THC and CBD Adaptation Varied Across Three Mouse Seizure-Threshold Tests

A 1980 mouse study found that repeated THC could produce tolerance, no change or increased sensitivity depending on the seizure-threshold test. CBD also varied by test, so one experimental threshold did not represent all anticonvulsant activity.

Electrical stimulation paradigms were compared

Researchers examined maximal, 60-Hz and 6-Hz electroshock-threshold tests after subacute cannabinoid or conventional anticonvulsant treatment. THC tolerance appeared in the maximal test, while activity was unchanged in the 60-Hz test and sensitivity increased in the 6-Hz test. CBD did not show tolerance in the tested paradigms.

Withdrawal excitability was another endpoint

After THC cessation, increased excitability appeared in selected tests. Phenobarbitone withdrawal also produced test-specific hyperexcitability. These findings concern electrically induced responses in mice, not a direct count of spontaneous seizures in patients.

Historical clinical speculation is not clinical proof

The authors raised concern about seizure control based on the withdrawal results. That proposal does not establish the effect of every cannabis formulation in people with epilepsy. Purified compounds, repeated dosing, withdrawal conditions and seizure types require separate evaluation.

The experiment demonstrates strong dependence on how seizure-related activity is operationally tested. It cannot establish a treatment recommendation or justify changing prescribed therapy. The important evidentiary distinction is among anticonvulsant action during dosing, adaptation over time and excitability after cessation.

Related: interpreting cannabis tolerance claims.

Research cited

Karler R; Turkanis SA. Subacute cannabinoid treatment: anticonvulsant activity and withdrawal excitability in mice. British journal of pharmacology (1980). doi:10.1111/j.1476-5381.1980.tb14562.x. Findings discussed from the study abstract.