Biomedical subjects

Y Ikarashi

Publications and source records attributed to Y Ikarashi.

At least 55 records · Page 3Linked to original sources

PubMed1998

Control of endotoxin shock by the dried preparation of low virulent Streptococcus pyogenes OK-432.

Bacterial endotoxin, lipopolysaccharide (LPS), is a causative agent of Gram-negative septic shock. However, if preadministered at a low dose, LPS makes mice resistant to subsequent endotoxin challenge, the phenomenon known as LPS tolerance. Here we demonstrated that the pharmaceutical preparation of Gram-positive Streptococcus pyogenes, OK-432, also induced a state analogous to LPS tolerance if administered 6-48 h prior to LPS challenge. The preadministration of OK-432 increased the lethal dose of LPS threefold in BDF1 mice, and this was accompanied by reduced gene expression of IL-6, IFN-gamma, inducible nitric oxide synthase, and IL-10 in spleen and peritoneal cells. Serum concentrations of IL-6 and IFN-gamma were also suppressed by the preadministration of OK-432. In contrast to the LPS tolerance, the levels of TNF-alpha mRNA were not suppressed in OK-432-administered mice, and their peritoneal cells produced high levels of TNF-alpha and soluble TNF receptor p75 in response to LPS in vitro. Peritoneal cells from OK-432 but not LPS-administered mice were hyporesponsive to IFN-gamma in terms of nitric oxide synthesis, and this hyporesponsiveness to IFN-gamma was abrogated by anti-IL-10 antibodies. Likewise, peritoneal cells from both OK-432- and LPS-administered mice were hyporesponsive to LPS, serum, TNF-alpha, IFN-gamma, and PMA in terms of IL-6 production. Anti-IL-10 antibodies increased IL-6 production eightfold in cells from OK-432-administered mice, but marginally in cells from LPS-administered mice. Even in peritoneal cells from OK-432-administered mice, anti-IL-10 antibodies failed to fully restore IL-6 production. Thus, the hyporesponsive state of peritoneal cells was mediated by both IL-10-dependent and -independent mechanisms. These results demonstrated that OK-432 controlled endotoxin shock by blocking the cytokine cascade from TNF-alpha.

Animals↗

PubMed1998

Direct regulation of acetylcholine release by N-methyl-D-aspartic acid receptors in rat striatum.

The aziridinium ion of ethylcholine (AF64A), a cholinergic neurotoxin, was injected into the right striatum of a rat. The unilateral injection of 10 nmol AF64A reduced the activity of choline acetyltransferase (CAT) and the tissue content of acetylcholine (ACh) in the striatum. The striatal contents of dopamine (DA), norepinephrine (NE), 5-hydroxyindoleacetic acid (5-HIAA) and gamma-aminobutyric acid (GABA) were unchanged. These results suggest that the cholinospecificity in the striatal lesion was induced by the 10 nmol dose of AF64A. The number of N-methyl-D-aspartic acid (NMDA) receptors in the striatum treated with 10 nmol AF64A was determined by a specific binding assay using [3H](+/-)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([3H]CPP), a selective ligand for NMDA receptors. The number of the NMDA receptors decreased significantly in the injected area. On the other hand, in a microdialysis using normal rats, the perfusion of 50 microM NMDA into the striatum increased ACh release. The perfusion of 100 microM MK801 which is the specific and non-competitive NMDA receptor antagonist, decreased the basal levels of ACh release and blocked NMDA-elicited ACh release. Taken together, the present results strongly suggest that a population of NMDA receptors exists on cholinergic interneurons within the striatum, and it directly regulates ACh release.

Acetylcholine↗

PubMed1998

NGF delays rather than prevents the cholinergic terminal damage and delayed neuronal death in the hippocampus after ischemia.

Cerebral ischemia induces damage of cholinergic terminals in the hippocampus, which preceded the delayed neuronal death (DND) of the CA1 pyramidal cells. We investigated the effects of nerve growth factor (NGF) on the cholinergic terminal damage after ischemia. Continuous NGF infusion (0.5 microg/7 days) into the lateral ventricle before and after 5 min ischemia prevented a decrease in choline acetyltransferase (ChAT)-immunoreactivity and disturbance of acetylcholine (ACh) release on the 4th day after ischemia, but not on day 7, i.e., NGF infusion caused delay in the progress of the cholinergic terminal damage. These findings show that the cholinergic terminal damage may result from deficiency of endogenous NGF in an ischemic brain. In addition, we investigated whether NGF would prevent the DND after ischemia. NGF infusion also caused delay in the progress of the DND until day 14. Our results suggested that the neuroprotective effect of NGF on the DND may be secondarily yielded by maintenance of communication between cholinergic terminal and the target CA1 cell, and that prevention of cholinergic terminal damage may be useful for the treatment of cerebrovascular disease.

