THC aggravates rat muricide behavior induced by two levels of magnesium deficiency.

A severe magnesium deprivation induces an interspecific aggressive behavior (muricidal behavior, MB) in different strains of rats. Delta9-tetrahydrocannabinol (THC) is also known to induce MB even after a single injection (11 mg/kg) in starving, isolated rats. In the present work, we investigated the MB behavior, for six successive assays 1 h delayed, of two groups of male Long-Evans rats fed 50- or 150-ppm Mg(2+)-deficient diets, for 42 days after a single injection of THC at doses (2, 4 or 8 mg/kg) that did not induce aggressiveness in control rats. This treatment led to Mg(2+) plasma levels of 5+/-0.3 and 12.3+/-0.9 mg/ml vs. 21+/-1.5 mg/ml initially. In the 50-ppm Mg-deficient rat group, all the rats were muricidal but the MB pattern was severely aggravated by THC. In the 150-ppm Mg-deficient rat group, no rat was muricidal but all doses of THC induced a 100% MB. In addition, by quantifying the three phases of MB, we showed through six consecutive hourly muricidal assays, that the two first phases (attack latency and attack on the living mouse) decreased progressively, whereas the third phase (attack on the dead mouse) increased dramatically. This indicates firstly that Mg-deprivation decreases the responsiveness threshold of rats to THC. Secondly, these very low doses of THC induced an aggravation of MB and an acquired hyper-aggressiveness in both 50- and 150-ppm Mg-deficient rats, probably involving different neurotransmitters, mainly serotonin, which is decreased by both treatments.