Interaction between naloxone and serotonin in the control of the cardiovascular system in hemorrhaged cats.
We investigated the mechanism for the pressor effect of intravenous administration of naloxone in pentobarbital-anesthetized cats. Comparisons were made between groups of hemorrhaged animals that received either naloxone or an equivalent volume of saline after 1 h of hemorrhage. Two other groups of hemorrhaged animals were depleted of serotonin by pretreatment with para-chlorophenylalanine 40-48 h before the experiment. One group of serotonin-depleted animals received naloxone after 60 min of hemorrhage and the other group received saline. Animals with normal brain serotonin content showed a significant pressor effect following naloxone when compared with animals given saline. Animals with reduced brain serotonin content also had a pressor response following naloxone administration. Serotonin-depleted animals showed an increase in maximum left ventricular dP/dt following naloxone administration when compared to serotonin-depleted animals given saline. Our data are consistent with the hypothesis that naloxone can exert a pressor effect in hemorrhaged cats by actions at central and at peripheral sites. In cats with normal serotonin values, the peripheral action of naloxone is predominant. In serotonin-depleted animals given naloxone, central and peripheral sites contribute to the pressor effect.
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D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D002415:Cats; D004347:Drug Interactions; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D006470:Hemorrhage / Q000503:physiopathology*; D007427:Intracranial Pressure / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D012701:Serotonin / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects; D013997:Time Factors
D012701:Serotonin; D009270:Naloxone