion while intravenous administration (5-500 nmol per rat) was completely ineffective. 3. I.c.v. microinjections of mepyramine, tiotidine and thioperamide (51 nmol per rat), selective antagonists at H1-, H2- and H3-sites respectively, failed to modify the acid secretory response to pylorus ligation. 4. The antisecretory effect of R-alpha-methylhistamine (5 nmol per rat, i.c.v.) was selectively prevented by the H3-blocker, thioperamide (51 nmol per rat, i.c.v.), mepyramine and tiotidine pretreatment being completely inactive. 5. Unlike acid secretion, pepsin production was not significantly affected by all the tested compounds. 6. These findings provide the first pharmacological evidence that the activation of central H3 histamine receptors exerts a negative control in the regulation of gastric acid secretion in conscious pylorus-ligated rats.

Regional differences in motor responsiveness to antimuscarinic drugs in rabbit isolated small and large intestine

The pirenzepine-related analogue, nuvenzepine, and the antagonists selective for the three muscarinic receptor subtypes 4-DAMP (M1 and M3 receptors), pirenzepine (M1 receptors), methoctramine (M2 receptors) have been tested on rabbit isolated small and large intestinal regions provided with spontaneous motor activity. The employed drugs differently affected intestinal motility patterns. The ileum pendular movements as well as the proximal colon and taenia coli tone, spike amplitude and frequency were concentration-dependently inhibited by the compounds here employed. Their pIC50 values followed the rank order of potency generally reported for the involvement of the M3 muscarinic receptors (4-DAMP > or = atropine > nuvenzepine > or = pirenzepine > methoctramine). Unlike nuvenzepine and the other antimuscarinics assayed, the M1 selective antagonist pirenzepine, at nanomolar concentrations, was able to enhance the proximal taenia coli motility patterns suggesting that a M1-inhibitory pathway might operate in the physiological modulation of taenia coli motility. At variance with longitudinal ileum and colon contractile activity, proximal circular colon motility was resistant to muscarinic as well as to alpha 1-, H1-, 5-HT-blockade indicating that NANC neuronal mechanisms could act at this level. In summary, these data provide evidence that, at intestinal level, nuvenzepine is almost completely devoid of reliable M1-linked effect thus possessing a different pharmacological selectivity at muscarinic receptor subtypes with respect to pirenzepine. Furthermore, it emerges that rabbit spontaneous small and large intestinal motility is probably driven by different physiological mechanisms regional-related. The peculiar circular colon refractoriness deserves further studies to be extended to the human tissue.

Functional comparison between nuvenzepine and pirenzepine on different guinea pig isolated smooth muscle preparations

The antimuscarinic agents nuvenzepine and pirenzepine were tested on four guinea pig isolated smooth muscle preparations in order to better investigate the existence of differences in the functional activities of such antagonists, as suggested by previous reports. The effects of both compounds were compared to those of atropine. Nuvenzepine showed a four-fold higher affinity than pirenzepine in competitively antagonizing acetylcholine-induced contractions on isolated ileal musculature (pA2 = 7.08 +/- 0.15) and on longitudinal ileum dispersed cells (pA2 = 7.11 +/- 0.19). By contrast, unlike pirenzepine which was ineffective, nuvenzepine inhibited histamine-induced ileal motor activity in a dualistic manner, behaving as an irreversible competitive H1 antagonist (pA2 = 5.02 +/- 0.11). Nuvenzepine was almost equipotent to pirenzepine in competitively preventing bethanechol-induced gall-bladder contractions (pA2 = 7.23 +/- 0.16) and it displayed a four-fold higher potency than pirenzepine in blocking vagal-stimulated tracheal constrictions (pIC50 = 6.77 +/- 0.06). Both compounds were definitely less potent than atropine. On the whole, these findings indicate that, on the selected preparations, nuvenzepine substantially shares the antimuscarinic properties of pirenzepine but it is also endowed with a (weak) H1-blocking action. Furthermore, based on some observations, the presence in gallbladder smooth muscle of muscarinic receptors distinguishable from those of ileum could be speculated.

