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Baker KB, Wray SP, Ritter R, Mason S, Lanthorn TH, Savelieva KV. Male and female Fmr1 knockout mice on C57 albino background exhibit spatial learning and memory impairments. Genes Brain Behav 2010; 9:562-74. [PMID: 20398059 DOI: 10.1111/j.1601-183x.2010.00585.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Impaired spatial learning is a prominent deficit in fragile X syndrome (FXS). Previous studies using the Fmr1 knockout (KO) mouse model of FXS have not consistently reported a deficit in spatial learning. Fmr1 KO mice bred onto an albino C57BL/6J-Tyr(c-Brd) background showed significant deficits in several primary measures of performance during place navigation and probe trials in the Morris water maze. Fmr1 KO mice were also impaired during a serial reversal version of the water maze task. We examined fear conditioning as an additional cognitive screen. Knockout mice exhibited contextual memory deficits when trained with unsignaled shocks; however, deficits were not found in a separate group of KO mice trained with signaled shocks. No potentially confounding genotypic differences in locomotor activity were observed. A decreased anxiety-like profile was apparent in the open field, as others have noted, and also in the platform test. Also as previously reported, startle reactivity to loud auditory stimuli was decreased, prepulse inhibition and social interaction increased in KO mice. Female Fmr1 KO mice were tested along with male KO mice in all assays, except for social interaction. The female and male KO exhibited very similar impairments indicating that sex does not generally drive the behavioral symptoms of the disorder. Our results suggest that procedural factors, such as the use of albino mice, may help to reliably detect spatial learning and memory impairments in both sexes of Fmr1 KO mice, making it more useful for understanding FXS and a platform for evaluating potential therapeutics.
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Affiliation(s)
- K B Baker
- Neuroscience Research, Lexicon Pharmaceuticals Inc., The Woodlands, TX 77381-1160, USA
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2
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Zhang W, Rajan I, Savelieva KV, Wang CY, Vogel P, Kelly M, Xu N, Hasson B, Jarman W, Lanthorn TH. Netrin-G2 and netrin-G2 ligand are both required for normal auditory responsiveness. Genes, Brain and Behavior 2008; 7:385-92. [DOI: 10.1111/j.1601-183x.2007.00361.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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3
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Zhao S, Edwards J, Carroll J, Wiedholz L, Millstein RA, Jaing C, Murphy DL, Lanthorn TH, Holmes A. Insertion mutation at the C-terminus of the serotonin transporter disrupts brain serotonin function and emotion-related behaviors in mice. Neuroscience 2006; 140:321-34. [PMID: 16542782 DOI: 10.1016/j.neuroscience.2006.01.049] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2005] [Revised: 01/23/2006] [Accepted: 01/27/2006] [Indexed: 11/17/2022]
Abstract
The 5-hydroxytryptamine transporter (5-HTT) regulates 5-hydroxytryptamine (5-HT) neurotransmission by removing 5-HT from the synaptic cleft. Emerging evidence from clinical and genetic studies implicates the 5-HTT in various neuropsychiatric conditions, including anxiety and depression. Here we report that a 5-HTT null mutant mouse line was generated by gene trapping that disrupted the sequence encoding the C-terminus of 5-HTT. This mutation resulted in significant reduction of 5-HTT mRNA and loss of 5-HTT protein. Brain levels of 5-HT and its major metabolite, 5-hydroxyindoleacetic acid, were markedly decreased in C-terminus 5-HTT -/- mice, while 5-HT uptake or 5-HT content in platelets was absent. Behavioral phenotyping showed that C-terminus 5-HTT -/- mice were normal on a screen for gross behavioral, neurological, and sensory functions. In the tail suspension test for depression-related behavior, C-terminus 5-HTT -/- mice showed increased immobility relative to their +/+ controls. By comparison, a previously generated line of 5-HTT -/- mice lacking exon 2, encoding the N-terminus of the 5-HTT, showed abnormally high immobility in response to repeated, but not acute, exposure to the tail suspension test. In a novel, brightly-lit open field, both C-terminus 5-HTT -/- mice and N-terminus 5-HTT -/- mice displayed decreased center time and reduced locomotor activity compared with their +/+ controls. Both mutant lines buried significantly fewer marbles than their +/+ controls in the marble burying test. These findings further demonstrate the neurobiological functions of the 5-HTT and add to a growing literature linking genetic variation in 5-HTT function with emotional abnormalities.
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Affiliation(s)
- S Zhao
- Lexicon Genetics Incorporated, 8800 Technology Forest Place, The Woodlands, TX 77381, USA.
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4
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Mealing GA, Lanthorn TH, Small DL, Murray RJ, Mattes KC, Comas TM, Morley P. Structural modifications to an N-methyl-D-aspartate receptor antagonist result in large differences in trapping block. J Pharmacol Exp Ther 2001; 297:906-14. [PMID: 11356910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2023] Open
Abstract
Differences in the degree of trapping of initial block by N-methyl-D-aspartate (NMDA) receptor antagonists may affect their safety and, hence, suitability for clinical trials. In this comparative study, 23 compounds structurally related to the low-affinity, use-dependent NMDA receptor antagonist (S)-alpha-phenyl-2-pyridineethanamine dihydrochloride (AR-R15896AR) were examined to determine the degree of trapping block they exhibit. Compounds were tested at concentrations that produced a comparable initial 80% block of NMDA-mediated whole-cell current in rat cortical cultures. A wide range of values of trapping block was found, indicating that trapping is not an all-or-none event. Fifteen of the compounds trapped significantly more than the 54 +/- 3% of initial block trapped by AR-R15896AR. The off-rates of these compounds were slower than that of AR-R15896AR. Only 2 of the 23 compounds trapped significantly less than AR-R15896AR. AR-R15808, the piperidine analog of AR-R15896AR, appeared to trap only 8 +/- 3% of its initial block, although its fast off-rate confounded accurate quantification of trapping. AR-R26952, which, like AR-R15896AR, contains a pyridine in place of a phenyl group, trapped 40 +/- 5% of its initial block and exhibited kinetics comparable with AR-R15896AR. Structure-activity analysis suggested that the presence of two basic nitrogen atoms and decreased hydrophobicity led to decreased trapping. There was no correlation between trapping and lipophilicity as would be expected if closed-channel egress was due to escape through the lipid bilayer. However, there was a positive correlation between off-rate and degree of trapping. Models that can account for partial trapping are presented.
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Affiliation(s)
- G A Mealing
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada.
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5
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Danysz W, Lanthorn TH. Uncompetitive NMDA receptor antagonists--is low affinity better? Amino Acids 2001; 19:131-2. [PMID: 11026481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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6
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Abstract
NMDA antagonists like AR-R15896 have been selected on the basis of their good therapeutic indices. As Dr. Rogawski has pointed out, there may be a number of molecular factors which can improve the therapeutic index of NMDA antagonists. In this paper we will consider three factors; use-dependence, low affinity/fast kinetics, and partial trapping.
