The effects of ethanol exposure on radial arm maze learning and behavior of offspring rats.

The effects of maternal drinking on offspring have been studied epidemiologically, in human beings, and experimentally, in rats. The physical growth of offspring of female alcoholic rats, including histological growth of brain, lung, thymus gland, liver, and kidney, was previously reported by us. In the present study, we observed the effect of ethanol intake by the mother rat on learning ability and behavior of offspring rats using an eight radical arm maze. At the same time histological observations of the cerebrum were carried out. The mother rat was exposed to ethanol from a young age to delivery (P-DEL) or to weaning (P-NURS). After weaning, the offspring was exposed to ethanol until the tests began (P-WEAN). Experimental groups, classified by length of ethanol exposure, as mentioned above, disclosed the following: (1) Number of trials required for fulfilling learning criterion was significantly large in P-DEL and P-NURS rat groups relative to the controls; that is, P-DEL and P-NURS rats were slow in learning. (2) Numbers of rats which did not fulfill the learning criterion were: Group P-DEL, one male of eight; Group P-NURS, three males of seven. The behavior of the rats in Group P-WEAN differed from those in other groups; while they were receiving acclimation training, they were, unlike ordinary rats, not watchful of the device, slow to find the feed, and indifferent. They seemed to lack carefulness and sometimes failed to eat the feed even though they succeeded in selecting correct arms. Their motion was abrupt and they ran at extraordinarily high speeds. (3) In the observations of correct choices in the first eight choices, groups P-DEL and P-NURS showed significantly low values. This suggested the lowering of their learning ability. (4) In the observations of continuous correct choices, Group P-DEL showed a significantly low value. This suggested the rats did not learn thoroughly enough to retain their acquisition long. (5) Body weight, learning ability, and hippocampal neurons were affected by ethanol exposure more severely in Group P-NURS than in Group P-DEL. An even more severe effect was observed in Group P-WEAN.