Impact of paraoxon followed by acetylcholinesterase reactivator HI-6 on gastric myoelectric activity in experimental pigs.

OBJECTIVES: Organophosphorus compounds represent nerve agents, pesticides and several industrial compounds. Treatment after exposure to organophosphates involves the use of parasympatolytics, acetylcholinesterase (AChE) reactivators/modulators and anticonvulsive drugs. Wider clinical use of several AChE reactivators/modulators might be limited because of possible side effects, including gastrointestinal toxicity. In this study we evaluated the effect of paraoxon and an AChE reactivator (HI-6) on the gastric myoelectric activity in experimental pigs.

METHODS: Six female experimental pigs (mean weight 33 kg) entered the study. Intramuscular paraoxon (1.5 g) was administrated after the baseline gastric electrogastrography (EGG) recording, followed by HI-6 dimethansulphonate (1.5 g i.m.) 10 min. later. A further ten 15-minute-interval EGG recordings were performed. Running spectral analysis was used for the elemental evaluation of the EGG. The results were expressed as dominant frequency of slow waves at all intervals of EGG recordings. EGG power analysis was performed in all animals.

RESULTS: Paraoxon induced a non-significant decrease of dominant frequency (2.8±0.6 vs. 2.6±0.5 cycles per min.; p=0.092). Subsequent administration of HI-6 normalised dominant frequency to basal values and increased it significantly within the subsequent 30 minutes (3.0±0.4; p<0.001). Paraoxon administration did not influence the power (within a 10-minute exposure). However, the amplitudes increased significantly 90 minutes after administration of HI-6 (819±109 vs. 5054±732 μV2; p<0.001).

CONCLUSIONS: AChE reactivator HI-6 blocked the gastric effect of paraoxon significantly. Subsequent myoelectric changes in the dominant frequency and power were executed by HI-6. The effect of paraoxon was non-significant.