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Biomedical subjects

M D Carceles

Publications and source records attributed to M D Carceles.

5 recordsLinked to original sources
PubMed1991

Naloxone modifies the inotropic decrease induced by halothane on isolated left atria.

1. The present study evaluates the interaction between naloxone and halothane on the left atria. 2. Halothane produced significant decrease in auricular inotropism at concentrations ranging from 0.3 to 2.5 v/v%. 3. Naloxone modified the concentration response curve to halothane. The antagonism between both drugs is consistent with a competitive antagonism since the curve obtained had a slope which did not differ significantly from -1. 4. These results suggest that the negative inotropic effects induced by halothane could be mediated by opioid receptors.

Animals↗
PubMed1990

Interaction between halothane and morphine on isolated heart muscle.

The present study describes the effects of halothane on morphine activity in the isolated left atria of the rat. Concentration-response curves were obtained for the negative inotropic effects of morphine on electrically stimulated left atria. Morphine significantly decreased the contractile force, with an inhibitory concentration 16 (IC16) of 3.130.698 +/- 22.5 X 10(-9) M. The opiate agonist was more potent in reserpinized rats, causing a consistent negative inotropic action over a wide range (10(-8)-10(-4) M) or morphine concentrations. The IC16 of morphine was significantly (P less than 0.001) decreased in the presence of 1.5% v/v halothane. The administration of L-naloxone (3 X 10(-7)-10(-6) M) but not D-naloxone (10(-6) M) antagonized the inhibitory effects of morphine in the presence of halothane. These results demonstrate that halothane increases the potency of morphine on the isolated left atria and suggest that this effect is mediated by opioid receptors.

Animals↗
PubMed1989

Interactions between diltiazem and inhalation anaesthetics in the isolated heart.

It has been postulated that inhalation anaesthetics may interfere with calcium movement across cell membranes. We have evaluated the interaction between diltiazem and the inhalation anaesthetics halothane and isoflurane on sinus automaticity in the isolated right atrium (SAIRA). Isoflurane significantly reduced atrial rate at all concentrations tested. However, halothane produced only a small but significant decrease at the higher concentrations used (1-2 v/v%). Diltiazem modified the maximal negative chronotropic response to inhalation anaesthetics. Maximum depression of SAIRA was significantly greater in the presence of two different doses of diltiazem compared with exposure to halothane and isoflurane alone. These results suggest that inhalation anaesthetics may block the influx of extracellular calcium through voltage-dependent calcium channels inhibited by diltiazem.

Animals↗
PubMed1989

Effects of halothane, isoflurane and enflurane on isolated rat heart muscle.

Since the effects in the intact organism are complicated by central as well as peripheral effects, we compared the direct cardiac effects of three commonly used inhalational anaesthetics--halothane, isoflurane and enflurane--on isolated heart muscle. Concentration-response curves for inotropic, chronotropic and ventricular automaticity effects of halothane, isoflurane and enflurane (0.1-2% v/v) on electrically stimulated left atria, right atria and right ventricles of the rat were obtained. All three inhalational anaesthetics significantly decreased contractile force; the inhibitory concentration 50 (IC50) of enflurane was 0.55 +/- 0.06% v/v, significantly lower than halothane (0.96 +/- 0.08% v/v) and isoflurane (0.67 +/- 0.05% v/v). Similar results were obtained on atrial nomotopic rate. Halothane, isoflurane and enflurane produced negative chronotropic effects in this preparation. On the other hand, halothane and isoflurane significantly reduced the ventricular ectopic automaticity. However enflurane (0.3, 0.5, 1% v/v) increased ventricular rate. There were statistically significant differences between the IC50 values of atrial and ventricular rate for halothane and isoflurane. These results indicate: (a) direct negative inotropic and chronotropic effects for the three inhalational anaesthetics tested; (b) anti-dysrhythmic actions for halothane and isoflurane; and (c) dysrhythmogenic effects of enflurane.

Animals↗