Interaction of experience with adrenal and sex hormones on the behaviour of hamsters in the open field test

Abstract

The behaviour of hamsters in the open field can be influenced by many environmental and hormonal factors. The sexual dimorphism in ambulation characteristic of mature animals was not evident before puberty. Weanlings of both sexes were much more active than adults. Pre-pubertal testing prevented the later expression of this sex difference. The ambulation score of mature females which had been tested at weaning was lower than that of naive females of the same age and similar to that of males. Other sex-differences, e.g. increased rearing in the open field and more rapid emergence from a box, were also abolished by pre-pubertal testing of females. Previous testing did not affect the behaviour of males. The sex-typical behaviour pattern persisted in naive animals gonadectomized after puberty and subsequently tested, which suggested that sex hormones are not directly involved in the mediation of open field behaviour. The effect of early handling on increasing ambulation was confirmed. Whether or not the adrenals take part in the mediation of this effect in infancy, the adult behavioural response to the open field situation appears to be independent of the adrenals since it was unaffected by adrenalectomy.