Low-Dose THC Stimulation Diminished With Repetition in Female Rats

THC does not produce the same movement response at every dose or exposure history. A female-rat study found tolerance to the initial activity-increasing effects of low THC doses in both adolescent and adult animals.

The comparison included several separate drugs

Rats received saline or one of several drugs across repeated dosing periods, with locomotor activity recorded after treatment. Cocaine, ketamine, MDMA and THC were studied as separate conditions, not as one combined exposure.

The THC result differed from sensitization

The abstract reports diminishing initial stimulation with low-dose THC at both ages. Other drugs produced different adaptive patterns, including progressive increases or changes that depended on age. A repeated-drug study can therefore show tolerance for one response and sensitization for another.

Movement is not a universal impairment scale

An increase in locomotor activity does not establish improved cognition, and disappearance of that increase does not establish absence of a drug effect. The doses, timing and observation chamber determine what the result means.

The paper compared some findings with earlier male-rat work. Those historical comparisons should not be treated as a fully concurrent randomized comparison of both sexes in this experiment. These animal data help characterize endpoint-specific adaptation without establishing a safe cannabis dose, an age-specific human response or an individual driving conclusion.

Related: interpreting cannabis tolerance claims.

Research cited

Wiley JL; Evans RL; Grainger DB; Nicholson KL. Locomotor activity changes in female adolescent and adult rats during repeated treatment with a cannabinoid or club drug. Pharmacological reports : PR (2011). doi:10.1016/s1734-1140(11)70627-2. Findings discussed from the study abstract.