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Biomedical subjects

M Tonini

Publications and source records attributed to M Tonini.

At least 109 records · Page 6Linked to original sources
PubMed1982

Mode of action of ATP on propulsive activity in rabbit colon.

ATP induced a concentration-dependent reduction of the velocity of propulsion in isolated segments of rabbit colon as assessed by the aboral displacement of an intraluminal rubber balloon, and delayed the onset of the propulsive wave. ATP depressed both the reflex contraction of the circular coat above the distended balloon and the response of the circular muscle to transmural (cholinergic) stimulation. On the contrary, ATP (up to 200 muM), while causing relaxation of the circular muscle, had no effect on either the muscular contractile response induced by carbachol and histamine or the non-adrenergic inhibitory responses elicited by electrical stimulation and by radial distension of the gut wall. Within the concentration range used (10-200 muM), ATP concentration-depression curves for propulsion and transmural excitatory stimulation were shifted to the right in the presence of theophylline (10 muM). Theophylline, however, had no influence on either the direct inhibitory action of ATP on circular smooth muscle or the non-adrenergic relaxation in response to electrical stimulation. These data are consistent with the concept that at least two populations of purinergic receptors are present in intestinal tissue. Those populations located presynaptically, unlike those located postsynaptically, are blocked by theophylline. Since the contractile machinery does not appear to be affected by ATP concentrations up to 200 muM, the mechanism by which ATP impairs propulsive activity is probably dependent on activation of presynaptic purinergic receptors located on the nervous pathways subserving the wave of contraction, without having any appreciable influence on descending inhibition.

Adenosine Triphosphate↗
PubMed1982

Effects of desensitization to adenosine 5'-triphosphate and adenosine on non-adrenergic inhibitory responses in the circular muscle of rabbit colon.

An approximate eight fold desensitization of the circular coat of the distal rabbit colon to adenosine 5'-triphosphate (ATP) and adenosine could be achieved by repeatedly exposing the organ to relatively low concentrations (10-100 microM) of these compounds. The desensitization was specific and reversible after prolonged washing. It could be overcome by increasing the concentrations of the purine agonists. Dipyridamole potentiated the non-adrenergic inhibition in response to transmural stimulation but failed to influence the caudad relaxation evoked by radial distension. Desensitization to ATP and adenosine (and to ATP + adenosine simultaneously) did not affect the non-adrenergic inhibition in response to radial distension or transmural stimulation. These results suggest that neither ATP nor adenosine are the final transmitters mediating the non-adrenergic inhibitory responses in the distal colon of the rabbit.

Adenosine↗
PubMed1982

Motor responses of rat stomach in vitro after subacute oral administration of trithiozine.

The effects of ten days' oral treatment with 200 mg/kg/d of 4-(3,4,5-trimethoxythiobenzoyl)tetrahydro-1,4-oxazine (trithiozine) on the mechanical responses of rat stomach in vitro have been studied. Gastric muscular excitation due to vagal stimulation was partially reduced in the trithiozine-pretreated animals, while the amount of acetylcholine (Ach) released both at rest conditions and in response to field stimulation was similar in both controls and drug-pretreated rats. Also muscular responses induced by dopamine (DA) and by serotonin (5-HT) were of similar degree in both groups of rats. On the contrary, the nonadrenergic and non-cholinergic inhibitory response evoked by vagal stimulation in the presence of muscarinic and alpha- and beta-adrenergic receptor blockade, respectively, was enhanced in the drug-pretreated animals. Moreover, trithiozine pretreatment caused an increase of spontaneous motor activity and a remarkable degree of potentiation of the contractile response to prostaglandins (PGs), both exogenously applied or endogenously released by ATP. Our results give further evidence that trithiozine has no anticholinergic activity and that some therapeutic properties of the molecule could be accounted for by an involvement of endogenous PGs.

Acetylcholine↗
PubMed1981

Hyoscine-resistant peristalsis in guinea-pig ileum.

The effect of hyoscine on the peristaltic activity of the proximal and distal ileum of the guinea-pig was studied. Hyoscine strongly impaired peristalsis as indicated by the elevation of the threshold pressure and by the increased number of incomplete peristalses and blockades. Functional activity of the circular musculature was more markedly impaired. However, particularly in the distal ileum, complete peristalses occurred even after 70 min exposure to hyoscine at a concentration of 10(-6) g/ml. A tenfold increase in hyoscine concentration failed to produce further impairment of peristaltic activity and of the oral reflex contraction. The activity which remained in the presence of hyoscine was blocked by methysergide and by d-tubocurarine. The hypothesis is advanced that once the muscarinic receptors have been blocked, increased radial stretch of the circular coat results in activation of a separate, tetrodotoxin sensitive, excitatory nervous pathway, which is sufficient to maintain a discrete degree of peristaltic activity.

Animals↗
PubMed1980

Effects of metopimazine on gastro-intestinal and biliary tract smooth muscle in vitro.

The effects of the phenothiazine derivative metopimazine on the spontaneous or induced activities of guinea-pig isolated stomach and of the rabbit biliary and intestinal tracts were studied. A predominant inhibitory effect was observed except for the circular muscle layers of the duodenum and colon where activation appeared. Evidence from in vitro experiments suggest that metopimazine exerts an inhibitory action partly through a direct effect on smooth muscle cells and partly by reducing stimulated acetylcholine release (at least in the stomach). Finally the involvement of a non-adrenergic, non-cholinergic inhibitory system is postulated.

Acetylcholine↗
PubMed1978

Chronic prostato-vesiculitis and sperm-cell mobility in male infertility.

The purpose of this research has been to value the importance of chronic inflammation of the prostatovesicular apparatus in sterile patients. The authors wish to underline the high incidence of chronic inflammation if this apparatus in such patients, the low incidence of bacterial forms and the high frequence of association with bradycinesia. The therapy of such forms gives excellent results.

Adult↗
PubMed1977

Effects of pentazocine on the intestine and biliary tract of the rabbit in vitro.

Pentazocine impairs peristaltic activity and relaxes longitudinal muscle in the colon and in the ileum. The circular coat is excited in the colon, while in the ileum pentazocine exhibits both excitatory and inhibitory effects depending on the concentration employed. Pentazocine does not exert a spasmogenic effect in the smooth muscle of terminal bile duct but instead reduces the electrically-induced contraction. The effect of pentazocine does not seem to involve endogenous acetylcholine or catecholamine release.

Acetylcholine↗
PubMed1977

The mechanism of action of narcotic analgesics in the guinea-pig ileum.

1. Intracellular recordings were made from neurones in the myenteric plexus of the guinea-pig ileum. Single myenteric ganglia were maintained in vitro and drugs were applied by adding them to the perfusing solution. 2. Narcotic analgesics hyperpolarized the membrane of a proportion of neurones in the myenteric plexus. 3. The membrane hyperpolarization was sometimes associated with a decrease in input resistance. These effects reduced the excitability of myenteric neurones. 4. The effects of narcotics occurred at low concentrations (10 nM to 1 micrometer), were stereospecific and were reversed by naloxone. 5. It is proposed that the morphine-sensitive neurones may be the cholinergic efferents to the muscle layers. By hyperpolarizing these neurones, morphine may prevent their excitation by electric field stimulation. This may explain why narcotic analgesics reduce the output of acetylcholine and the contractile response of this preparation when it is excited by field stimulation.

Action Potentials↗