Search PubMed⌕ Search

Biomedical subjects

E Contreras

Publications and source records attributed to E Contreras.

At least 91 records · Page 5Linked to original sources
PubMed1979

Sensitivity of mouse vas deferens to neurotransmitters: changes after morphine treatment.

1. The pharmacological responses of the isolated vas deferens of the mouse were investigated after acute and chronic treatment with morphine. 2. The addition of morphine to the bath did not alter the responses of the vas deferens to exogenous noradrenaline, adrenaline or dopamine. 3. Low doses of morphine depressed the responses to acetylcholine. Very high concentrations of the opioid (8.5 x 10(-4) M) completely abolished, in about 50% of the preparations, the responses to exogenous acetylcholine, while in the other 50% a potentiation of the responses to low concentrations of acetylcholine was observed. 4. The vas deferens of mice chronically treated with morphine showed increased sensitivity to exogenous noradrenaline, but decreased sensitivity to acetylcholine. 5. A fresh amount of morphine added to the bath enhanced the responses of morphine-tolerant preparations to noradrenaline but not to dopamine or acetylcholine. The specificity of this phenomenon was demonstrated by the use of pentobarbitone instead of the opioid. 6. These results are in agreement with the theory that tolerance could result from a form of disuse supersensitivity.

Acetylcholine↗
PubMed1978

Partial inhibition of the abstinence syndrome in morphine tolerant-dependent mice following pharmacological denervation.

Mice were chronically treated with either atropine, methysergide or pentobarbital in order to induce sensitivity changes resulting from adaptative adjustments in the central nervous system (CNS), and to examine the degree of tolerance to and physical dependence on morphine several days after the discontinuation of pretreatments. Subsequently to the chronic blockade of muscarinic or serotonergic receptors, the intensity of tolerance was unaffected, but some manifestations of the abstinence behavior induced by naloxone were reduced in part. This attenuation of the abstinence syndrome in the pretreated mice was reverted by an additional dose of either atropine or methysergide administered a few min before naloxone. Additional experiments with physostigmine or 5-hydroxytryptophan (5-HTP) in morphine-dependent mice yielded results compatible with the hypothesis that morphine physical dependence may be the manifestation of compensatory changes of sensitivity to serotonin and acetylcholine in the CNS. These results do not exclude the participation of other neurotransmitters or neurohormones in morphine dependence.

5-Hydroxytryptophan↗
PubMed1977

Effects of tricyclic compounds and other drugs having a membrane stabilizing action on analgesia, tolerance to and dependence on morphine.

Several drugs affecting nerve cell excitability, by opposing ion movements in membranes, were tested in mice rendered tolerant to or dependent on morphine. The purpose of the study was to investigate whether these drugs share the ability to attenuate morphine tolerance and dependence exhibited by tricyclic antidepressants. Tolerance to morphine was decreased by the administration of imipramine, doxepin, promethazine, propranolol, lidocaine and quinidine. Chlorpromazine and carbamazepine were ineffective. The intensity of the abstinence syndrome provoked by naloxone was decreased by chlorpromazine, imipramine, doxepin, lidocaine, quinidine and propranolol. Diphenyl. hydantion and carbamazepine had no effect. The results are discussed in relation with the blockade of ion conductance and their interference with the release of neurotransmitters produced by the drugs assayed.

Analgesia↗
PubMed1975

Sensitivity changes to morphine and other drugs induced by cholinergic blockade.

Mice were given several atropine injections at a high dosage level. After 2 to 5 days of cessation of treatment the effects of morphine, arecoline, amphetamine, pentylenetetrazol, reserpine, and hexobarbital were determined and compared with those found in saline injected controls. The influence of atropine treatment on tolerance development to morphine was also studied. After withdrawal of atropine a reduction of the analgesic responses to morphine and arecoline was observed. A decrease in hexobarbital sleeping time was also found. There was no significant influence on the analgesic effect of amphetamine, on the depressant action of reserpine, and on the convulsant effect of pentylenetetrazol. The influence of the administration and further withdrawal of atropine on tolerance development to morphine was masked by the concomitant reduction of morphine analgesia. It was impossible to observe a supersensitivity to the pharmacological agents studied.

Amphetamine↗