Effects of subchronic soman on avoidance-escape behavior and cholinesterase activities
I Geller1, A Sawa, W B Stavinoha
1Southwest Foundation for Biomedical Research, San Antonio, TX 78284.
Abstract:
Male Sprague-Dawley rats were trained on a discriminated avoidance-escape task. They were administered subchronically saline, 12.7 micrograms/kg (0.125 LD50) soman, or 25.5 micrograms/kg (0.25 LD50) soman. Injections were given 5 days per week for 4 weeks. Injections were given subcutaneously immediately following the avoidance behavior test session. Soman produced a reduction in avoidance behavior efficiency in a dose dependent manner. When soman was discontinued, the rats recovered their pre-soman control baselines. Untrained rats given soman according to the same soman regimen were used to measure acetylcholine in brain and cholinesterase activities in brain, blood, and diaphragm. After 18 soman injections at 12.7 and 25.5 micrograms/kg acetylcholine was reduced significantly only in the amygdala. Blood cholinesterase was inhibited as much as 57% after 12.7 micrograms/kg soman and 74% after 25.5 micrograms/kg. Plasma cholinesterase was inhibited to 24% by the 12.7 micrograms/kg dose of soman and to 38% by the 25.5 micrograms/kg dose. Plasma cholinesterase recovered to control levels 11 days after cessation of soman, and whole blood cholinesterase recovered 25 days after cessation of the higher soman dose. Cholinesterase was inhibited significantly in the hippocampus and amygdala in a dose dependent manner. The cholinesterase activities appear to parallel the soman induced decrement in avoidance behavior and the subsequent recovery to control levels following withdrawal of soman.
Related Concept Videos
Direct-Acting Cholinergic Agonists: Pharmacokinetics
Indirect-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship
Reversible inhibitors display short to medium durations of action. Short-acting agents include simple alcohols with...
Indirect-Acting Cholinergic Agonists: Mechanism of Action
Reversible inhibitors like edrophonium bind to a specific part of the enzyme called the anionic catalytic site. They form noncovalent bonds, which means they are not strongly attached to the enzyme. This creates a temporary and less stable enzyme–inhibitor complex, leading to...
Indirect-Acting Cholinergic Agonists: Pharmacokinetics
Reversible agents containing quaternary amines, such as neostigmine and edrophonium, are not easily absorbed orally because they are...
Indirect-Acting Cholinergic Agonists: Pharmacological Actions
At the neuromuscular junction, these agents work by inhibiting the breakdown of acetylcholine, allowing it to remain bound to the receptor and bind to nearby receptors. This process leads to repetitive firing of the endplate, causing muscle...
Anticholinesterase Agents: Poisoning and Treatment
Irreversible agents form a strong bond with the cholinesterase enzyme, making it inactive. The breakdown of the phosphorylated enzyme is slower than the...


