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Zacharie B, Abbott SD, Baigent CB, Doyle C, Yalagala RS. An Efficient Two-Step Preparation of α-, β-, γ- or δ-Amino Acids from 2-Pyrazinones, 2-Hydroxypyrimidines or 2-Pyridones Respectively. European J Org Chem 2018. [DOI: 10.1002/ejoc.201801134] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Boulos Zacharie
- Prometic Biosciences Inc.; 500 boul. Cartier Ouest, Bureau 150 H7V 5B7 Laval Québec Canada
| | - Shaun D. Abbott
- Prometic Biosciences Inc.; 500 boul. Cartier Ouest, Bureau 150 H7V 5B7 Laval Québec Canada
| | - Christopher B. Baigent
- Prometic Biosciences Inc.; 500 boul. Cartier Ouest, Bureau 150 H7V 5B7 Laval Québec Canada
| | - Christopher Doyle
- Prometic Biosciences Inc.; 500 boul. Cartier Ouest, Bureau 150 H7V 5B7 Laval Québec Canada
| | - Ravi Shekar Yalagala
- Prometic Biosciences Inc.; 500 boul. Cartier Ouest, Bureau 150 H7V 5B7 Laval Québec Canada
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Manocha A, Sharma KK, Mediratta PK. On the mechanism of anticonvulsant effect of tramadol in mice. Pharmacol Biochem Behav 2005; 82:74-81. [PMID: 16140368 DOI: 10.1016/j.pbb.2005.07.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2005] [Revised: 07/06/2005] [Accepted: 07/07/2005] [Indexed: 11/16/2022]
Abstract
The present study was conducted to examine the effects of tramadol, an atypical opioid on convulsive behaviour in maximal electroshock (MES) seizure test on mice. Moreover, an attempt was also made to investigate the role of possible receptor mechanisms involved. MES seizures were induced via transauricular electrodes (60 mA, 0.2 sec). Seizure severity was determined by (1) the duration of tonic hindlimb extensor (THE) phase and by (2) mortality due to electroconvulsions. Intraperitoneal (i.p.) administration of tramadol dose-dependently (10-50 mg/kg) decreased the duration of THE phase of MES. The anticonvulsant effect of tramadol was antagonized by the opioid antagonists, naloxone in high dose, and MR2266, a selective kappa antagonist but not by naltrindole, a delta opioid antagonist. Coadministration of either gamma-aminobutyric acid (GABA)-ergic drugs (diazepam, GABA, muscimol and baclofen) or N-methyl-D-aspartate (NMDA) receptor antagonist, MK801 with tramadol augmented the anticonvulsant effect of the latter drug. By contrast, flumazenil, a central benzodiazepine (BZD) receptor antagonist, counteracted the diazepam-induced facilitation of anti-MES effect of tramadol. Similarly, delta-aminovaleric acid (DAVA), a GABAB receptor antagonist, abolished the facilitatory effect of baclofen, a GABAB agonist on anti-MES action of tramadol. These BZD-GABAergic antagonists, flumazenil or DAVA, on their own also antagonized the anti-MES effect of tramadol administered alone. No significant effect on mortality was observed in any of the studied groups. Taken together, the current results have demonstrated a possible role for multitude of important neurotransmitter systems, i.e., opioid (kappa), GABAA-BZD receptors system, GABAB receptors and NMDA channel involvement in the antielectroshock effect of tramadol in mice.
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Affiliation(s)
- Anshu Manocha
- Department of Pharmacology, University College of Medical Sciences and GTB Hospital, Shahdara, Delhi-110095, India.
