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E Contreras

Publications and source records attributed to E Contreras.

At least 73 records · Page 4Linked to original sources
PubMed1986

Effects of morphine in the isolated mouse urinary bladder.

Acute morphine increased the responses to acetylcholine of the isolated mouse urinary bladder. A chronic morphine treatment did not change the responses of the urinary bladder to acetylcholine or ATP. The acute administration of morphine did not modify the contractile response to ATP in the urinary bladders from untreated or chronically morphine treated mice. Methadone and ketocyclazocine decreased the responses to the electrical stimulation of the urinary bladder. These depressant effects were not modified by naloxone. The results suggest the nonexistence of opiate receptors in the mouse urinary bladder and the lack of direct effects of morphine on the neuroeffector junction.

Acetylcholine↗
PubMed1985

Effects of ethylenediamine on morphine analgesia and tolerance-dependence in mice.

Ethylenediamine, a GABA receptor agonist induced a small hyperalgesic state in mice, but increased morphine analgesia. The interaction with this morphine effect was not dose-dependent. Ethylenediamine significantly antagonized tolerance development at relatively low doses (5-10 mg/kg). The GABA mimetic agent increased the frequency of abstinence signs in the naloxone-precipitated morphine withdrawal in mice. The effect of ethylenediamine on morphine withdrawal was suppressed by the irreversible GABA transaminase inhibitor, gamma-vinyl GABA.

Analgesia↗
PubMed1985

Possible involvement of adenine nucleotides in the neurotransmission of the mouse urinary bladder.

The urinary bladder of the mouse contracts to several agonists, namely acetylcholine, noradrenaline, adrenaline, histamine, angiotensin, serotonin, purine nucleotides and prostaglandin F2 alpha. Atropine partially reduced the contraction induced by electrical stimulation, whereas propranolol and tolazoline were ineffective. The atropine resistant component of the neurogenic response was reduced by indomethacin. Methysergide and diphenhydramine were ineffective. Desensitization of the bladder by alpha,beta-methylene ATP abolished the response to ATP and greatly reduced the non-adrenergic non-cholinergic component of the neurogenic response. The results suggest that ATP could be the transmitter responsible for the non-cholinergic non-adrenergic contraction of the mouse urinary bladder.

Acetylcholine↗
PubMed1984

Effects of taurine on tolerance to and dependence on morphine in mice.

The effects of taurine on the analgesic response to morphine, on the intensity of tolerance and on physical dependence were examined. Taurine induced a hyperalgesic state and attenuated morphine analgesia in mice. The hyperalgesia was maximal at a dose level of 1.5 mg/kg i.p., while the effects of higher doses (6.0 and 10.0 mg/kg) were masked by a depression of the animals' gross behavior. Taurine induced a dose related antagonism of morphine tolerance. The amino acid administered 30 min before naloxone, produced a partial reduction in the abstinence signs in the chronically treated mice. Taurine also attenuated the abstinence behavior when administered during the course of dependence. The results are consistent with taurine antagonism to the known effects of morphine on intracellular calcium disposition in nervous tissue.

Analgesia↗
PubMed1983

A dual action of valproic acid upon morphine analgesia and morphine withdrawal.

Effects of valproic acid administration on morphine analgesia and on morphine tolerance and dependence were investigated in mice. Valproate increased the reaction time to thermal stimulation in naive animals. This effect was additive with morphine when valproate was administered shortly before the analgesic. However, an antagonism was observed if a 4-hour period elapsed between valproate and morphine administration. When administered to mice receiving a sustained release preparation of morphine, valproate antagonized the development of tolerance to morphine. Valproate elicited a dual action on the abstinence signs observed after naloxone administration in morphine-treated mice. The effect consisted in a reduction of abstinence behavior if the anticonvulsant was administered a few minutes before naloxone; the same treatment increased the severity of the abstinence behavior when valproate was injected 1 h before the precipitating dose of naloxone. In this latter schedule, concomitant administration of gamma-vinyl-GABA failed to reduce the severity of the convulsions observed during the abstinence syndrome. These results suggest that valproate is metabolized to a compound responsible for decreased analgesia and intensified withdrawal signs.

