Search PubMed⌕ Search

Biomedical subjects

T Nabeshima

Publications and source records attributed to T Nabeshima.

At least 145 records · Page 8Linked to original sources
PubMed1997

Effects of VA-045 on learning and memory deficits in traumatic brain injury (TBI)-induced retrograde and anterograde amnesic mice.

1. No specific regimen has been developed to treat post-traumatic amnesia in man. In the present study, we examined the effects of (+)-eburnamenine-14-carboxylic acid (2-nitroxyethyl) ester (VA-045), a novel derivative of apovincaminic acid, on learning and memory deficits associated with a mild traumatic brain injury (TBI) in mice. 2. Two kinds of amnesia, TBI-induced retrograde amnesia (TRA) and anterograde amnesia (TAA), were produced by means of post- and pre-acquisition head injury, respectively, by a simple weight-drop device. A novel procedure of water-finding task was used to assess learning and memory functions. 3. Both TRA and TAA mice were dramatically impaired in the task performance, with prolonged latencies for finding and drinking in either retention test or retest, indicating that retention was impaired in TRA mice while learning and retention were impaired in TAA mice. 4. VA-045 administered 30 min post-trauma in TRA mice dramatically shortened the prolonged latencies for finding and drinking in both retention test and retest, indicating that VA-045 significantly improved the retention deficit observed in TRA mice. 5. VA-045 administered 30 min post-trauma in TAA mice dramatically attenuated the prolonged latencies for finding and drinking in both retention test and retest, indicating that VA-045 significantly improved the learning and retention deficits observed in TAA mice. 6. Administration of VA-045 30 min pre-trauma in normal mice markedly attenuated the delay of latencies for finding and drinking after trauma in both retention test and retest, which shows that VA-045 significantly prevented learning and retention deficits after TBI. 7. Motor activities were not significantly affected by either the TBI or the chemical treatment at the time of task examination in either experimental model. 8. It is concluded that VA-045 may have potential effects on learning and memory deficits observed in either TBI-induced retrograde or anterograde amnesia.

Amnesia↗
PubMed1997

Simultaneous measurement of nitrite and nitrate levels as indices of nitric oxide release in the cerebellum of conscious rats.

We examined the modulation of nitric oxide production in vivo by measuring levels of nitrite (NO2-) and nitrate (NO3-) in the dialysate of the cerebellum in conscious rats, by using an in vivo brain microdialysis technique. The levels of both NO2- and NO3- were decreased by the intraperitoneal injection of NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, whereas NG-nitro-D-arginine methyl ester had no effect. L-Arginine by itself increased NO2- and NO3- levels and diminished the reduction of their levels caused by NG-nitro-L-arginine methyl ester. Direct infusion of L-glutamate, N-methyl-D-aspartate, or KCl into the cerebellum through a dialysis probe resulted in an increase in NO2- and/or NO3- levels. The effects of N-methyl-D-aspartate and KCl were dependent on extracellular calcium. Furthermore, the stimulatory effects of L-glutamate and N-methyl-D-aspartate were inhibited by NG-nitro-L-arginine methyl ester and (+/-)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), an N-methyl-D-aspartate receptor antagonist. These results suggest that NO2- and NO3- levels may be related to nitric oxide production in vivo.

Animals↗
PubMed1997

A concussive-like brain injury model in mice (I): impairment in learning and memory.

The modeling of human concussive brain injury (CBI) in the laboratory has been challenging. In the present study, we developed an experimental CBI model in mice using a novel weight-drop device. Various injury levels were examined by adjusting the height of the falling weight (diameter 10 mm, length 20 cm, weight 21 g). At a height of 50 cm, the impact resulted in a mortality rate of 46.7% with a skull fracture rate of 28.6%. At a height of 25 cm, however, the impact produced a concussive-like brain injury (CLBI) to the mice without skull fracture. A series of pathophysiological and neurobehavioral responses was evaluated at this injury level. The CLBI mice lost muscle tone and righting reflex response immediately following the trauma and recovered from the latter within a short duration of 1.6 +/- 0.32 min (mean +/- SE). Brain edema formation started at 12 h, reached a maximum at 24 h and recovered 48 h. Typically edema was found in the neocortex, hippocampus, and cerebellum, but not in the brain stem. Deficits in the feeding behaviors lasted for 2 days, accompanied by lower body weight persisting for 5 days. The body weight growth rate for 24 h returned to the control levels by the third day postinjury. Learning and memory were evaluated at the end of 1-3 weeks after the trauma using a water-finding task. At 1 week, exploratory behaviors were slightly inhibited while learning and memory were profoundly impaired. Interestingly, the learning and memory deficits lasted for 2 weeks while recovering to the control levels by 3 weeks. No motor disability was found in the CLBI mice during the 3-week evaluations. These results indicate that the weight-drop impact produced graded injury to the brain, and at the injury level of 25 cm it produced a CLBI in the mice in which the characteristics of transient loss of neurobehavioral responses, short duration of brain edema, and long-lasting learning and memory deficits are similar to those of human CBI.