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Ovsepyan SV, Veselkin NP. Involvement of GABA(B) receptors in presynaptic inhibition of fibers of the descending projections of the spinal cord in the frog Rana ridibunda. ACTA ACUST UNITED AC 2004; 33:873-81. [PMID: 14969425 DOI: 10.1023/a:1025944704898] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Isolated spinal cord preparations from Rana ridibunda frogs were used for studies of the effects of the GABA(B) receptor agonists (-)-baclofen (50 and 100 microM) and GABA (4-8 mM) and the specific GABA(B) receptor antagonist 2-hydroxysaclofen (100 microM) on the transmission of signals from fibers of the ventral columns monosynaptically connected with motoneurons in segments 9 and 10. These experiments showed that (-)-baclofen (50 and 100 microM) produced significant and dose-dependent suppression of excitatory postsynaptic potentials (EPSP) in motoneurons and ventral root potentials evoked by stimulation of fibers of the ipsi- and contralateral ventral columns. The inhibitory effect of (-)-baclofen (100 microM) on descending EPSP was 35-50% blocked by the GABA(B) receptor antagonist 2-hydroxysaclofen (0.2 mM). The inhibitory effect of GABA (4-8 mM) on descending EPSP was 60% blocked by the GABA(A) receptor antagonist picrotoxin (0.05 mM). (-)-Baclofen (50 microM) and GABA (4 and 6 mM) were found to have inhibitory effects on ventral root potentials evoked by stimulation of the ipsi- and contralateral ventral columns. The data obtained here, as well as data obtained by pharmacological analysis and conditioning by stimulation of the ipsi- and contralateral ventral columns, are regarded as a significant argument supporting the existence of GABA(B) receptor-mediated presynaptic inhibition of descending fibers connected monosynaptically to spinal cord motoneurons in the frog Rana ridibunda.
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Affiliation(s)
- S V Ovsepyan
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Moris Torez Prospekt, 194223 St. Petersburg, Russia
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Manocha A, Sharma KK, Mediratta PK. Possible mechanism involved in the anticonvulsant action of butorphanol in mice. Pharmacol Biochem Behav 2003; 74:343-50. [PMID: 12479953 DOI: 10.1016/s0091-3057(02)01004-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The study was designed to examine the effect of butorphanol, a classical opioid on convulsive behaviour using maximal electroshock (MES) test. An attempt was also made to investigate the role of possible receptor mechanisms involved. MES seizures were induced in mice via transauricular electrodes (60 mA, 0.2 s). Seizure severity was assessed by the duration of tonic hindlimb extensor phase and mortality due to convulsions. Intraperitoneal administration of butorphanol produced a dose-dependent (0.25-2 mg/kg) protection against hindlimb extensor phase. The anticonvulsant effect of butorphanol was antagonized by all the three opioid receptor antagonists (i.e., naloxone [mu], MR2266 [kappa], and naltrindole [delta], respectively). Coadministration of gamma-aminobutyric acid (GABA)-ergic drugs (diazepam, GABA, muscimol, and baclofen) and N-methyl-D-aspartate (NMDA) receptor antagonist, dizocilpine (MK801), with butorphanol augmented the anticonvulsant action of the latter drug. In contrast, flumazenil, a central benzodiazepine (BZD) receptor antagonist, reversed the facilitatory effect of diazepam on the anti-MES effect of butorphanol. Similarly, delta-aminovaleric acid (DAVA), a GABA(B) receptor antagonist, antagonized the facilitatory effect of baclofen, a GABA(B) agonist on anti-MES action of butorphanol. These BZD-GABAergic antagonists, flumazenil or DAVA, per se also counteracted the anti-MES effect of butorphanol given alone. These data exemplify the benefits of using the MES test, which is sensitive to opioidergic compounds and distinguished convulsive behavioural changes associated with GABAergic and NMDAergic effects. Taken together, the results implicate a role for multitude of neurotransmitter systems, i.e., opioid (mu, kappa, delta), NMDA channel, BZD-GABA(A) chloride channel complex, and GABA(B) receptors in the anti-MES action of butorphanol.
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Affiliation(s)
- Anshu Manocha
- Department of Pharmacology, University College of Medical Sciences and GTB Hospital, Shahdara, Delhi 110095, India.
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5
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Abstract
Electrophysiological recordings of the H-reflex and nonnociceptive flexion reflex were obtained from pentobarbital-anesthetized Intact rats and from both, anesthetized and unanesthetized groups of Acute and Chronic Spinal rats. Results showed that the flexor, but not H-reflex, of Chronic Spinal rats was significantly larger than that of all other groups, which did not differ among themselves. The antispastic drug baclofen dose-dependently decreased the flexion response of Chronic Spinal rats (A(50)=4.3 mg/kg+/-2.1 and 9.0 mg/kg).
