Table 1.

Structural features of active zones at the presynaptic terminal.

Synapse	Species	Age	Active Zone Number Per Presynaptic Terminal	Presynaptic Terminal Size	Active Zone Density	Active Zone Size	Reference
NMJ	Mouse	Day 54	780	295 μm2	2.6/μm2	0.082 μm2	[17]
NMJ	Mouse	Adult	850	335.9 μm2	2.5/μm2 *	N.P.	[15]
NMJ	Human	67 years	N.P.	122.7 μm2	N.P.	N.P.	[18]
NMJ	Human	Adult	N.P.	N.P.	2.6/μm2	N.P.	[19]
Stratum radiatum in CA1 hippocampus	Mouse	Adult	one for more than 90% of synapses	0.086 μm3	13.4/μm3 *	0.039 μm2	[20]
Piriform cortex layer 1a	Mouse	7 months	one for more than 90% of synapses	0.367 μm3	3.1/μm3 *	0.095 μm2	[21]
Piriform cortex layer 1b	Mouse	7 months	one for more than 90% of synapses	0.208 μm3	5.5/μm3 *	0.097 μm2	[21]
Calyx of Held	Rats	Day 9	554	1022 μm2	0.54/μm2 *	N.P.	[22]
Calyx of Held	Rats	Day 14	678	N.P.	N.P.	0.089 μm2	[24]

* Calculated from data in the papers. N.P.: not provided.