Rate of Accumulation of Acetylcholine in Discrete Regions of the Rat Brain After Dichlorvos Treatment

Abstract

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/.,

Differential Modulation of Muscarinic Receptors in the Rat Brain by Repeated Exposure to Methyl Parathion.

“…Previous study showed a significant regional variation on the density of cholinergic innervation to the brain and also in the level, synthesis or turnover rate of endogenous ACh (Stavinoha et al, 1974). In addition, Stavinoha et al (1976) measured the accumulation of ACh in rat brain regions after administration of dichlorvos and demonstrated that the striatum had the highest rate of accumulation of ACh followed by cerebral cortex and hippocampus, and the cerebellum had the lowest. The larger accumulation of neurotransmitter, ACh, may explain the greater downregulation of receptor in this region.…”

Determination of biogenic quaternary ammonium compounds on fused silica capillary columns with a splitless injector as a chemical reactor/pyrolysis chamber

“…First, solutions of choline ester salts denature far more slowly in acetonitrile than in methanol (presumably an aprotic solvent effect). Secondly, acetonitrile is routinely used in the extraction of choline esters from biological samples [9,12,14,15,20].…”

LEVELS OF CYCLIC NUCLEOTIDES IN MOUSE REGIONAL BRAIN FOLLOWING 300 ms MICROWAVE INACTIVATION1

“…The finding that cyclic GMP changes very slowly while cyclic AMP changes very rapidly complicates the postulated relationship of these nucleotides with the cholinergic and adrenergic systems. In brain tissue, the calculated synthesis rate for norepinephrine is of the order of 0.7 nmol/g/h (NEFF et al., 1971) while acetylcholine is approx 200nmol/g/h (STAVINOHA et al, 1976). Thus, while the kinetics seem reversed, it may be possible that the neurohumoral responsiveness of cyclic nucleotide systems is related t o factors which are independent of basal synthesis levels.…”