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Affiliation(s)
- M Duke
- Department of Psychology 236 Audubon Hall Louisiana State University, 70803, Baton Rouge, LA, USA
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Batueva I, Tsvetkov E, Sagatelyan A, Buchanan JT, Vesselkin N, Adanina V, Suderevskaya E, Rio JP, Reperant J. Physiological and morphological correlates of presynaptic inhibition in primary afferents of the lamprey spinal cord. Neuroscience 1999; 88:975-87. [PMID: 10363832 DOI: 10.1016/s0306-4522(98)00239-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Patch-clamp recordings in a whole-cell mode were performed on dorsal sensory cells enzymatically isolated from the spinal cord of two lamprey species, Ichthyomyzon unicuspis and Lampetra fluviatilis. The voltage-activated currents through calcium channels were analysed. GABA and the specific GABA(B) receptor agonist baclofen reduced the peak amplitude of inward Ba2+ current, as a robust alternate charge carrier through voltage-dependent Ca2+ channels. These effects were dose-dependent and reversible. GABA(B) receptor antagonists, 2-hydroxysaclofen and delta-amino-n-valeric acid, blocked the reduction of Ba2+ currents by GABA and baclofen, while bicuculline, a GABA(A) receptor antagonist, had no blocking action. GABA and baclofen did not modify the dorsal sensory cell membrane conductance, indicating that they did not activate ligand-gated channels. However, GABA, but not baclofen, considerably increased membrane conductance and induced Cl- currents in isolated multipolar neurons (presumably interneurons and/or motoneurons). These findings suggest that GABA and baclofen action on lamprey dorsal sensory cells is mediated by GABA(B) receptors. We concluded that GABA-mediated presynaptic inhibition of lamprey dorsal sensory cell fibers results from GABA(B) receptor activation followed by a decrease of inward voltage-activated calcium currents. Appositions of GABA-immunoreactive boutons to horseradish peroxidase-labeled fibers from the dorsal root were observed at the ultrastructural level in the dorsal column using postembedding immunogold cytochemistry. It seems likely that these appositions represent the morphological substrate of dorsal sensory cell fiber presynaptic inhibition. In very rare cases, ultrastructural features were observed which could be interpreted as synaptic specializations between the GABA-immunoreactive boutons and the primary afferent fibers. The extrasynaptic action of GABA as a basis of presynaptic inhibition of this population of primary afferent neurons is discussed.
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Affiliation(s)
- I Batueva
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St Petersburg
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7
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Batueva IV, Buchanan JT, Tsvetkov EA, Sagatelyan AK, Veselkin NP. The effects of baclofen on calcium channel currents in dorsal sensory cells of the spinal cord in the lamprey. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1999; 29:79-89. [PMID: 10088153 DOI: 10.1007/bf02461361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
Abstract
Dorsal sensory cells isolated from the spinal cord of the lamprey species Ichthyomyzon unicuspis and Lampetra fluviatilis were used for whole-cell patch-clamp studies of the effects of baclofen on calcium channel currents, evoked in conditions in which Na+, K+ currents were blocked, by depolarizing membranes from constant holding potentials of -100 or -80 mV to +30 mV. Ba ions were used as carriers of currents through calcium channels. These studies demonstrated that baclofen (0.5 mM) decreased the peak amplitude of the Ba2+ current by an average of 22.5 +/- 4.2% (n = 12) in dorsal sensory cells of the lamprey Ichthyomyzon unicuspis and by 28.4 +/- 3.3% in the dorsal sensory cells of Lampetra fluviatilis (n = 25). The conductivity of dorsal sensory cell membranes in the presence of baclofen (and GABA) did not change. The blocking action of baclofen persisted in the presence of bicuculline (100 microM) and was lifted by addition of delta-aminovaleric acid and 2-hydroxysaclofen to the perfusing solution. These results are interpreted as evidence for the presence of GABAB receptors in dorsal sensory cell membranes. The data were compared with published results, and the question of the functional significance of GABAB receptors in the dorsal sensory cells (primary afferent cells) of cyclostomata is discussed.
