Effects of acute and chronic administration of cannabis sativa and (-) delta9-trans-tetrahydrocannabinol on the behavior of rats in an open-field arena

Interactions between delta9-tetrahydrocannabinol and phencyclidine hydrochloride in rats

delta9-Tetrahydrocannabinol (THC; 2.5, 5.0, 10.0 mg/kg, PO) impaired avoidance and rotarod performance, and caused bradycardia and hypothermia. Phencyclidine (PCP; 1.25, 2.5, 5.0 mg/kg, IP) impaired avoidance and rotarod performance and caused a marked increase in photocell activity. When combined, the depressant properties of each drug were enhanced and the stimulation of photocell activity cg/kg THC and its interactions with PCP followed subacute treatment for six days, whereas many of the effects of PCP were enhanced after subacute treatment with a dose of 2.5 mg/kg. Open-field behavior was affected by each drug alone and in combination in a similar way as photocell activity, but the depression caused by their interaction was greater; both drugs caused an increase in urination. Response rates on an FR-10 schedule of food reinforcement were decreased by 2.5 mg/kg PCP, but not by 5.0 mg/kg THC; the combination caused greater response suppression than either drug alone. The functional interactions between THC and PCP were not related to changes in the concentrations of 14C or 3H in plasma or brain derived from 14C-delta9-THC and 3H-PCP, respectively.

Marihuana and human physical activity

Adult male volunteers with a prior history of either moderate (N = 12) or heavy (N = 14) marihuana use were systematically observed before, during and after a 21-day period of free access to 1 g 2% delta-9 THC marihuana cigarettes. A matched sample of casual alcohol drinkers (N = 11) served as a control group. Sleep and other molar behaviors were observed hourly to obtain a representative sample of daily activity. Both moderate and heavy users were less active immediately after marihuana use and slept more on days following heavier consumption. Heavy users reduced their waking activity on days following heavier consumption, as well as during the entire period of marihuana availability. These reactions did not persist beyond the period of availability for either group. The findings suggest a dose-related delayed reaction to heavy marihuana consumption which disappears following the cessation of regular use. However, changes in activity following single doses of marihuana may be related more to the social circumstances of its use than to its pharmacological action.

Effects of delta9-tetrahydrocannabinol on social behaviour in mice: comparison between two vehicles

Two vehicles for the intraperitoneal administration of delta9-tetrahydrocannabinol (delta9-THC) were compared, using aspects of social behaviour in mice and 5 doses of delta9- THC, with vehicle alone and saline control groups. 10% propane-1,2-diol-1% Tween 80-saline (vehicle B) seemed to be more effective than 1% Tween 80-saline (vehicle A) since depressant effects of --1 delta9-THC on behaviour tended to occur at lower doses with this vehicle. Few differences in behaviour could be detected among the three control groups. In general the overall number of behavioural acts decreased with increasing doses of delta9-THC, but with vehicle B low doses selectively decreased the number of 'social' (including aggressive) as distinct from 'individual' acts. Low doses of the drug in vehicle A sometimes stimulated behaviour, whereas with vehicle B such doses mostly produced depression; however, 2.5 mg/kg delta9-THC, in either vehicle, markedly increased the percentage of animals which showed both aggression and flight acts--a rare combination among controls. Our findings are consistent with other evidence that propylene glycol is an effective vehicle for the i.p. administration of delta9-THC.

Mouse-killing and motor activity: effects of chronic delta9-tetrahydrocannabinol and pilocarpine

Chronic administration of delta9-tetrahydrocannabinol (THC) for 5--8 weeks at 4 dose levels (2, 10, 20, 50mg/kg/day) or of pilocarpine (12.5, 25 mg/kg/day) for 3 weeks induced mouse-killing in 25--70% of previously "non-killer" rats of the Sprague-Dawley strain. The maximum percent of drug-induced mouse-killing depended on the daily dose and housing conditions, 20mg/kg/day THC and 25 mg/kg/day pilocarpine in single-housed rats being the most effective treatments. Drug-induced mouse-killing appeared to be a form of behavioral pathology, differing from the species-specific predatory response, when it first appeared. Concurrent assessment of locomotor and rearing activities showed dose-dependent depressant effects of THC and pilocarpine without evidence for tolerance. Different dose-dependencies and time courses suggest that changes in motor activities are not directly linked to the appearance of the killing behavior.

Chronic administration of delta-9-tetrahydrocannabinol to pregnant rats: studies of pup behavior and placental transfer

Tritiated delta-9-tetrahydrocannabinol was administered orally to female rats throughout pregnancy at a dose level of 2 mg/kg/day. Chemical analysis of rat pup tissues indicated an average drug level near 20 ng/gm was attained via placental transfer. Although there was no teratogenicity, the pups showed both transient and relatively permanent behavioral effects. A deficit in acquisition of a passive avoidance response at 21 days of age was observed. This effect was not apparent during retraining and testing at 90 days of age. Rats whose dams had received the drug forced control animals to back out of a push tube in 67% of the tests at 21 days of age and 94% of the tests at 90 days of age.

Tolerance to the effect of delta9-tetrahydrocannabinol in mice on intestinal motility, temperature and locomotor activity

The onset and duration of tolerance to three effects of delta9-tetrahydrocannabinol (delta9-THC) given orally to mice were compared. The effects of delta9-THC studied were: hypothermia, the depression of intestinal motility and the effect on spontaneous locomotor activity. When mice were dosed and tested at 24 hrs intervals it was apparent that tolerance was complete to its hypothermic and locomotor depressant effects after the first doses and to depression of intestinal motility after the fourth dose. Duration of tolerance also differed so that the normal hypothermic response had returned after 12 dose-free days, but not after 5 drug-free days; the effect on locomotor activity had returned within 4 days; and apparent partial tolerance to the depressant effect of an acute challenging dose of delta9-THC on intestinal motility still existed after 19 dose-free days. It is apparent that the time of onset and the duration of tolerance to delta9-THC in mice showed a different pattern in the three parameters studied. It seems unlikely therefore that any one mechanism, such as metabolic tolerance, explains all the results observed and that several mechanisms should be explored to explain the phenomenon of tolerance to delta9-THC.

Pharmacologic interaction between cannabinol and delta9-tetrahydrocannabinol

The pharmacological activities of delta9-THC [(minus)-delta9-trans-tetrahydrocannabinol], CBN (Cannabinol) and mixtures of delta9-THC + CBN were studied in rabbits, rats and mice. CBN, although in general less active, mimicked the effects of delta9-THC in several pharmacological tests: corneal arreflexia in rabbits; climbing rope, open-field, irritability and aggressiveness after REM sleep deprivation in rats; catatonia, analgesia and sleeping time in mice. When the mixture delta9-THC + CBN was used, a synergistic effect occurred on most of the depressant effects. On the other hand CBN did not interfere with or slightly inhibited the excitatory effects of delta9-THC. In the one peripheral test used, CBN did not alter the delta9-THC effect.