Chronic vs acute carbamate administration in exercising rats

Area of Science:

• Pharmacology
• Toxicology
• Exercise Physiology

Background:

• Organophosphate poisoning is a significant health concern.
• Physostigmine (PH) and pyridostigmine (PY) are carbamates used as antidotes.
• Acute administration of carbamates can impair exercise performance and thermoregulation.

Purpose of the Study:

• To investigate if chronic administration of physostigmine (PH) attenuates the negative effects on endurance and thermoregulation observed with acute PH treatment.
• To compare the effects of acute versus chronic PH administration on exercise capacity and physiological responses in rats.

Main Methods:

• Rats received acute intravenous (iv) physostigmine (PH) or chronic infusion via osmotic mini-pump.
• Groups included control, acute PH (200 ug/kg), chronic PH (7 days), and chronic PH (14 days).
• Exercise testing involved running to exhaustion at a set speed and temperature; heating rates and run times were recorded.

Main Results:

• Acute PH administration significantly decreased endurance and increased heating rates.
• Chronic PH administration (7 and 14 days) attenuated these decremental effects, with 14-day treatment showing near-control performance.
• Ultrastructural changes in diaphragms were less pronounced in chronically treated animals compared to acutely treated ones.

Conclusions:

• Chronic administration of physostigmine (PH) mitigates the adverse effects on exercise performance, thermoregulation, and cellular ultrastructure associated with acute PH exposure.
• These findings suggest a potential therapeutic advantage of chronic PH administration in managing organophosphate poisoning.