Muscarinic M1 and M3 receptor antagonist effects of a new pirenzepine analogue in isolated guinea-pig ileal longitudinal muscle-myenteric plexus

The new pirenzepine analogue DF 545 has been tested for its muscarinic M1 and M3 receptor antagonist properties in guinea-pig longitudinal muscle-myenteric plexus preparations. McN-A-343-induced inhibition of twitch contractions was taken as a parameter for muscarinic M1 receptor activation while electrical and acetylcholine-induced contractions were considered as a model for muscarinic M3 receptor stimulation. An unexpected contractile effect evoked by McN-A-343 was also investigated. In contrast to pirenzepine, DF 545 only weakly counteracted the M1-mediated McN-A-343 inhibitory effect but blocked M3-related twitch- or acetylcholine-stimulated responses with a 2-fold higher affinity than pirenzepine. Therefore, in this preparation, our findings suggest that DF 545 does not share the selectivity profile exhibited by pirenzepine at ileal muscarinic receptors. Studies on the McN-A-343 contractile effect provide evidence that this agonist may interact with ileal muscarinic effector sites in a different way from other cholinergic agents.

Pharmacological profile of new thioperamide derivatives at histamine peripheral H1-, H2-, H3-receptors in guinea-pig

The recent availability of potent and selective ligands, namely R-(alpha)-methylhistamine and thioperamide, led to conclusive progresses as regards histamine H3-receptor knowledge. The aim of this work is to investigate by in vitro tests the pharmacological properties of new amino and methyl derivatives of the H3-antagonist thioperamide. Such original compounds, developed by the modulation of the thioperamide imidazolyl moiety, were assayed at guinea-pig ileal contractile H1-, atrial chronotropic H2- and enteric neuronal H3-receptors. None of the drugs exhibited interaction with H1 or H2 sites. On electrically stimulated ileum, two of the thioperamide methyl derivatives competitively antagonized the inhibitory effect of the H3-agonist R-(alpha)-methylhistamine. On the basis of the Schild analysis, the more active isomer (compound IV) displayed an affinity at H3-receptors only five times lower than thioperamide. These results could contribute to elucidate further the structural features required to develop potent and selective H3-antagonists. On the other hand, to prove the hypothesized apparent heterogeneity between peripheral and central H3-sites, as emerged by pharmacological and binding studies, autoradiographic investigations are in progress.

Interaction of selective compounds with muscarinic receptors at dispersed intestinal smooth muscle cells

1. The characterization of muscarinic receptors on single cells of the guinea-pig ileum longitudinal smooth muscle, devoid of neuronal elements, was functionally studied by estimating the affinities of muscarinic antagonists on acetylcholine-induced contractions. 2. Atropine (5 x 10(-11) to 5 x 10(-6) M), 4-diphenylacetoxy-N-methyl-piperidine methiodide (4-DAMP, 5 x 10(-8) to 5 x 10(-6) M), cyclohexyl(4-fluoro-phenyl) (3-piperidinopropyl) silanol (pFHHSiD, 5 x 10(-7) to 5 x 10(-5) M) as well as pirenzepine (5 x 10(-7) to 5 x 10(-5) M) competitively antagonized the acetylcholine-dependent contractions with different affinities (atropine > 4-DAMP > pFHHSiD > pirenzepine). 3. Methoctramine (5 x 10(-7) to 5 x 10(-5) M), and AF-DX 116 (5 x 10(-6) and 5 x 10(-5) M) also showed antagonist properties but these deviated from simple competition. These compounds, which discriminate between M2 and M3 receptors, showed a potency lower than that of pirenzepine, the rank order of potencies being pirenzepine > methoctramine > AF-DX 116. When concentrations of AF-DX 116, methoctramine and pirenzepine were increased an unspecific contractile effect occurred. 4. McN-A-343, a partial agonist on intact guinea-pig longitudinal smooth muscle strips, on this preparation induced a weak contraction (about 7% in comparison to control) that was not reversed by antimuscarinic agents. 5. These data indicate that M3 rather than M2 receptor sites are present on this tissue.

