The effect of ageing on RNA content in neurons from the thalamic reticular nucleus visual sector

In this paper we investigate nucleic acid content in neurons from the dorsocaudal region of the thalamic reticular nucleus in ageing Wistar rats. Nucleic acid per surface unit was analysed by calculating mean extinction using cytophotometric methods. Once the mean extinction and nuclear and cytoplasmic areas were known, nucleic acid total content was calculated. There was an increase in nucleic acid total content and in nuclear and cytoplasmic areas from the age of 3 months onwards. We interpreted these findings as a compensatory response, by 'neuronal hypertrophy', to the deterioration process occurring in the ageing rats. Between the 24th and 30th month, i.e. old age, nucleic acid per surface unit and total content in the cytoplasm exhibited a considerable decrease.