It has been reported that female rats retain passive avoidance behavior more poorly than males (3, 5). The purpose of this study was to investigate the hormonal determinants of sex differences in passive avoidance behavior.
On the first two days, each rat was placed in the white compartment of a black/white chamber and allowed to enter the black compartment. On Day 3, the rat was shocked upon entering the black compartment. During the retention session (on Days 4-10), shocks were not given and the number of trials was counted on which the rat entered the black compartment within five minutes.
Among control animals, females entered the black compartment within five minutes more frequently than did males in the retention session. Gonadectomy of both sexes in adulthood eliminated this sex difference (Exp. I). Neonatal castration produced males whose passive avoidance behavior was indistinguishable from that of females (Exp. II), while neonatal testosteron injections masculinized female behavioral patterns (Exp. III).

View full abstract

The experiment here described constitutes the first step in an attempt to compare spontaneous tool use and tool making in captive chimpanzees and other primates, with a view to elucidate the basis of the more frequent and diverse types of tool use observed in wild chimpanzees. A milk bottle, filled up to 3 cm. with fruit juice was secured outside the cage within reaching distance of two young female chimpanzees (7 year old). Foliage was provided in the cage as a potential material for sponge making. The uses of foliage for absorbing and drinking juice were observed. Experiments, lasting 1 hour each, were repeated 21 times over a period of 4 months. A stepwise progression was seen in the successively appearing behaviors : from introducing leaves in the bottle, withdrawing them with a finger and licking, to the use of twigs of various lengths and finally to the munching of the extremity of a branch into spongelike condition. Nevertheless, it is important to notice that new modes of tool use did not replace earlier and less efficient ones. Also, though a newly discovered particularly efficient mode of tool use tended to be practiced intensively at the beginning of the next session, in general various of tool use appeared in any given order, regardless of their order of invention. Though the stepwise progression in the use and modification of the available material would seem to indicate that the animal acquired steadily a more accurate grasp of the situation and aimed at the production of increasingly efficient drinking tools, the apparently random alternation of various modes of tool use fails to support this interpretation. Comparison with a similar experiment undertaken by LETHMATE (1976) with young orangs reveals overall similarities and some differences partly due, perhaps, to the slightly different experimental setup.

View full abstract

This experiment was conducted to examine the effect of change of catecholamine (CA) by catecholaminergic drug on animal emotional behavior. 32 male wister strain albino rats were randomly allocated to one of four groups. As summerized in Table 1, α-methyl-p-tyrosine (α-MT, 75 mg/kg, i. p.), namely CA synthesis inhibitor was administered 4.5hr. before test for Group A and Group AD. For Group D and Group AD, L-DOPA (50 or 100 mg/kg, i. p.), namely the precursor of CA was administered 1.5 hr. before test. For Group S, saline was administered. Animals were tested by conditioned emotional response (CER) in operant conditioning in Skinner box.
L-DOPA significantly increased conditioned suppression in CER. α-MT alone did not affect conditioned suppression in CER, but pretreatment of α-MT significantly suppressed the increase of conditioned suppression by L-DOPA (Fig. 2, Fig. 3). According to the above results, it is supposed that increase of CA by L-DOPA enhanced emotionality and CER in Skinner box, whereas α-MT suppressed the enhancement of emotionality by L-DOPA. It was suggested that CER test measure is sensitive to slight increase of CA by low dose of L-DOPA.

View full abstract

[in Japanese]

View full abstract