Coexistence of histamine H1 and H2 receptors coupled to distinct signal transduction pathways in isolated intestinal muscle cells

Histamine receptors were characterized in muscle cells isolated from the longitudinal muscle layer of guinea pig intestine. Histamine caused concentration-dependent contraction and stimulated significant increases in [Ca++]i (141 +/- 16 nM, P < .001) and cyclic AMP (cAMP) (10.3 +/- 0.5 pmol/10(6) cells, P < .001). The H1 receptor antagonist, mepyramine, inhibited contraction and the increase in [Ca++]i, whereas the H2 receptor antagonist, cimetidine, augmented contraction and the increase in [Ca++]i (277 +/- 31 nM, P < .01) and abolished the increase in cAMP. In cells maximally contracted with a nonhistamine agonist [cholecystokinin octapeptide (CCK)], histamine caused concentration-dependent relaxation when the contractile effect mediated by H1 receptors was blocked with mepyramine; relaxation was inhibited by cimetidine in a concentration-dependent fashion. The effects mediated by H1 and H2 receptors were characterized further in cells in which only one receptor type was preserved by selective receptor protection. In cells in which only H1 receptors were preserved, histamine caused contraction that was inhibited by mepyramine; no relaxation of CCK-induced contraction could be elicited by histamine in the presence of mepyramine. Conversely, in cells in which only H2 receptors were preserved, histamine had little or no contractile effect by itself but caused relaxation of CCK-induced contraction in the absence of mepyramine. We conclude that in, intestinal muscle cells, H1 receptors mediating Ca(++)-dependent contraction coexist with H2 receptors mediating cAMP-dependent relaxation. The effect of histamine reflects activation of dominant H1 receptors as well as of H2 receptors which act to attenuate [Ca++]i and contraction by stimulating an increase in intracellular cAMP.

Pharmacological properties of new 1,2-benzisothiazolyloxypropanolamines on cardiac and tracheal beta-receptors

This paper reports the pharmacological assessment of beta-blocking properties of new benzisothiazole and benzisoxazole derivatives, substituted in position 3-, 5- or 7- with the oxypropanolaminic side chain (I-VI), to of which contain the -OCH3 group in position 3- (III, V) in comparison with propranolol. The results, obtained on isoprenaline-induced chronotropic response of rat isolated atria and on isoprenaline-induced relaxation of guinea-pig tracheal strips precontracted by carbachol, suggest that the compounds (I, II, IV, VI), at variance with the methoxy-substituted (III, V), possess a beta 1-blocking activity 4-300 times lower than propranolol. pA2 values drop from 8.36 to 7.56 and 7.04 from the relative compounds substituted in position 7- (IV), 3- (I) and 5- (II), thus indicating that the position of the oxypropanolaminic chain in the benzisothiazole ring affects the ability of the molecules to interact with the beta 1-adrenoceptor. Furthermore, benzisothiazole rather than benzisoxazole ring seems to facilitate the drug-beta 1 adrenoceptor interaction, the compound (I) displaying a 10-fold higher affinity than compound (VI).

Omeprazole-like compounds on histamine-stimulated acid and peptic secretions in conscious dog and cat

A newly synthetized aniline derivative series has been tested on histamine-stimulated gastric acid secretion in conscious cats and dogs and compared to the proton pump inhibitors omeprazole and NC 1300. The compounds markedly and long-lastingly inhibited acid output with a potency lower than omeprazole but very close to the reference compound NC 1300. The results show that the introduction of a nitrogen atom, irrespective of the position in the benzimidazole ring does not seem to influence the gastric antisecretory activity.

Neuronal and myogenic muscarinic effects of McN-A-343 on guinea pig longitudinal smooth muscle-myenteric plexus

Among muscarinic agonists, the compound McN-A-343, originally proposed as selective stimulant of M1 cholinergic site, was subsequently questioned as a useful pharmacological tool in the classification of muscarinic receptors. In this work, evidence is presented for a dual response of McN-A-343 on longitudinal muscle-myenteric plexus preparation. On electrically-stimulated preparation, this agonist exhibited a pirenzepine-sensitive inhibition of the twitch contractions due to the involvement of neural M1-muscarinic receptor. On the other hand, a direct myogenic contractile action on the unstimulated tissue was observed using McN-A-343 in the same range of concentrations. This latter response, on the basis of the effects of muscarinic and non-muscarinic antagonists tested, seems to involve effectorial muscarinic sites with an unusual mechanism.

