Decrease In AChE Activity Research Articles

Peripheral airway hyperresponsiveness in the choline-deficiently fed rat

Rats fed with choline-deficient diets are known as a model of aging and learning impairments due to acetylcholine (ACh) deficiency in the brain which may be associated with a decrease in acetylcholinesterase (AChE; EC 3.1.1.7). To determined the role of AChE in bronchial responsiveness, we examined the contractile response of isolated lung parenchymal strips to ACh in control rats and rats fed with choline-deficient diets. Concentration-response curves to ACh shifted to the lower concentrations and the maximum respose to ACh was greater in rats fed with choline-deficient diets than in control rats ( P<0.01). Physostigmine (10 −6 M) mimicked effects of choline-deficient diets on the contractile response to ACh. However, concentration response curves to carbachol and 5-hydroxytryptamine did not differ between control rats and rats fed with choline-deficient diets. Choline-deficient diets significantly decreased the AChE activity from homogenates of lung parenchymal tissues ( P<0.01). These results suggest that a decrease in AChE activity of lung tissues may relate to airway hyperresponsiveness to ACh.

Cholinergic hyperinnervation in the cerebral cortex of microencephalic rats does not result in muscarinic receptor down-regulation or in alteration of receptor-stimulated phosphoinositide metabolism.

Administration of methylazoxymethanol (MAM; 25 mg/kg) to pregnant rats at gestational day 15 (GD 15) induces a marked reduction of telencephalic areas of the offspring brain. Previous neurochemical studies demonstrated a marked cholinergic hyperinnervation in the cerebral cortex of microencephalic rats. In this study we have evaluated whether this cholinergic hyperinnervation could result in altered functionality of muscarinic receptors. Acetylcholinesterase activity (AChE) was increased by 69% in the cerebral cortex of MAM treated rats, confirming a relative hyperinnervation, whereas in the hippocampus and striatum no significant changes were observed. Despite the marked hyperinnervation, in the cerebral cortex of microencephalic rats neither muscarinic receptor-stimulated phosphoinositide metabolism nor muscarinic receptor density were altered. No differences in receptor density were also observed in the hippocampus and striatum. Chronic diisopropylfluorophosphate (DFP) administration induced a marked decrease of AChE activity and down-regulation of muscarinic receptors whereas atropine administration resulted in receptor up-regulation in cerebral cortex, striatum and hippocampus of both control and MAM rats. The results confirm a relative cholinergic hyperinnervation in the cerebral cortex of microencephalic rats and demonstrate that the regulation of muscarinic receptor-stimulated phosphoinositide metabolism and muscarinic receptor plasticity is not modified in a condition of increased cholinergic presynaptic terminals.

Effect of thiopental sodium and barbitone sodium on the total acetylcholine content and acetylcholinesterase activity in the brain tissue of Arvicanthis niloticus

1. 1. The total ACh content and AChE activity were determined 1 hr after the i.p. injection of different doses of thiopental sodium (5, 10 and 20 mg/ml/100 g body wt) and barbitone sodium (20, 40 and 80 mg/ml/100 g body wt). 2. 2. The effect of different time intervals (1 min, 10 min, 30 min, 1 hr, 2.5 hr, 5 hr, 8 hr, 12 hr, 24 hr and 48 hr) on the total ACh content and AChE activity was investigated after i.p. injection of 10mg thiopental sodium and 40 mg barbitone sodium/ml/100 g body wt. 3. 3. Both thiopental sodium and barbitone sodium increased the total ACh content in the brain tissue of Arvicanthis niloticus. Both drugs inhibited the brain AChE activity. 4. 4. It is thought that the increase in the total ACh content in the brain tissue of Arvicanthis niloticus may be due to a decrease in the release of ACh from the neuronal tissue and a decrease in AChE activity.

Cultures of central neurons grown in the presence of phencyclidine.

