Abstract— Heating with 2450 MHz microwave radiation has been investigated as a means for animal sacrifice concurrent with enzyme inactivation. Uniform inactivation of cholinesterase (EC 3.1.1.8) in the entire brain can be effected in the rat within 4 s and in the mouse within 2 s without destruction of acetylcholine. The acetylcholine content in the whole brain of a rat was found to be 25.4 ± 1.5 nmol/g after irradiation, in comparison to 13.8 ± 1.7 nmol/g after standard methods of sacrifice. In the mouse whole brain, the comparable acetylcholine contents were 25.5 ± 2.6 and 13.7 ± 1.7 nmol/g, respectively. The value of this procedure for rapid inactivation of enzymes in the study of acetylcholine turnover is discussed.

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—The effects of 2 methods of killing on norepinephrine and dopamine in mouse brain regions were examined. One method utilized decapitation, while the other method utilized heating with microwave irradiation concentrated on the head. The norepinephrine and dopamine contents of the cerebellum, medulla‐pons, midbrain, diencephalon, hippocampus, corpus striatum, and cerebral cortex were determined by methods using liquid chromatography with electrochemical detection. Dopamine content in striatum was also quantitated by the method of gas chromatography with mass fragmentography. A significantly lower value for decapitated animals, as compared to the microwave heated group, was found only for dopamine exclusively in the striatum. Activities of the enzymes tyrosine hydroxylase, DO PA decarboxylase, monoamine oxidase, and catechol‐o‐methyltransferase in the striatum were also examined. These enzymes were totally inactivated by the microwave heating, except catechol‐o‐methyltransferase which was decreased approx 80%. These results support either (1) the existence of a substantial pool of dopamine in the striatum with a very rapid turnover rate or (2) a decapitation‐related release and destruction of striatal dopamine. Measurements of 3‐methoxytyramine in the striatum exhibit post‐mortem increases corresponding to the decreases of dopamine. Use of the rapid tissue enzyme inactivation technique suggests that in vivo levels of this O‐methylated dopamine metabolite are an order of magnitude lower than the results normally obtained after killing by decapitation.

The time course for accumulation of acetylcholine was measured in rat brain regions after treatment with 15 mg/kg, i.v., dichlorvos. With this dose of dichlorvos 84-96;; of the brain cholinesterase is inhibited within 1 min. After killing and concomitant enzyme inactivation through microwave irradiation, the acetylcholine levels were measured by pyrolysis-gas chromatography. In the brain regions studied, the striatum had the highest rate of accumulation of acetylcholine and the cerebellum had the lowest. The calculated turnover time in minutes for the regions of the brain were cerebral cortex 0.9; hippocampus 1 ; striatum 1.4; cerebellum 1.7; medulla-pons 2.2: midbrain 4.5; thalamus 5.6. ADMINISTRATION of the cholinesterase inhibitor dichlorvos causes a marked rapid increase in brain levels of acetylcholine (MODAK et al., 1975). In the adrenergic system, the use of drugs t o block specific steps of the dynamics of biogenic monoamines has been common approach (BRODIE et gl., 1966;NEFF et a/., 1968). The resultant rate of accumulation or decline of the substrate in question is then used t o obtain the synthesis rate of that substrate. By combining rapid enzyme inactivation through microwave irradiation (STAVINOHA et a/., 1970; STAVINOHA et a/.,