Latest research on Morphine

The principal alkaloid in opium and the prototype opiate analgesic and narcotic. Morphine has widespread effects in the central nervous system and on smooth muscle. [PubChem]

Latest findings

Furthermore, when animals breathing 5% CO2 in air were administered Morphine (10 mg/kg), there was no significant decrease in plasma corticosterone levels (177.4±20.7 ng/ml, N=10, data were compared using one-way ANOVA with Bonferroni's comparison). [source, 2016]
These results indicate that Morphine depressed respiration directly and not through an indirect anxiolytic mechanism. [source, 2016]
To induce tolerance to Morphine, we exposed animals to Morphine continuously for up to 6 days by implanting a Morphine pellet (75 mg) subcutaneously. [source, 2016]
Animals that had been implanted with a Morphine pellet showed significant respiratory depression (Figure 2a) as well as antinociception in the tail-flick latency test (Figure 2b) when tested 1 day later, whereas those animals that received a placebo pellet did not. [source, 2016]
Although the depression of respiration declined on subsequent days, it did not reach pre-pellet levels until 5 days after pellet implantation even though the levels of Morphine in the brain and plasma were still elevated (Figure 2c and d). [source, 2016]
The plasma level of Morphine after 6 days of pellet implantation was only slightly lower than that achieved in naive mice following injection with 10 mg/kg Morphine (compare data in Figure 2c and d). [source, 2016]
In contrast to respiratory depression, tail-flick latencies returned to baseline 2 days after pellet implantation at a time when plasma Morphine levels were still raised (Figure 2d). [source, 2016]
This suggests that tolerance develops to the antinociceptive effects of Morphine more rapidly than to its respiratory depressant effect. [source, 2016]
To investigate further the different time courses of tolerance development between the respiratory depressant and antinociceptive effects of Morphine, we injected mice twice daily with Morphine (10 mg/kg i.p.) for 5 days and measured respiration and tail-flick latency after the second injection on each day (Figure 2e and f). [source, 2016]
The injection of Morphine produced a lower brain level of Morphine than Morphine pellet implantation (Figure 2c). [source, 2016]