Animals↗

PubMed1998

A novel monoclonal antibody permitting recognition of NKT cells in various mouse strains.

By immunizing mouse lymphoma cell line tMK-2U derived from intermediate TCR cells of BALB/c nude mouse, U5A2-13 monoclonal antibody (mAb, a rat IgG2a) was established. U5A2-13 antigen (Ag) was expressed on around 65% of TCRint cells in the liver of the various mouse strains including both NK1.1- and NK1.1+ mouse strains, while NK1.1 Ag was expressed only in NK1.1+ C57BL/6 mouse strain. Among CD3+ cells, 26.3% cells co-expressed U5A2-13 Ag and NK1.1+ Ag, while small proportions of the CD3+ cells were U5A2-13+NK1.1- (9.2%) or U5A2-13-NK1.1+ (4.4%). Among NK1.1+ cells, 54.9% cells co-expressed CD3 and U5A2-13 Ag, while some proportions of the cells were U5A2-13+CD3- (19.4%) or U5A2-13-CD3+ (9.8%). It was found that approximately 85% of NK1.1+CD3+ cells coexpressed U5A2-13 Ag. U5A2-13 Ag with low fluorescence intensity was also expressed on 55% of NK1.1+CD3-NK cells. U5A2-13 Ag immunoprecipitated from tMK-2U cells consisted of three proteins, which were 65 kDa, 33 kDa and 32 kDa under both reducing and non-reducing conditions and these were apparently different from NK 1.1 Ag. These results indicated that U5A2-13 mAb was able to define a similar population to NK1.1+CD3+T cells and to 55% of NK1.1+CD3-NK cells in various strains, through recognizing a different molecule from NK1.1 Ag.

Animals↗

PubMed1998

Mouse NK1.1+ cytotoxic T cells can be generated by IL-2 exposure from lymphocytes which express an intermediate level of T cell receptor.

NK-like T cells which express the NK1.1 molecule and CD3 (or TCR) of intermediate level (CD3int or TCRint cells) were recently demonstrated to be present in various immune organs, and to have NK-like cytotoxic activity against NK target cells. In this study, we investigated whether NK1.1- T cells could express NK1.1. We found that NK1.1+ TCRint cells were much more abundant in the liver (20%) than in the spleen (2%). When hepatic and splenic mononuclear cells (MNCs) were cultured either in the absence of IL-2 or in the presence of CD3/TCR cross-linking, the original NK1.1+ TCRint cells disappeared. However, when they were cultured in the presence of a high dose of IL-2 for 4 days, a new type of NK1.1+ T cell was formed to the extent of approximately 15-20%, and the liver and spleen contained similar percentages of this new type of NK1.1+ T cells. The phenotypes of the original and the new type of NK1.1+ T cells were clearly distinct. The freshly obtained NK1.1+ TCRint cells consisted of double-negative (DN) CD4-CD8- cells and single-positive (SP) CD4+ cells, whereas the new type of NK1.1+ T cells predominantly consisted of DN CD4-CD8- cells and SP CD8+ cells and expressed a high level of CD3 (CD3high or TCRhigh cells). When NK1.1- cells or IL-2 receptor beta-chain (IL-2Rbeta)- cells were isolated from the liver and spleen, and cultured in the presence of IL-2 for 4 days, NK1.1+ T cells were generated from NK1.1- cells, but not from IL-2Rbeta- cells. Our results suggested that the NK1.1- cells, but not IL-2Rbeta- cells, contained the precursor of IL-2-stimulated NK1.1+ TCRhigh cells. When purified NK1.1- IL-2Rbeta+ TCRint cells were cultured in the presence of IL-2 for 4 days, approximately 10% of the cells became NK1.1+ TCRhigh cells. Approximately 60% of the purified NK1.1+ TCRint cells lost NK1.1 expression. The IL-2-stimulated NK1.1+ TCRhigh cells that had arisen from NK1.1- TCRint cells exerted an NK cell-like cytotoxic activity similar to that of the original NK1.1+ T cells. Thus, NK1.1- TCRint cells could express NK1.1 and exert NK-like cytotoxic activity regardless of their origin. It appears that NK1.1+ TCRhigh cells can only be induced through an IL-2-stimulation pathway but not via CD3/TCR cross-linking.