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Affiliation(s)
- T H Lanthorn
- AstraZeneca R&D Boston, Rochester, New York 14602, USA
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7
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Li C, Peoples RW, Lanthorn TH, Li ZW, Weight FF. Distinct ATP-activated currents in different types of neurons dissociated from rat dorsal root ganglion. Neurosci Lett 1999; 263:57-60. [PMID: 10218910 DOI: 10.1016/s0304-3940(99)00114-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rat dorsal root ganglion neurons can be classified into at least three distinct groups based on cell size, afferent fiber diameter, electrophysiological properties, sensitivity to vanilloid agonists such as capsaicin, and function. In the present study, ATP-activated current in these neurons was characterized using whole-cell patch-clamp recording. Small diameter (<30 microm) cells had high capsaicin sensitivity, high affinity for ATP, and rapidly desensitizing ATP-activated current. Medium diameter (30-50 microm) cells had no capsaicin sensitivity, lower affinity for ATP and slowly desensitizing ATP-activated current. Large diameter (>50 microm) cells were insensitive to both capsaicin and ATP. These findings suggest that distinct types of ATP receptor-ion channels are expressed in different types of dorsal root ganglion neurons, and may contribute to the functional differences among these types of neurons.
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Affiliation(s)
- C Li
- Laboratory of Molecular and Cellular Neurobiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-8115, USA.
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8
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Mealing GA, Lanthorn TH, Murray CL, Small DL, Morley P. Differences in degree of trapping of low-affinity uncompetitive N-methyl-D-aspartic acid receptor antagonists with similar kinetics of block. J Pharmacol Exp Ther 1999; 288:204-10. [PMID: 9862772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
This study characterizes the trapping of block of N-methyl-D-aspartic acid (NMDA)-induced currents by three structurally distinct, use-dependent NMDA receptor antagonists with similar rapid on-off rates. The antagonism of whole-cell currents in cultured rat cortical neurons by AR-R15896AR, ketamine, and memantine was examined. All three compounds produced a steady-state block after a 30-s coapplication, which was fully relieved after 50 s of NMDA exposure. The amplitudes of block caused by 50 microM AR-R15896AR, 10 microM ketamine, or 10 microM memantine were not significantly different, being 82 +/- 1%, 80 +/- 2%, and 81 +/- 2%, respectively. All three NMDA receptor antagonists exhibited trapping of block that was not significantly increased by extending the agonist/antagonist coapplication beyond 30 s. Although the initial blocks were similar, after 120 s of washout without agonist present, there were significant differences in trapping of block between antagonists, as only 54 +/- 3% of the AR-R15896AR block, 86 +/- 1% of the ketamine block, and 71 +/- 4% of the memantine block remained trapped. The lack of complete trapping is consistent with closed-channel egress by these compounds. Higher antagonist concentrations produced larger initial blocks, but the degree of trapping block was not significantly different from that at lower antagonist concentrations. The results demonstrate that differences in the degree of trapping exist among use-dependent NMDA receptor antagonists even when on and off rates are similar. These differences are correlated with measures of therapeutic index.
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Affiliation(s)
- G A Mealing
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
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9
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Abstract
The 5-HT3 receptor (5-HT3R) is part of a superfamily of ligand-gated ion channels which includes nicotinic acetylcholine receptors (nAChR). cRNA derived from the long isoform cloned mouse 5-HT3R was used to drive expression of 5-HT3Rs in Xenopus oocytes. 5-HT-induced currents were monitored using two-electrode voltage-clamp. Eight nicotinic agonists, including ACh and nicotine, but not alpha-anatoxin, were found to antagonize 5-HT-induced currents. With the exception of 3-(2,4)-dimethoxybenzylidene-anabaseine (DMXB-anabaseine; GTS-21) this antagonism appeared to be competitive since it could be overcome by increasing concentrations of 5-HT. Potency of 5-HT3 antagonism was comparable to reported values for nAChR alpha7 activation. These results confirm the notion of families of receptors and further indicate that strong similarities can exist in some critical binding domains.
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Affiliation(s)
- D A Gurley
- Astra Arcus USA, Rochester, NY 14534, USA.
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10
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Mealing GA, Lanthorn TH, Small DL, Black MA, Laferriere NB, Morley P. Antagonism of N-methyl-D-aspartate-evoked currents in rat cortical cultures by ARL 15896AR. J Pharmacol Exp Ther 1997; 281:376-83. [PMID: 9103520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The purpose of this study was to characterize the kinetics and voltage-dependence of the block of N-methyl-D-aspartate (NMDA)-induced currents in primary cultures of rat cortical neurons by the neuroprotective, low-affinity, NMDA antagonist ARL 15896AR, using whole-cell voltage-clamp techniques. ARL 15896AR caused rapid and reversible inhibition of NMDA (50 microM)-evoked currents from neurons held at -60 mV, with an IC50 of 9.8 microM. The EC50 for NMDA was not significantly affected by 10 microM ARL 15896AR (P > .05), consistent with a noncompetitive mechanism of block. ARL 15896AR antagonism was use-dependent, because application of the drug 60 sec before NMDA did not attenuate the initial NMDA-evoked current, although the block developed rapidly thereafter. Once bound, ARL 15896AR remained trapped upon removal of NMDA until subsequent NMDA re-exposure, whereupon currents recovered rapidly. The forward and reverse binding rate constants were estimated to be 2.406 x 10(4) M(-1) sec(-1) and 0.722 sec(-1), respectively. Antagonism was strongly voltage-dependent; the K(D) values at 0 and -60 mV were 60 and 11 microM, respectively. Additionally, there was a component of the block by ARL 15896AR that was voltage-insensitive. This component of the block did not act at the ligand binding site, because it was not influenced by NMDA concentration, or at the polyamine site, because it was not affected by spermine. However, there was an interaction of ARL 15896AR with the glycine regulatory site. In contrast to many uncompetitive NMDA antagonists, like MK-801, ARL 15896AR exhibited rapid kinetics. This property may result in a large margin of safety while maintaining the efficacy associated with use-dependent NMDA antagonists, making this compound an excellent candidate for clinical trials.
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Affiliation(s)
- G A Mealing
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario
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11
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Abstract
The anticonvulsant phenytoin has been reported to block anoxia-induced losses of synaptic activity in the rat hippocampal slice and experimental ischemia-induced losses of synaptic activity in the guinea pig hippocampal slice. We examined phenytoin in our rat hippocampal slice model of experimental ischemia (anoxia +2 mM D-glucose). In this model, ischemic depolarization (ID) occurs 4-5 min after the introduction of anoxic medium, and oxygen and D-glucose are restored 1 min after the onset of ID. In control slices, synaptic recovery is never observed following ID in 2 mM D-glucose. Phenytoin (30,100 and 300 microM), perfused for 20 min prior to, and for 10 min following anoxia, did not allow for synaptic recovery following ID. At the higher concentrations, however, it did increase the latency to ID. In addition, the presynaptic volley (PV), which normally disappears at the time of ID, was lost substantially earlier in the presence of phenytoin. These findings suggest that the anti-ischemic effects of phenytoin reported by others are due to delay of ID. This may suggest that phenytoin will be effective in preventing global ischemia-induced damage only when the ischemic insult is of short duration.
