Morphine potentiates dextromethorphan-induced vasodilation in rat superior mesenteric artery

Environmentally oriented models and methods for the evaluation of drug × drug interaction effects

This detailed review compares known and widely used methods for drug interaction estimation, some of which now have historical significance. Pharmaceutical application has been noted as far back as several thousand years ago. Relatively late in the 20th century, however, researchers became aware that their fate and metabolism, which still remain a great challenge for environmental analysts and risk assessors. For the patient's well-being, treatment based on the mixing of drugs has to be effective and should not cause any side effects (or side effects should not have a significant impact on health and mortality). Therefore, it is important to carefully examine drugs both individually and in combinations. It should be also stated that application form/way of entering the living organism is of great importance as well as the age and the place in the trophic system of the organism in order to eliminate harmful dosages in the case of infants' accidental intoxication.

Morphine, opioids, and the feline pulmonary vascular bed

BACKGROUND

Opioid-induced vasodepressor responses have been reported in a variety of species and laboratory models. The aim of this study was to ascertain the relative potencies of different clinically relevant opioids compared with traditional vasodepressor agents in the feline pulmonary vascular bed. A second aim was to study the effects of morphine and to identify the receptors involved in the mediation or the modulation of these effects.

METHODS

This was a prospective vehicle-controlled study involving an intact chest preparation of adult mongrel cats. The effects of various opioids, morphine, fentanyl, remifentanil, sufentanil, and meperidine were compared with other vasodepressor agents. Additionally, the effects of L-N(5)-(1-iminoethyl) ornithine hydrochloride (L-NIO) (nitric oxide synthase inhibitor), nimesulide [selective cyclooxygenase (COX)-2 inhibitor], glibenclamide (ATP-sensitive K+ channel blocker), naloxone (non-selective opioid receptor antagonist), and diphenhydramine (histamine H(1)-receptor antagonist) were investigated on pulmonary arterial responses to morphine and other selected agonists in the feline pulmonary vascular bed. The systemic pressure and lobar arterial perfusion pressure were continuously monitored, electronically averaged, and recorded.

RESULTS

In the cat pulmonary vascular bed of the isolated left lower lobe, morphine, remifentanil, fentanyl, sufentanil, and meperidine induced a dose-dependent moderate vasodepressor response and it appeared that sufentanil was the most potent on a nanomolar basis. The effects of morphine were not significantly altered after administration of L-NIO, nimesulide, and glibenclamide. However, the vascular responses to morphine were significantly attenuated following administration of naloxone and diphenhydramine.

CONCLUSION

The results of the present study suggest that sufentanil appears to have slightly more potency and morphine the least of the five opioid agonists studied on a nanomolar basis. Morphine-induced vasodilatory responses appeared to be mediated or modulated by both opioid receptor and histamine-receptor-sensitive pathways.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

The effect of morphine in rat small mesenteric arteries

We investigated the effect of morphine in phenylephrine (PE)- or KCl-precontracted rat small mesenteric arteries. Morphine (10(-6)-10(-4) M) administration caused concentration-dependent relaxation responses in small mesenteric arteries precontracted by PE or KCl. Removal of endothelium did not significantly alter the relaxation responses to morphine. The relaxant responses to morphine were partially inhibited by pre-treatment of tissues with naloxone (NAL, 10(-5) M) for 20 min. The inhibitory effect of NAL on relaxant responses to morphine in PE- or KCl-precontracted arteries did not differ significantly between endothelium-intact and endothelium-denuded preparations. Incubation of endothelium-intact or endothelium-denuded arterial segments with NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) or cyclooxygenase (COX) inhibitor indomethacin (10(-5) M) or histamine H(1)-receptor blocker diphenhydramine (10(-6) M), for 20 min did not inhibit the relaxation responses to morphine. Small mesenteric arterial segment contractions induced by stepwise addition of calcium to high KCl solution with no calcium were almost completely inhibited by morphine. These findings suggested that morphine-induced relaxation responses in isolated rat small mesenteric arteries were neither dependent on endothelium nor blocked by NOS or COX inhibition but they rather seem to depend on an interaction of morphine with calcium influx pathways.