Axonal energy metabolism, and the effects in aging and neurodegenerative diseases

Table 5 Mitochondrial comparison in myelinated and unmyelinated axon segments

	Species	Brain region/Cell type	Age	Myelinated axon	Boutons	Reference
Volume	Mouse	S1 cortex	Adult	N/A	0% ≥ 0.2 μm³~ 50% ≤ 0.05 μm³	[72]
	Mouse	Hippocampal CA1 pyr. neurons	4 m	~ 30% ≥ 0.2 μm³		[73]
	Mouse	Hippocampal CA1 pyr. neuron	Adult	N/A	0% ≥ 0.2 μm³~ 70% ≤ 0.05 μm³	[72]
	Mouse	Hippocampal DG granule neurons	4 m	~ 20% ≥ 0.2 μm³		[73]
	Mouse	Nucleus accumbens	11 m	N/A	0% ≥ 0.2 μm³~ 65% ≤ 0.05 μm³	[72]
	Mouse	Dorsal cochlear nucleus	P17	N/A	~ 45% ≥ 0.2 μm³	[72]
% Area occupied by mito	Rat	S1 L1-4	Juvenile	0.40±0.28 %	(Exc.) 11.19± 1.25%; (Inh.) 3.41±0.65%	[75]
% Area occupied by mito	Mouse	S1	Adult	~ 2.87%	6.64% in average	[181]

Abbreviations: ~ , about, L cortical layer, m month, P postnatal, pyr. Pyramidal, V1 primary visual cortex, S1 primary somatosensory cortex, Exc. Excitatory, Inh. inhibitory

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