Comparison of the development of the fatty acid content and composition of the brain of a precocial species (guinea pig) and a non-precocial species (rat).

The fatty acid compositions of the brains of a precocial (guinea pig) and a non-precocial (rat) species have been studied as a function of development. In the rat brain the total fatty acid content expressed as mg g wet wt.-1 increased more than fourfold during the period from 5 days after birth to adulthood. However, the percentage composition of this total fatty acid content when expressed per individual fatty acid remained fairly constant, with the exception of nervonic acid (C24:1) which also increased fourfold on a percentage basis. In the guinea pig brain, however, at birth the total fatty acid content, expressed as mg g wet wt-1, is the same as that of the adult, the concentration doubling during the period from 25 days before birth until birth. Again, if the fatty acid content is analysed and expressed on a percentage basis, the relative concentrations of the individual fatty acids remain fairly constant over the period from 25 days before birth until adulthood, with the exception of nervonic (C24:1) acid which increases about fivefold from 25 days before birth to birth and only marginally (20%) from birth to adulthood. These results are discussed in relationship to the onset of neurological competence in the two species. It is concluded that the increase in fatty acid content (both total and individually) of the brains of these species as a function of the foetal and neonatal development follows a pattern which is similar to the pattern of development of certain key enzymes of energy metabolism and of neurological competence.