Search PubMed⌕ Search

Biomedical subjects

E Contreras

Publications and source records attributed to E Contreras.

101 records · Page 6Linked to original sources
PubMed1970

Hyposensitivity to drugs induced by morphine and some related substances in the cat.

1. Hyposensitivity to noradrenaline occurred concomitantly with morphine tachyphylaxis in the absence of any obvious depressant effect on the heart or peripheral circulation.2. The actions of adrenaline, noradrenaline and angiotensin and, occasionally, other drugs were tested before and after repeated injections of morphine or one of ten related substances in various preparations of the spinal cat.3. Tachyphylaxis in response to morphine could be related to a simultaneous decrease in the tissue responses to adrenaline, noradrenaline and angiotensin but such a parallelism has not been shown for the substances related to morphine.

Angiotensin II↗
PubMedDate not supplied

Effect of ethanol on human placental transport and metabolism of adenosine.

It has been suggested that adenosine is involved in the acute effects of ethanol in a number of tissues. The present study was undertaken to evaluate the role of adenosine on the vascular responses of perfused isolated human placental cotyledons after the acute administration of ethanol. The possibility that ethanol may effect the uptake and metabolism adenosine was also investigated. Uptake of adenosine was studied using the single-circulation paired-tracer dilution technique. Both adenosine and ethanol caused a dose-related increase in perfusion pressure of placental lobules. Pharmacologically relevant concentrations of ethanol (10-65 mM) significantly inhibited the uptake of [3H]adenosine between 25 and 50 per cent. Thin-layer chromatographic analysis of the perfusate after the administration of ethanol showed in a 17.9 +/- 0.6 per cent reduction of [3H]adenosine metabolism. These findings support the working hypothesis that placental adenosine, at least partially, mediates the placental disturbance elicited by the administration of acute ethanol, which may contribute to the pathogenesis of fetal alcohol syndrome.

Adenosine↗
PubMedDate not supplied

Diazepam, adenosine analogues and calcium channel antagonists inhibit the contractile activity of the mouse urinary bladder.

The main neurotransmitter of the mouse urinary bladder is ATP, which is hydrolyzed to AMP and adenosine; the latter compound, in contrast to ATP, relaxes the smooth muscle. Diazepam also relaxes the urinary bladder and, since some peripheral and central effects of the benzodiazepines are thought to be induced by inhibition of adenosine uptake or by inhibiting calcium channels, the effects of diazepam, adenosine, R-phenylisopropyladenosine, cyclohexyladenosine, and of the calcium channel antagonists, diltiazem, verapamil and nifedipine, were studied on the contractile responses of the mouse isolated urinary bladder. The contractile responses of the bladder's smooth muscle were elicited by transmural stimulation and by application of ATP or acetylcholine. All drugs mentioned decreased the contractile responses of the bladder. The inhibitory effect of diazepam was similar to that induced by adenosine, R-phenylisopropyladenosine, cyclohexyladenosine, and nifedipine. 8-Phenyltheophylline, an adenosine receptor antagonist, did not decrease the relaxatory response of diazepam, which might exclude a P1 purinoceptor-mediated mechanism in the response studied. Diazepam did not significantly change the inhibitory effects of diltiazem and nifedipine on the contractile response to acetylcholine. The similar patterns of relaxant effects, exerted by diazepam, adenosine analogues and calcium channel antagonists, suggest the interference of benzodiazepine, and adenosine and its analogues on calcium channels of the urinary bladder smooth muscle. The inability of diazepam to further increase the effects of diltiazem and nifedipine on the responses to acetylcholine, reinforces the hypothesis that diazepam is acting through a common mechanism with calcium antagonists.

Acetylcholine↗