THE EFFECT OF AGE ON DENDRITES IN THE RAT SUPERIOR CERVICAL-GANGLION

Intracellular injection of a biotinylated probe in fixed superior cerv ical ganglia followed by confocal microscopy was used to investigate t he effects of age on the dendritic arborisation of sympathetic neurons in rats aged 6 wk (young adult), 7 months (fully grown adult) and 24 months (aged). In accordance with other studies considerable dendritic growth was observed during postnatal development. However, in old age dendritic growth did not continue, and significant atrophy was observ ed. Quantitation of neuronal morphology showed significant reductions in soma size, total dendritic length, number of branch points and tota l area of dendritic arborisation in old age. Unexpectedly, significant reductions in the numbers of primary dendrites were observed in matur ity and in old age. Concomitant with this atrophy there was an increas e in age-related morphological abnormalities. The similarities between the atrophy and dendritic abnormalities shown by our aged neurons and those seen in other studies of young adult sympathetic neurons follow ing axotomy or trophic factor deprivation are discussed.