Introduction
Materials and methods
Tissue preparation
Three-dimensional electron microscopy
Identification of synapses and their postsynaptic targets
Statistical analysis
Results
Distribution of synapses on spines and shafts
Layer | |||||||
---|---|---|---|---|---|---|---|
I | II | III | IV | V | VI | Average (I–VI) | |
AS on dendritic spine heads |
70.95
|
84.09
|
76.51
|
69.93
|
72.71
|
69.27
|
73.91%
|
(425) | (814) | (1671) | (858) | (477) | (381) | ||
AS on dendritic spine necks |
1.17
|
1.14
|
1.97
|
2.20
|
1.52
|
1.82
|
1.64%
|
(7) | (11) | (43) | (27) | (10) | (10) | ||
AS on dendritic shafts |
15.36
|
8.88
|
13.74
|
15.16
|
17.23
|
18.00
|
14.73%
|
(92) | (86) | (300) | (186) | (113) | (99) | ||
SS on dendritic spine heads |
2.50
|
0.72
|
0.82
|
4.24
|
0.91
|
2.55
|
1.96%
|
(15) | (7) | (18) | (52) | (6) | (14) | ||
SS on dendritic spine necks |
1.50
|
0.62
|
0.27
|
0.57
|
0.46
|
0.73
|
0.69%
|
(9) | (6) | (6) | (7) | (3) | (4) | ||
SS on dendritic shafts |
8.51
|
4.55
|
6.68
|
7.91
|
7.16
|
7.64
|
7.08%
|
(51) | (44) | (146) | (97) | (47) | (42) | ||
Total |
100
|
100
|
100
|
100
|
100
|
100
| |
(599) | (968) | (2184) | (1227) | (656) | (550) |
Layer II
| Type of postsynaptic target | |||
---|---|---|---|---|
Spine | Shaft | Totals | ||
Type of synapse | AS |
825
|
86
| 911 |
(788.65) | (122.35) | |||
SS |
13
|
44
| 57 | |
(49.35) | (7.65) | |||
Totals | 838 | 130 | 968 |
Layer IV
| Type of postsynaptic target | |||
---|---|---|---|---|
Spine | Shaft | Totals | ||
Type of synapse | AS |
885
|
186
| 1071 |
(823.98) | (247.02) | |||
SS |
59
|
97
| 156 | |
(120.02) | (35.98) | |||
Totals | 944 | 283 | 1227 |
Distribution of synapses on dendritic shafts of spiny and aspiny dendritic segments
Density of AS and SS on spines and dendritic shafts
Layer | |||||||
---|---|---|---|---|---|---|---|
I | II | III | IV | V | VI | Avg | |
Density of all synapses (AS+SS) | 0.83 | 1.13 | 0.94 | 1.16 | 0.83 | 0.47 | 0.89 |
Percent synapses on spines | 76.13 | 86.57 | 79.58 | 76.94 | 75.61 | 74.36 | 78.20 |
Percent synapses on shafts | 23.87 | 13.43 | 20.42 | 23.06 | 24.39 | 25.64 | 21.80 |
Density of synapses on spines | 0.63 | 0.98 | 0.75 | 0.89 | 0.63 | 0.35 | 0.70 |
Density of synapses on dendritic shafts | 0.20 | 0.15 | 0.19 | 0.27 | 0.20 | 0.12 | 0.19 |
Density of AS synapses | 0.73 | 1.05 | 0.86 | 1.02 | 0.76 | 0.40 | 0.81 |
Percent AS on spines | 82.44 | 90.56 | 85.10 | 82.63 | 81.17 | 79.80 | 83.62 |
Percent AS on shafts | 17.56 | 9.44 | 14.90 | 17.37 | 18.83 | 20.20 | 16.38 |
Density of AS on spines | 0.61 | 0.95 | 0.73 | 0.84 | 0.62 | 0.32 | 0.68 |
Density of AS on dendritic shafts | 0.13 | 0.10 | 0.13 | 0.18 | 0.14 | 0.08 | 0.13 |
Density of SS synapses | 0.10 | 0.08 | 0.08 | 0.14 | 0.07 | 0.06 | 0.09 |
Percent SS on spines | 32.00 | 22.81 | 14.12 | 37.82 | 16.07 | 30.00 | 25.47 |
Percent SS on shafts | 68.00 | 77.19 | 85.88 | 62.18 | 83.93 | 70.00 | 74.53 |
Density of SS on spines | 0.03 | 0.02 | 0.01 | 0.05 | 0.01 | 0.02 | 0.02 |
Density of SS on dendritic shafts | 0.07 | 0.06 | 0.07 | 0.09 | 0.06 | 0.04 | 0.06 |
Spines with multiple synapses
Count | % | |
---|---|---|
Spines with a single synapse | 4304 | 94.43 |
One AS | 4246 | 98.65 |
One SS | 58 | 1.35 |
Spines with multiple synapses | 254 | 5.57 |
Two AS | 146 | 57.48 |
One AS and one SS | 84 | 33.07 |
Two AS and one SS | 9 | 3.54 |
Three AS | 6 | 2.36 |
Two SS | 6 | 2.36 |
Three SS | 2 | 0.79 |
One AS and two SS | 1 | 0.39 |