The Suprachiasmatic Nucleus and the Circadian Timing System - Progress in Molecular Biology and Translational Science - page 12

Table 1.2 Neurotransmitter/peptide phenotype of SCN neurons
Transmitter/
peptide
phenotype

Perikaryal
area
( m m 2 SD)

Perikaryal
diameter
( m m 2 SD)

Percentage of
total SCN
population

Number of
neurons SD

AVP 3176 43 44.0 9.8 10.2 1.4 37

VIP 2081 81 41.7 10.4 9.7 1.3 24

CAR 1237 105 41.4 9.3 10.1 1.3 14

GRP 1169 77 29.6 7.7 8.9 1.2 14

NT 316 60 43.8 10.0 10.5 1.5 4

3 a

ENK 530 129 45.7 11.9 10.5 1.4

3 a

SS 277 28 51.1 13.6 11.4 1.6

SP 164 36 57.6 13.9 12.1 1.6 2

Total peptide b

8630 - - 100

(79) e

Total GABA c

7945 115 - - -

Total Nissl
neurons d

10,972 1179 - - -

a Approximately 50% of ENK þ neurons colocalize AVP, and this is accounted for in the total percent of
characterized neurons. Similarly, 20% of SS þ neurons colocalize AVP, and this is also corrected for the
final count.
b The total number of SCN neurons characterized by peptide phenotype is corrected for a 50% coloc-
alization of AVP with ENK and a 20% colocalization of AVP with SS. Similarly, quantitative data for
angiotensin II are not shown because all angiotensin II neurons colocalize AVP.
c
Total number of GABA neurons is taken from Moore and Speh (1993).
d Total neurons is from two brains (4 SCNs) which were embedded in paraffin, 20 m m coronal sections
were stained with cresyl violet and neuronal number in the SCN was estimated using an unbiased ste-
reological method.
e The total number of neurons characterized by peptide phenotype is 79% of the total number of SCN
neurons determined without correction from Nissl material. The lower number of peptide-containing
neurons most likely represents the lower sensitivity of the immunohistochemical method compared to
the Nissl stain.
Table from Ref. 6 . Reproduced with permission (Elsevier license ID 3058031028613).

estimated from Nissl material ( Table 1.2 ). This difference between total
neuron number determined fromNissl material as opposed to from immu-
nocytochemical material is almost certainly a result of an underestimate
due to limitations of immunocytochemical sensitivity. The total number
from Nissl material is consistent with prior studies (see earlier). Thus,
the immunocytochemical method can be viewed as 80% as sensitive as
the Nissl method. It is noteworthy that the perikaryal size of the individual
groups is quite comparable except for the GRP neurons which are signif-
icantly smaller ( p < 0.05, t test) than the AVP, VIP, and ENK groups.