Animals↗

PubMed1998

The role of nitric oxide in striatal acetylcholine release induced by N-methyl-D-aspartate.

Effect of nitric oxide (NO) on striatal acetylcholine (ACh) release induced by N-methyl-D-aspartate (NMDA) was investigated in freely moving rats by means of microdialysis. NMDA caused a significant increase in ACh release in the striatum, which was blocked by the specific NMDA receptor antagonists, (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), indicating that agonist-evoked increase in ACh release in the striatum was through an NMDA receptor-mediated mechanism. NG-monomethyl-L-arginine acetate salt (L-NMMA; a NO synthase inhibitor) facilitated NMDA-evoked increase in ACh release, while L-arginine (the precursor of NO) inhibited the ACh release. The increase by L-NMMA of ACh release induced by the NMDA was also blocked by L-arginine. These results suggest that NO induced by NMDA receptor-mediated mechanism in cholinergic neurons may mediate an inhibitory regulation of ACh release.

Acetylcholine↗

PubMed1998

Stimulation of rat hypothalamus by microdialysis with K+: increase of ACh release elevates plasma glucose.

The effects of stimulation of the ventromedial hypothalamus (VMH) or lateral hypothalamus (LH) with potassium chloride through a microdialysis probe were studied. The concentrations of ACh and norepinephrine (NE) in the dialysate obtained from the hypothalamic nuclei and plasma glucose concentration were measured. Stimulation of the hypothalamic nuclei, VMH and LH, with potassium increased the plasma glucose level as well as the extracellular concentrations of ACh and choline. Addition of atropine, a muscarinic ACh receptor antagonist, into the potassium solution reduced the increase in the level of plasma glucose. Cholinergic stimulation of these nuclei with neostigmine increased the extracellular concentrations of ACh and plasma glucose. Stimulation of the nuclei with potassium also increased the release of NE. However, stimulation of the VMH or LH with NE and/or pargyline, a monoamine oxidase inhibitor, through the dialysis probe membrane did not significantly increase the plasma glucose concentration. These results suggest that activation of the muscarinic cholinergic or ACh-receptive neurons in the hypothalamic nuclei, VMH and LH, contribute to the elevation of plasma glucose level.

Acetylcholine↗

PubMed1998

Effect of vitamin E on contact sensitization responses induced by 2,4-dinitrochlorobenzene in mice.

The effect of vitamin E on the contact sensitization responses induced in mice by 2,4-dinitrochlorobenzene (DNCB) was studied. Mice were fed a vitamin E-adequate or a vitamin E-deficient diet for 5 weeks. The amounts of thiobarbituric acid-reactive substances in the spleens and draining auricular lymph nodes of mice were decreased by dietary vitamin E. Dietary vitamin E prevented lipid peroxidation in the spleens and lymph nodes of mice. Contact sensitization develops in two phases, induction (sensitization) and elicitation. Following sensitization to DNCB on ears, draining lymph node responses, i.e., lymph node weight, total lymph node cell number and in vitro lymph node cell proliferation as assessed by [3H]methyl thymidine incorporation, were examined. These responses, activated by DNCB, were lower in the mice fed a vitamin E-deficient diet as compared with those of the mice fed a vitamin E-adequate diet. In the elicitation phase, lymphocytes from sensitized mice respond to the antigen and blastogenate in vitro. The blastogenesis of spleen lymphocytes in the DNCB-sensitized mice was decreased by vitamin E deficiency, which was enhanced by exogenously adding vitamin E. It was found that vitamin E deficiency decreases the contact sensitization responses to DNCB in mice, but responses were restored by exogenous vitamin E. In conclusion, vitamin E may participate in the lymphocyte responses to contact allergens through scavenging reactive oxygen species.

Animals↗

PubMed1997

Memory disturbance and hippocampal degeneration induced by continuous intraventricular infusion of a protease inhibitor, leupeptin.

