Comparison of two methods for estimating the acetylcholine turnover in discrete rat brain structures.

The acetylcholine turnover rate was determined in olfactory tubercle, nucleus accumbens and striatum of rat brain. The calculation of turnover rates was carried out by means of two different methods: a two compartment analysis and the finite differences method. After pulse injection of [3H]choline the radioactivity of both [3H]acetylcholine and [3H]choline was measured in the above mentioned brain areas. The contents of acetylcholine and choline were measured radioenzymatically. By using the two compartment model the following acetylcholine turnover rates were obtained: olfactory tubercle, 0.577; nucleus accumbens, 0.679; striatum, 1.110 (mumoles/g X hr). When using the finite differences method the values were: olfactory tubercle, 0.517; nucleus accumbens, 0.822; striatum, 1.115 (mumoles/g X hr). This demonstrates that the results obtained by applying the two different methods are nearly identical. Advantages and disadvantages of the two methods are discussed.