Methamphetamine-induced striatal apoptosis in the mouse brain: comparison of a binge to an acute bolus drug administration

Abstract

Methamphetamine (METH) is a psychostimulant that induces neural damage in experimental animals and humans. A binge (usually in the 5-10 mg/kg dose range 4 x at 2 h intervals) and the acute bolus drug administration (20-40 mg/kg) of METH have been employed frequently to study neurotoxicity in the brain. In this study we have compared these drug delivery schedules to determine their efficacy to induce striatal apoptosis. Exposure of male mice to a binge of METH at 10mg/kg 4x at 2 h intervals (cumulative dose of 40 mg/kg) was approximately four times less effective in inducing apoptotic cell death (TUNEL staining) 24 h after METH treatment in the striatum than a single bolus administration of 30 mg/kg of METH. The residual TUNEL staining observed three days after METH treatment is proportionately equivalent between a binge and the acute bolus drug administration. Interestingly, a binge of METH induces a hyperthermic response of longer duration. This study demonstrates that an acute bolus drug administration of METH is more effective inducing striatal apoptosis in mice, and therefore, is more suitable for studies assessing the impact of METH on sites post-synaptic to the striatonigral dopamine terminals.

Fig. 1

Striatal subregions assessed in this study. Cross sectional representation in schematic form of the striatum in one hemisphere of the mouse brain. DM, dorsal-medial; DL, dorsal-lateral; VM, ventral-medial; VL, ventral-lateral. Cell counts were taken from the areas within the rectangular enclosures. Reproduced from Hof et al. (2000).

Fig. 2

Comparison of an acute bolus drug administration (30 mg/kg, i.p.) with a binge (10 mg/kg × 4 at 2 h intervals, i.p.) of METH on induction of apoptosis in the striatum of mice. Cell death was detected using the TUNEL assay. (A) Epifluorescent micrographs of TUNEL-stained mouse striata. Scale bar = 120 μm. Note the appearance of green fluorescent nuclei against a dark background in the striatum of mice treated with METH. (B) Percent of TUNEL-positive staining (mean ± S.E.M.) relative to total neuronal cell counts (data not shown) are shown for the dorsal-medial (DM), dorsal-lateral (DL), ventral-medial (VM), and ventral-lateral (VL) aspects of the striatum. Note that an acute bolus drug administration of METH is significantly more effective in inducing striatal apoptosis. ^*p < 0.001 compared to all saline treatments. ^#p < 0.005 compared to METH 30 mg/kg. (C) Scattergraphs for DM, DL, VM, and VL regions of the striatum demonstrate the percent of TUNEL-positive neurons is variable within treatment groups. Each dot represents one animal within each treatment group. () Saline-1 day, () Saline × 4–1 day, () Saline-3 days, () Saline × 4–3 days, () METH 30 mg/kg-1 day, () METH 10 mg/kg × 4–1 day, () METH 30 mg/kg-3 days, (●) METH 30 mg/kg-3 days. n = 10 for all saline groups. n = 13 for METH treatment groups at day 1. n = 14 for METH treatment groups at day 3.

Fig. 2

Comparison of an acute bolus drug administration (30 mg/kg, i.p.) with a binge (10 mg/kg × 4 at 2 h intervals, i.p.) of METH on induction of apoptosis in the striatum of mice. Cell death was detected using the TUNEL assay. (A) Epifluorescent micrographs of TUNEL-stained mouse striata. Scale bar = 120 μm. Note the appearance of green fluorescent nuclei against a dark background in the striatum of mice treated with METH. (B) Percent of TUNEL-positive staining (mean ± S.E.M.) relative to total neuronal cell counts (data not shown) are shown for the dorsal-medial (DM), dorsal-lateral (DL), ventral-medial (VM), and ventral-lateral (VL) aspects of the striatum. Note that an acute bolus drug administration of METH is significantly more effective in inducing striatal apoptosis. ^*p < 0.001 compared to all saline treatments. ^#p < 0.005 compared to METH 30 mg/kg. (C) Scattergraphs for DM, DL, VM, and VL regions of the striatum demonstrate the percent of TUNEL-positive neurons is variable within treatment groups. Each dot represents one animal within each treatment group. () Saline-1 day, () Saline × 4–1 day, () Saline-3 days, () Saline × 4–3 days, () METH 30 mg/kg-1 day, () METH 10 mg/kg × 4–1 day, () METH 30 mg/kg-3 days, (●) METH 30 mg/kg-3 days. n = 10 for all saline groups. n = 13 for METH treatment groups at day 1. n = 14 for METH treatment groups at day 3.

Fig. 3

METH-induced hyperthermia. Body core temperature was measured with a mouse rectal probe. (A) The mice were injected i.p. with METH (30 mg/kg) at time 0 and body core temperature was measured at 2 h intervals up to 6 h post-METH. (B) Mice received four i.p. injections of METH (10 mg/kg each) at 2 h intervals. The mice were given METH at 0, 2, 4, and 6 h. Body core temperature was measured at 1, 3, 5, and 7 h. Note that the hyperthermic response elicited by the binge of METH is sustained longer than that observed with a single bolus administration (compare Fig. 2A and B). ^*p < 0.05 compared to control group (Student’s t-test).