Animals↗
PubMed1997

A concussive-like brain injury model in mice (II): selective neuronal loss in the cortex and hippocampus.

A novel concussive-like brain injury (CLBI) model characterized by transient neurobehavioral depression, short duration of brain edema, and long-lasting memory deficits has been reported in our companion paper. This was achieved by dropping a 21-g weight from a height of 25 cm onto the head of a mouse. In the present study, we examined the histopathological changes in this model. Male ddY mice were subjected to either the trauma or sham injury. Gross pathological examination of the brain 1 h posttrauma did not demonstrate subdural, subarachnoid, intraventricular, periventricular, and intraparenchymatous hemorrhage, focal lesions or contusions. Microscopic examination 24 h posttrauma with Nissl staining (cresyl violet), however, revealed a selective bilateral neuronal cell loss in the cerebral cortex and hippocampus but not in the regions of the thalamus, cerebellum, and brain stem. The characteristics of neuronal cell loss in the cortex suggested that this pathology was related in part, to the head impact dynamics, since the cell loss was noted in the central portion of the supraventricular cerebral cortex (p < 0.001), the site of the weight impact, gradually decreasing peripheral to this site, and disappearing in the areas remote from this locus. In contrast, neuronal cell loss seen in the hippocampus did not suggest that this pathology was directly associated with the impact site. Neuronal cell loss was concentrated in the pyramidal cell layer of CA2 (p < 0.01) and CA3 (p < 0.01), and a lesser degree was noted in the subfields of CA3c (p < 0.05) and the hilar region (p < 0.05) but not in the subfields of CA1 and the dentate gyrus layers. The present study characterized the histopathological change seen in the CLBI model, demonstrating the selective neuronal cell loss following weight-drop concussion in mice.

Animals↗
PubMed1997

NGFI-B, c-fos, and c-jun mRNA expression in mouse brain after acute carbon monoxide intoxication.

The expression of immediate early genes (IEG) has been documented in the brain after various kinds of insults such as ischemia and hypoxia. To determine whether acute carbon monoxide intoxication (ACOI) might trigger IEG expression, adult ddY mice were subjected to carbon monoxide exposure at a rate of 30 mL/min for 35 seconds. The levels of NGFI-B, c-fos, and c-jun mRNA were determined by Northern blot analysis. A time-course study in the cerebral cortex indicated that the induction of NGFI-B, c-fos, and c-jun mRNA started as early as 15 minutes, reached a peak at 30 minutes, and returned to the basal level at 1 hour after the ACOI. In addition, the temporal feature of the induction of these IEG mRNA in the hippocampus was very similar to that in the cerebral cortex. Examination of brain regions at 30 minutes after the ACOI revealed a significant induction of NGFI-B mRNA in the cerebellum, thalamus-hypothalamus, brainstem. as well as in the cortex and hippocampus, but not in the striatum or olfactory bulb. Furthermore, the neuroanatomical distribution of c-fos mRNA at 30 minutes after the ACOI was very similar to that of the NGFI-B mRNA. The widespread distribution of these IEG in the brain, especially in the cerebellum and brainstem, indicates that the major cause for the triggering of IEG expression in the brain by the ACOI might be a diffuse hypoxia. These findings show for the first time the temporal and spatial expression of IEG in the brain after ACOI.