Characterization of antigastrin activity in vivo of CR 2194, a new R-4-benzamido-5-oxo-pentanoic acid derivative

The antigastrinic activity, in vivo, of CR 2194 (R-4-(3-chlorobenzamido)-5-(8-azaspiro[4.5]decan-8-yl) -5-oxo pentanoic acid) was assessed in various animal species. CR 2194 antagonized pentagastrin-stimulated gastric acid secretion in the rat (ID50 = 11 mg/kg i.v.), dog (ID50 = 5.9 mk/kg i.v. or 28.8 mg/kg os) and cat (ID50 = 15.5 mg/kg i.v.). CR 2194, in the cat, inhibited both competitively and non-competitively the gastric acid secretion stimulated with increased doses of pentagastrin, with a pA2 of 4.89. In the rat and in the dog the antagonism seemed to be non-competitive and the respective pD'2 calculated were 4.54 and 4.42. The interaction of CR 2194 with the gastrin receptors appeared reversible, as demonstrated by the return to normal values of the acid output after the conclusion of the i.v. infusion, during pentagastrin continuous stimulation in the dog. The antigastrin activity was specific: CR 2194 was unable to antagonize the gastric acid secretion stimulated by carbachol or histamine in the rat up to the dose of 100 mg/kg. CR 2194 was effective to antagonize the gastric acid secretion stimulated by gastrin release after meal ingestion in the Heidenhain pouch dog model. The ID50 calculated was 2.89 mg/kg after oral administration. All these characteristics make CR 2194 an important compound in the investigation of the biological effects of gastrin and a potential agent for diagnostic or therapeutic use.

4-(1,2-Benzisothiazol-3-yl)alkanoic and phenylalkanoic acids: synthesis and anti-inflammatory, analgesic and antipyretic activities

Continuing their studies on benzisothiazolyl derivatives, Authors refer to the preparation and pharmacological properties of 4-(1,2-benzisothiazol-3-yl) alkanoic and phenylalkanoic acids. All substances were tested for anti-inflammatory, analgesic and antipyretic properties. As reference compounds, 1,2-benzisothiazolin-3-one and 4-(3-oxo-1,2-benzisothiazolin-3-yl) phenylacetic acid, as prototypes of benzisothiazolinonic derivation. Ibuprofen, as a prototype of substituted arylalkanoic acids, and Phenylbutazone were used. Analysis of the data leaded to the following conclusions. Introduction of the aryl moiety, passing from benzisothiazolylalkanoic to benzisothiazolyl-phenylalkanoic structures, produced a remarkable increase of activity. 2-[4-(1,2-benzisothiazol-3-yl)phenyl] propionic and 2-[4-(1,2-benzisothiazol-3-yl)phenyl]butyiric acids showed anti-inflammatory, analgesic and antipyretic properties comparable to those of Ibuprofen. Substantial differences in variations in activities were observed comparing the properties of benzisothiazolylphenylalcanoic acids with those of the benzisothiazolinonic series, object of preceding studies.

Anomalous responses to histamine stimulation of guinea-pig oesophageal muscularis mucosae

The incomplete tachyphylaxis of the contractile response to the H1-stimulants observed on guinea-pig oesophageal muscularis mucosae seems to be H2- and H3-antagonist as well as atropine- and tetrodotoxin-resistant. Lidocaine and eserine partially prevented this process probably by a mechanism independent of their main activity. The dualistic antagonism exerted by mepyramine and methysergide on reproducible histamine responses could be explained by a kinetic condition of "hemi-equilibrium state" together with changes of drug-receptor interaction and by non-specific properties of methysergide. On the whole, the present data indicate that the role of histamine in this tissue has still to be defined.