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Affiliation(s)
- I V Batueva
- Laboratory for the Evolution of Interneuron Interactions, I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
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Koh HC, Shin IC, Hwang SJ, Kang JS, Lee CH, Ha JH, Paik DJ. Mediation of the cardiovascular response of adenosine A1 receptor through a GABA(B) receptor in the spinal cord of the rat. Neurosci Lett 1998; 243:81-4. [PMID: 9535118 DOI: 10.1016/s0304-3940(98)00089-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cardiovascular inhibitory effects induced by intrathecal (i.t.) administration of adenosine A1 receptor agonist and its modulation by cyclic AMP was suggested by our previous report. In this experiment, we examined the mediation of cardiovascular effects of adenosine A1 receptor by gamma-aminobutyric acid receptors A and B [GABA(A) and GABA(B)] in the spinal cord. I.t. administration of 10 nmol of N6-cyclohexyladenosine (CHA), an adenosine A1 receptor agonist, and pretreatment with bicuculline (10 nmol, i.t), a GABA(A) receptor antagonist, and 5-aminovaleric acid (50 nmol, i.t.), a GABA(B) receptor antagonist, prior to injection of CHA were performed in anesthetized, artificially ventilated Sprague-Dawley rats. I.t. injection of 50 nmol of 5-aminovaleric acid significantly attenuated the inhibitory cardiovascular effects of CHA but 10 nmol of bicuculline did not alter CHA-induced cardiovascular actions. It is suggested that cardiovascular responses of adenosine A1 receptor is mediated by GABA(B) receptor in the spinal cord.
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Affiliation(s)
- H C Koh
- Department of Pharmacology, College of Medicine, Hanyang University, Seoul, South Korea
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Platt B, Withington DJ. Response habituation in the superficial layers of the guinea-pig superior colliculus in vitro. Neurosci Lett 1997; 221:153-6. [PMID: 9121687 DOI: 10.1016/s0304-3940(96)13314-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Response habituation (RH) has been suggested to reflect the role of the mammalian superior colliculus (SC) as a novelty detector. In the present study, we show that RH occurs in the SC slice preparation and is caused partially by the activation of inhibitory GABA receptors. No evidence for the contribution of presynaptic transmitter release was found and the block of N-methyl-D-aspartate (NMDA) receptors facilitated RH for a higher stimulation frequency. Since RH could not be abolished completely by any treatment, it appears that other mechanisms such as a general metabolic fatigue may contribute to RH. Nevertheless, RH must be taken into account when performing repeated stimulation in the SC slice preparation.
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Affiliation(s)
- B Platt
- University of Leeds, Department of Physiology, Worsley Medical and Dental Building, UK.
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Simpson RK, Gondo M, Robertson CS, Goodman JC. The influence of glycine and related compounds on spinal cord injury-induced spasticity. Neurochem Res 1995; 20:1203-10. [PMID: 8746806 DOI: 10.1007/bf00995384] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Spasticity is a frequent and complex sequel to spinal cord injury. The neurochemical basis for the origin of spasticity is largely unknown. Glycine is among the most abundant neurotransmitters in the spinal cord. However, the role of glycine and related compounds in spasticity have received little attention. An ischemic spinal cord injury was created in rabbits, by an intraaortic balloon occlusion technique, which produced lower limb spasticity. A catheter was inserted into the cisterna magna and the spinal cord was bathed with 100 microM solutions of glycine, strychnine, D-serine, beta-alanine, MK-801, or artificial CSF for 4 hours at a rate of 10 microliters/min. H-reflexes were monitored before and during infusion by stimulating the posterior tibial nerve and recording from the plantar surface of the foot. Glycine, D-serine, and MK-801 depressed the H wave, strychnine produced a heightened H wave, and beta-alanine caused no significant changes. These results indicate that glycine and related compounds may influence spasticity.