Acute Disease↗
PubMed1997

Involvement of activation of dopaminergic neuronal system in learning and memory deficits associated with experimental mild traumatic brain injury.

Much evidence has indicated that a disturbance in dopamine neurotransmission following mild to moderate traumatic brain injury is involved in the development of post traumatic memory deficits. In the present study we examined the effects of a dopamine receptor agonist and some antagonists on latent learning and memory deficits associated with a concussive traumatic brain injury in mice. Anaesthetized animals were subjected to mild traumatic brain injury by dropping a weight onto the head, and a single-dose injection of apomorphine (0.3-3.0 mg/kg) or haloperidol (0.3-3.0 mg/kg) was made i.p. 15 min after the trauma. One week later, a water-finding task consisting of an acquisition trial, a retention test and a retest was employed to assess learning and memory functions. Mice that had received a traumatic brain injury were impaired in task performance, with prolonged latencies for finding and drinking in the retention test and retest. Administration of haloperidol but not of apomorphine significantly shortened the prolonged latency in both of the tests, indicating that antagonism of dopamine receptors is beneficial for the recovery of post traumatic memory deficits. In order to evaluate which receptor subtype plays the major role in this model, we examined the effects of SCH-23390 (0.03-0.3 mg/kg), a D1 receptor antagonist, and sulpiride (3.0-30 mg/kg), a D2 receptor antagonist, in the same experimental paradigm. The results showed that administration of sulpiride but not of SCH-23390 significantly improved the deficits in task performance, indicating that D2 receptors are the major site of action. However, combined treatment with SCH-23390 (0.03-0.3 mg/kg) and sulpiride (3.0 mg/kg) at doses that had no effect when the antagonists were given alone exerted a significant additive effect in improving these deficits, indicating that interaction between D1 and D2 receptors is involved in these processes. The present results suggest that a dopaminergic mechanism contributes to the memory dysfunction associated with traumatic brain injury.

Animals↗
PubMed1997

Structure-related pharmacokinetics of xanthines after direct administration into the peritoneal cavity of rats.

The pharmacokinetic characteristics, peritoneal permeability and hydrophobicity of three xanthine derivatives, theophylline, enprofylline and 1-methyl-3-propylxanthine (MPX), were investigated in rats. Isotonic saline (30 ml) containing xanthine (2.5, 5 and 10 mg/kg) and blue dextran (0.2%) was administered intraperitoneally. The pharmacokinetic parameters of these xanthines were estimated using concentration-time data obtained from the peritoneal cavity and systemic circulation. Disappearance of these xanthines from the peritoneum declined in almost a monoexponential manner regardless of the dose administered. The volume of distribution (33.9 ml) in the peritoneal cavity was similar to the injection volume, indicating that dialysate was not diluted by the fluid in the peritoneal cavity and the effect of drug adsorption on the peritoneal membrane was minimal. The pharmacokinetics of MPX was dose-dependent, but that of theophylline and enprofylline was not. The fraction of the administered dose absorbed through the peritoneal cavity was 0.71, 0.85, 0.93 for theophylline, enprofylline and MPX, respectively. The peritoneal clearance was significantly different (p < 0.05) among the three xanthines by two-way analysis of variance, and a strong correlation was noted between their peritoneal clearance and hydrophobicity (r = 0.98, p < 0.01). These findings suggest that hydrophobicity is an important determinant in the peritoneal permeation of these xanthines.

Animals↗
PubMed1997

Continuous infusion of beta-amyloid protein into the rat cerebral ventricle induces learning impairment and neuronal and morphological degeneration.

To investigate the toxicity of beta-amyloid protein, a component of the senile plaques in Alzheimer's disease, it was infused into the cerebral ventricle of rats for 14 days by a mini-osmotic pump. Performances in the water maze and passive avoidance tasks in beta-amyloid protein-treated rats were impaired. Choline acetyltransferase activity significantly decreased in the hippocampus both immediately and 2 weeks after the cessation of the infusion. However, the learning impairment was recoverable 2 weeks after cessation of the infusion. Both immediately and 2 weeks after the cessation of the infusion, glial fibrillary acidic protein immunoreactivity increased. Furthermore, beta-amyloid protein altered the staining in the nuclei of hippocampal cells for only 2 weeks after the cessation. These results suggest that beta-amyloid protein produces some damage in the central nervous system in vivo.