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Affiliation(s)
- G B Watson
- Neurological Diseases Research, Searle Research and Development, Skokie, IL 60077, USA
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12
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Watson GB, Lopez OT, Charles VD, Lanthorn TH. Assessment of long-term effects of transient anoxia on metabolic activity of rat hippocampal slices using triphenyltetrazolium chloride. J Neurosci Methods 1994; 53:203-8. [PMID: 7529859 DOI: 10.1016/0165-0270(94)90178-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Hippocampal slices maintained in an oxygen-rich static interface chamber remained viable, as determined by the mitochondrial marker 2,3,5-triphenyltetrazolium chloride (TTC), for over 20 h in vitro. By contrast, slices exposed, after 1 h in vitro, to an anoxic environment for 25 min and then allowed to recover for 1-18 h, showed an initial slight decrease in TTC staining followed by a dramatic decrease at time points greater than 6.5 h after anoxia. These data are suggestive of delayed neuronal death. Furthermore, the decreases in TTC staining induced by anoxia could be prevented by conditions known to prevent cell death either in vitro or in vivo. For example, pretreatment of the slices with the N-methyl-D-aspartate antagonist 3-((RS)-2-carboxy-piperazin-4-yl)-propyl-1- phosphonic acid dose-dependently prevented the loss of TTC staining induced by 25 min anoxia. In addition, high-intensity TTC staining correlated with normal CA1 synaptic activity, even after more than 20 h in vitro, suggesting that TTC staining reflects functional neuronal activity. These data suggest that the use of TTC staining of in vitro hippocampal slices may represent a novel and convenient screen for anti-ischemic compounds.
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13
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Abstract
The present study utilized in vitro gerbil and rat hippocampal slices to compare responses to experimental ischemia without species differences in the cerebrovasculature as a variable. Ischemic depolarization occurred faster in the gerbil (2.53 +/- 0.05 min) than in the rat (4.59 +/- 1.1 min). These results indicate that the gerbil's greater propensity to neuronal damage following short ischemic periods may be due to greater sensitivity of the gerbil brain itself.
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14
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Quartermain D, Mower J, Rafferty MF, Herting RL, Lanthorn TH. Acute but not chronic activation of the NMDA-coupled glycine receptor with D-cycloserine facilitates learning and retention. Eur J Pharmacol 1994; 257:7-12. [PMID: 8082709 DOI: 10.1016/0014-2999(94)90687-4] [Citation(s) in RCA: 139] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The memory-enhancing potential of D-cycloserine (cycloserine) a partial agonist at the glycine recognition site on the NMDA receptor, was evaluated in mice using a thirst-motivated linear maze learning task. Immediate acute post-training injections (10, 20 and 80 mg/kg) significantly improved retention relative to vehicle-injected controls. Retention was also facilitated if cycloserine (3 and 10 mg/kg but not 20 or 40 mg/kg) was administered 20 min before the retention test. Acquisition of the habit was accelerated if cycloserine (3 mg/kg) was injected 20 min before the training session. Acute post-training injections failed to facilitate retention if mice were pretreated with cycloserine (3 mg/kg) b.i.d. for 15 days before training on the maze. These results indicate that acute cycloserine administration can enhance consolidation and retrieval of memory but that desensitization may occur with chronic exposure to the drug.
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Affiliation(s)
- D Quartermain
- Laboratory of Behavioral Neurology, New York University Medical Center, NY 10016
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15
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Abstract
D-cycloserine, a partial agonist of the NMDA receptor-associated glycine site, can enhance cognition. The present experiment examines the behavioral effects of D-cycloserine on cognitive deficits in male Fischer-344 rats, 24 months old. Rats 24 months old (n = 42) received either vehicle or one of 3 doses of D-cycloserine prior to testing. Young rats, 4 months old (n = 13), received vehicle prior to testing. Place discrimination and repeated acquisition were tested in the water maze and a variety of sensorimotor tasks were given. Aging impaired performance in all tasks. D-cycloserine improved performance in place discrimination and repeated acquisition. No doses affected sensorimotor function. These results support the hypothesis that D-cycloserine has cognition enhancing properties and that it may be useful in treating disorders involving cognitive impairment.
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Affiliation(s)
- M G Baxter
- Department of Psychology, Johns Hopkins University, Baltimore, MD 21218
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16
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Abstract
The Mongolian gerbil displays spontaneous seizures and is used as a model for global ischemia. This study investigated the electrophysiological events associated with 0-Mg(2+)-induced seizures in gerbil hippocampal slices. In the rat hippocampal slice, 0-Mg2+ medium leads to rapid extracellular epileptic depolarization (ED) accompanied by long-term synaptic failure. Both evoked and spontaneous epileptiform activity was observed in the gerbil hippocampal slice after the introduction of the 0-Mg2+ aCSF. However, unlike the rat, ED was rarely observed in the gerbil hippocampal slice (2/17). When ED occurred, synaptic responses recovered (75%) within 20 min. This resistance to epileptic depolarization did not generalize to experimental ischemia-induced depolarization. Anoxia in 2 mM D-glucose produced anoxic depolarization in all gerbil hippocampal slices tested (6/6).
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17
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Abstract
Lactate supports normal synaptic function and may be neuroprotective following an anoxic insult. The present study investigated the effects of lactate on epileptic depolarization and long-term synaptic failure during a zero-magnesium-induced epileptic insult using the hippocampal slice preparation. In artificial cerebrospinal fluid (aCSF) containing 10 mM D-glucose, no epileptic depolarization was observed. At lower concentrations of D-glucose, epileptic depolarization occurred and often was followed by long-term synaptic failure. Low concentrations of lactate, in place of D-glucose, supported normal synaptic transmission. However, no concentration of lactate tested (up to 30 mM) blocked the occurrence of epileptic depolarization. High concentrations of lactate allowed for partial recovery of synaptic responses following epileptic depolarization. Reinstatement of D-glucose was necessary to observe this recovery. The results confirm that lactate can replace D-glucose in maintaining synaptic responses, but demonstrate that lactate cannot replace D-glucose in blocking an insult-induced depolarization. The inability of lactate to mimic all the effects of D-glucose is consistent with the notion of compartmentation of energy utilization within neurons.
