动态监测清醒自由活动大鼠纹状体细胞外液乙酰胆碱和胆碱水平的方法

目的　建立动态监测正常清醒自由活动大鼠纹状体细胞外液中乙酰胆碱 (ACh)和胆碱 (Ch)水平的方法。方法　应用脑内微透析与高效液相色谱 (HPLC ) 柱后固定化酶反应器 (IMER ) 电化学检测法 (ED)相结合的技术 ,动态监测正常清醒自由活动大鼠纹状体细胞外液中ACh和Ch水平。结果　大鼠纹状体细胞外液中ACh和Ch浓度在灌流开始时较高 ,然后逐渐降低 ,ACh在灌流进行 2 4 0min后达到较稳定水平 ;Ch浓度则在灌流的 4 5 0min内持续下降。HPLC IMER ED检测ACh和Ch的极限可达 15 0fmol,且至少在 0 12 5～ 1 0 μmol·L-1的范围内线性关系良好。结论　HPLC IMER ED是一种灵敏且可靠的测定ACh和Ch的方法 ,和微透析技术相结合可以动态监测清醒自由活动大鼠脑内细胞外液中ACh和Ch的水平。     

Effect of the ''antidementia drug'' pantoyl-GABA on high affinity transport of choline and on the contents of choline and acetylcholine in rat brain.

1. Effect of pantoyl-gamma-aminobutyric acid (pantoyl-GABA) on high affinity transport of choline into synaptosomes and on the choline (Ch) and acetylcholine (ACh) concentrations of rat brain were studied. 2. Pantoyl-GABA was injected intraperitoneally four times at a dose of 500 mg kg-1 at intervals of 30 min. One hour after the last injection, rats were killed by decapitation for measurement of high affinity transport of Ch into synaptosomes or by microwave irradiation for the measurement of Ch and ACh concentrations. 3. Transport of Ch was increased into synaptosomes prepared from the cerebral cortex and hippocampus, but not into those from the striatum. 4. In the cerebral cortex and hippocampus, Ch concentration was increased and ACh concentration decreased. 5. Since treatments that enhance the activity of cholinergic neurones in vivo are reported to increase high affinity transport of Ch measured in vitro, the present results suggest that pantoyl-GABA may increase cholinergic activity in vivo. This action of the drug may be related to changes in the Ch and ACh concentrations.     

Effect of physostigmine and atropine on acetylcholine turnover in mouse brain

Summary The effect of physostigmine salicylate (0.5 mg/kg, i.p.) alone and in combination with atropine sulfate (25 mg/kg, i. p.) on levels of acetylcholine (ACh) and choline (Ch) and turnover of ACh has been studied in whole brain and striatum of mice. The animals were killed by focussed microwave irradiation and the turnover of ACh was studied after i.v. injection of deuterium labelled Ch by employing mass fragmentography. Physostigmine increased the levels of ACh in whole brain from 24.5–28.0 nmol/g (P<0.001) whereas there was no significant increase in striatum. The levels of Ch were also increased. The turnover rate of ACh was decreased in whole brain from 15.4 to 8.4 and in striatum from 52.9 to 24.4 nmol/g · min. Physostigmine given before or after atropine did not completely block the ACh lowering effect of atropine. When atropine was given before physostigmine the turnover rate of ACh in whole brain was increased to 24.2 nmoles/g · min. The results seem to indicate that there is no clear cut relation between the turnover rate and level of ACh in vivo. The increase of the turnover rate induced by atropine is masked unless a cholinesterase inhibitor is given to protect the newly synthesized labelled ACh released by atropine.A preliminary account of this work was reported at the Symposium on Current Topics in Drug Research, held October 19–21, 1977, at Uppsala, Sweden     

Effects of T-82, a new quinoline derivative, on cholinesterase activity and extracellular acetylcholine concentration in rat brain

