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Biomedical subjects

F De Ponti

Publications and source records attributed to F De Ponti.

81 records · Page 5Linked to original sources
PubMed1986

A re-appraisal of the mode of action of 5-HT in inhibiting GABA-induced cholinergic contractions in the guinea-pig ileum.

In the guinea-pig ileum, pretreatment with 5-hydroxytryptamine (5-HT) (5 microM) for 4-5 min inhibited both 5-HT- and gamma-aminobutyric acid (GABA)-induced cholinergic contractions without consistently altering those induced by electrical field stimulation. Cisapride (1 micron) antagonized 5-HT-induced cholinergic contractions but left those induced by GABA or twitch responses unchanged. These results indicate that the 5-HT action in inhibiting GABA-induced cholinergic responses may arise at the interneuronal level, thus suggesting that GABA may also indirectly activate cholinergic terminal neurons. These findings rule out the possibility of 5-HT acting as an intermediate transmitter in this type of response.

Animals↗
PubMed1985

Depression by morphine of the excitability of intrinsic inhibitory neurons in the guinea-pig colon.

The mechanical responses to morphine were examined in isolated preparations of longitudinal and circular muscle of the guinea-pig colon. In the longitudinal coat, morphine induced a relaxation which was prevented by naloxone, hyoscine and tetrodotoxin. Conversely, in the circular coat morphine caused a contraction which was antagonized by naloxone, mimicked by tetrodotoxin and left unaltered by hyoscine, chlorpheniramine and methysergide. In both muscular layers, morphine depressed (and tetrodotoxin abolished) the non-adrenergic relaxation induced by field stimulation. The action of morphine in the two preparations can thus be explained in terms of inhibition of the tonic excitatory cholinergic or inhibitory non-adrenergic neural control prevailing in the longitudinal and circular muscle respectively.

Animals↗
PubMed1985

Subsensitivity of enteric cholinergic neurones to alpha 2-adrenoceptor agonists after chronic sympathetic denervation.

The concentration-effect relationships of noradrenaline, dopamine and clonidine in inhibiting resting and stimulated acetylcholine output have been studied in intact and in sympathetically denervated preparations of guinea pig isolated distal colon. The order of potencies for the inhibition of resting acetylcholine release in intact preparations was clonidine greater than dopamine greater than noradrenaline while the order of intrinsic activities was noradrenaline greater than dopamine greater than clonidine. Sympathetic denervation was able to modify the potency of either clonidine, dopamine and noradrenaline. Noradrenaline was 6 times more potent in inhibiting resting acetylcholine release in denervated than in intact preparations, while clonidine and dopamine underwent a 18-fold and a 11-fold decrease in potency after denervation. The potency of clonidine relative to noradrenaline was 110 in intact preparations and only 1.2 in denervated organs. The intrinsic activities of noradrenaline, dopamine and clonidine were almost unchanged in denervated organs. A dose-dependent facilitatory effect of yohimbine on both the resting acetylcholine output and the peristaltic reflex could be observed in intact but not in sympathetically denervated preparations at concentrations ranging from 2.5 X 10(-8) M to 2.5 X 10(-7) M. Yohimbine was able to counteract the inhibitory effect of dopamine and to remove the inhibitory effect of periarterial nerve stimulation on both acetylcholine release and the peristaltic reflex. Our results are consistent with the existence of a tonic physiological modulation of enteric cholinergic neurones by postganglionic sympathetic fibres. The order of potencies of adrenoceptor agonists and the antagonism by yohimbine is consistent with such a modulation being entirely carried out through alpha 2-heteroceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1985

Effect of chronic anticonvulsant monotherapy on lymphocyte subpopulations in adult epileptic patients.

Sixty-five patients undergoing long-term monotherapy for at least 3 months with phenytoin, carbamazepine or phenobarbital were screened for lymphocyte and immunoglobulin abnormalities. In 57% of patients the duration of therapy was longer than 12 months. The control subjects were matched for sex and age and none of them was taking drugs. The average serum immunoglobulin (IgG, IgA, IgM) values did not differ in control and patient groups. A significant decrease of OKT4+ cells was seen with all drugs, while other lymphocyte subpopulations were differently affected depending on the drug used. It is concluded that long-term single-drug treatment with phenytoin, carbamazepine and phenobarbital exhibits immunosuppressant effects through a complex action which involves more than one lymphocyte subpopulation. Moreover, the possible interference of the disease state with the immune functions of epileptic patients is discussed.

Adolescent↗
PubMedDate not supplied

Prolonged monitoring of colonic spike activity by a computerized system: application to the rabbit colon.

In the present paper, we describe and validate a computerized system for the quantitative analysis of colonic spike activity in the conscious rabbit. This system allowed data acquisition at 160 Hz on 8 channels simultaneously during the recording session. Data analysis at the end of the recording session took approximately 10 min for each hour of recording. The spike recognition procedure was carried out on the basis of a discriminant function which discarded artifactual fast events. Data could be presented as histograms or be transferred into an ASCII file for later statistical analysis. Reliability tests showed that the misrecognition rate was only 3.88%. In conclusion, this computerized system is a reliable, timesaving tool for the quantitative analysis of colonic spike activity.

Action Potentials↗