kappa-Opioid withdrawal in Planaria
by
Raffa RB, Stagliano GW, Umeda S.
Temple University School of Pharmacy,
3307 N. Broad Street,
Philadelphia, PA 19140, USA.
robert.raffa@temple.edu
Neurosci Lett. 2003 Oct 9;349(3):139-42.

ABSTRACT

Many drug-abusers engage in poly-drug abuse, but there has been relatively little quantification of withdrawal from poly-drug use. Planarians are an advantageous model for these studies due to mammalian-relevant neurotransmitter systems (e.g. dopamine, opioid, and 5-HT). We recently developed a metric that quantified an acute cocaine withdrawal phenomenon in planarians. However, despite much indirect evidence, we lacked direct evidence of a receptor- or carrier-mediated effect. We now report dose-related, naloxone- and nor-binaltorphine-sensitive acute abstinence-induced withdrawal and naloxone-precipitated withdrawal from the kappa-opioid agonist U-50,488H (trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)-benzeneacetamide). The less active enantiomer [1R,2R]U-50,488 produced significantly less withdrawal and U-50,488H withdrawal was not due to pH or osmolarity. These data provide pharmacologic evidence of a kappa-opioid receptor-mediated withdrawal phenomenon and neuroadaptation to a pharmacologic stimulus (adaptations in transduction mechanisms) in this model.

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