Morphine and d-amphetamine nullify each others' hypothermic effects in mice

Area of Science:

• Pharmacology
• Neuroscience
• Toxicology

Background:

• Opioids can induce hypothermia, a complex physiological response.
• The interaction between opioids, psychostimulants, and body temperature regulation is not fully understood.
• Dopamine system modulation may influence opioid effects on thermoregulation.

Purpose of the Study:

• To investigate the effects of d-amphetamine and haloperidol on opioid-induced hypothermia.
• To differentiate between central and peripheral mechanisms of opioid-induced hypothermia.
• To explore potential clinical implications of drug interactions on thermoregulation.

Main Methods:

• Mice were injected with various opioids (morphine, fentanyl, sufentanil, loperamide) to induce hypothermia.
• Dose-response relationships were established for opioids, d-amphetamine, and haloperidol.
• Interactions were studied by co-administering opioids with d-amphetamine or haloperidol, measuring rectal body temperature.

Main Results:

• D-amphetamine reversed hypothermia induced by central opioids (morphine, fentanyl, sufentanil) but not peripheral loperamide.
• Haloperidol potentiated hypothermia from central opioids but did not affect loperamide-induced hypothermia.
• D-amphetamine showed biphasic effects on body temperature, while haloperidol induced dose-related hypothermia.

Conclusions:

• Central opioid-induced hypothermia is modulated by dopamine system alterations, unlike peripheral mechanisms.
• The combination of central opioids and d-amphetamine can lead to thermogenesis, reversing hypothermia.
• Drug interactions, particularly involving psychostimulants and opioids, have clinical implications for toxicity and hyperpyrexia.