In order to study the mode of action of phencyclidine at the cellular level differentiating cultures of dissociated nerve cells from brain and spinal cord have been used. Cells were grown in the presence of 50-500 microM of PCP or tritium labelled PCP, for the periods of 1-11 days. PCP in the concentration of 500 microM caused progressive degeneration of nerve cells, already noticeable after 24 h. No significant morphological changes were observed in cells exposed to PCP at concentrations up to 200 microM. In brain cultures exposed to 200 microM PCP, 50% decrease of AChE activity was observed. No decrease in enzyme activity was found in cultures of spinal cord.

Enzyme histochemical changes after transection or hemisection of the spinal cord of the rat

The spinal cords of 84 young adult female rats were transected or hemisected at T7 to T8 and the animals autopsied at intervals from 6 h to 14 months postoperatively. Frozen sections of the unfixed spinal cord on either side of the lesion were prepared for enzyme histochemistry, immunocytochemistry, and histology. The most striking enzymatic alterations and their physiological implications were: (i) (Na +K +)-activated ATPase activity decreased in axons of the gray and white matter within 6 h after spinal transection and did not return subsequently, whereas the decrease in activity that occurred contralateral to a hemisection was transient. The decreased activity occurred so promptly as to suggest possible roles in the genesis of the initial flaccid paralysis (spinal shock) in the spinal animal and in the temporary paraplegia seen after subtotal spinal injury. (ii) During the first week postoperatively, many axons in the white matter developed large swellings or small varicosities that reacted strongly only for enzymes normally present in the neuronal perikaryon (e.g., AChE, acid phosphatase, NADH-diaphorase, and G6PDH). This histopathological reaction gradually spread rostrally and caudally from the site of injury, but it disappeared as axonal degeneration supervened. (iii) Within 7 days after spinal transection, many neuronal perikarya were chromatolytic and exhibited decreased AChE activity but normal or increased NADH-diaphorase activity. This response is similar to that seen in the cell bodies of regenerating peripheral axons where anabolic processes are favored over neurotransmission-related functions. (iv) Increased cellularity of the spinal parenchyma adjacent to the lesion resulted largely from the proliferation and hypertrophy of astrocytes. These hypertrophied cells, whose identity was confirmed by GFAP immunocytochemistry, reacted with marked intensity for NADH-diaphorase, G6PDH, and Gly3PDH. Such enzyme changes, characteristic of increased protein turnover, indicate that experimental attempts to control gliosis (e.g., by reducing protein turnover or by other means) could be effectively monitored by enzyme histochemistry.

Molecular species of acetylcholinesterase in denervated rat skeletal muscle

Acetylcholinesterase (AChE, E.C. 3.1.1.7) activity was investigated in homogenates of control and denervated rat extensor digitorum longus muscle. Denervation produced a large, rapid decrease in AChE activity. Calculated on a whole-muscle basis, this decrease was 18% at 2 days after denervation and 75% at 7 days. NaCl (1 m), 0.5% Triton X-100 extracts of extensor digitorum longus muscle were subjected to velocity sedimentation in sucrose gradients. Three peaks of AChE activity were found with sedimentation coefficients of 3.9 S, 9.9 S, and 16.0 S. In control muscles, the distribution of AChE activity among the three peaks was 39, 39, and 14%, respectively. Two days after denervation, this distribution was greatly altered, but the sedimentation coefficients remained the same. Whereas the AChE activity associated with the 3.9 S and 16.0 S peaks was reduced, that of the 9.9 S peak was increased. The greatest quantitative loss in AChE activity was associated with the 3.9 S peak. Seven days after denervation, the AChE activity of each of the three forms was greatly reduced.

Alterations in striatal acetylcholine, acetylcholine esterase and dopamine after methadone replacement in morphine-dependent rats

Chronic treatment of rats with morphine was found to produced a significant increase in endogenous ACh and DA as well as a decrease in AChE activity of rat striatum. Narcotic withdrawal for 48 hr resulted in a reversal of morphine-induced changes in striatal ACh levels and AChE activity whereas the enhanced striatal DA remained unaltered. Methadone replacement failed to affect the changes in striatal ACh and AChE activity but abolished the increases in striatal DA seen in morphine-withdrawn rats. Our results suggest that ‘morphine addiction’ in rats may involve alterations in the cholinergic and dopaminergic mechanisms of the striatum and that methadone replacement influences primarily the changes in the dopaminergic system produced by chronic morphine and its subsequent withdrawal.

