Behavioral effects of hashish in mice. II. Nursing behavior and development of the sucklings

Adult mice were treated from parturition to weaning of their first litter with a hashish extract containing 40% delta 9-tetrahydrocannabinol (delta 9-THC), 45% cannabidiol, 9% cannabinol, and 6% other cannabinoids. Oral administrations of 20 mg delta 9-THC/kg three times a week decreased the weight gain of pups from days 3-6 and 6-10 significantly, resulting in about 15% lower body weights on days 6 and 10 compared with control sucklings. Other parameters of development such as the general appearance of the pups were little affected, except for a slight tendency by day 13, when some additional control pups already had both eyes open. The effects of hashish in sucklings might be caused by drug intake with mother's milk, as well as by a decreased lactation of drugged dams. In addition, our pup retrieving tests at the day 3, 1.5-2 h after the second application of hashish extract, showed a decrease in the mother's locomotive and nonsocial activities and pointed to at least transient impairment of the maternal behavior. By day 10, after the fifth administration of hashish extract, a partial tolerance occurred, with normal care for the young, but still decreased nonsocial activities of the drugged dams. Thus our experiments showed distinct effects of cannabis on mice litters when the parents were drugged postnatally during the period of lactation only.