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18
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Abstract
The agonist properties of SC-46275 have been investigated in EP receptor subtype-specific smooth muscle assays. In the isolated guinea pig vas deferens (GPVD), prostaglandin E2 (PGE2), via the EP3 receptor, potently inhibited electrically induced contractions with an EC50 of 5.4 +/- 1.1 nM. Sulprostone and misoprostol were both potent relaxers of the GPVD yielding EC50s of 1.6 +/- 0.4 nM and 4.3 +/- 0.9 nM, respectively, while butaprost (10,000 nM) was inactive. SC-46275 was by far the most potent agonist in the GPVD exhibiting an EC50 of 0.04 +/- 0.02 nM. PGE2, via the EP1 receptor, stimulates contractions in the longitudinal muscle layer of the guinea pig ileum (GPIL) with an EC50 of 74.4 +/- 10.6 nM. SC-46275 was extremely weak in this preparation, generating only 33% of the maximal PGE2 effect at 30,000 nM. The circular muscle layer of guinea pig ileum (GPIC) is responsive to inhibition of electrically stimulated contractions by PGE2 (EC50 = 179.6 +/- 20.8 nM) via the EP2 receptor. SC-46275 (up to 10,000 nM) was completely inactive in this preparation. We conclude from these findings that SC-46275 is a very potent and highly selective EP3 receptor agonist. SC-46275 should prove to be an extremely valuable tool in probing the physiological significance of EP3 receptors. The high potency of SC-46275 at the EP3 receptor may account for its antisecretory and cytoprotective actions, while its lack of activity at the EP1 or EP2 sites may explain its very weak diarrheagenic potential.
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Affiliation(s)
- M A Savage
- Neurological Diseases Research, Searle Research and Development, Skokie, IL 60077
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19
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Abstract
Various opioid agonists and antagonists were examined for their ability to alter extracellularly and intracellularly recorded CA1 pyramidal cell activity. All opioid agonists tested, with the exception of [D-ala2]deltorphin II, increased primary population spike amplitude. Of these active agonists, all except DPDPE and p-Cl-DPDPE produced secondary population spikes. DSLET and DAMGO, but not DPDPE, reduced the amplitude of the orthodromically stimulated IPSP. Naltrexone antagonized the actions of all agonists tested. The actions of DPDPE and p-Cl-DPDPE, but not those of DSLET, DAMGO or morphine, were antagonized by the delta antagonist naltrindole. Similarly, the delta antagonist ICI-174,864 blocked the actions of DPDPE, but not DSLET or DAMGO. Based on the inactivity of [D-ala2]deltorphin II and the lack of delta antagonist-sensitive actions of DSLET, the data suggest that the delta 1 subtype is the predominant delta subtype in the CA1 region of the hippocampus.
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MESH Headings
- Analgesics/pharmacology
- Animals
- Electric Stimulation
- Electrophysiology
- Endorphins/pharmacology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalin, D-Penicillamine (2,5)-
- Enkephalin, Leucine/analogs & derivatives
- Enkephalin, Leucine/antagonists & inhibitors
- Enkephalin, Leucine/pharmacology
- Enkephalins/antagonists & inhibitors
- Enkephalins/pharmacology
- Evoked Potentials/drug effects
- Hippocampus/drug effects
- Hippocampus/physiology
- In Vitro Techniques
- Indoles/pharmacology
- Ligands
- Male
- Morphinans/pharmacology
- Morphine/pharmacology
- Naltrexone/pharmacology
- Narcotic Antagonists/pharmacology
- Pyramidal Tracts/cytology
- Pyramidal Tracts/drug effects
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/drug effects
- Receptors, Opioid, delta/physiology
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/drug effects
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Affiliation(s)
- G B Watson
- Neurological Diseases Research, Searle Research and Development, Skokie, IL 60077
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20
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Abstract
Glycine has been shown to modulate N-methyl-D-aspartate (NMDA) subclass of acidic amino acid receptors which have been implicated in learning and memory. We report that d-cycloserine (DCS) which has a high affinity for the glycine modulatory site in the NMDA receptor complex modulated memory processing in a dose-dependent manner. Mice were trained on a footshock avoidance task. Immediately after training DCS was administered (2.5 to 50 mg/kg s.c.). When retention was tested a week later, 20 mg/kg facilitated retention the best with lower and higher doses be less effective in weakly trained young mice. DCS also facilitated retention in 'senescence-accelerated mice' in which impairment of learning and memory increases with age. DCS had to be administered at higher doses to improve retention as impairment of learning and memory increased.
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Affiliation(s)
- J F Flood
- VA Medical Center, Geriatric Research Educational and Clinical Center, St. Louis, MO 63106
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21
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Davies MS, Baganoff MP, Grishin EV, Lanthorn TH, Volkova TM, Watson GB, Wiegand RC. Polyamine spider toxins are potent un-competitive antagonists of rat cortex excitatory amino acid receptors. Eur J Pharmacol 1992; 227:51-6. [PMID: 1385187 DOI: 10.1016/0922-4106(92)90141-h] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We examined the effect of argiopine and argiopinine 3, low molecular weight polyamine venom components of the spider Argiope lobata, on rat cortical excitatory amino acid (EAA) receptors expressed in Xenopus oocytes. Responses to 100 microM N-methyl-D-aspartate (NMDA) with 10 microM glycine were blocked by both of the polyamine toxins in a dose-dependent manner. Both compounds had similar potencies against 100 microM kainate or 50 microM (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (L-AMPA). Oscillatory responses to 2 microM quisqualate were unaffected by either polyamine toxin. Increasing concentrations of either NMDA, kainate or AMPA were unable to overcome the antagonism by either spider toxin. We were able to demonstrate a use-dependent phenomenon similar to that of phencyclidine; neither polyamine toxin affected the NMDA, kainate or AMPA response without the presence of the respective agonist.
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Affiliation(s)
- M S Davies
- Monsanto Corporate Research, Chesterfield, MO 63198
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22
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Hood WF, Gray NM, Dappen MS, Watson GB, Compton RP, Cordi AA, Lanthorn TH, Monahan JB. Characterization of indole-2-carboxylate derivatives as antagonists of N-methyl-D-aspartate receptor activity at the associated glycine recognition site. J Pharmacol Exp Ther 1992; 262:654-60. [PMID: 1386886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We have synthesized a series of indole-2-carboxylate derivatives and, with the use of radioligand binding, electrophysiological techniques and an in vivo transient bilateral carotid occlusion model of ischemic damage known to be sensitive to NMDA antagonists, have evaluated the indole-2-carboxylate derivatives ability to inhibit N-methyl-D-aspartate (NMDA) receptor activity through the associated glycine modulatory site. By using [3H]glycine to label this modulatory site, we found that the compounds with the highest affinity (Ki less than 1 microM) contained a chloro group at position C-6 and a polar, hydrogen-bond-accepting group at position C-3 of the indole ring. When these compounds were tested for their ability to modulate [3H]MK-801 [(+)-[3H]-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclophepten-5,10- imine maleate) binding, a functional assessment of NMDA receptor activation, binding was inhibited, indicative of NMDA receptor antagonist character. Schild regression analysis indicated that this antagonism was competitive with glycine. Next, several of these indole-2-carboxylate derivatives were analyzed electrophysiologically in rat cortex mRNA-injected Xenopus oocytes shown to express a functional NMDA receptor channel complex. These compounds inhibited NMDA receptor activity in a manner noncompetitive with NMDA. They also produced a parallel right-ward shift in the glycine dose response for potentiation of the NMDA responses in the oocytes and thus provided further evidence for a competitive interaction at the glycine site. Finally, in vivo transient bilateral carotid artery occlusion experiments revealed that these compounds were capable of reducing the damage typically associated with an ischemic insult in Mongolian gerbil hippocampal neurons.