The effects of T-82 (2-[2-(1-benzylpiperidin-4-yl)ethyl]-2,3-dihydro-9-methoxy-1H-pyrrolo [3,4-b]quinolin-1-one hemifumarate), a new quinoline derivative, on acetylcholinesterase (AChE) activity and acetylcholine (ACh) release were compared with those of the well-known cholinesterase inhibitors tacrine and E2020. T-82, tacrine and E2020 all concentration-dependently inhibited AChE in rat brain homogenate (IC50 = 109.4, 84.2 and 11.8 nM, respectively). In addition, although tacrine strongly inhibited butyrylcholinesterase (BuChE), T-82 and E2020 showed only weak activity on BuChE in human plasma. In ex vivo experiments, intraperitoneal administration of T-82 at a dose of 30 mg/kg inhibited AChE activity in the hippocampus, frontal cortex and parietal cortex of rats. The effect of T-82 on the extracellular ACh concentration in rat brain was measured using in vivo microdialysis. T-82 at doses of 10 and 30 mg/kg, i.p. increased the extracellular ACh concentration in the hippocampus and striatum in a dose-dependent manner. These findings suggest that T-82 activates the central cholinergic system by selectively inhibiting AChE activity, while weakly affecting peripheral BuChE activity, and that T-82 increases the extracellular ACh concentration in the brain, which is followed by inhibited AChE activity.     

In vitro effects of soman on bronchial smooth muscle

The in vitro exposure of rat bronchial smooth muscle to the cholinesterase inhibitor soman (O-[1,2,2-trimethylpropyl]-methyl-phosphonofluoridate) potentiated the rapid and concentration dependent increase in the contraction induced by acetylcholine (ACh). There was a substantial increase in the response to ACh when soman was present in concentrations from 10 nM to 1 microM which correspond to a 65-100% inhibition of acetylcholinesterase (AChE). The apparent affinity (pD2) to ACh increased from 3.7 to 6.7 without any change in intrinsic activity (alpha) in this concentration interval. In contrast, soman did not alter the apparent affinity or intrinsic activity of carbachol, which supports the suggestion that the effect of soman is entirely due to its anticholinesterase activity. Soman by itself induced contraction which begun at 1-10 nM. This may be explained from its anticholinesterase activity and the subsequent increase in the synaptic concentration of spontaneously released ACh. The effect of soman on inhibition of cholinesterase and carboxylesterases have also been examined. The results demonstrate that low concentrations of soman induces contraction of the airway smooth muscle.     

Effects of chronic lead exposure on levels of acetylcholine and choline and on acetylcholine turnover rate in rat brain areas in vivo

Rats were exposed to lead acetate from birth, and were killed at the age of 44–51 days for analysis of levels and turnover rates of acetylcholine (ACh). Steady-state levels of ACh were not altered in midbrain, cortex, hippocampus, or striatum of lead-exposed rats. Similarly, no changes in choline (Ch) concentrations were found in cortex, hippocampus, or striatum. In the midbrain, however, a 30% reduction in Ch levels was observed. Changes in specific activity of Ch and ACh were measured as a function of time in selected brain areas of rats infused with a radio-labeled precursor of Ch. Specific activities of ACh were not altered. Ch specific activities were, however, significantly elevated in all brain areas examined, as compared with age-matched control rats. The in vivo ACh turnover rate in cortex, hippocampus, midbrain, and striatum was diminished by 35%, 54%, 51% and 33%, respectively. These findings provide direct evidence for an inhibitory effect of lead exposure from birth on central cholinergic function in vivo. Since a significant reduction of body weight was found in those animals treated with lead acetate, the alteration of central cholinergic function may partially be attributed to malnutrition observed in the lead-exposed animals.Part of this work was presented in abstract form (Fed. Proc. 36. 977 (1977))     

A simple method for determination of choline (Ch) and acetylcholine (ACh) in rat brain regions using high-performance liquid chromatography with electrochemical detection (HPLC-ED)

A simple method for the determination of choline (Ch) and acetylcholine (ACh) in rat brain regions by application of high performance liquid chromatography with electrochemical detection (HPLC-ED) is described. Separation of endogenous Ch, ACh, and ethylhomocholine (EHC) as internal standard on a chemcosorb 3C-18 column is followed by electrochemical detection of hydrogen peroxide (H2O2) derived from the compounds. H2O2 was enzymatically produced in the reaction coil (10 m). The assay limit for quantitation was 10--30 pmole for both compounds. The brain tissue was homogenized with 15%-1N formic acid in acetone and centrifuged. The supernatant was washed with either once and then blown off using N2 gas before an aqueous solution was immediately applied for analysis. Recovery rates were 96.1 +/- 1.4% for Ch and 95.6 +/- 2.2% for ACh. The levels of Ch and ACh in rat brain regions after sacrifice either by decapitation or microwave irradiation (10 kW, 2450 MHz, Magnetic-field type) were compared with those previously reported.     

Dose-related inhibition of brain and plasma cholinesterase in neonatal and adult rats following sublethal organophosphate exposures.

