CENTRAL AND PERIPHERAL EFFECT OF MPTP VIA DOSE-DEPENDENT MAGNESIUM MODULATION

Abstract

Background: Recent studies suggested that MPTP could cause gastrointestinal motility deficits additionally to its nonconclusive and controverted effects on the CNS (behavior and brain oxidative stress) in rats. A possible interaction between MPTP typical impairments and magnesium modulatory potential was previously suggested, as magnesium role was described in neuroprotection, gastrointestinal function, and oxidative stress.

Aim: To investigate the possible modulatory effect of several magnesium intake formulations (via drinking water) in MPTP neurotoxicity and functional gastrointestinal impairment induction.

Materials and methods: Adult male Wistar rats were subjected to 3-week magnesium intake-controlled diets (magnesium depleted food and magnesium enriched drinking water) previously to acute subcutaneous MPTP treatment (30 mg/ kg body weight). Gastrointestinal motility (one hour stool collection test), and behavioral patterns (Y maze task, elevated plus maze test, open field test, forced swim test) were evaluated. Followingly, brain and bowel samples were collected, and oxidative stress was evaluated (glutathione peroxidase activity, malondial-dehyde concentrations).

Results: MPTP could lead to magnesium intake-dependent constipation-like gastrointestinal motility impairments, anxiety- and depressive-like affective behavior changes, and mild pain tolerance defects. Also, we found similar brain and intestinal patterns in magnesium-dependent oxidative stress.

Conclusion: While the MPTP effects in normal magnesium intake could be regarded as not fully relevant in rat models and limited to the current experimental conditions, the abnormalities observed in the affective behavior, gastrointestinal status, pain tolerance, peripheric and central oxidative status could be indicative of the extent of the systemic effects of MPTP that are not restricted to the CNS level, but also to gastro-intestinal system.

Keywords: MPTP; Parkinson’s disease; animal model; anxious behavior; depressive-like behavior; gastrointestinal; locomotor impairment.

Figure 1

Experimental design and procedures.

Figure 2

Gastrointestinal transit performances, as evaluated by One-hour Stool Collection Test. Parameters: (a) Defecation frequency (fecal boluses/hour); (b) Stool weight (%) (c) Stool water content (%). Results are expressed as means ± SEM (Control, n = 23; 3,5 μM Mg/ L water + 30 mg MPTP/kg bw, n = 25; 35 μM Mg/ L water + 30 mg MPTP/kg bw, n = 22; 350 μM Mg/ L water + 30 mg MPTP/kg bw, n = 25; *p < 0,05, as compared to control group, **p < 0.01, as compared to control group, †p < 0.05, as compared to 3,5 μM Mg/ L water + 30 mg MPTP/kg bw, ††p < 0.01, as compared to 3,5 μM Mg/ L water + 30 mg MPTP/kg bw, ‡‡p < 0,01, as compared to 350 μM Mg/ L + 30 mg MPTP/ kg bw, ‡‡‡p < 0.0001, as compared to 350 μM Mg/ L water + 30 mg MPTP/kg bw).

Figure 3

Short-term memory performances, as evaluated by Y maze test. Behavioural parameters: (a) Spontaneous alternation; (b) Locomotor activity. Results are expressed as means ± SEM (Control, n = 23; 3.5 μM Mg/ L water + 30 mg MPTP/kg bw, n = 25; 35 μM Mg/ L water + 30 mg MPTP/kg bw, n = 22; 350 μM Mg/ L water + 30 mg MPTP/kg bw, n = 25; *p < 0.05, as compared to control group).

Figure 4

Anxiety-like behavior assessment, as observed in Elevated plus maze. Behavioral parameters: (a) Open arms entries (no.); (b) Open arms time (s); (c) Closed arms entries (no.); (d) Stretching behavior frequency; (e) Head dipping behavior frequency; (f) Grooming behavior frequency. Results are expressed as means ± SEM (Control, n = 23; 3,5 μM Mg/ L water + 30 mg MPTP/kg bw, n = 25; 35 μM Mg/ L water + 30 mg MPTP/kg bw, n = 22; 350 μM Mg/ L water + 30 mg MPTP/kg bw, n = 25; *p < 0.05, as compared to control; **p < 0.01, as compared to control; †p < 0,05, as compared to 3,5 μM Mg/ L + 30 mg MPTP/ kg bw; ††p < 0,01, as compared to 3,5 μM Mg/ L + 30 mg MPTP/ kg bw; ‡p < 0.05, as compared to 35 μM Mg/ L + 30 mg MPTP/ kg bw; ‡‡‡p < 0.001, as compared to 35 μM Mg/ L + 30 mg MPTP/ kg bw).

Figure 5

Locomotor activity and anxiety-like behavior in spatial exploration, as observed in Open field test. Behavioral parameters: (a) Locomotor activity (no. of crossings); (b) Central area exploration (s); (c) Rearing behavior frequency; (d) Defecation frequency (no. of fecal boluses). Results are expressed as means ± SEM (Control, n = 23; 3,5 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 25; 35 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 22; 350 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 25; *p < 0,05, as compared to control group; ‡p < 0.05, as compared to 35 μM Mg/ L water + 30 mg MPTP/ kg bw).

Figure 6

Behavioral dispair, as observed in Forced swimming test. Brahvioral parameters: (a) Swimming time (s); (b) Mobility time (s); (c) Floating time (s); (d) Struggling time (s). Results are expressed as means ± SEM (Control, n = 23; 3.5 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 25; 35 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 22; 350 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 25; *p < 0,05, as compared to control; †p < 0.05, as compared to 3.5 μM Mg/ L water + 30 mg MPTP/ kg bw; ‡‡p < 0.001, as compared to 35 μM Mg/ L + 30 mg MPTP/ kg bw; ‡‡‡p = 0.06, as compared to 3.5 μM Mg/ L water + 30 mg MPTP/ kg bw; ■p = 0.06, as compared to control).

Figure 7

Tolerance to pain, as observed in Hot-plate test. Behavioral parameter: latency time (s). Results are expressed as means ± SEM (Control, n = 23; 3.5 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 25; 35 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 22; 350 μM Mg/ L water + 30 mg MPTP/ kg bw, n = 25; †p < 0.05, as compared to 3.5 μM Mg/ L water + 30 mg MPTP/ kg bw).

Figure 8

Effects of MPTP and dietary Mg intervention on oxidative stress parameters: (a) GPx enzyme activity in rat brain and colon tissue (U GPx/ mg protein); (b) MDA content in rat brain and colon tissue (µmol MDA/ mL tissue extract). Results are expressed as means ± SEM (Control, n = 23; 3.5 μM Mg/ L water + 30 mg MPTP/kg bw; n = 25; 35 μM Mg/ L water + 30 mg MPTP/kg bw, n = 22; 350 μM Mg/ L water + 30 mg MPTP/kg bw, n = 25; *p < 0,05, as compared to control, same tissue; **p < 0.01, as compared to control, same tissue; ‡p < 0.05, as compared to 35 μM Mg/ L + 30 mg MPTP/ kg bw).