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Affiliation(s)
- W F Hood
- G. D. Searle & Co., Central Nervous System Diseases Research, Chesterfield, Missouri
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23
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Abstract
BMY-14802, a selective sigma ligand currently under investigation as an atypical antipsychotic agent, was tested for potential anti-ischemic activity. BMY-14802 (10, 30 and 50 mg/kg) did not produce any stereotyped behavior, ataxia or seizures. When gerbils were pretreated with 10, 30 or 50 mg/kg of BMY-14802 30 min prior to bilateral occlusion of carotid arteries for 5 min, BMY-14802 significantly protected against ischemia-induced neuronal loss in the hippocampus. Thus, BMY-14802 may also be useful as an anti-ischemic agent that does not produce psychotomimetic effects.
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Affiliation(s)
- P C Contreras
- CNS Diseases Research, G. D. Searle & Co., Chesterfield, MO 63198
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24
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Pellicciari R, Natalini B, Marinozzi M, Sadeghpour BM, Cordi AA, Lanthorn TH, Hood WF, Monahan JB. Synthesis, absolute configuration and activity at N-methyl-D-aspartic acid (NMDA) receptor of the four D-2-amino-4,5-methano-adipate diastereoisomers. Farmaco 1991; 46:1243-64. [PMID: 1667358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The four D-2-amino-4,5-methano-adipates 26, 27, 32, 33 were synthesized and their biological activity at the N-methyl-D-aspartate (NMDA) receptor was assessed. The synthesis involved as a key step a rhodium acetate dimer catalyzed addition of ethyl diazoacetate to the protected D-allylglycine (17). In vitro receptor binding using L-[3H]glutamate as the radioligand provided affinity data, while modulation of [3H]TCP binding was used as a functional assay. The analogues were also evaluated in [3H]kainate and [3H]AMPA binding to assess selectivity over non-NMDA glutamate receptors. Three of the four diastereoisomer, D-CAA B (27), C (32) and D (33) were shown to have agonist properties at the NMDA-site, while the fourth, (2R,4R,5R) D-CAA A (26) was characterized as an NMDA-site atypic antagonist.
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Affiliation(s)
- R Pellicciari
- Istituto di Chimica Farmaceutica e Tecnica Farmaceutica, Università Degli Studi, Perugia, Italy
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25
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Contreras PC, Ragan DM, Bremer ME, Lanthorn TH, Gray NM, Iyengar S, Jacobson AE, Rice KC, de Costa BR. Evaluation of U-50,488H analogs for neuroprotective activity in the gerbil. Brain Res 1991; 546:79-82. [PMID: 1649669 DOI: 10.1016/0006-8993(91)91161-s] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
U-50,488H, a kappa (kappa) opioid ligand with moderate potency at sigma (sigma) receptors, protects against mechanical and ischemia-induced injury. The purpose of this study was to evaluate the possibility that sigma-receptors may be involved in mediating the neuroprotective actions of U-50,488H. This possibility was examined by testing the potential of a series of U-50,488H analogs, which are potent sigma-ligands with minimal activity at kappa-opioid receptors, to protect against ischemia-induced neuronal damage in the gerbil. Like U-50,488H, BD-449 (20 mg/kg), the cis-diastereomer of U-50,4888H, protected against ischemia-induced neuronal damage as did BD-737 (50 and 30 mg/kg) and BD-738 (50 mg/kg). All 3 compounds interacted selectively with sigma-receptors. In contrast, BD-601 (50 mg/kg), did not protect against ischemia-induced neuronal damage, although it also interacted potently with sigma-receptors. One difference between the compounds that were neuroprotective and BD-601 is that only BD-601 produced sigma-like behavioral effects in the rat. Thus, it is possible that BD-601 may interact differently or at a different sigma-subtype than BD-449, BD-737 and BD-738 with sigma-receptors. However, these results clearly indicate that an interaction with kappa-opioid receptors is not required for anti-ischemic activity, and that sigma-receptors may play a role in neuroprotection.
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26
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Rao TS, Cler JA, Mick SJ, Ragan DM, Lanthorn TH, Contreras PC, Iyengar S, Wood PL. Opipramol, a potent sigma ligand, is an anti-ischemic agent: neurochemical evidence for an interaction with the N-methyl-D-aspartate receptor complex in vivo by cerebellar cGMP measurements. Neuropharmacology 1990; 29:1199-204. [PMID: 1963477 DOI: 10.1016/0028-3908(90)90045-s] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Opipramol, a potent sigma ligand and a tricyclic antidepressant compound, provided significant neuronal protection (P less than 0.0001) against ischemia-induced neuronal cell loss in the hippocampus in Mongolian gerbils, at a dose of 50 mg/kg (30 min pretreatment). However, opipramol did not offer protection when given 60 min after the ischemic insult. Opipramol decreased basal levels of cGMP in the cerebellum of the mouse and harmaline-induced increases in levels of cGMP, with approximate ED50 values of 4 and 27 mg/kg. Opipramol antagonized methamphetamine- and pentylenetetrazol-induced increases in levels of cGMP. Parenteral administration of opipramol also antagonized the increases in levels of cGMP in the cerebellum of the mouse after the local administration of D-serine, an agonist at the N-methyl-D-aspartate (NMDA)-associated, strychnine-insensitive glycine receptor. These results indicate that opipramol attenuates responses mediated through the NMDA receptor complex. These results further support the functional modulation of the NMDA receptor complex by sigma ligands and provide a neurochemical correlate for the observed anti-ischemic properties of opipramol.
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Affiliation(s)
- T S Rao
- CNS Diseases Research, G.D. Searle & Co., Monsanto Company, St Louis, Missouri 63198
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27
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Watson GB, Lanthorn TH. Pharmacological characteristics of cyclic homologues of glycine at the N-methyl-D-aspartate receptor-associated glycine site. Neuropharmacology 1990; 29:727-30. [PMID: 2177161 DOI: 10.1016/0028-3908(90)90125-b] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In Xenopus oocytes, injected with mRNA from the brain of the rat, the characteristics of the cyclic homologues of glycine, ACPC, ACBC and cycloleucine have been examined. 1-Aminocyclopropane-1-carboxylate was a potent agonist at the NMDA-associated glycine site (EC50 = 0.09 +/- 0.02 microM) and exhibited characteristics consistent with a partial agonist. 1-Aminocyclobutane-1-carboxylate, in addition to its previously described antagonist properties, was found to possess agonist properties of low efficacy. Furthermore, ACBC did not completely block NMDA/glycine-induced currents, which is also consistent with partial agonist characteristics. In addition, small concentrations of glycine (less than 3 microM) did not alter the potency of ACBC, possibly suggesting that it is not simply a competitive glycine antagonist. Cycloleucine was a very weak glycine antagonist. These results suggest that as the size of the ring of cyclic homologues of glycine increases, there is a resulting transition from agonist to mixed agonist/antagonist to antagonist properties.