Developing mammals are markedly more sensitive to acute toxicity from exposure to a variety of organophosphorus (OP) pesticides. The present study examined dose-related inhibition of both brain and plasma cholinesterase activity in neonatal and adult rats exposed to sublethal doses of one of three common OP pesticides, methyl parathion, parathion and chlorpyrifos. Effective dose 50 (i.e., ED50 or dose which would inhibit 50% of the cholinesterase activity) values were determined and then correlated with an indicator of acute toxicity, the maximal tolerated dose (MTD). It was found that ED50 estimates for both brain and plasma cholinesterase correlated highly (r = 0.932-0.992) with previously derived MTD values. In no case was there a significant difference between in vivo brain and plasma cholinesterase inhibition across doses in neonatal rats was high (r = 0.962-0.975) but lower in adults (r = 0.700-0.943). The results suggest that in vivo inhibitory potency of the three OPs towards either brain or plasma ChE activity is highly correlated with sensitivity to acute toxicity in both neonatal and adult rats. Additionally, under defined experimental conditions, plasma ChE inhibition may be a useful quantitative index for the degree of brain cholinesterase inhibition following OP exposures.     

Cerebral acetylcholine and choline contents and turnover following low-dose acetylcholinesterase inhibitors treatment in rats

Male Sprague-Dawley rats were treated for 3 weeks with (1) regular tap drinking water plus subcutaneous (s.c.) saline (0.5 ml/kg) injections three times/week, (2) pyridostigmine bromide (PB) in drinking water (80 mg/L) plus s.c. saline injections three times/week, (3) regular tap drinking water plus s.c. sarin (0.5 × LD₅₀) injections three times/week, or (4) PB in drinking water plus s.c. sarin injections three times/week. Repeated doses of sarin, in the presence or absence of PB, were devoid of acute toxicity during the three-week treatment period. Two, 4, and 16 weeks post-treatment, animals were given an intravenous pulse injection of choline labeled with 4 deuterium atoms (D4Ch) followed, after 1 min, by microwave fixation of the brain in vivo. Tissue levels of endogenous acetylcholine (D0ACh), endogenous choline (D0Ch), D4Ch, and ACh synthesized from D4Ch (D4ACh) were measured by gas-chromatography mass-spectrometry in hippocampus, infundibulum, mesencephalon, neocortex, piriform cortex, and striatum. Ch uptake from blood and ACh turnover were estimated from D4Ch and D4ACh concentrations in brain tissue, respectively. Statistically significant differences among brain regions were found for D0Ch, D4Ch, D0ACh and D4ACh at 2, 4 and 16 weeks post-treatment. However, differences in the values of these parameters between control and drug treatments were found only for D0ACh and D0Ch at 2 and 4 weeks, but not at 16 weeks post-treatment. In conclusion, the results from these experiments do not support a delayed or persistent alteration in cholinergic function after exposure to low doses of PB and/or sarin.     

Identification of drug receptors in porcine dental pulp by the radioligand binding assay

1. The acetylcholine (ACh), histamine and serotonin (5-HT) receptors in porcine dental pulp were characterized by the radioligand binding assay. 2. For [3H]nicotine binding site, Kd was 8.06 +/- 1.65 nM and Bmax was 270.83 +/- 32.68 fmol/mg protein. 3. For [3H]QNB binding site, Kd was 1.04 +/- 0.14 nM and Bmax was 24.83 +/- 3.09 fmol/mg protein. 4. For [3H]histamine binding site, Kd was 1.22 +/- 0.1 nM and Bmax was 283.15 +/- 33.1 fmol/mg protein. 5. For [3H]5-HT binding site, Kd was 1.41 +/- 0.1 nM and Bmax was 53.1 +/- 3.4 fmol/mg protein. 6. These findings indicate that the specific receptors for ACh, histamine and 5-HT are present in the porcine dental pulp, and that the ACh receptor is predominantly nicotinic.     

Acetylcholine and choline in mouse brain—Influence of peripherally acting cholinergic drugs

The effects of muscarinic drugs on levels of choline (Ch) in brain and blood and on levels and turnover of acetylcholine (ACh) in brain were studied in mice by means of a pulse injection of ²H₆-Ch and analysis of Ch and ACh by mass fragmentography. Oxotremorine (OT) increased the levels of Ch and ACh and reduced the turnover of ACh. Muscarine, which is supposed not to penetrate into brain increased Ch but not ACh levels and reduced ACh turnover. Methylatropine had no effect by itself but when given before OT it abolished the increase in blood Ch and counteracted the OT effect on levels and turnover of ACh. The results demonstrate, that the concentration of ACh does not solely regulate its turnover and that apart from the central actions of OT its peripheral actions play an important role for the turnover of ACh and levels of ACh and Ch in brain.     

