Significant Increase In Choline Acetyltransferase Activity Research Articles

Evaluation of the neurorestorative effects of the murine β-nerve growth factor infusions in old rat with cognitive deficit

The nerve growth factor (NGF) is known to participate in the regulation of the expression levels and activity of the choline acetyltransferase (ChAT) in the nervous system. This enzyme is sensitive to the degenerative changes found in Alzheimer’s disease (AD). We compared the effectiveness of intraparenchymal (ip) and intracerebroventricular (icv) administration of the murine β-NGF (β-NGFm) produced in our laboratories, through the determination of the expression levels and activity of the ChAT, and the evaluation of behavioral recovery in aged rat with cognitive deficit. Our results indicated that icv infusion of β-NGFm stimulates the expression levels of ChAT gene in the striatum of old rats. Remarkable losses in the ChAT activity were observed in the septum and striatum of old rats. Exogenous administration of β-NGFm produced a significant increase of ChAT activity in these brain regions differentially according to the administration pathway. The behavioral studies demonstrated that the administration pathway is an important factor in order to obtain the best results for a neurorestorative treatment.

CENTRAL AND PERIPHERAL ALTERATION OF THE CHOLINERGIC ENZYMES ACTIVITIES OF THE RAT IN RESPONSE TO REPEATED AND ACUTE THALLIUM EXPOSURE

Many of the reported symptoms of thallium toxicity are effects known to be mediated by the autonomic nervous system through the cholinergic pathway. The present study examines the effect of acute and repeated exposure to thallium on the activity of the cholinergic enzym es, acetyl cholinesterase (AChE) and choline acetyltransferase (ChAT), in various brain regions, segments of the gastrointestinal (GI) tract, and regions of the urinary bladder. Adult male Sprague-Dawley rats were injected (ip) with either saline, 0.1, 1.0, or 5.0 mg/kg of thallium acetate, daily for 5 days (for the repeated study) or a single dose of 25 mg/kg (for the acute study). The activity of the cholinergic enzymes was measured at either 24 or 48 h after the last dose. The highest dose of thallium (5 mg/kg) was fatal at 48 h after the last injection (6 rats out of 8 died). At lower doses, repeated thallium exposure caused a decrease in AChE activity in som e brain regions (nucleus accum bens and hypothalamus) and urinary bladder regions and an increase in AChE activity in the striatum and m idbrain regions. The effect of a single dose of 25 mg/kg was m ore pronounced, resulting in a significant decrease in AChE activity in the hypothalamus, nucleus accumbens, and the duodenal segment of the GI tract as well as in the two regions of the urinary bladder. Thallium exposure, especially in the high single dose, resulted in a significant increase in ChAT activity 24 h after injection in the nucleus accumbens, brain stem, ileum and duodenum segments of the GI tract, and both regions of the urinary bladder. Thus, the altered activities of the cholinergic enzymes reported here in response to thallium exposure may support a role for the cholinergic system in som e pathological conditions associated with thallium toxicity.

Enhancements of choline acetyltransferase activity and nerve growth factor secretion by Polygalae radix-extract containing active ingredients in Kami-untan-to

The effects of Kami-untan-to (KUT) and component herbs on choline acetyltransferase (ChAT) activity of basal forebrain cells and nerve growth factor (NGF) secretion from astroglial cells were examined. When rat embryo basal forebrain cells were cultured in the presence of the extracts of KUT or Polygalae radix (PR) for 3 days, a significant increase of ChAT activity was observed. An extract of KUT minus Polygala radix did not enhance the ChAT activity in basal forebrain cells. Polygalae Radix extract at 12.5-50 μg/ml increased ChAT activity of basal forebrain cells and 25 μg/ml of Polygalae radix extract time-dependently enhanced ChAT activity and ChAT mRNA. Oral administration of PR-extract or its hydrolyzed common constituents, 3, 5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid), in Polygalae radix, induced ChAT activity in cerebral cortex of basal forebrain lesioned rats. PR-extract also induced the NGF secretion in astroglial cells. These results suggest that Polygala radix has an important role on the enhancing effects of KUT on ChAT activity and NGF secretion.