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Affiliation(s)
- G B Watson
- Central Nervous System Diseases Research, G. D. Searle & Co., St Louis, Missouri 63198
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28
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Lanthorn TH, Hood WF, Watson GB, Compton RP, Rader RK, Gaoni Y, Monahan JB. Cis-2,4-methanoglutamate is a potent and selective N-methyl-D-aspartate receptor agonist. Eur J Pharmacol 1990; 182:397-404. [PMID: 2146136 DOI: 10.1016/0014-2999(90)90036-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cis- and trans-2,4-methanoglutamate were compared with L-glutamate as acidic amino acid ligands. Cis-2,4-methanoglutamate had a Ki of 0.052 microM against N-methyl-D-aspartate (NMDA)-specific L-[3H]glutamate binding compared with 0.050 microM for L-glutamate. Cis-2,4-methanoglutamate exhibited no significant affinity against [3H]kainate or [3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate ([3H]AMPA) binding. Trans-2,4-methanoglutamate had no significant affinity for any of these sites. Cis-2,4-methanoglutamate increased [3H]N-1[2-thienyl]cyclohexyl-3,4-piperidine [( 3H]TCP) binding with EC50 of 0.35 +/- 0.14 microM. It produced an inward current in rat brain mRNA-injected Xenopus oocytes which was blocked by the NMDA antagonist, D-2-amino-7-phosphonoheptanoate (D-AP7). Cis-2,4-methanoglutamate (EC50 = 15.9 microM) was 100-fold more potent than L-glutamate (EC50 = 1,584 microM) in reducing the excitatory postsynaptic potential in CA1 of hippocampal slices. Cis-2,4-methanoglutamate is the most potent, selective NMDA agonist known.
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Affiliation(s)
- T H Lanthorn
- CNS Diseases Research, G.D. Searle & Co., St. Louis, MO
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29
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Monahan JB, Biesterfeldt JP, Hood WF, Compton RP, Cordi AA, Vazquez MI, Lanthorn TH, Wood PL. Differential modulation of the associated glycine recognition site by competitive N-methyl-D-aspartate receptor antagonists. Mol Pharmacol 1990; 37:780-4. [PMID: 2163012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The competitive N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphonopentanoate and two other five-atom linkage (C-5) omega-phosphono-alpha-amino acid analogs reduced [3H]glycine binding, in a dose-dependent manner, to a maximum of 45-55%, whereas seven-atom linkage (C-7) analogs had significantly less effect. The IC50 of the C-5 antagonists for the inhibition of [3H]glycine binding closely paralleled their potency both in displacing NMDA-selective L-[3H]glutamate binding and in negatively modulating (+)-[3H]5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imi ne maleate ([3H]MK-801) binding. Additionally, reduction of glycine binding by the C-5 antagonists was reversed by both NMDA receptor agonists and C-7 competitive NMDA antagonists, providing evidence that the site of action of these C-5 antagonists is the NMDA recognition site, resulting in indirect modulation of the glycine site. These data imply a functional coupling between the NMDA and associated glycine recognition sites and, furthermore, suggest a differential interaction of C-5 and C-7 competitive NMDA antagonists with the NMDA receptor complex.
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Affiliation(s)
- J B Monahan
- Central Nervous System Diseases Research, G.D. Searle & Co., St. Louis, Missouri 63198
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30
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Abstract
In the CA1 region of the rat hippocampal slice, epileptiform activity was induced by the GABAA antagonist penicillin (PEN, 3.4 mM). The competitive N-methyl-D-aspartate (NMDA) receptor antagonists D-2-amino-7-phosphonoheptanoate (D-AP7) and D-2-amino-5-phosphonovolerate (D-AP5) attenuated extracellularly recorded evoked burst duration, the number of population spikes per evoked bursts and the frequency of spontaneously occurring bursts, but did not affect the sum of the population spike amplitudes or the evoked burst coastline measures due to increases in amplitude of the remaining secondary population spikes. Intracellular recordings showed that many of the secondary action potentials in the PEN burst were decreased in amplitude and broadened in duration, perhaps due to spike inactivation. D-AP7 allowed these secondary action potentials to increase in amplitude, which could explain the increases in secondary population spike amplitude seen extracellularly. Decrements in stimulus strength can mimic the effect of D-AP7 on PEN bursts. These data suggest that there is a portion of the PEN-induced epileptiform burst which is sensitive to NMDA antagonists.
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Affiliation(s)
- G B Watson
- Central Nervous System Diseases Research, G.D. Searle & Company, Monsanto Company, St. Louis, MO 63198
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31
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Watson GB, Monaghan DT, Lanthorn TH. Selective activation of oscillatory currents by trans-ACPD in rat brain mRNA-injected Xenopus oocytes and their blockade by NMDA. Eur J Pharmacol 1990; 179:479-81. [PMID: 1694771 DOI: 10.1016/0014-2999(90)90194-b] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- G B Watson
- CNS Diseases Research, G.D. Searle & Company, Chesterfield, MO 63198
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32
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Watson GB, Bolanowski MA, Baganoff MP, Deppeler CL, Lanthorn TH. D-cycloserine acts as a partial agonist at the glycine modulatory site of the NMDA receptor expressed in Xenopus oocytes. Brain Res 1990; 510:158-60. [PMID: 2157524 DOI: 10.1016/0006-8993(90)90745-w] [Citation(s) in RCA: 127] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In the Xenopus oocyte preparation, D-cycloserine (DCS) had the profile of a partial agonist at the glycine modulatory site of the NMDA receptor. Maximal NMDA responses in the presence of DCS were only 40-50% of those in the presence of glycine. Glycine and D-serine were agonists at this site. The actions of DCS were competitively antagonized by HA-966, a known glycine antagonist.
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Affiliation(s)
- G B Watson
- CNS Diseases Research, G.D. Searle & Company St. Louis, MO 63198
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33
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Abstract
A large, extracellular negative DC shift, termed epileptic depolarization, could be elicited during zero magnesium-induced epileptic activity in the rat hippocampal slice. In 10 mM glucose medium, epileptic depolarization was elicited by high-frequency synaptic stimulation. During epileptic depolarization synaptic responses were abolished, but recovered in 10.4 +/- 2.1 min. In low glucose (2 mM) medium, epileptic depolarization either occurred spontaneously or could be elicited by high frequency synaptic stimulation, and no recovery of synaptic responses was observed for at least 30 min. This long-term synaptic failure was blocked by the competitive NMDA antagonists, 3-[+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP, 100 microM) and D-2-amino-7-phosphonoheptanoate (D-AP7, 100 microM) when added at the peak of epileptic depolarization, but not 5 min afterwards. Intracellular analysis showed that this extracellular DC shift was correlated with a membrane depolarization which approached 0 mV. With 10 mM glucose medium, the membrane potential returned to resting level in 6.3 +/- 1.9 min. In 2 mM glucose medium, neurons remained depolarized and no recovery was observed. This persistent depolarization could account for the loss of synaptic function recorded extracellularly. Application of 100 microM CPP blocked persistent depolarization and allowed for the recovery of the membrane potential. Epileptic depolarization was also observed during picrotoxin-induced epileptic activity. Both anoxic depolarization during experimental ischemia and epileptic depolarization can trigger long-term synaptic failure and persistent depolarization. Epileptic depolarization and anoxic depolarization may be triggers which can lead to neuronal failure in diseases associated with neuronal degeneration.
