Cannabis-Fed Mice Showed Temperature Tolerance Without Detected Brain Radiolabel Changes
A 1973 mouse study found tolerance to THC hypothermia without a detected change in brain radioactivity assigned to THC or its metabolites. The same exposure history did not produce tolerance on an immobility measure.
Voluntary consumption preceded an injected challenge
Mice consumed cannabis in milk for fifteen days before receiving radiolabeled THC intravenously. The exposure route and later challenge route differed. This was neither ordinary dietary endocannabinoid signaling nor a modern consumer-product trial.
Two endpoints gave different answers
Cooling became tolerant, while the immobility index remained responsive. The result limits a general claim that the animals had become insensitive to THC. It also demonstrates why one physiological response cannot stand in for all behavioral effects.
The chemical finding constrained a metabolic explanation
Researchers detected no corresponding change in brain radioactivity assigned to the parent compound or metabolites. They concluded that altered metabolism or distribution did not explain the hypothermic tolerance in this model. That assay-specific result does not exclude every exposure difference at every time or establish a modern active-THC concentration threshold.
The study provides a functional-versus-chemical comparison after voluntary cannabis intake. It does not determine human impairment from a measured concentration or establish that tolerance always occurs without pharmacokinetic change. The particular endpoint, matrix and analytical method remain central.
Related: interpreting cannabis tolerance claims.
Research cited
Lawrence DK; Pertwee RG. Brain levels of delta1-tetrahydrocannabinol and its metabolites in mice tolerant to the hypothermic effect of delta1-tetrahydrocannabinol. British journal of pharmacology (1973). doi:10.1111/j.1476-5381.1973.tb08388.x. Findings discussed from the study abstract.