Effects of a protease inhibitor, leupeptin, on the memory function and the morphological changes in the hippocampus were examined in rats. The leupeptin was infused by an implanted-osmotic minipump into the lateral ventricle of the rats for 14 days. The acquisition and the maintenance of memory were evaluated by a step-down passive avoidance task. The control rats, infused with an artificial cerebral spinal fluid, showed good retention for the passive avoidance training for 21 days after training. The leupeptin-treated rats showed good retention for 7 days following training; however, pronounced impaired retention was observed on day 10 and thereafter. These rats were accompanied by a degeneration of the dentate gyrus in the histological examinations on Days 14 and 21. The granule cells in the dentate gyrus of the hippocampus appeared much more eosinophilic pyknotic. Numerous eosinophilic spherical structures of the cell processes were seen in the neuropil beneath the granule cell layer. Electron microscopic examination disclosed a marked accumulation of lipofuscin-like granules in the perikaryon of the cells and in the dendrites and the axons. These findings suggest that the memory impairment is closely related to the degeneration of the dentate gyrus in the hippocampus in the leupeptin-treated rats.

Animals↗

PubMed1997

Uric acid changes in serum during different forms of hepatic vascular inflow occlusion.

The present study was conducted to develop an efficient marker which can evaluate the influence of the occlusion of hepatic vascular inflow, which technique is commonly used in major liver surgery or in liver transplantation. Serum samples from the rats induced by hepatic vascular inflow occlusion were analyzed with high performance liquid chromatography with the electrochemical detection, and a substance which changed in accordance with the duration of the occlusion was obtained. Both the retention time and the ultraviolet absorption spectra of the substance completely agreed with those of an authentic uric acid and the substance was ultimately determined to be uric acid. To evaluate the changes in serum uric acid during different forms of hepatic vascular inflow occlusion we devised the four types of experimental model, viz. the occlusion of hepatic artery, portal vein, both hepatic artery and portal vein and both hepatic artery and portal vein of left hepatic lobes. From the device of experiments our results indicated that in the early stage of hepatic vascular inflow occlusion the high values of serum uric acid did not reflect the damage of hepatic circulation but rather responded to the intestinal congestion. Our results also indicated that even after the declamping of hepatic vascular inflow if high values of serum uric acid are prolonged it means the deterioration of the portocaval circulation including both intestinal and hepatic circulation. So that the evaluation of the severity of injured liver due to hepatic vascular inflow occlusion should be done with the caution especially in vivo study when uric acid values are used as a marker.

Animals↗

PubMed1997

Effects of ventromedial hypothalamus stimulation on glycogenolysis in rat liver using in vivo microdialysis.

In vivo microdialysis was applied to study the effects of ventromedial hypothalamus (VMH) stimulation on liver glycogenolysis under anesthesia. We examined glucose output and norepinephrine (NE) outflow from the liver through analysis of glucose and NE in the liver dialyzate. Stimulation of the VMH increased glucose output and NE outflow from the liver and increased the plasma glucose level. Similar results were obtained on hepatic nerve stimulation. Bilateral adrenalectomy did not abolish the glycogenolysis induced by VMH stimulation. NE outflow increased to a much greater extent in adrenalectomized rats. These data show that VMH stimulation causes glycogenolysis and glucose output from the liver mainly via the hepatic nerves, and that microdialysis is a simple and useful method for the study of liver metabolism in vivo.

Adrenalectomy↗

PubMed1997

Suppression of cholinergic activity via the dopamine D2 receptor in the rat striatum.

The effect of dopamine (DA) D2 receptor on extracellular choline (Ch) and acetylcholine (ACh) levels in rat caudate-putamen (striatum) was investigated by means of microdialysis. The systemic, intraperitoneal (i.p.), injection of (+/-)-2-(N-phenylethyl-N-propyl) amino-5-hydroxytetralin (N-434), a specific DA D2 receptor agonist decreased striatal ACh release in a dose-dependent manner and the i.p. injection of sulpiride, a specific DA D2 receptor antagonist, increased the ACh release in a dose-dependent manner. In contrast, extracellular Ch levels were increased by the agonist and decreased by the antagonist. An increased Ch uptake was observed in sulpiride-treated rats and a decreased Ch uptake was observed in N-434-treated rats. The effects of the D2 agonist on extracellular Ch, ACh and Ch uptake were completely antagonized by the D2 antagonist. These results suggest clearly an inhibition of ACh release by D2 receptor activation, contrasting with previous findings on DA-ACh interaction. The inverse relationship between extracellular Ch and ACh reflects a change in the Ch uptake owing to a change in cholinergic neuron activity via the D2 receptor mechanisms.