Amyloid beta-Peptides↗
PubMed1997

[Effects of administration of Clostridium butyricum to patients receiving long-term tube feeding].

In patients who require total parenteral or enteral nutrition the intestinal lining may atrophy and the ability to absorb nutrients may be lost. To prevent atrophy of the small intestine, we administered a suspension of Clostridium butyricum to elderly patients receiving tube feeding, and then measured the activation of serum diamine oxidase and the number, form, water content, and bacteria content of stools, indicators of intestinal structure. We found a significant increase in diamine oxidase activity and an improvement in stool condition: the number of stools per day decreased, form improved, and water content and the number of aerobic bacteria decreased significantly. These results indicate that in patients receiving long-term tube feeding, administration of Clostridium butyricum can restore condition to a near-normal state.

Aged↗
PubMed1996

In vivo functional interaction between phencyclidine binding sites and sigma receptors to produce head-weaving behavior in rats.

To investigate the in vivo functional interaction between phencyclidine (1-(1-phenylcyclohexyl)piperidine; PCP) binding sites and sigma receptors, we examined the effects of sigma receptor ligands on stereotyped head-weaving behavior induced by PCP, a putative PCP/sigma receptor ligand, and (+)-5-methyl-10,11-dihydroxy-5H-dibenzo(a,d)cyclo-hepten-5,10-imin e ((+)-MK-801; dizocilpine), a selective PCP binding site ligand, in rats. PCP (7.5 mg/kg, i.p.)-induced head-weaving behavior was inhibited by both N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)-phenyl]-ethylamine (NE-100; 0.03-1.0 mg/kg, p.o.), a selective sigma1 receptor ligand, and alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperidine butanol (BMY-14802; 3 and 10 mg/kg, p.o.), a prototype sigma receptor ligand, in a dose-dependent manner, whereas NE-100 (0.1-1.0 mg/kg, p.o.) and BMY-14802 (3 and 10 mg/kg, p.o.) did not inhibit dizocilpine (0.25 mg/kg, s.c.)-induced head-weaving behavior. These results suggest that NE-100 and BMY-14802 act via sigma receptors. Dizocilpine-induced head-weaving behavior was potentiated by 1,3-di-o-tolyl-guanidine (DTG; 0.03-0.3 microg/kg, i.v.) and (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ((+)-3-PPP; 3 and 6 mg/kg, i.p.), sigma1/sigma2 receptor ligands, as well as by (+)-N-allyl-normetazocine ((+)-SKF-10,047: 8 mg/kg, i.p.), a sigma1 receptor ligand, while DTG (0.3 microg/kg, i.v.), (+)-3-PPP (6 mg/kg, i.p.) and (+)-SKF-10,047 (8 mg/kg, i.p.) did not induce this behavior. Potentiation of dizocilpine-induced head-weaving behavior by DTG (0.3 microg/kg, i.v.), (+)-3-PPP (6 mg/kg, i.p.) and (+)-SKF-10,047 (8 mg/kg, i.p.) was completely blocked by NE-100 (0.1 mg/kg, p.o.) and BMY-14802 (10 mg/kg, p.o.). These results suggest that PCP binding sites and sigma receptors are involved in PCP-induced head weaving behavior, and that sigma1 receptors play an important role in modulation of the head-weaving behavior.

Animals↗
PubMed1996

Acute phencyclidine induces aversion, but repeated phencyclidine induces preference in the place conditioning test in rats.

Phencyclidine (PCP) is a drug that has been widely abused in the past two decades. PCP produces place aversion, but not preference, in the place conditioning test. The present study examined PCP-induced place conditioning behavior in rats treated with PCP repeatedly. In naive rats, PCP (2-8 mg/kg i.p.) dose dependently produced place aversion, but did not produce any effect in rats treated with PCP (10 mg/kg i.p.) for 14 days. indicating that tolerance developed to PCP-induced place aversion on repeated PCP treatment. In rats treated with PCP (10 mg/kg i.p.) for 28 days, PCP (2-8 mg/kg i.p.) dose dependently produced place preference. These findings suggest that some changes in neuronal function induced by the repeated PCP treatment may play an important role in the addiction to this drug.

