ENDOGENOUS ACETYLCHOLINE CONCENTRATIONS IN RAT IRIS-CILIARY BODY

The technique of microwave irradiation, whereby enzymes are inactivate d within milliseconds, was employed to accurately determine the in viv o acetylcholine (ACh) concentration in the iris-ciliary body (ICB). Ra ts were sacrificed by microwave irradiation at 9.5 kW at 2,450 MHz for 0.9 seconds. The eyes were enucleated, the ICBs isolated and 10 ICBs from 10 eyes were treated as one sample. ACh levels were determined us ing high performance liquid chromatography in an immobilized-enzyme re actor. Endogenous ACh levels in the rat ICB were 58.8 +/- 5.0 nmoles ( 8.58 +/- 0.73 mu g) per gram tissue protein (mean +/- SE, 9 samples). A single instillation of 5 mu l of 0.05% atropine in one eye of an ani mal lowered the ACh level in the ICB of the eye (P < 0.02).