Effects of tacrine (THA) on spatial reference memory and cholinergic enzymes in specific rat brain regions

Cognitive function of rats treated with saline (control), THA (8 mg/kg, i.p.), scopolamine (5 mg/kg, i.p.), or a combination of THA (8 mg/kg) and scopolamine (5 mg/kg) was tested in the Morris water maze. The latency to find the platform in the water maze was used to evaluate performance. THA did not significantly alter the latency period as compared to control rats. Scopolamine resulted in a highly significant (p < 0.01) increase in latency period (183% increase) as compared to saline treated controls. However, when THA was concurrently administered with scopolamine, it was able to completely reverse the performance decrement induced by scopolamine. Immediately following spatial reference memory testing, animals were sacrificed by decapitation one hour post injection. Brains were immediately removed and the cortex, hippocampus, hypothalamus, and pituitary were dissected and their choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity were determined spectrophotometrically. THA administration resulted in a significant increase in ChAT activity in the cortex (23% increase). However, when THA was concurrently administered with scopolamine, a significant increase in ChAT activity was observed in cortex (77% increase), hippocampus (32% increase), hypothalamus (97% increase), and pituitary (92.5% increase). THA administration resulted in a significant decrease in AChE activity (p < 0.001) in cortex (62% decrease), hippocampus (78% decrease), and hypothalamus (90% decrease). When tacrine was administered with scopolamine, a significant increase was found in the cortex (197% increase) and the hippocampus (207% increase). In conclusion, the increase in ChAT activity produced by tacrine may in part explain its ability to reverse the scopolamine induced decrease in spatial reference memory and may play a role in its beneficial effect in improving cognitive ability.

Biochemical, morphological, and functional changes during peripheral nerve regeneration

The success of axon regeneration after nerve injury should be judged by the extent to which the target organs regain their function. Recovery of muscle contraction involves axon regeneration, reestablishment of nerve-muscle connections, recovery of transmission, and muscle force. All these processes were investigated under the same experimental conditions and correlated in order to better understand their time-course and interdependence. The sciatic nerve of a rat was crushed in the thigh. The ingrowth of regenerating motor axons into the soleus (SOL) and extensor digitorum longus (EDL) muscles was monitored by measuring the activity of choline acetyltransferase (ChAT), a marker enzyme for cholinergic nerve terminals, in the muscles. The electron microscopic cytochemistry of acetylcholine esterase (AChE) was used to estimate the reestablishment of neuromuscular junctions in these two muscles. The recovery of muscle contraction was followed by measuring the force of isometric contraction in the triceps surae muscle in vivo. The pattern of ChAT recovery during reinnervation was similar in the EDL and SOL. The statistically significant increase of ChAT activity in these muscles, 14 d after the nerve crush, signified the entry of regenerating axons into the calf muscles. Electron microscopic cytochemistry revealed the first small nerve endings in contact with the denervated end plates 12 d after denervation. Subsequently, the number of reinnervated motor end plates and the surface area of the neuromusclar junctions steadily increased. The recovery of muscle force started between d 14 and 21 after the nerve crush. Thirty-five days after denervation, the difference between the muscle force of the reinnervated muscle and the control became statistically insignificant. Morphological normalization of the motor end plates was practically complete 33 d after denervation, concomitant with the normalization of the muscle force. At that time, however, ChAT activity in both muscles was still clearly subnormal (33.5% in EDL and 45% of the control in SOL) and therefore does not reflect the true extent of muscle force recovery. Yet, it seems that in spite of this, the regenerated nerve terminals contained sufficient amounts of acetylcholine (ACh) to trigger normal muscle contractions.

Altered brain cholinergic enzymes activity in the genetically obese rat

Genetically obese male Zucker rats (fa/fa) and their lean littermates (Fa/-) were used in this experiment. Fourteen-week-old obese and lean littermates were sacrificed and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) enzymes were assayed in specific brain regions. The assays of these enzymes indicate that obese animals had a significantly lower ChAT activity in the cerebellum, pons, and cerebral cortex and a significant increase in ChAT activity in the thalamus and hypothalamus. Meanwhile, the cerebral cortex, cerebellum, midbrain, thalamus and hypothalamus of the obese animals showed significantly higher AChE activity than their lean littermates. It was concluded from this study that obesity may be associated with changes in the enzymes of the brain cholinergic system.

