The effects of male parents on later parental behavior of their pups were investigated in ICR mice. Male parents were vasectomized to prevent female parents from giving birth to the second litter before weaning of the first one. The subjects were reared by a female parent alone or by both parents until 30 days old. When they were exposed to stimulus pups at 10-11 weeks of age (Exp. 1), their parental behaviors didn't differ from each other for their rearing conditions. However, when they were tested after experiencing copulation (Exp. 2), nest-building significantly decreased in the females reared by both parents. These results suggest that in mice the effects of cohabitation with a male parent in the early rearing environment on parental behavior were modifiable by the experience of copulation, but such effects were largely limited.

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This study examined the effects of administration of anticholinergic drugs and medial septum lesion on the performance of the successive delayed matching-to-sample (S-DMTS) task in rats in order to clarify the relationship between the central cholinergic system and the modality effect in rats' short-term memory. A pair of visual and/or auditory stimuli was presented with delay intervals to rats. They were required to distinguish whether the modality of the 2nd stimulus (S2) for the pair was the identical to or different from that of the 1st stimulus (S1). Scopolamine at 0.03-0.1mg/kg (i. p.) and mecamylamine at 1-3mg/kg (i. p.) disrupted the performance of S-DMTS task irrespective of the modality of S1, whereas methyl-scopolamine and hexamethonium did not. These results suggest that muscarinic and nicotinic receptors in rats' brain are correlated with short-term memory for both visual and auditory stimuli. Lesion to medial septum also disrupted the performance of S-DMTS task when the visual stimulus was presented as S1, however, the performance was not changed when the auditory stimulus was employed. These findings suggest that the medial septum is correlated with the mnemonic processes of visual but not of auditory stimuli.

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Food-carrying behavior in foraging situation is supposed to be affected by risk avoidance tendency. In the present study, food-carrying behavior for 190, 300, 500, and 750mg food pellets was compared in Tsukuba High and Low Emotional strains (THE and TLE) of rats. Food-carrying ratios of THE did not differ among all sizes of food, while those of TLE significantly increased as the food size became larger. Although there was no significant difference in the ratio between two strains for each food size, the ratios of TLE were relatively higher than those of THE except for the smallest food. These results imply that food carrying is not affected by risk avoidance based on the emotionality. However, ‘emotionality’ in THE and TLE is supposed to be defined as the reactivity to novel situations, so it might be different from emotion of fear and/or anxiety necessary for risk avoidance tendency to affect food carrying postulated here. Further studies are necessary to ascertain the postulate.

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