Heptyl‐physostigmine enhances basal forebrain control of cortical cerebral blood flow

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Abstract
This study sought to determine the effect of heptylphysostigmine (H‐PHY), a reversible cholinesterase (ChE) inhibitor with greater lipophilicity and longer duration of action than physostigmine, on resting and basal forebrain (BF)‐elicited increases in cortical cerebral blood flow (CBF). Laser‐doppler flowmetry (LDF) was used to monitor changes in frontal cortical microvascular perfusion in urethane anesthetized rats. Responses were measured before, early after, and 1 hr following H‐PHY, 3 mg/kg, i.m. Electrical stimulation (100 μA) of the BF elicited up to 220% increases in CBF at 50 Hz, an effect that was graded with frequency. At 15 min following H‐PHY (3 mg/ kg) resting cortical CBF was unchanged, whereas BF‐elicited increases were potentiated 47% at 50 Hz. At 1 hour, resting cortical CBF remained unchanged, and the BF‐elicited responses were remarkably potentiated by 354% at 10 Hz and 67% at 50 Hz. Acetylcholinesterase (AChE) activity measured in the tissue directly beneath the LDF probe was decreased by 84% at a time when these CBF responses were enhanced. These data suggest that H‐PHY substantially enhances the regulation of cortical CBF by the BF, an effect that may be linked to inhibition of cortical AChE activity. This enhancement of cortical CBF may contribute to the efficacy of H‐PHY as a treatment for Alzheimer' disease.