Fasting and exercise increase plasma cannabinoid levels in THC pre-treated rats: an examination of behavioural consequences
- Alexander WongAffiliated withThe Discipline of Pharmacology, The University of Sydney
- , Kirily KeatsAffiliated withThe School of Psychology, The University of Sydney
- , Kieron RooneyAffiliated withThe Discipline of Exercise and Sport Science, The University of Sydney
- , Callum HicksAffiliated withThe School of Psychology, The University of Sydney
- , David J. AllsopAffiliated withThe School of Psychology, The University of Sydney
- , Jonathon C. ArnoldAffiliated withThe Discipline of Pharmacology, The University of Sydney
- , Iain S. McGregorAffiliated withThe School of Psychology, The University of Sydney Email author
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Δ9-Tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, accumulates in fat tissue where it can remain for prolonged periods. Under conditions of increased fat utilisation, blood cannabinoid concentrations can increase. However, it is unclear whether this has behavioural consequences.
Here, we examined whether rats pre-treated with multiple or single doses of THC followed by a washout would show elevated plasma cannabinoids and altered behaviour following fasting or exercise manipulations designed to increase fat utilisation.
Behavioural impairment was measured as an inhibition of spontaneous locomotor activity or a failure to successfully complete a treadmill exercise session. Fat utilisation was indexed by plasma free fatty acid (FFA) levels with plasma concentrations of THC and its terminal metabolite (-)-11-nor-9-carboxy-∆9-tetrahydrocannabinol (THC-COOH) also measured.
Rats given daily THC (10 mg/kg) for 5 days followed by a 4-day washout showed elevated plasma THC-COOH when fasted for 24 h relative to non-fasted controls. Fasted rats showed lower locomotor activity than controls suggesting a behavioural effect of fat-released THC. However, rats fasted for 20 h after a single 5-mg/kg THC injection did not show locomotor suppression, despite modestly elevated plasma THC-COOH. Rats pre-treated with THC (5 mg/kg) and exercised 20 h later also showed elevated plasma THC-COOH but did not differ from controls in their likelihood of completing 30 min of treadmill exercise.
These results confirm that fasting and exercise can increase plasma cannabinoid levels. Behavioural consequences are more clearly observed with pre-treatment regimes involving repeated rather than single THC dosing.
KeywordsAdipocytes Cannabis Food deprivation Lipolysis THC Exercise Reintoxication Fat Cannabinoids
- Fasting and exercise increase plasma cannabinoid levels in THC pre-treated rats: an examination of behavioural consequences
Volume 231, Issue 20 , pp 3987-3996
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- 1. The Discipline of Pharmacology, The University of Sydney, Darlington, NSW, 2006, Australia
- 2. The School of Psychology, The University of Sydney, Darlington, NSW, 2006, Australia
- 3. The Discipline of Exercise and Sport Science, The University of Sydney, Darlington, NSW, Australia