Animals↗
PubMed1996

Functional changes in neuronal systems induced by phencyclidine administration.

To analyze the mechanisms of PCP abuse, we investigated the changes in PCP-induced motivational properties and neuronal functions in animals. First, we determined that PCP-induced withdrawal syndrome may, in part, be produced by 5-HTergic neuronal systems. Second, using rats treated with subacute PCP, we established that subacute PCP may produce behavioral changes (stereotyped behaviors and hyperlocomotion), mediated by both dopaminergic, 5-HTergic neuronal, and NO systems. Third, using the place conditioning paradigm, we confirmed that (1) both dopamine-D1 and 5-HT2A receptors, but not sigma receptors, may be involved in PCP-induced place aversion, and (2) subacute PCP produces place preference. Finally, we demonstrated that subacute PCP may produce neurochemical changes (the number of 5-HT2A receptors, dopamine turnover, NO synthesis, and immediate early gene expression). These results suggested that several neuronal changes may be related to behavioral changes induced by subacute PCP. Furthermore, it is hypothesized that the alternations of several neuronal systems may establish PCP abuse via the changes of the immediate early gene expression and NO activity induced by subacute PCP treatment. Further studies using receptor selective ligands and sensitive probes that could associate with the pharmacological actions of PCP may elucidate the mechanisms of PCP abuse.

Animals↗
PubMed1996

Protective effect of interleukin-6 against the death of PC12 cells caused by serum deprivation or by the addition of a calcium ionophore.

Interleukin-6 (IL-6) is known to differentiate the rat pheochromocytoma cell line PC12 to neuron-like cells. We examined the effect of IL-6 on the death of PC12 cells. IL-6 significantly blocked the death of PC12 cells by serum deprivation. The protective effect of IL-6 was increased by preincubation of PC12 with IL-6 for 20 hr before serum deprivation. The inhibition of protein synthesis by cycloheximide had no effect on the protective effect of IL-6 on the serum deprivation-induced cell death. IL-6 also inhibited the death of PC12 cells induced by addition of the calcium ionophore A23187 to the culture medium. Specific in situ labeling of DNA cleavage was observed in PC12 cells subjected to both serum deprivation and A23187 for 24 hr. IL-6 inhibited DNA fragmentation in PC12 cells following serum deprivation. These results suggest that the death of PC12 cells induced by serum deprivation or by the addition of calcium ionophore is apoptosis, and that IL-6 blocks apoptosis of PC12 cells.

Animals↗
PubMed1996

(+)-SKF-10,047 and dextromethorphan ameliorate conditioned fear stress via dopaminergic systems linked to phenytoin-regulated sigma 1 sites.

Mice exhibited a marked suppression of motility when they were re-placed in the same environment in which they had previously received an electric footshock. (+)-SKF-10,047 ([2S-(2 alpha, 6 alpha, 11R*)]-1,2,3,4,5,6-hexahydro-6,11-dimethyl-3-(2-propenyl)-2,6-me tha no-3-benzazocin-8-ol hydrochloride; (+)-N-allylnormetazocine hydrochloride) and dextromethorphan, putative sigma receptor agonists, have been reported to reserve this psychological stress-induced motor suppression, defined as conditioned fear stress, through phenytoin-regulated type sigma 1, receptors. In the present study, we investigated the involvement of dopaminergic neurons in the ameliorating effects of (+)-SKF-10,047 and dextromethorphan on conditioned fear stress. (+)-SKF-10,047 and dextromethorphan attenuated conditioned fear stress at low doses (4 and 20 mg/kg, respectively) when they were co-administered with phenytoin (10 mg/kg), an anticonvulsant drug. The effects were antagonized by the sigma receptor antagonists. NE-100 (N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine monohydrochloride) and BMY-14802 (a-(4-fluoro-phenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazine-butanol hydrochloride). Furthermore, the effects of (+)-SKF-10,047 or dextromethorphan in combination with phenytoin were blocked by the dopamine D1 receptor antagonist. SCH 23390 (R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3- benzazepine), and the dopamine D2 receptor antagonist, (-)-sulpiride, and they were also attenuated by 6-hydroxydopamine-induced lesions of dopaminergic neurons. The ameliorating effects of (+)-SKF-10,047 and dextromethorphan on conditioned fear stress at high doses (5 and 30 mg/kg, respectively) were also blocked by both the dopamine receptor antagonists. These results suggest that the stress-induced motor suppression is restored by the activation of dopaminergic neuronal systems as a result of the stimulation of phenytoin-regulated type sigma 1 receptors.