Neuronal plasticity in the developing chick brain: interaction of ethanol and neuropeptides

We have examined the influence of ethanol on cholinergic and catecholaminergic neuronal expression in the chick embryonic brain using choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH) activities as respective neuronal markers. Ethanol (5–20 mg/50 μ1/day), administered to embryos in ovo from day 1 to 3 of development produced a dose-dependent decrease in ChAT activity while TH activity exhibited a dose-dependent increase when embryos were sacrificed on embryonic day 8. The optimal neurotoxic dose of ethanol following this paradigm was 15 mg/day and the LD 50 was 17.5 mg/day for the 3 days. Subsequently, embryos were administered ethanol (15 mg) either alone or concomitantly with growth hormone-releasing hormone (GH-RH; 100 ng/50 μ1/day). Previous studies from this laboratory have demonstrated both potent cholinotropic and catecholaminotropic effects for this neuropeptide, results confirmed in this study. Co-administration of ethanol and GH-RH resulted in a significant increase in ChAT activity as compared to both saline- and ethanol-treated controls when examined on day 8 of embryonic growth. No additive effect was observed in TH activity following co-administration of ethanol and GH-RH. The findings from this study are interpreted to mean that GH-RH represents a potent secondary signal to undifferentiated neuroblasts which may lead to a restoration of the cholinergic neuronal population following neurotoxic insult by ethanol.

Effect of Acute Cocaine Administration on the Cholinergic Enzyme Levels of Specific Brain Regions in the Rat

Adult male Sprague-Dawley rats weighing between 170 and 204 g and maintained under controlled lighting and temperature conditions were used in this experiment. One group of animals was treated with 30 mg/kg of cocaine hydrochloride and the other group with saline. Rats were decapitated 20 min after cocaine injection and their brains were removed and the different regions including the medulla, pons, midbrain, cerebellum, hypothalamus, thalamus, hippocampus, and the cortex were dissected. All brain regions were assayed for choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities. The results obtained indicated that the administration of cocaine was associated with significant increases (p less than 0.01) in AChE activity in the medulla, pons, midbrain, hypothalamus, thalamus, and also in the hippocampus (p less than 0.05). A significant decrease in ChAT activity was found in the pons (p less than 0.01), hypothalamus, and thalamus (p less than 0.05), while a significant increase in ChAT activity was found in the cortex (p less than 0.05). The results suggest that the changes in general activity followed by stereotypic behavior may be related to the changes in the levels of cholinergic enzymes in specific brain regions.

Effect of diabetes on the enzymes of the cholinergic system of the rat brain

Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities were determined in several brain regions of normal and streptozotocin-induced diabetic rats. The diabetic rats exhibited significant increase in ChAT activity (p less than 0.05) in all brain regions studied except for the cortex and the midbrain. Meanwhile, the diabetes condition was associated with significant increase (p less than 0.05) in AChE activity of the bulbus olfactorius, medulla oblongata and cerebellum. These data suggest that uncontrolled diabetes is associated with significant alterations in the brain cholinergic systems.

Brain cholinergic involvement in the diurnal variations of the rapid development of tolerance to the hypothermic effect of apomorphine.

Male Sprague-Dawley rats maintained under controlled environmental conditions were used. Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities were determined in the cerebral cortex, bulbus olfactorius, midbrain, hypothalamus, hippocampus, cerebellum, pons and medulla oblongata of control rats and rats treated with apomorphine (15 mg/kg, i.p.) after a single dose or after a second dose administered 24 h later at 10.00 or 22.00 h. Results of this experiment indicate that the repeated administration of apomorphine at 10.00 h was associated with rapid development of tolerance to the hypothermic action of this drug. A single injection of apomorphine resulted in significant (p less than 0.01) decrease of AChE and significant increase of ChAT activity (p less than 0.01) in the cortex, hypothalamus and pons. There were no significant differences between tolerant and control animals in the activities of AChE or ChAT in the bulbus olfactorius, cerebral cortex, midbrain, pons or medulla. On the other hand, repeated administration of apomorphine at 22.00 h was not associated with tolerance to the hypothermic action of this drug. A single injection of apomorphine at 22.00 h resulted in significant (p less than 0.01) increase in AChE activity of the midbrain, hippocampus, and the medulla oblongata with no significant changes in the cerebral cortex and bulbus olfactorius. There was a significant decline (p less than 0.01) of ChAT activity of the hypothalamus, hippocampus, cerebral cortex and the medulla oblongata (p less than 0.05). Meanwhile, there was a significant (p less than 0.05) increase of ChAT activity of the midbrain with no significant changes in the cerebellum, pons and the bulbus olfactorius.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cell division, cell density, and cyclic nucleotides on choline acetyltransferase activity in a cholinergic neuroblastoma cell line (S-20Y).