Localization of central prostaglandin E2 antisecretory effects

Intracerebroventricular prostaglandin E2 (PGE2) inhibits stimulated gastric acid secretion; however, the central site of action is unknown. Specific PGE2 binding sites have been localized to the ventromedial hypothalamic nucleus and central amygdala (A). The nuclear accumbens has been shown to play a role in central neurotensin-induced antisecretory effects. These studies tested the hypothesis that microinjections of PGE2 into the ventromedial hypothalamic nucleus, central amygdala, and nuclear accumbens inhibit stimulated gastric acid secretion. The hippocampus served as a cerebral control region. Two days before the experiments, metal cannulas were stereotaxically positioned bilaterally into specific areas of the brain, and metal gastric cannulas were operatively implanted, under nembutal anesthesia, in male 250-g Sprague-Dawley rats. On the experimental day, the rats, fasted for 14 hours, were given saline or PGE2 (0.1-1.0 micrograms in 0.2 microL/side) through the central cannulas 10 minutes before administering pentagastrin (40 micrograms/kg SC). Gastric secretion was measured at 30-minute intervals and expressed as acid output, micromoles per hour. Acid output (mean +/- SE) in control animals was 161 +/- 14 mumol/h. Prostaglandin E2 administration at doses of 0.10, 0.50, and 1.0 micrograms/side (a) into ventromedial hypothalamic nucleus reduced acid output to 53 +/- 11,* 36 +/- 10,* and 27 +/- 11* mumol/h regularly; (b) into NACB reduced acid output to 157 +/- 36, 60 +/- 12,* and 38 +/- 12* mumol/h; and (c) into A reduced acid output to 144 +/- 31, 141 +/- 26, and 90 +/- 19* mumol/h, respectively (*P less than 0.05 by Neuman-Keuls test). Prostaglandin E2 (0.50 micrograms/side) administration into hippocampus had no significant effect on acid output (134 +/- 28 mumol/h). Although central PGE2 administration was associated with hyperthermia, this occurred at lower doses than those required to inhibit acid secretion. Prostaglandin E2 administration into specific brain areas known to have PGE2 receptors, the central amygdala and ventromedial hypothalamic nucleus, and into nuclear accumbens inhibits stimulated gastric acid secretion. These observations suggest that PGE2 may have a physiological role in the central control of gastric acid secretion.

Histological examination of gastric mucosal lesions induced by isolation in saline and cimetidine treated rat

It has been recently pointed out that the most reliable method of assessment of gastric mucosal injury is the microscopic examination of the tissue. The purpose of the present paper was, therefore, to study the histological features of gastric lesions induced by a six week isolation in rats. It has also been investigated whether a two week treatment, beginning four weeks after isolation, with cimetidine 80 and 160 mg kg-1 p.o. daily could protect the gastric mucosa. In saline treated rats, histological examination of haemorrhagic areas showed that both surface epithelium and gastric pits were damaged or even completely absent with a consequent surfacing of subepithelial vessels. Damage extended deeply into the gastric glands with evidence of necrotic cells in the corpus and fundus. Simultaneous occurrence of the process of restitution was evident. Cimetidine partially lessened the severity of damage and appeared to favour the restitution processes.

Gastrointestinal activities of a new pirenzepine-analog, nuvenzepine, in the cat

Nuvenzepine, a new pirenzepine-analog, administered intraduodenally, displayed a long-lasting and dose-dependent inhibition of neostigmine-induced intestinal motility in anaesthetized cats. On ileal motor activity, the compound showed a potency 10 times greater than that of pirenzepine, and, although to a lesser extent, it was also active, unlike pirenzepine, on colonic stimulated motility. Furthermore, in conscious cats, nuvenzepine inhibited pentagastrin-stimulated gastric acid secretion resulting 25-30 times more potent than pirenzepine. The observed differences between antisecretory and antispastic activities displayed by nuvenzepine and pirenzepine suggest that the new pirenzepine-analog may act on gastrointestinal functions through an additional non-anticholinergic mechanism.

Synthesis and local anesthetic activity of alkylaminoacyl derivatives of 3-amino-1,2-benzisothiazoles

Two series of new alkylaminoacylamino-1,2-benzisothiazoles were synthetized and assayed for anesthetic activity. The above-mentioned compounds were prepared by reaction between the appropriate amines and 3-(haloacyl)amino-1,2-benzisothiazoles, which had been obtained by acylation of a 3-amino-1,2-benzisothiazole with the required haloacylchloride. The local anesthetic activity of the compounds, isolated as hydrochlorides, was tested for surface, infiltration and trunkular anesthesia. Several compounds proved to be active in infiltration and trunkular anesthesia, whereas no compound showed local surface anesthesia. On the basis of the results obtained the structure-activity relationships were examined.

Receptor type for cholecystokinin on isolated intestinal muscle cells of the guinea pig

