DOES EARLY MATERNAL ENVIRONMENT MODIFY GENETICALLY DETERMINED ABNORMALITY IN PUBS BEHAVIOR?

Olga I. Petrenko

Laboratory of Evolutionary Genetics, Institute of Cytology & Genetics, Novosibirsk, Russia

Introduction

In contrast to a strong tendency to consider a common environment as the major cause of the parent-offspring similarity in humans, the animal behavior genetics seems to be more tolerable to the purely genetic interpretations of such similarity. However, there is some evidence indicating that, even in the case of animals, the nature-nurture dichotomy is not so simple. The findings of long-lasting effects of challenge in maternal environment on adulthood behavior may revise the traditional concept of the predominance of genetic factors in determination of animal character. In the present research, I studied the influence of changes in maternal environment by-fostering and cross-fostering on such a behavior abnormality as genetically determined predisposition to enlarged cataleptic reaction in rats. This abnormality is of interest for our group, because we assume that it might serve as a possible animal model of biological basis for a special psychopathological condition similar to that in humans (Kolpakov et al., 1996).

Method

Two rat strains - GC bred from a Wistar stock for the predisposition to catalepsy (Barykina et al., 1983), and the control Wistar stock - were used as the experimental animals. The items of natural and foster-mothers` nursing behavior were studied according to Myers et al. (1989). The pinch-induced catalepsy of the offspring was tested at the age of 2 weeks. In order to elucidate the influence of the main studied factors (genotype vs. type of fostering) and their interaction, the data were analyzed by means of two-way ANOVA with genotype and type of fostering as the main independent factors.

Results

Reciprocal pup substitution (cross-fostering) to GC and Wistar females showed the attenuation of cataleptic predisposition in GC rats fostered by Wistar foster-mothers that demonstrate more intense maternal care than GC mothers. A significant negative correlation was found between the frequency of mother return to the nest and the duration of pinch-induced catalepsy. In the home cage retrieval test of the females of the compared strains showed significant dependence of the latencies of approach to, and retrieval of the pups from the genotype (either their own or the adopted pups` genotype).

Discussion

The results suggest that the expression of catalepsy seems to be dependent not only upon the genetic predisposition as earlier was shown by Kolpakov et al. (1999), but also upon the maternal environment. Thus, the abnormality of behavior can be corrected to some extent by the mother's behavior. The maternal environment is an essential part of ontogenetic niche till weaning, and it may be considered as an envelope of deploying the intrinsic genetic program throughout the first period of life. The obtained data indicate that the attenuation of cataleptic predisposition found in GC rats nursed by Wistar foster-mothers might be caused by better nursing of the Wistar foster-mothers of the adopted GC pups compared to the nursing of the biological mothers. It is possible that the predisposition to catalepsy includes the elements of anaclitic depression known in humans.

Conclusion and application

These data are in accordance with several other studies suggesting that the changes of maternal environment can modify in a specific way the influence of some genetically determined behavioral characteristics, i. e. mother behavior can correct certain inherited abnormalities. Besides, these results support earlier evidence of the importance of interaction between mother and her children for the development of normal children's mentality. This is especially true for human as the most social (eusocial) mammals.

Acknowledgement

This project was carried out at the Institute of Cytology & Genetics under supervision of Viktor Georgievitch Kolpakov, Doctor of Science. I also thankful to T.A. Alekhina, N.N. Barykina, and V.F Chuguy for the support of this research.