Table 1.

Selected values of α and γ obtained with radiolabel, RTI, RTP and IOI methods.

Molecule	Mr	dH	D	°C	Species	Region	α	λ	Method	Ref
sucrose	342	1.0	7.0	37	rabbit	caudate	0.21	1.60	radio	5
methotrexate	508	1.3	5.3	37	monkey	caudate	0.28	2.43	radio	5
TMA+	74	< 1.0	11.1	37	rat	cortex	0.18 – 0.22	1.54 – 1.65	RTI	27
TMA+	74	< 1.0	11.1	37	mouse	cortex	0.23	1.67	RTI	1
TMA+	74	< 1.0	9.82	21–23	turtle	cb. ml	0.31	1.44, 1.95, 1.58	RTI	22
α-NS−	174	< 1.0	7.60	37	rat	cb. ml	0.18	1.54	RTI	15
Ca2+	40	< 1.0	9.4	34	rat	cortex	n/a	2.05	RTP	9
AF488	547	1.2	5.19	34	rat	cortex	n/a	1.54	IOI	9
Dex3	3000	3	2.2	37	rat	cortex	n/a	2.04	IOI	34
Dex70	70,000	14	0.47	37	rat	cortex	n/a	2.69	IOI	34
EGF	6600	3.7	1.7	34	rat	cortex	n/a	1.79	IOI	32
BSA	66,000	7.4	0.83	34	rat	cortex	n/a	2.26	IOI	30
lactoferrin	80,000	9.3	0.71	37	rat	cortex	n/a	3.50	IOI	33

Molecule: TMA⁺, tetramethylammonium; α-NS⁻, α-naphthalenesulfonate; AF488, Alexa Fluor 488 hydrazide (Molecular Probes, Invitrogen, Carlsbad, California, USA); Dex3, dextran 3000 M_r; Dex70, dextran 70,000 M_r; EGF, epidermal growth factor; BSA, bovine serum albumin.

M_r. Relative molecular weight.

d_H. Hydrodynamic diameter (units: nm). Estimated from Stokes-Einstein equation.

D. Free diffusion coefficient (units: × 10⁶ cm² s⁻¹).

°C. Temperature at which D was measured (units: degrees Celsius).

Species. Animal species in which measurements were made.

Region: Brain region where measurements were made: caudate, caudate nucleus; cortex, various areas of neocortex; cb. ml. cerebellum, molecular layer.

α. Volume fraction of ECS (units: non-dimensional).

λ. Tortuosity of ECS (units: non-dimensional).

Method. Diffusion method employed: radio, radiolabel; RTI, real-time iontophoresis; RTP, real-time pressure; IOI, integrative optical imaging.

Ref. Reference.