Figure 8.
Sprague Dawley rats show reduced sensitivity to systemic 3-NP. A, Plots of tetanus-induced long-term synaptic plasticity at dorsomedial corticostriatal synapses are shown. No difference was found in the tetanus-induced plasticity between slices taken from saline-injected Sprague Dawley rats and Sprague Dawley rats injected 24 h earlier with 25–35 mg/kg 3-NP. A trend toward reduced LTD was seen in slices taken from rats injected once a day for 3 d with 3-NP (15, 10, and 10 mg/kg). B, Bar graphs showing distribution of cells expressing tetanus-induced potentiation (>100%) and depression (<100%) for STP and LTP under each experimental condition (saline, single injection, and 3× injection). C, Systemic injection of 3-NP creates regionally dependent decreases in dopamine release in the striatum. The amount of dopamine release was determined at 5 regions within the striatum including (1) midstriatum, (2) dorsomedial, (3) dorsal, (4) dorsolateral, and (5) ventrolateral (inset). Bar graph illustrates peak dopamine released by a single intrastriatal stimulus (200 μA, 0.1 ms) applied to striatal brain slices at each of the above indicated regions for saline-injected rats, rats injected 24 h earlier with 3-NP (25–35 mg/kg 3-NP), and rats injected once a day for 3 d with 3-NP (15, 10, and 10 mg/kg) and killed 24 h after the last injection. No differences were observed between saline-injected and single injected (25–35 mg/kg 3-NP) Sprague Dawley rats. A significant reduction in dopamine release was seen in rats injected once a day for 3 d with 3-NP across all 5 sampling sites (repeated-measures ANOVA; p < 0.03). Post hoc analysis showed reduced release at sites 1, 3, 4 (*p < 0.01) and 2 (**p < 0.02).