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Affiliation(s)
- G B Watson
- Central Nervous System Diseases Research, G.D. Searle & Company, Monsanto Company, Chesterfield, MO 63198
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34
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Watson GB, Bolanowski MA, Baganoff MP, Deppeler CL, Lanthorn TH. Glycine antagonist action of 1-aminocyclobutane-1-carboxylate (ACBC) in Xenopus oocytes injected with rat brain mRNA. Eur J Pharmacol 1989; 167:291-4. [PMID: 2556287 DOI: 10.1016/0014-2999(89)90590-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
ACBC has been reported to have the binding profile of an antagonist at the glycine site of the NMDA receptor. In Xenopus oocytes injected with rat brain mRNA, we have confirmed the antagonist action of ACBC on NMDA responses. ACBC and HA-966, a known glycine antagonist, blocked NMDA responses in a non-competitive manner and blocked the potentiation of NMDA responses by glycine in a competitive manner. We conclude that ACBC blocks NMDA responses via a competitive interaction at the glycine modulatory site.
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Affiliation(s)
- G B Watson
- CNS Diseases Research, G.D. Searle and Company, St. Louis, MO 63198
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35
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Abstract
Early physiological events induced by hypoxia plus low D-glucose were investigated by intracellular recording in the rat hippocampal slice. A rapid intracellular depolarization corresponded to the extracellularly recorded anoxic depolarization. This intracellular depolarization consisted of two pharmacologically distinct components, an initial depolarization and a persistent depolarization. The persistent phase of depolarization was selectively blocked by lowering calcium and raising magnesium and by N-methyl-D-aspartate (NMDA) antagonists. This persistent depolarization can account for the long-term synaptic failure seen following experimental ischemia in vitro.
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Affiliation(s)
- R K Rader
- Central Nervous System Diseases Research, G.D. Searle and Co., c/o Monsanto Co., St. Louis, MO 63198
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36
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Lanthorn TH, Fagg GE. Gostatin blocks physiological actions and binding of acidic amino acids in rat brain. Neuropharmacology 1989; 28:429-32. [PMID: 2546088 DOI: 10.1016/0028-3908(89)90041-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Gostatin, an inhibitor of aspartate aminotransferases isolated from Streptomyces sumanensis NK-23, was tested as an antagonist of acidic amino acid-mediated responses in the in vitro hippocampal slice and of acidic amino acid binding. Gostatin blocked responses to N-methyl-aspartate (AMPA) or L-glutamate. Gostatin also displaced N-methyl-D-aspartate-sensitive [3H]-L-glutamate binding (Ki = 22.0 microM) more potently than [3H]-kainate binding. Gostatin appears to be a relatively nonselective acidic amino acid antagonist in the mammalian central nervous system.
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Affiliation(s)
- T H Lanthorn
- 1Central Nervous System Diseases Research, G. D. Searle & Co., Chesterfield, Mo. 63198
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37
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Contreras PC, Monahan JB, Lanthorn TH, Pullan LM, DiMaggio DA, Handelmann GE, Gray NM, O'Donohue TL. Phencyclidine. Physiological actions, interactions with excitatory amino acids and endogenous ligands. Mol Neurobiol 1987; 1:191-211. [PMID: 2855791 DOI: 10.1007/bf02936608] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Phenycyclidine (PCP) produces many profound effects in the central nervous system. PCP has numerous behavioral and neurochemical effects such as inhibiting the uptake and facilitating the release of dopamine, serotonin, and norepinephrine. PCP also interacts with sigma, mu opioid, muscarinic, and nicotinic receptors. However, the psychotomimetic effects induced by PCP are believed to be mediated by specific PCP receptors, where PCP binds with greater potency than sigma compounds. Electrophysiological, behavioral, and neuro-chemical evidence strongly suggests that at least some of the many PCP actions result from antagonism of excitatory amino acid-induced responses via PCP receptors. The recent isolation and partial characterization of the alpha and beta endopsychosins and the identification of other endogenous ligands for the PCP and sigma receptors, is another promising area of research in the elucidation of the physiological role of an endogenous PCP and sigma system.
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Affiliation(s)
- P C Contreras
- Central Nervous Systems Research, G.D. Searle & Co., Chesterfield, MO 63198
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38
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Fagg GE, Lanthorn TH. Cl-/Ca2+-dependent L-glutamate binding sites do not correspond to 2-amino-4-phosphonobutanoate-sensitive excitatory amino acid receptors. Br J Pharmacol 1985; 86:743-51. [PMID: 2998527 PMCID: PMC1916736 DOI: 10.1111/j.1476-5381.1985.tb08954.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A series of phosphono and phosphino analogues of glutamate were used to compare the pharmacological properties of (a) Cl-/Ca2+-dependent, 2-amino-4-phosphonobutanoate (AP4)-sensitive L-[3H]-glutamate binding sites in rat brain synaptic plasma membranes (SPMs) and (b) AP4-sensitive excitatory synaptic responses by use of electrophysiological techniques. In the presence of Cl- and Ca2+, L-[3H]-glutamate bound to SPMs with Kd 804 nM and Bmax 53 pmol mg-1 protein. The AP4-sensitive (Ki 7.3 microM) population of binding sites represented 61% of L-glutamate specifically bound. omega-Substituted analogues of AP4 were potent inhibitors of L-[3H]-glutamate binding (Ki values 2.4-38 microM), whereas N-substituted compounds or propionic acid derivatives were inactive. Experiments with AP4 alone and in combination with other analogues demonstrated that the primary target of all substances was the AP4-sensitive population of L-glutamate binding sites. In the hippocampal slice in vitro, AP4 antagonized lateral perforant path-evoked field potentials with an IC50 of 2.7 microM. In contrast to their actions at AP4-sensitive L-glutamate binding sites, all other compounds (except for the omega-carboxymethylphosphino analogue, IC50 19 microM) were weak or inactive as antagonists of this synaptic response (IC50 values greater than 100 microM). Inactive compounds which exhibited activity in the binding assay did not reverse the synaptic depressant effects of AP4, indicating that they were neither agonists nor antagonists at AP4-sensitive synapses. 4 The lack of correspondence between (a) the Cl- /Ca2 -dependent, AP4-sensitive population of L- [3H]-glutamate binding sites and (b) AP4-sensitive synaptic responses indicates that these binding sites are not the receptors through which AP4 exerts its neuropharmacological effects. The possibility that Cl- /Ca2+-dependent 'binding sites' represent transport into resealed SPM vesicles is discussed. 5 Electrophysiological data demonstrate that AP4-sensitive synaptic receptors display a high degree of ligand selectivity. High antagonist potency is shown only by glutamate analogues with unmodified alpha-amino and alpha-carboxyl groups, and with a bifunctional (dianionic) omega-terminal.