Analgesia↗
PubMed1982

Effects of denervation on the sensitizing effect to noradrenaline induced by morphine in the vas deferens of mice treated chronically with morphine.

The acute administration of morphine to the isolated vas deferens from mice chronically exposed to this analgesic, induced a facilitatory effect on the responses of the muscle to exogenous noradrenaline. It has been suggested that this sensitizing property of morphine might reflect a dependence-like state of the vas deferens. In the present paper, the capability of met- and leu-enkephalin to substitute for morphine was studied, as well as the influence of innervation on the apparent dependence state. The contractile responses to noradrenaline and to acetylcholine were increased after the administration of morphine to the bath containing a denervated vas deferences, prepared from chronically morphinized mice. Morphine administration facilitated noradrenaline- but not acetylcholine-induced contractile effects in vas deferens isolated from mice which had been chronically treated with either morphine or morphine plus guanethidine. The presence of met- or leu-enkephalin in the isolated vas deferens from chronically morphinized mice (either intact, denervated or treated with guanethidine) failed to sensitize contractile responses to noradrenaline or acetylcholine. It is concluded that (a) the sensitizing effect induced by morphine in the vas deferens from mice chronically treated with morphine is specific for the adrenergic neurotransmitter; (b) the effect of morphine is not mimicked by opiate peptides; and (c) denervation of the vas deferens of mice treated chronically with morphine does not suppress the noradrenaline-sensitizing property of morphine.

Acetylcholine↗
PubMed1982

Sensitivity changes after morphine treatment in the mouse uterus.

The addition of morphine to a bath containing the vas deferens from chronically morphinized mice induces a facilitatory effect on noradrenaline contractile responses. This facilitatory effect of morphine has been thought to be a dependence-like effect. In the present work the possibility that a pretreatment with morphine might induce a similar effect on the contractile responses of the mouse uterus to acetylcholine and serotonin was examined. The acute effect of morphine on the uteri of untreated mice consisted in an attenuation of the responses to both substances, whereas a long term pretreatment with morphine induced a supersensitivity state. Tolerance to the depressant action of morphine on the contractile responses induced by the stimulating compounds was also observed. Acute morphine in the uteri from morphinized mice did not induce a facilitatory effect on acetylcholine or serotonin responses. Naloxone did not modify the effects of morphine in the naive or chronically treated mice. The supersensitivity state and the intensity of tolerance were unaffected by changes in the concentration of calcium in the bath medium. Caffeine or theophylline decreased the tolerance observed in the uterus from chronically morphinized mice. The attenuation of tolerance suggests that methylxanthines induce effects opposed to those of chronic morphine in the calcium distribution within the cell.

Acetylcholine↗
PubMed1980

Effects of glycine, beta-alanine and diazepam upon morphine-tolerant-dependent mice.

The effects in mice of glycine, beta-alanine and diazepam on the analgesic response to morphine, on the intensity of tolerance and on the physical dependence on the analgesic have been examined. The two amino acids increased the analgesic response to morphine in a dose-related manner. However, both compounds were ineffective in the analgesic test (hot plate) when administered without morphine. Diazepam was ineffective in the analgesic test and it did not alter morphine analgesia, except when administered in a high dose which decreased and analgesic response. Glycine, either in single or repeated doses, did not modify tolerance to morphine, whereas beta-alanine induced a dose-related partial antagonism, which promptly reached a plateau. Diazepam induced a small decrease in the intensity of tolerance to the analgesic. The abstinence syndrome to morphine, induced by naloxone administration to primed mice, was reduced by single doses of glycine or beta-alanine. Diazepam behaved as a weak inhibitor of the abstinence syndrome when administered at a high dose. The potentiation of morphine analgesia and the antagonism of the abstinence syndrome induced by the amino acids may be related to their hyperpolarizing action in the c.n. system. The effects of beta-alanine on morphine tolerance cannot be explained by the same mechanism.

Alanine↗