Aging and synaptic changes in the paraventricular hypothalamic nucleus of the rat.

Abstract

The age-related differences in the synapses of the paraventricular hypothalamic nucleus (PVN) were studied with transmission electron microscopy in young (3-month-old) and senescent (25-month-old) Wistar rats. The changes in the axodendritic (ADS) and axospinous (ASS) synapses in the PVN neuropil were determined by morphometry. The majority of synapses were of the ADS type. In senescent rats the density of both ADS and ASS was diminished. The mean area of the ASS presynaptic boutons in aged rats was more enlarged than of the boutons in the ADS. The parameters characterising synaptic vesicles (SV) were diminished in aging rats. The number of SV per synaptic bouton decline was not significantly different. The changes in the length of synaptic contact zone (SCZ) were not significant with the exception of the total SCZ length per 1000 microm2 and the total area of the SCZ per 1000 microm3 in the ADS. The decrease of the number of dendritic spines (DS) per 1000 microm2 in the neuropil was significantly age-related diminished. Moreover, the mean area of the DS was significantly enlarged.