Acetylcholine↗

PubMed1997

A difference in responsiveness of isolated hepatic artery, aorta, portal vein and vena cava of pig to flavin adenine dinucleotide including liver extract.

1. Tension of isolated hepatic artery, aorta, portal vein and vena cava of pigs was measured isometrically to study the mode of action of flavin adenine dinucleotide, including liver extract (FADLE). 2. FADLE showed concentration-dependent relaxation of norepinephrine contraction in the hepatic artery, but FADLE had little influence on the aorta, portal vein and vena cava contracted by norepinephrine (NE). 3. In Ca(2+)-free solution, FADLE-induced relaxation in both the hepatic artery and aorta contracted by NE was significantly reduced, and its reduction was greater in the hepatic artery than in the aorta. Furthermore, extracellular Ca2+ dependence of norepinephrine-induced contraction was much larger in the hepatic artery than in the aorta. 4. Results suggest that FADLE shows regional variations in vasorelaxation through the alteration of Ca2+ movement by the cell, and that this may reflect one of the mechanisms in its ability to increase blood flow in hepatic tissue.

Animals↗

PubMed1997

Effects of MK-801 and pentobarbital on cholinergic terminal damage and delayed neuronal death in the ischemic gerbil hippocampus.

The present study covers both the effects of MK-801, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, and pentobarbital on cholinergic terminal damage and delayed neuronal death (DND) in ischemic gerbil. To study the above effects, in vivo microdialysis, immunohistochemical, and morphological techniques were used. MK-801 (3 mg/kg) or pentobarbital (50 mg/kg) were injected intraperitoneally 1 h or 30 min before 5 min ischemia, respectively. Each estimation was then carried out 4, 7, or 14 days after ischemia. Ischemia induced a significant decrease in acetylcholine (ACh) release and a disappearance of choline acetyltransferase (ChAT)-immunoreactivity in the hippocampus in addition to inducing DND. On day 4, MK-801 protected ischemia-induced DND in the hippocampal CA1 subfield. However, MK-801 had no effect against the decrease in ACh release in spite of protection of the decrease in ChAT-immunoreactivity. On day 7 and 14, no protective effect of MK-801 was observed in all estimations. It became clear that the mechanism of cholinergic terminal dysfunction is different from that involved in pyramidal cell death, i.e., excitative neurotoxicity induced by overabundant extracellular glutamate. Pentobarbital also provided protection against DND. However, protective effects of pentobarbital on the decrease in ACh release and the low ChAT-immunoreactivity were incomplete. Our present study indicated a limitation on the efficacy of NMDA receptor antagonist and barbiturate against cerebral ischemia.

Acetylcholine↗

PubMed1997

Regulation of dopamine D1 and D2 receptors on striatal acetylcholine release in rats.

The effects of dopamine (DA) D1 and D2 receptors on striatal acetylcholine (ACh) releases were investigated by in vivo microdialysis. All drugs were applied via dialysis membrane directly to the striatum. The levels of ACh release were increased by 10(-4) M SKF38393, a D1 receptor agonist. Although 10(-4) M SCH23390, a D1 receptor antagonist, exhibited an increase in the levels of ACh release, the agonist (10(-4) M) induced-increase in the levels of ACh release was suppressed by coperfusion of the antagonist (10(-4) M). In contrast, the levels of ACh release were decreased by the D2 receptor agonist, N-434, in a dose-dependent manner (10(-4) M to 10(-7) M) and increased by the D2 receptor antagonist, sulpiride, in a dose-dependent manner (10(-5) M to 10(-7) M). The agonist (10(-5) M) induced-decrease in the levels of ACh release was suppressed by coperfusion of the antagonist (10(-4) M). Coperfusion of D1 (10(-4) M) and D2 (10(-5) M) agonists blocked both effects of respective drug alone. In order to clarify the effect of endogenous DA, two drugs with different mechanisms for enhancing DA concentration in the synaptic cleft, the DA release-inducer methamphetamine, and the DA uptake inhibitor nomifensine were perfused separately. Both (10(-4) M to 10(-5) M) produced a dose- and a time-dependent decrease in the levels of ACh release. Significant higher levels of ACh release were observed in the striatum of the 6-hydroxydopamine (8 micrograms/10 microliters)-treated rats with significant depletion of striatal DA content. These results suggest that in striatal DA-ACh interaction ACh release, as cholinergic interneuron's activity, is tonically inhibited via the D2 receptor, mainly by dopaminergic input, and the D1 receptor probably modifies the effect of the D2 receptor indirectly.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1997

Hypothalamic cholinergic activity and 2-deoxyglucose-induced hyperglycemia.

