Table 5.

The effects of DA are diminished by Na⁺ channel blockers but not by blockers of other voltage-gated ion channels

Drug	Condition	αPSP summation
		−70 mV	−55 mV
TTX (1 μm) (n = 9)	Baseline	1.37 ± 0.14	2.35 ± 0.15
	TTX	1.33 ± 0.2	0.76 ± 0.07*
	+DA	1.10 ± 0.2	0.80 ± 0.20
4-AP (3 mm) (n = 7)	Baseline	1.47 ± 0.18	2.14 ± 0.2
	4-AP	1.68 ± 0.20*	4.63 ± 0.21*
	+DA	1.61 ± 0.20	5.07 ± 0.2*
BaCl2 (250 μm) (n = 6)	Baseline	1.42 ± 0.17	2.37 ± 0.16
	BaCl2	1.72 ± 0.18*	2.98 ± 0.17*
	+DA	1.75 ± 0.17	3.32 ± 0.18*
ZD7288 (20 μm) (n = 7)	Baseline	1.49 ± 0.15	2.28 ± 0.2
	ZD7288	1.89 ± 0.18*	2.31 ± 0.2
	+DA	2.02 ± 0.16	2.79 ± 0.2*
NiCl2/nimodipine (50/10 μm) (n = 6)	Baseline	1.55 ± 0.19	2.38 ± 0.2
	NiCl2/nim	1.61 ± 0.18	2.44 ± 0.17
	+DA	1.57 ± 0.21	2.96 ± 0.18*

Application of DA causes an increase in PSP summation at depolarized membrane potentials, even when blockers of K⁺, Ca²⁺, or h-channels are present. *p < 0.05 (paired t test) compared with previous condition at the same voltage.