[Drainage characteristic of the brain interstitial fluid detected by using fluorescence and magnetic tracer method]

Compare the results of molecular diffusion and mass flow in the interstitial space(ISS) displayed by using optical and magnetic probes and study partitioned drainage of the brain interstitial fluid (ISF).

In the study, 36 male SD rats were randomly divided into fluorescent inspection group (18), magnetic tracer group (18). Then they were divided equally into caudate nucleus (Cn), thalamus (T) and substantia nigra (Sn) subgroup, 6 rats in each subgroup. Referencing the brain stereotaxic atlas, the coronal globus pallidus as center level, Cn, T or Sn were acted as puncture positioning target. A 10 μL microsyringe was stereotaxically positioned and the lucifer yellow (LY) solution of 2 μL 10 mmol/L was infused into centric position. The coronary slices undergo cardiac perfusion and fix respectively in time point Cn 3 h, T 2 h and Sn 1 h. The rat brain was placed in rat stainless steel brain matrices and cut backward along visual intersection. The injection point of coronal slice as the center level, take 3 slices in front of the center level and 2 slices behind of it. 1 mm for each slice and 6 slices in total. Then slices were detected by laser scanning confocal microscope (LSCM). Simultaneous, in the same coordinate brain regions of another three groups, a gadolinium-diethylene triamine pentaacetic acidm (Gd-DTPA) solution of 2 μL 10 mmol/L was infused into different injection and detected by MRI tracer-based method. Then the Radiant can be used to measure distribution area of Gd-DTPA.

LY and Gd-DTPA have different distribution regions in Cn, T and Sn. After LY and Gd-DTPA were introduced into the Cn subgroup 3 h, compare the 1 to 6 levels distribution area of LY and Gd-DTPA as follows: (10.95±4.27) mm² vs. (8.33±2.25) mm², (18.16±4.74) mm² vs. (16.42±2.88) mm², (24.57±3.65) mm² vs. (20.75±2.29) mm², (34.81±3.32) mm² vs. (28.88±1.51) mm², (30.53±3.12) mm² vs. (20.92±2.75) mm², (12.15±4.92) mm² vs. (10.00±1.89) mm². The statistical analysis of every level was made by T test, and the difference of the distribution area between the two tracers were not statistically significant (t=0.940, P=0.400; t=0.546, P=0.614; t=1.534, P=0.200; t=2.809, P=0.480; t=2.693, P=0.055; t=0.707, P=0.518); After LY and Gd-DTPA were introduced into the T subgroup 2 h, compare the 1-6 levels distribution area of LY and Gd-DTPA as follows: (5.56±4.61) mm² vs. (3.33±2.25) mm², (16.21±3.36) mm² vs. (11.42±2.88) mm², (19.00±5.21) mm² vs. (15.75±2.29) mm², (25.32±5.49) mm² vs. (22.33±3.25) mm², (17.34±5.31) mm² vs. (15.92±2.75) mm², (7.67±6.19) mm² vs. (5.00±1.89) mm². The statistical analysis of every level was made by T test, and the difference of the distribution area between the two tracers were not statistically significant (t=0.753, P=0.493; t=1.875, P=0.134; t=0.990, P=0.378; t=0.810, P=0.464; t=0.413, P=0.701; t=0.716, P=0.514); After LY and Gd-DTPA were introduced into the Sn subgroup 1 h, compare the 1-6 levels distribution area of LY and Gd-DTPA as follows: (6.78±4.56) mm² vs. (4.75±2.00) mm², (12.65±5.04) mm² vs. (10.44±1.13) mm², (19.51±6.54) mm² vs. (17.55±0.30) mm², (28.72±5.45) mm² vs. (24.48±1.32) mm², (21.34±4.42) mm² vs. (17.72±0.25) mm², (13.00±5.46) mm² vs. (12.00±2.88) mm². The statistical analysis of every level was made by T test and the difference of the distribution area between the two tracers were not statistically significant (t=0.705, P=0.519; t=0.743, P=0.499; t=0.517, P=0.656; t=1.310, P=0.260; t=1.416, P=0.292; t=0.281, P=0.793), but the distribution area of LY is slightly more than Gd-DTPA.

LSCM imaging technology confirmed partitioned drainage of the brain ISF found by MRI tracer-based method and provided technology and method validation for MRI tracer-based method. LSCM imaging technology with higher contrast and resolution, therefore more sophisticated partitioned drainage of the brain interstitial fluid were got.