Effects of diazepam on blood choline and acetylcholine turnover in brain of mice

The effect of diazepam on the acetylcholine (ACh) synthesizing system has been studied in mouse brain in vivo. ACh and choline (Ch) were analyzed by gas chromatography - mass spectrometry using deuterated internal standards. Turnover of ACh was studied by following the incorporation of Ch into ACh after an intravenous injection of [2H6]-Ch. The mice were killed by focussed microwave irradiation on the head. Diazepam was found to increase the endogenous level of Ch, while the concentration of [2H6]-Ch was only half of that of the controls. The incorporation of [2H6]-Ch into [2H6]-ACh was decreased, while the endogenous level of ACh was slightly increased. The turnover rate of ACh was decreased, consistent with a decrease in neuronal excitability induced by diazepam. The elevated endogenous Ch-level and the lower concentration of [2H6]-Ch in the brain, might be explained by an effect of diazepam on the Ch-transport across the blood-brain barrier. This theory is supported by experiments where levels of endogenous and [2H6]-labelled Ch were analyzed in blood following an intravenous injection of [2H6]-Ch. The [2H6]-Ch was found to be eliminated faster in blood from diazepam treated mice. The increased blood level of endogenous Ch, induced by the [2H6]-Ch injection also returned more rapidly to normal in these animals. This is consistent with peripheral Ch being eliminated faster when the central Ch supply is decreased.     

Pharmacological properties of donepezil hydrochloride (Aricept), a drug for Alzheimer's disease

One of the most consistent changes associated with Alzheimer's disease (AD) is a deficit in central cholinergic neurotransmission. Donepezil hydrochloride (DPZ), a novel class of cholinesterase (ChE) inhibitors, inhibits degradation of acetylcholine (ACh) and activates central cholinergic system. In in vitro studies, DPZ more selectively inhibited acetylcholinesterase (IC50: 6.7 nM) than butyrylcholinesterase (IC50: 7400 nM), while tacrine inhibited both acetylcholinesterase (IC50: 77 nM) and butyrylcholinesterase (IC50: 69 nM). After oral dosing, DPZ (ID50: 2.6 mg/kg) inhibited brain ChE dose-dependently without any remarkable effect on ChE in the heart and small intestine, whereas tacrine (ID50: 9.5 mg/kg) inhibited ChE equally in the brain and peripheral tissues. Brain microdialysis revealed that DPZ (2.5 mg/kg) enhanced extracellular ACh concentrations in the cerebral cortex and hippocampus in rats. In behavioral studies, DPZ counteracted both the deficit in passive avoidance induced by lesioning of the nucleus basalis magnocellularis (0.125-1.0 mg/kg) and the impairment in acquisition of a hidden-platform water maze task after lesioning of the medial septum in rats (0.5 mg/kg). DPZ also inhibited the scopolamine-induced impairment of radial maze performance (0.5 mg/kg). Placebo-controlled clinical studies of 12- and 24-week treatments of DPZ (5 mg, 10 mg/day) clearly showed an improvement in cognitive scores of probable AD patients.     

Regulation of vascular nitric oxide in vitro and in vivo; a new role for endogenous hydrogen sulphide?

BACKGROUND AND PURPOSE: The aim of these experiments was to evaluate the significance of the chemical reaction between hydrogen sulphide (H2S) and nitric oxide (NO) for the control of vascular tone. EXPERIMENTAL APPROACH: The effect of sodium hydrosulphide (NaHS; H2S donor) and a range of NO donors, such as sodium nitroprusside (SNP), either alone or together, was determined using phenylephrine (PE)-precontracted rat aortic rings and on the blood pressure of anaesthetised rats. KEY RESULTS:Mixing NaHS with NO donors inhibited the vasorelaxant effect of NO both in vitro and in vivo. Low concentrations of NaHS or H2S gas in solution reversed the relaxant effect of acetylcholine (ACh, 400 nM) and histamine (100 microM) but not isoprenaline (400 nM). The effect of NaHS on the ACh response was antagonized by CuSO(4) (200 nM) but was unaffected by glibenclamide (10 microM). In contrast, high concentrations of NaHS (200-1600 microM) relaxed aortic rings directly, an effect reduced by glibenclamide but unaffected by CuSO4. Intravenous infusion of a low concentration of NaHS (10 micromol kg(-1) min(-1)) into the anaesthetized rat significantly increased mean arterial blood pressure. L-NAME (25 mg kg(-1), i.v.) pretreatment reduced this effect. CONCLUSIONS AND IMPLICATIONS: These results suggest that H2S and NO react together to form a molecule (possibly a nitrosothiol) which exhibits little or no vasorelaxant activity either in vitro or in vivo. We propose that a crucial, and hitherto unappreciated, role of H2S in the vascular system is the regulation of the availability of NO.     

