kappa-Opioid withdrawal in Planaria.

Area of Science:

• Neuroscience
• Pharmacology
• Addiction Research

Background:

• Poly-drug abuse is common, but withdrawal quantification is limited.
• Planarians possess mammalian-relevant neurotransmitter systems, making them a suitable model.
• Previous work quantified cocaine withdrawal in planarians, but receptor mechanisms were unclear.

Purpose of the Study:

• To provide direct pharmacologic evidence of kappa-opioid receptor-mediated withdrawal in planarians.
• To investigate neuroadaptation to kappa-opioid receptor stimulation.
• To characterize withdrawal precipitated by the kappa-opioid agonist U-50,488H.

Main Methods:

• Administered the kappa-opioid agonist U-50,488H to planarians.
• Assessed withdrawal responses dose-dependently.
• Utilized opioid receptor antagonists (naloxone, nor-binaltorphine) to block withdrawal.
• Compared withdrawal effects of U-50,488H and its less active enantiomer.
• Ruled out withdrawal due to changes in pH or osmolarity.

Main Results:

• U-50,488H induced dose-related, naloxone- and nor-binaltorphine-sensitive withdrawal.
• The less active enantiomer of U-50,488H produced significantly less withdrawal.
• Withdrawal was not attributable to pH or osmolarity changes.
• Demonstrated acute abstinence-induced withdrawal.

Conclusions:

• These findings provide pharmacologic evidence for kappa-opioid receptor-mediated withdrawal in planarians.
• The study supports the role of neuroadaptation to pharmacologic stimuli in this model.
• Planarians serve as a valuable model for studying opioid withdrawal mechanisms.