The Journal of Neuroscience, December 15, 2000, 20(24):9284-9289
Cannabinoid Withdrawal Syndrome Is Reduced in
Pre-Proenkephalin Knock-Out Mice
Olga
Valverde1,
Rafael
Maldonado1,
Emmanuel
Valjent1,
Anne M.
Zimmer2, and
Andreas
Zimmer2
1 Laboratori de Neuropharmacologia, Facultat de
Ciéncies de la Salut i de la Vida, Universidat Pompeu Fabra,
08003 Barcelona, Spain, and 2 Laboratory of Genetics,
National Institute of Mental Health, Bethesda, Maryland 20892
The functional interactions between the endogenous
cannabinoid and opioid systems were evaluated in
pre-proenkephalin-deficient mice. Antinociception induced in the
tail-immersion test by acute
9-tetrahydrocannabinol was reduced in
mutant mice, whereas no difference between genotypes was observed in
the effects induced on body temperature, locomotion, or ring catalepsy.
During a chronic treatment with
9-tetrahydrocannabinol, the
development of tolerance to the analgesic responses induced by
this compound was slower in mice lacking enkephalin. In addition,
cannabinoid withdrawal syndrome, precipitated in
9-tetrahydrocannabinol-dependent mice by the injection of SR141716A,
was significantly attenuated in mutant mice. These results indicate
that the endogenous enkephalinergic system is involved in the
antinociceptive responses of
9-tetrahydrocannabinol and participates
in the expression of cannabinoid abstinence.
Key words:
cannabinoid; opioid; mice; mutation; withdrawal; addiction; tolerance
Copyright © 2000 Society for Neuroscience 0270-6474/00/20249284-06$05.00/0