Animals↗
PubMed1996

Propentofylline prevents neuronal dysfunction induced by infusion of anti-nerve growth factor antibody into the rat septum.

We have reported that the continuous infusion of anti-nerve growth factor (NGF) monoclonal antibody into the septum of rats produces neuronal dysfunction in the cholinergic system. Propentofylline has potent stimulatory effects on NGF synthesis/secretion in mouse astrocytes in vitro. To investigate the pharmacological effects of propentofylline, we used an animal model of dementia in which anti-NGF antibody was infused into the septum for 16 days via a mini-osmotic pump. The rats were treated with propentofylline orally once a day throughout the period during which performance in learning and memory tasks was observed. In the vehicle-treated dementia rats, learning and memory ability and choline acetyltransferase and cholinesterase activity were reduced compared to values in the control rats. The administration of propentofylline prevented the decreased learning capacity and the deficit in cholinergic marker enzyme activities. These results suggest that the use of NGF stimulators may provide a new approach to the treatment of dementia.

Administration, Intranasal↗
PubMed1996

(+)-SKF-10,047 and dextromethorphan ameliorate conditioned fear stress through the activation of phenytoin-regulated sigma 1 sites.

Mice exhibited a marked suppression of motility when they were replaced in the same environment in which they had previously received an electric footshock. This psychological stress-induced motor suppression, known as conditioned fear stress, was dose dependently attenuated by (+)-N-allylnormetazocine ((+)-SKF-10,047) and by dextromethorphan, putative sigma receptor agonists, but not by other sigma receptor ligands, (+)-pentazocine and 1,3-di-(2-tolyl)guanidine (DTG). Unlike (+)-SKF-10,047 and dextromethorphan, the non-competitive NMDA receptor antagonists, phencyclidine and dizocilpine, attenuated the conditioned fear stress only at high doses that induced marked hypermotility in non-stressed mice. The effects of (+)-SKF-10,047 and dextromethorphan, but not phencyclidine and dizocilpine, on the conditioned fear stress were antagonized by the sigma receptor antagonists, NE-100 (N,N-dipropyl-2-[4-methoxy-3-(2- phenylethoxy)phenyl]-ethylamine monohydrochloride) and BMY-14802 (alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazine- butanol hydrochloride). Interestingly, the effects of (+)-SKF-10,047 and dextromethorphan on the stress response were enhanced by combination with phenytoin, an anticonvulsant drug, whereas those of (+)- pentazocine, DTG, phencyclidine, and dizocilpine were not. These results suggest that activation of phenytoin-regulated type sigma 1 receptors, but not of phencyclidine receptors, is involved in the ameliorating effects of (+)-SKF-10,047 and dextromethorphan on stress-induced motor suppression.

Animals↗
PubMed1996

Role of dopaminergic neuronal system in dizocilpine-induced acetylcholine release in the rat brain.

The effects of dopaminergic receptor antagonists on dizocilpine-induced increase in extracellular acetylcholine (ACh) levels in the rat parietal cortex were examined in freely-moving rats, using an in vivo brain microdialysis method. Dizocilpine (0.5 mg/kg) significantly increased extracellular ACh levels in the rat parietal cortex and hippocampus, but not in the striatum. Pretreatment with alpha-methyl-p-tyrosine methyl ester (alpha MpT) delayed the onset but prolonged the duration of the dizocilpine-induced increases in extracellular ACh levels. The dopamine D2 receptor antagonist, haloperidol, showed dual effects similarly to alpha MpT, while the dopamine D1 receptor antagonist, SCH23390, prolonged, but did not delay, the onset of the dizocilpine-induced increases in ACh levels. These results suggest that the dopaminergic system is involved in the dizocilpine-induced increase in the extracellular ACh level in the parietal cortex in two ways, through both dopamine D1 and D2 receptors.

Acetylcholine↗