To clarify the role of the hypothalamic cholinergic system in the regulation of peripheral glucose metabolism, we investigated hypothalamic cholinergic activities after administration of 2-deoxyglucose (2-DG). Intravenous administration of 2-DG (500 mg/kg) caused neuroglycopenia and marked hyperglycemia; the level of plasma glucose increased to 210% of the initial levels of 20 min. For evaluation of the cholinergic activity, we employed a microwave device and subsequently analyzed the contents of acetylcholine (ACh) and choline after microdissection of the hypothalamic nuclei, ventromedial hypothalamic nucleus (VMH), lateral hypothalamus (LH), and paraventricular nucleus (PVN). In addition, we analyzed fluctuation of extracellular levels of ACh using in vivo brain microdialysis. A decrease in the ACh content, and a corresponding increase in the choline content, was observed in those hypothalamic nuclei min after administration of 2-DG. In the microdialysis perfusate, on the other hand, extracellular level of ACh was increased by 2-DG administration. These data show that ACh release, which is cholinergic activity, was increased after 2-DG administration. Our results suggest the involvement and importance of the hypothalamic cholinergic system in 2-DG-induced hyperglycemia.

Acetylcholine↗

PubMed1997

Comprehensive analysis of neurotransmitters and their metabolites including acetylcholine and choline in rat brain nuclei.

We have designed this method for the comprehensive and adequate analysis of neurotransmitters and metabolites including acetylcholine (ACh) and choline in specific brain nuclei. In physiological and pharmacological studies, the role of specific neurotransmitters in the central nervous system (CNS) has often been studied by microinjection of their agonist and antagonist into the target regions, with the action and role of the transmitter in question being deduced in a relatively straightforward manner from the results. However, none of these studies have investigated fluctuation in neurotransmitter and metabolite contents in response to a variety of stimuli in vivo. No comprehensive analysis of neurotransmitters in small specific area in the CNS has been undertaken due to the difficulties of proper analysis of ACh and choline. Different types of neuronal systems in the CNS affect each other. Thus, it is not necessarily clear that different types of neurons do in fact respond to an administered agonist and antagonist. For example, dopaminergic neuron mediated control of cholinergic interneuron in the striatum and dopaminergic regulation of cortical ACh release have been documented. Similarly, the cholinergic system affects dopaminergic and noradrenergic neurons. Intraventricular administration of an ACh esterase inhibitor, neostigmine, increases dopamine and noradrenaline release in the hypothalamus. So, an adequate comprehensive analysis of the transmitters and the metabolites in the same tissue sample provides valuable aid to clarify what types of neurons truly respond to the administered drugs and the excitation of physiological events. For an appropriate analysis we employed a microwave device, which made the estimation of ACh and choline possible. In addition to this, we employed a punch technique for the microdissection of the specific nuclei and area from the brain slice.

Acetylcholine↗

PubMed1997

Relations between the extracellular concentrations of choline and acetylcholine in rat striatum.

Changes in extracellular levels of acetylcholine (ACh) and choline (Ch) in the striatum of rats were examined by in vivo microdialysis after intraperitoneal injections of drugs. A dopamine D2 antagonist, sulpiride (20 mg/kg), and a muscarinic antagonist, atropine (3.5 mg/ kg), increased ACh levels and decreased Ch levels. On the contrary, the D2 agonist (+/-)-2-(N-phenylethyl-N-propyl)amino-5-hydroxytetralin (N-434; 5 mg/kg) and an anesthetic, pentobarbital (50 mg/kg), decreased ACh levels and increased Ch levels. Perfusion of 10 microM hemicholinium-3 (HC-3), a Ch uptake inhibitor, through the striatum induced a complete inhibition of ACh release and increased Ch levels in all drug-treated groups. The degree of relative increase in the level of Ch induced by HC-3 differed among the drug-pretreated groups; compared with the control group, the relative increase was larger in the sulpiride- and atropine-treated groups and smaller in the N-434 and pentobarbital-treated groups. Thus, we demonstrated reciprocal relations between extracellular concentrations of Ch and ACh after treatments by drugs. The data suggest that in the striatum, which is rich in cholinergic innervation, the extracellular Ch concentration is to a large extent determined by activity of the cholinergic transmission reflected in high-affinity choline uptake.

Acetylcholine↗