Guinea-pig heart acetylcholinesterase after continuous physostigmine administration

G1 and G4 acetylcholinesterase (AChE) molecular forms were separated in different regions of guinea-pig heart. The activities of both were highest in the left side of the left ventricle (LV(L)). The reversible anticholinesterase physostigmine, or saline, was administered continuously for six days. In saline-treated animals the activity of both molecular forms was markedly increased in both atria, G1 activity was increased on the left side of the right ventricle (LV(R)), and G4 activity was increased on both sides of the right ventricle compared to untreated animals. However, G1 activity was significantly decreased on the left side of the left ventricle. Physostigmine administration caused a significant reduction in G4 activity in the left atrium (LA), the left side of the right ventricle, and the left side of the left ventricle, and a significant increase in G1 activity on the right side of the right ventricle compared to saline-treated animals. The distribution of AChE indicates a role for parasympathetic nerves in the control of both ventricles and atria. The changes in AChE in saline-treated animals could have been due to the anaesthesia or stress of the surgical procedures. Physostigmine caused delayed changes in the enzyme in some regions, consistent with an effect on its expression.