A neurochemical study on brain cholinergic neuron; a newly improved pyrolysis gas chromatography/mass spectrometry (PY/GC/MS) method and its application

A new method for measuring the endogenous acetylcholine (ACh) and choline (Ch) levels using a PY/GC/MS was established, and then the alteration of cholinergic neurons in the iminodipropionitrile (IDPN) induced dyskinesia model rat brain was studied. In performing the determinations of small amounts of brain ACh and Ch levels using a curie point PY/GC/MS, the following points were improved upon in the present study: 1) We shortened the distance between the sample tube and injection port allowing the rapid transformation to an analytical system without sub-reaction and re-synthesis of demethylated products. 2) The suitable pyrolytic temperature (curie point) was adjusted to 333 degrees C. 3) Then the aqueous sample (2 microliters) was wrapped in a pyrofoil with a curie point of 333 degrees C followed by drying at 80 degrees C. Subsequently, the pyrofoil was formed by a 200 kgf/cm2 press. 4) A fused silica capillary column (DB-5) was used instead of a pre-packed column (Jenden Phase). By these improvements, both calibration curves of ACh and Ch have high linearities (r = 0.988) between 1 pmol and 2 pmol, and the apparent peak of quasi-molecular ion and less fragment ion of each Ch analog was obtained. In the globus pallidus, caudate nucleus, hippocampus and cerebellum of IDPN induced dyskinesia model rats, remarkable reductions of ACh levels were observed using our newly improved PY/GC/MS method. Thus, our improved method can be utilized for measuring ACh levels in small discrete brain regions.     

On the turnover of acetylcholine in mouse brain: Influence of dose size of deuterium labelled choline given as precursor

The influence of the dose size of precursor choline (Ch) on the turnover rate of acetylcholine (ACh) has been studied in whole brain and striatum of mice. Different doses of deuterium labelled Ch (d₆-Ch) were injected i.v. and concentrations of endogenous and d₆-labelled Ch and ACh were estimated at various times by mass fragmentography using deuterium labelled (d_9^?) Ch and ACh as internal standards. At doses of 1.25–20 μmole/kg of d₆-Ch the endogenous concentration of Ch in blood wastransiently elevated for 5 min. However, the endogenous concentrations of Ch and ACh in whole brain and striatum were not affected. The fractional rate constant of ACh synthesis and efflux, K_a a measure of the turnover rate of ACh, was influenced by the dose size of precursor d₆-Ch. In whole brain, K_a was ca. 0.7 at doses of 5–20 μmole/kg of d₆-Ch. At lower doses K_a increased to ca. 1.0. In striatum, K_a was ca. 0.7 at doses of 20–40 μmole/kg of the precursor. At lower doses K_a became smaller and decreased to 0.10 at a dose of 1.25 μmole/kg of d₆-Ch. When the calculations of K_a were corrected for the part of d₆-Ch concentration in the brain contained in blood the figures were invariably increased by 20–40%. However, the increase was not correlated with the precursor dose size. It was found that the ratio between S_ACh and S_Ch decreased with increasing dose of d₆-Ch until it reached plateau values at doses of 2.5 μmole/kg and higher in whole brain and at 10–20 μmole/kg and higher in striatum. It is proposed that the decreased ratio at low concentrations of d₆-Ch depends on saturation of the high affinity (HA) uptake system for Ch coupled to ACh synthesis. At higher doses of d₆-Ch, ACh synthesis by the low affinity (LA) uptake system for Ch became increasingly important and was not yet saturated at the highest dose given (40, μmole/kg). It is suggested that the synthesis rate of ACh can be studied with either very low doses of labelled Ch that do not saturate the HA uptake system or with sufficiently high doses at which the influence of the LA uptake system on the synthesis rate of ACh is dominant.     

