Ultrastructural features of neurons and synaptic contacts in the posterodorsal medial amygdala of adult male rats

Abstract

The aim of the present study was to describe the ultrastructure of neurons (from eight animals) and to analyse the synaptic terminal distribution (from two animals) in the posterodorsal subnucleus of the medial amygdala (MePD) of adult male rats. Using transmission electron microscopy, it was possible to identify many spiny and aspiny dendrites, unmyelinated axonal bundles, single axonal processes, a few myelinated axons, blood vessels and glial processes in the neuropil. Axodendritic synapses were the most frequently observed (67.5%), appearing to be of either the inhibitory or the excitatory types. The presynaptic region contained round or flattened vesicles that occurred either singly or with dense-cored vesicles (DCVs). The dendrites often received many synapses on a single shaft, and axon terminals displayed synaptic contacts with one or more postsynaptic structures. Dendritic spines showed different morphologies and the synapses on them (23.1%) formed a single and apparently excitatory synaptic contact with round, electron-lucid vesicles alone or, less frequently, with DCVs. Inhibitory and excitatory axosomatic synapses (8.2%) and excitatory axoaxonic synapses (1.2%) were also identified. The present report provides new findings relevant to the study of the MePD cellular organization and could be combined with other morphological data in order to reveal the functional activity of this area in male rats.

Glial and axonal perikaryal coverage and somatic spines in the posterodorsal medial amygdala of male and cycling female rats

“…The general ultrastructural appearance of the MePD neuronal perikarya is similar to that described previously for adult male rats (Hermel et al, ). However, we found that the MePD cell bodies had glial processes in close apposition to the perikaryal membrane, some with evident continuous glial processes covering the perikarya whereas others were intermingled among axons (Figs.…”

Persistent changes in neuronal structure and synaptic plasticity caused by proton irradiation

“…Dendritic spines are the structural correlates of learning and memory that regulate synaptic plasticity through dynamic changes in connectivity that are intimately dependent on changes in dendritic arborization (Yoshihara et al 2009). While some controversy exists regarding the precise function of specific spine types (Hermel et al 2006; Urbanska et al 2012), recent evidence suggests that thin spines are more plastic and involved in learning, while mature spines play a larger role in memory (Bourne and Harris 2007). Changes in morphology or spine density that adversely impact synaptic function have been found to compromise neurotransmission and behavioral performance (Matsuzaki et al 2004).…”

Morphological and Functional Features of the Sex Steroid-Responsive Posterodorsal Medial Amygdala of Adult Rats

“…Most spines showed synaptophysin puncta close to their head and neck, but some spines were not labeled or were characterized by multiple puncta [84]. Although ultrastructural data suggest that dendritic spines usually receive one asymmetrical synapse with round electron-lucent and dense core vesicles [103], inhibitory and multisynaptic contacts have also been found on the dendritic spines of adult male MePD [2].…”