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39
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Abstract
L-Aspartic acid-beta-benzyl ester blocks the mossy fiber-CA3 and medial perforant path-dentate gyrus synaptic responses in the rat hippocampal slice with an IC50 of about 1 mM. Higher concentrations (IC50 greater than 10 mM) are necessary to block the Schaffer collateral/commissural-CA1, commissural/associational-CA3 and lateral perforant path-dentate gyrus synaptic responses. These results indicate that it is possible to differentiate between excitatory synaptic responses which have previously appeared pharmacologically similar.
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40
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Lanthorn TH, Ganong AH, Cotman CW. 2-Amino-4-phosphonobutyrate selectively blocks mossy fiber-CA3 responses in guinea pig but not rat hippocampus. Brain Res 1984; 290:174-8. [PMID: 6318908 DOI: 10.1016/0006-8993(84)90750-9] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The acidic amino acid antagonist D,L-2-amino-4-phosphonobutyrate (DL-APB) is a potent blocker of synaptic transmission at guinea pig but not rat mossy fiber-CA3 synapses in hippocampal slices. The L-isomer of APB is responsible for the potent inhibition at the guinea pig synapse. The L-APB analogue L-serine-O-phosphate (L-SOP) also is more potent against the guinea pig response. These differences may reflect a difference in a synaptic acidic amino acid receptor in these two species. Other acidic amino acid antagonists are less potent than APB or L-SOP and do not discriminate between the mossy fiber responses in the two species.
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41
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Abstract
The relative potency of analogues of excitatory amino acids to produce depolarization when applied in the apical dendritic field of CA1 cells was studied in the hippocampal slice. The effect of these compounds was measured by recording focal potentials (FPs), the shift in the extracellular d.c. potential produced by the compounds applied. The ability of focal potentials to measure neuronal responses was evaluated. N-methyl-D-aspartate (NMDA)-type agonists were 10-20 times more potent, relative to L-glutamate, than reported from investigations in spinal cord. Quisqualate (QA), +/- alpha-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (AMPA) and kainate (KA) exhibited potencies on CA1 cells similar to those reported for spinal neurons. These data indicate that elements in CA1 cells possess a receptor with an affinity for N-methyl-D-aspartate-type agonists. Some putative antagonists were found to induce negative focal potentials suggesting a direct, excitatory action in this area.
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42
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Ganong AH, Lanthorn TH, Cotman CW. Kynurenic acid inhibits synaptic and acidic amino acid-induced responses in the rat hippocampus and spinal cord. Brain Res 1983; 273:170-4. [PMID: 6311346 DOI: 10.1016/0006-8993(83)91108-3] [Citation(s) in RCA: 256] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Kynurenic acid, a tryptophan metabolite, inhibits excitatory synaptic transmission in the rat hippocampal slice and the isolated immature rat spinal cord, but does not affect membrane potential or input resistance of hippocampal CA1 pyramidal cells. Kynurenic acid also antagonizes responses induced in the dentate gyrus by excitatory amino acids, particularly N-methyl-DL-aspartate and the endogenous excitant quinolinic acid. These results indicate that kynurenic acid antagonizes synaptic transmission probably by blocking postsynaptic transmitter receptors at putative amino acid mediated synapses.
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Fagg GE, Foster AC, Harris EW, Lanthorn TH, Cotman CW. Structure--activity relationships of L-glutamate receptor ligands: role of the omega-acidic terminal. Neurosci Lett 1982; 31:59-64. [PMID: 6126848 DOI: 10.1016/0304-3940(82)90054-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Acidic amino acid analogues varying in their omega-terminal were evaluated: (1) as neuronal excitants or antagonists of excitatory synaptic transmission, and (2) as inhibitors of L-[3H]glutamate binding to synaptic membranes. omega-Phosphonates were antagonists and inhibited L-glutamate binding to the 2-amino-4-phosphonobutyrate (APB)-sensitive population of binding sites; omega-sulfonates and omega-carboxylates were excitants and inhibited L-glutamate binding to APB-sensitive and -insensitive sites. The data indicate that properties of the omega-acidic group are important for establishing the relative potencies of antagonist substances and the overall excitatory/antagonist activity of these analogues.
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Abstract
The effect of baclofen was investigated on mossy fiber, Schaffer collateral and perforant path synaptic transmission in hippocampal slices. Baclofen completely inhibits mossy fiber and Schaffer collateral synaptic transmission with an IC50 of 3.8 microM. The lateral perforant path is insensitive to baclofen, while the response in the medial zone was partially blocked. Baclofen does not appear to act in a GABA-like manner.
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Isaacson RL, Lanthorn TH. Hippocampal involvement in the pharmacologic induction of withdrawal-like behaviors. Fed Proc 1981; 40:1508-1512. [PMID: 6783444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Kainic acid is an analog of glutamate. The CA3-4 field of the hippocampus is extremely sensitive to its toxic properties. Intracerebroventricular injection of of nontoxic doses of kainic acid in rats produces behaviors similar to morphine withdrawal. Lesion of CA3-4 abolishes this response to kainic acid. Destruction of CA3-4 blocks the ability of Met-enkephalin, ketocyclazocine, and 5-hydroxytryptophan, but not sodium valproate or ice water to induce withdrawal-like behaviors. The actions of kainic acid, endorphins, and ketocyclazocine are blocked by naloxone and enhanced by opiate agonists. Sodium valproate, ice water, and withdrawal itself are released by naloxone and blocked by opiate agonists. Similar discriminations by CA3-4 lesions and challenge by naloxone and morphine may indicate that two neural circuits exist through which withdrawal-like behaviors are evoked. The hippocampal circuit is not directly involved in dependence, but may modulate withdrawal. Withdrawal-like behaviors are observed in rats in situations where behavior is blocked. These withdrawal-like behaviors are reminiscent of verbal reports of anxiety. In particular, wet-dog shakes in these situations may be analogous to shuddering. In humans, monosodium glutamate intolerance is associated with shuddering.
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Webster DG, Lanthorn TH, Dewsbury DA, Meyer ME. Tonic immobility and the dorsal immobility response in twelve species of muroid rodents. Behav Neural Biol 1981; 31:32-41. [PMID: 7305807 DOI: 10.1016/s0163-1047(81)91034-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Green EJ, Isaacson RL, Dunn AJ, Lanthorn TH. Naloxone and haloperidol reduce grooming occurring as an aftereffect of novelty. Behav Neural Biol 1979; 27:546-51. [PMID: 230814 DOI: 10.1016/s0163-1047(79)92208-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Abstract
Systemic injection of GDEE (glutamate diethyl ester), an antagonist of glutamate and aspartate receptors, induces stretching and yawning in rats. This was not accompanied by excessive grooming. Coupled with previous work these findings give evidence that a glutamatergic mechanism is involved in stretching and yawning.
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