The effect of atropine on the turnover of acetylcholine in the mouse brain.

The effect of atropine on the acetylcholine (ACh) turnover in the mouse brain has been studied and related to the central effect (motor activity) of the drug. At the threshold dose for maximal increase in motor activity, atropine had no measurable effect in the brain on the initial rate of formation of labelled ACh from labelled choline (Ch) i.v. injected. However, if atropine was injected 3 min after the injection of labelled Ch, when the labelled ACh had reached its peak value in the brain, there was a more rapid exponential decline of labelled ACh. This was assumed to be an indication that atropine increases the turnover of ACh in the brain. The specific radioactivity of ACh was not changed 2-17 min after the atropine injection, which indicates that atropine does not preferentially increase the release of newly synthetized ACh.     

Action of tacrine on muscarinic receptors in rat intestinal smooth muscle

1 The reversible cholinesterase inhibitor, tacrine (THA) was examined against the contractions of rat duodenum to acetylcholine and carbachol (cholinesterase resistant). 2 Tacrine (10^–6 M ) showed a similar behaviour to physostigmine (10^–6 M ), changing the characters of the concentration–response curve to Ach. The contractual responses were shifted to the left at low concentrations of ACh to reveal a bell‐shaped curve with declaring contradictions at high concentrations of ACh. 3 Antagonism by atropine (10^–8 M ) was reduced in the presence of tacrine (10.54, dose‐ratio) compared with the shift of the curve in the absence of tacrine (73.9, dose‐ratio). The declining phase of the concentration–response curve to ACh was also antagonized by atropine. 4 Further evidence for muscarininc receptor antagonism by tacrine was a small rightward shift of the concentration‐response curve for carbachol, an agonist immune to cholinesterase. 5 This study has shown that tacrine acts both as a cholinesterase inhibitor and muscarinic antagonist on rat intestinal smooth muscle.     

Time course effects of soman on acetylcholine and choline levels in six discrete areas of the rat brain

The time course of changes in rat brain levels of acetylcholine (ACh) and choline (Ch) was investigated following a single SC injection of soman (0.9 LD₅₀, 120 g/kg) to understand the relationship between central neurotransmitter alteration and soman toxicity. Of the animals exposed to the dose of soman, 46% died within 24 h, with maximum mortality occurring during the first 40 min following soman administration. In a second group, surviving rats were killed at various times after treatment by a beam of focused microwave radiation to the head, and ACh and Ch levels were determined by gas chromatography-mass spectrometry. Soman produced a maximal ACh elevation in the brain stem at 20 min (34.4%), in cerebellum at 40 min (51.9%), in cortex and striatum at 2 h (320.3% and 35.2%, respectively), and in hippocampus and midbrain at 3 h (94.5% and 56.8%, respectively). ACh levels remained above normal approximately 30 min in the brain stem; 2 h in the midbrain, cerebellum, and striatum; 8 h in the cortex; and 16 h in the hippocampus. Ch levels were elevated in all areas except the striatum. Ch maxima occurred at 10–40 min and returned to control levels approximately 3 h after injection. Results suggest that perturbation of ACh levels due to soman was not uniform throughout the brain and that soman toxicity may reflect ACh changes in multiple areas, rather than changes in any given area. These data further suggest a possible relationship between elevated Ch levels and soman toxicity.The opinions or assertions contained herein are the private views of the author and are not to be construed as reflecting the views of the Department of the Army or the Department of Defense     

Effects of Pyridostigmine and Cholinolytics on Cholinesterasx and Acetylcholine in Soman Poisoned Rats

ABSTRACT

Soman reduced blood and brain cholinesterase (ChE) activity to less than 15% and increased cerebral acetylcholine (ACh) levels to 137.4% of control. When pyridostigmine (P) was used as a prophylatic adjunct, it reduced blood ChE activity to 31.6% of control, failed to significantly alter brain ChE activity, and protected more than 70% of the blood (but not brain enzyme) from phosphonylation by Soman

Benactyzine (B) was more effective than atropine (A) in reducing cerebral ACh concentrations, while a combination of the two was more effective than either alone. A prophylaxis of P + A + B was effective in controlling ACh levels in rats poisoned with one LD50 dose of Soman, Since P did not diminish the effects of the cholinolytics on cerebral ACh, this (together with the enzyme data) suggests that the two cholinolytics alone provided the central protection.