The effect of repeated stimulation on the escape reflex and the acetylcholinesterase activity in different parts of the central nervous system in the crayfish ( Pacifastacus leniusculus and Astacus astacus)

1. 1. Repeated mechanical stimulation caused a habituation of the escape reflex of the crayfish Pacifastacus leniusculus but did not change the activity of the AChE in the abdominal ganglia and supraoesophageal ganglion. 2. 2. Repeated electrical stimulation caused a waning of the escape reflex of the crayfish P. leniusculus and Astacus astacus and decreased the activity of AChE in the abdominal ganglia and supraoesophageal ganglion. 3. 3. The decreased AChE activity was not reversed by the addition of the substrate. Substrate concentration for V max (5 × 10 −3 M) and K m (1.6 × 10 −4 M) of the enzyme were the same in the test and control animals. It is suggested that the change in the activity of the AChE was due to a change in the number of active sites of the enzyme. 4. 4. The possible mechanism of the decrease of the activity of the AChE and the significance of the results in the habituation or waning of the escape reflex are discussed.

Biochemical effects of denervation on normal and dystrophic muscle: Acetylcholinesterase and choline acetyltransferase

The activities of AChE and ChAc in homogenates from normal, dystrophic and denervated (3–46 days) mouse gastrocnemii have been reported. When the results are expressed per muscle, AChE activity in normal muscle was 4-fold higher than dystrophic muscle. After denervation the decrease in AChE activity in the normal series paralleled the loss of muscle weight; in the dystrophic series the loss of activity was greater than loss of muscle weight. ChAc activity was approximately 2-fold higher in normal muscle than in dystrophic muscle. After denervation ChAc activity decreased more than 90% in both normal and dystrophic muscle. In both types of muscle a return of enzyme activity was observed after 28 days of denervation.

Studies on the variations of monoamineoxidase and acetylcholinesterase activities in the brain under some environmental conditions

In the previous report, the seasonal variations of monoamineoxidase (MAO) and acetylcholinesterase (Ach-E) activities were observed in the seven parts of rabbit's brains. In this report, the auther investigated the affections of the other environmental conditions (immobilization, cold and noise) on these enzyme activities in the brain parts.The term, geographic region and experimental procedures were the same as mentioned in the previous report ecxept for the exposure to different physical environmental conditions.The seasonal variations of enzymatic activities in the 51 adult male albino rabbits in 3 groups were observed in this report by exposing for 2 hours to the different environments: the first group was immobilized by wrapping up their limbs in supine position, the second group was exposed to the cold at -10±2°C, and the third group was exposed to a noise at the level of 100-105 phon characterized by wide octave-band specturm.The results were as follows:1. When the season was ignored, the increase of MAO activity in cerebellum and the decrease of Ach-E activity in myelencephalon and cerebellum under the cold condition, and the decrease of Ach-E activity in myelencephalon and cerebellum under the noise condition, were observed as compared with control groups, but under the immobilization signigcant change was not observed in any parts of the brain.2. The same response pattern of these enzyme activities was observed in the exposure to the different three conditions, as compared with control during the same seasons. But in spite of the exposure to the same condition, a different response pattern was observed in the different season.3. Without concerning the difference of the exposed conditions, the increase of MAO activity in the summer and the autumn, and the decrease of MAO activity in the winter and the spring, were observed especially in telencephalon, diencephalon, myelencephalon and cerebellum. On the contrary, the decrease of Ach-E activity in the summer and the autumn, and the increase of Ach-E activity in the winter and spring, were observed especially in telencephalon and myelencephalon.From these results, it may be concluded that the each of these different conditions affected on these enzyme activities but there was no difference in the affection of the each condition, and that the seasonal variation was important for providing the control levels of these enzyme activities in the homeostatic response to another new affection.