Smooth muscle cells isolated from the longitudinal muscle layer of guinea pig ileum were used to determine the presence and type of cholecystokinin/gastrin receptor mediating contraction. This was accomplished with a series of cholecystokinin and gastrin agonists (CCK-8, des(SO3)CCK-8, gastrin-17, des(SO3)gastrin-17 and pentagastrin) and antagonists (glutaramic acid derivatives CR 1392, CR 1409, CR 1505 and proglumide). The order of potency of agonists based on EC50 values derived from concentration-response curves was: CCK-8 greater than des(SO3)CCK-8 greater than gastrin-17 greater than des(SO3)gastrin-17. The inhibitory dissociation constant (Ki) for the antagonist CR 1505 derived from Schild plots was the same whether sulfated CCK-8 or desulfated gastrin-17 was used as agonist (4.47 +/- 0.76 versus 4.68 +/- 0.78 nM). Pentagastrin acted as a partial agonist and inhibited partially the response to CCK-8. The Ki values determined for all antagonists with pentagastrin as agonist were similar to those with CCK-8 as agonist. The order of potency of agonists and the independence of Ki values from the type of agonist used implied that CCK and gastrin interact with one receptor type; the receptor is more sensitive to CCK-8 but is minimally influenced by sulfation of the tyrosine residue. In this respect, the receptor appears to be distinct from the CCK receptor on gallbladder muscle cells and pancreatic acinar cells.

Effects of two new pirenzepine analogs on the contractile response of the guinea-pig oesophageal muscularis mucosae to acetylcholine, bethanechol, histamine and high potassium

The guinea-pig oesophageal muscularis mucosae was used to determine the affinity for muscarinic receptors of two new tricyclic compounds, DF 545 and DF 594, which are structurally related to pirenzepine. Both acetylcholine and bethanechol induced a concentration-dependent contraction of the muscularis mucosae. This contraction was competitively antagonized by DF 545 and DF 594 over the dose range 10(-7)-10(-5) M, while at higher concentrations both antagonists caused a depression of the maximal response to the cholinomimetics. The potency of DF 545 and DF 594 appeared to be comparable to that of pirenzepine and approximately 50 times lower than that of atropine. By comparing the affinities of DF 545 and DF 594 with those of selective antagonists (methoctramine and 4-DAMP) which discriminate between M2/M3 muscarinic receptor subtypes, it emerged that pirenzepine as well as DF 545 and DF 594 might act on M3 receptors, which seem to be predominant in the guinea-pig oesophageal muscularis mucosae. McN-A-343 exhibited no agonist activity while it acted as a competitive antagonist against acetylcholine and bethanechol. None of the compounds exhibited calcium antagonist properties. DF 545 inhibited the contractile responses to histamine, but DF 594 and pirenzepine did not.

H2-antagonists: synthesis and activity of 2-amino-5-thiazolyl derivatives

2-Amino- and 2-guanidinothiazole derivatives having in position 5 a methylthioalkyl side-chain with urea-equivalent moieties were prepared for comparison with H2-antagonists of cimetidine and tiotidine series. Examination of the pharmacological results obtained from experiments on guinea pig atria and in cat gastric fistula, suggests some general observations about the structure-activity relationship of the compounds synthesized. The activity trend of these products is different from that of H2-imidazole antagonists while it is similar to that of the tiotidine series. Unlike the tiotidine similar compounds, the 2-guanidino-5-thiazolyl derivatives are less potent than the corresponding 2-amino-5-thiazolyl products. The activity of the latter ones is reduced in comparison to that of tiotidine or cimetidine.

Pirenzepine prevents cysteamine-induced formation of gastroduodenal ulcers and reduction of mesenteric circulation

The effects of pirenzepine on gastric and duodenal ulceration and barrier mucus levels, as well as on changes of superior mesenteric artery diameter caused by cysteamine, were investigated in rats and compared with those of atropine. Cysteamine induced severe gastric and duodenal ulcers and decreased both barrier mucus levels and mesenteric blood flow. Pirenzepine reduced gastric and duodenal ulceration induced by cysteamine. Moreover, pirenzepine significantly increased basal mesenteric artery diameter and fully prevented cysteamine-induced decrease in mesenteric blood flow. Under the same conditions, atropine failed to prevent gastric and duodenal ulceration or mesenteric artery changes caused by cysteamine. Both pirenzepine and atropine were without any effect on cysteamine-induced inhibition of gastric and duodenal barrier mucus levels. The present results are consistent with the view that pirenzepine protects against gastroduodenal ulceration caused by cysteamine by increasing blood flow at the level of the ulcerated mucosa. The higher affinity of pirenzepine for the muscarinic receptors of sympathetic ganglia may explain the difference between the effects of pirenzepine and atropine. In addition to this, the measurement of superior mesenteric artery diameter changes may represent an accurate and reproducible method, suitable for studying the gastrointestinal protective mechanisms of the drugs.