Table 2

Brain and CSF entry of [³H]DPDPE (4.1 nM) in the presence of the endogenous peptide leucine-enkephalin, the large neutral amino acid transport inhibitor BCH and the polycation poly-l-lysine

[³H]DPDPE		n	R_Tissue%^2-a	Student’s t Test
Only	Brain	7	3.03 ± 0.37	—
	CSF	3	1.79 ± 0.19	—
+ Leucine-enkephalin (1 mM)^2-b	Brain	3	4.24 ± 0.18	NS
	CSF	3	1.86 ± 0.30	NS
+ BCH (10 mM)	Brain	4	5.17 ± 0.41	P < 0.01
	CSF	3	2.21 ± 0.33	NS
+ Poly-l-lysine (0.3 μM)	Brain	4	10.94 ± 0.72	P < 0.01

↵2-a Values ± S.E.M. have been corrected for [¹⁴C]sucrose/vascular space.
↵2-b For comparison, brain and CSF values taken from Figure 2 ofWilliams et al. (1996).