We investigated the effects of a number of experimental perturbations on choline acetyltransferase (ChAT) in a cholinergic mouse neuroblastoma cell line (S-20Y). ChAT specific activity increased by 4.5-fold during growth, suggesting that enzyme activity is dependent on increased cell density. This was confirmed by assessing enzyme activity at differential initial seeding densities. ChAT activity was also markedly enhanced by 1 mM dibutyryl cyclic-3',5'-AMP (dBcAMP), an effect that was blocked by cycloheximide. Confirmation of the dBcAMP effect was achieved with forskolin, a compound known to enhance intracellular cyclic AMP; forskolin (100 microM) caused a significant increase in ChAT activity. After a 20-h latent interval ChAT activity was also enhanced significantly by cytosine arabinoside. The common element in these diverse effects on ChAT activity may be cessation of cell division, although cell-cell interactions at the level of the cell membrane may also be important in the control of ChAT in S-20Y.

Changes in high affinity choline uptake in rat cortex following lesions of the magnocellular forebrain nuclei

High affinity choline uptake (HACU) and choline acetyltransferase (CAT) were measured in the cerebral cortex of rats 4 and 20 days after placing electrolytic lesions in the magnocellular forebrain nuclei (MFN) or in the pallidum. Four days after MFN lesion a 40–50% decrease in ipsilateral cortical HACU was found and a slightly smaller decrease was found 4 days after the pallidum lesion. Twenty days after the lesion, HACU activity returned to control values in the ipsilateral parietal cortex, its decrease was smaller than 4 days postlesion in the ipsilateral frontal cortex and a significant increase was found in the contralateral cortex. CAT activity showed a 40% decrease in the frontal, parietal and occipital ipsilateral cortex 4 days after MFN lesion. The same decrease was found 20 days postlesion. However, at this time a significant increase in CAT activity was detected in the contralateral cortex. The ipsilateral recovery of HACU activity 20 days after the lesions and the contralateral increase in HACU and CAT activity demonstrate the remarkable and widespread functional adjustment associated with discrete brain lesions. The existence of a large cholinergic pathway projecting to the neocortex from the basal forebrain region is also confirmed.

Increase in activity of choline acetyltransferase in the dorsal raphe nucleus following habenular deafferentation

In the rat the major source of afferents to the dorsal raphe nucleus (DR) is the lateral habenulal, 12,13, which receives a heavy projection from the entopenduncular nucleus (pallidal formation in rodents). This is especially interesting because the DR, in turn, projects to the neostriatum 14. Although the lateral habenula (LH) shows a strong acetyl cholinesterase reaction 11, as does the DR to a lesser degree s, pharmacological manipulations have suggested that the habenulo-raphe connection is mediated by gamma-aminobutyric acid 17. Nevertheless, enzyme assays of either choline acetyltransferase (CAT) or glutamic acid decarboxylase in the DR showed no changes after large lesions of the habenular complex 5. These results led us to study, by means of a radioenzymatic method, CAT activity (the enzyme that catalyzes the synthesis of acetyl choline from choline and acetyl-CoA) in the DR following very specific lesions of the LH. We now report a significant increase of CAT activity in the DR following its habenular deafferentation. Male adult (200-250 g body weight) white rats were used in these experiments, which included control (untouched), sham-operated and habenular-lesioned animals. They were placed under pentobarbital anesthesia (40 mg/kg) in a Kopf apparatus, without lesioning the tympanic membrane; stereotaxic coordinates were found after small corrections to a common atlas 15. The electrode was introduced to the LH either vertically or at a 10 ° angle in the transverse plane. Bilateral lesions of the LH were made using a tungsten electrode insulated with epoxy except at the tip (200 #m thick, 300/~m long). A small current (1 mA for 5-7 sec) passing through this electrode was used for lesioning, with excellent results (Fig. 1A). Sham-operated animals were treated identically, with the exception that the electrode tip was left just above the habenula and current was not passed. After 7 days animals were killed in sequence (one control, one sham, one lesioned) by decapitation; the brains were quickly removed and frozen on dry-ice. With a razor blade two blocks were made: (1) that one