The rodent as an experimental tool in gerontological research

Advances in basic gerontology has has brought along numerous methodological questions among which the growth-persistency as a function of ageing of the rodents, particularly the rat, plays an intriguing role. The fact that, the rat's growth may proceed for more than half of the lifetime was confirmed by many authors. Whether the senescent loss in body weight is induced by the subnormal food and water intake in old age, or rather, the former leads to the latter, has not yet settled. It is suggested however, that the apparent detrimental losses in masticatory function; i.e. defects of the maxillary incisors of the aged animals exert food consumption by all accounts. This can be either the consequence or cause of the unessential loss of body weight well before death. The reasons which explain the startling pecularity concerned of the rodents must be sought in the phylogenetical backgrounds of these species. Most of them are still in their flourishing-evolutionary period of the present. These small-sized, omnivorous, highly-variable animals are non-specialized but labile/flexible species to convert according to our requirements. Neverthless, particular attention should be paid when treating these animals, as rather primordial species, whose one or more characteristics, i.e. persistency in growth merit a special caution of gerontologists.