http://www2.cnrs.fr/en/1469.htm
Paris, July 3, 2009

The surprising effect of cannabis on morphine dependence

In order to study psychiatric disorders, neurobiologists use animal models, especially
maternal deprivation models. Depriving rats of their mothers for several hours a day
after their birth leads to a lack of care and to early stress. The lack of care, which
takes place during a period of intense neuronal development, is liable to cause lasting
brain dysfunction. Valérie Daugé’s team at the Laboratory for Physiopathology of
Diseases of the Central Nervous System (UPMC / CNRS / Inserm) analyzed the effects
of maternal deprivation combined with injections of tetrahydrocannabinol, or THC,
the main active principle in cannabis, on behavior with regard to opiates.

Previously, Daugé and her colleagues had shown that rats deprived of their mothers
at birth become hypersensitive to the rewarding effect of morphine and heroin
(substances belonging to the opiate family), and rapidly become dependent. In
addition, there is a correlation between such behavioral disturbances linked to
dependence, and hypoactivity of the enkephalinergic system(1), the endogenous
opioid system.

To these rats, placed under stress from birth, the researchers intermittently
administered increasingly high doses of THC (5 or 10 mg/kg) during the period
corresponding to their adolescence (between 35 and 48 days after birth). By
measuring their consumption of morphine in adulthood, they observed that, unlike
results previously obtained, the rats no longer developed typical morphine-dependent
behavior. Moreover, biochemical and molecular biological data corroborate these
findings. In the striatum, a region of the brain involved in drug dependence, the
production of endogenous enkephalins was restored under THC, whereas it
diminished in rats stressed from birth which had not received THC.

Such animal models are validated for understanding the neurobiological and
behavioral effects of postnatal conditions in humans. In this context, the findings
point to the development of new treatments that could relieve withdrawal effects and
suppress drug dependence.

[graph - see url at top]

Study of oral morphine (25 mg/L) self-administration behavior in the maternal
deprivation model. Deprived rats progressively increased their preference for the
bottle of morphine, whereas deprived rats treated with THC did not develop such
escalation behavior. *P<0.05, **P<0.01, ***P<0.001 vs morphine group.

P.-S.

Notes:

1] The enkephalinergic system produces endogenous enkephalins, which are
neurotransmitters that bind to the same receptors as opiates and inhibit pain
messages to the brain.

References:

Adolescent Exposure to Chronic Delta-9-Tetrahydrocannabinol Blocks Opiate
Dependence in Maternally Deprived Rats - Lydie J. Morel, Bruno Giros and Valérie
Daugé. Neuropsychopharmacology 24 June 2009, PMID: 19553915.

Contact information:

Researcher

Valérie Daugé l T 01.44.27.61.09 l This e-mail address is being protected from spambots. You need JavaScript enabled to view it

CNRS press office

Elsa Champion l T 01.44.96.43.09 l This e-mail address is being protected from spambots. You need JavaScript enabled to view it