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Affiliation(s)
- R K Simpson
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA
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Schwarz M, Schmitt T, Pergande G, Block F. N-methyl-D-aspartate and alpha 2-adrenergic mechanisms are involved in the depressant action of flupirtine on spinal reflexes in rats. Eur J Pharmacol 1995; 276:247-55. [PMID: 7601210 DOI: 10.1016/0014-2999(95)00043-k] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In urethane-chloralose anesthetised rats the muscle relaxant activity of flupirtine was investigated on the monosynaptic Hoffmann reflex recorded from plantar foot muscles and on the polysynaptic flexor reflex recorded from tibialis muscle. Intraperitoneal (i.p.; 2.5-25 mumol/kg) and intrathecal (i.t.; 33-330 nmol) administration of flupirtine depressed the polysynaptic flexor reflex in anesthetised rats in a dose-dependent manner without affecting the monosynaptic Hoffmann reflex. Flupirtine produced a similar pattern on spinal reflexes as NMDA receptor antagonists, such as (-)-2-amino-7-phosphonoheptanoic acid (500 nmol i.t.) and memantine (125 mumol/kg i.p.), the benzodiazepines diazepam (18 mumol/kg i.p.) and midazolam (80 nmol i.t.), and the alpha 2-adrenoceptor agonist tizanidine (2 mumol/kg). In contrast, the GABAA receptor agonist muscimol (21 mumol/kg i.p.; 20 nmol i.t.) and the GABAB receptor agonist baclofen (47 mumol/kg i.p.; 2 nmol i.t.) reduced the magnitude of both the flexor and the Hoffmann reflex, whereas the non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX; 10 nmol i.t.) depressed the Hoffmann reflex without affecting the flexor reflex. The effect of i.t. injection of flupirtine was prevented by coadministration of the mixed alpha 1/alpha 2-adrenoceptor antagonist yohimbine (10 nmol) and the excitatory amino acid N-methyl-D-aspartate (NMDA; 0.1 nmol), but neither by coadministration of the alpha 1-adrenoceptor antagonist prazosine (10 nmol), the GABAA receptor antagonist bicuculline (1 nmol), the GABAB receptor antagonist phaclofen (100 nmol), the non-NMDA receptor agonist alpha-amino-3-hydroxy-5-tertbutyl-4-isoxazolepropionic acid (ATPA; 0.1 pmol) nor by pre-treatment with the benzodiazepine receptor antagonist flumazenil (16 mumol/kg).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Schwarz
- Department of Neurology, RWTH Aachen, Germany
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Mott DD, Lewis DV. The pharmacology and function of central GABAB receptors. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1994; 36:97-223. [PMID: 7822122 DOI: 10.1016/s0074-7742(08)60304-9] [Citation(s) in RCA: 195] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In conclusion, GABAB receptors enable GABA to modulate neuronal function in a manner not possible through GABAA receptors alone. These receptors are present at both pre- and postsynaptic sites and can exert both inhibitory and disinhibitory effects. In particular, GABAB receptors are important in regulating NMDA receptor-mediated responses, including the induction of LTP. They also can regulate the filtering properties of neural networks, allowing peak transmission in the frequency range of theta rhythm. Finally, GABAB receptors are G protein-coupled to a variety of intracellular effector systems, and thereby have the potential to produce long-term changes in the state of neuronal activity, through actions such as protein phosphorylation. Although the majority of the effects of GABAB receptors have been reported in vitro, recent studies have also demonstrated that GABAB receptors exert electrophysiological actions in vivo. For example, GABAB receptor antagonists reduce the late IPSP in vivo and consequently can decrease inhibition of spontaneous neuronal firing following a stimulus (Lingenhöhl and Olpe, 1993). In addition, blockade of GABAB receptors can increase spontaneous activity of central neurons, suggesting the presence of GABAB receptor-mediated tonic inhibition (Andre et al., 1992; Lingenhöhl and Olpe, 1993). Despite these electrophysiological effects, antagonism of GABAB receptors has generally been reported to produce few behavioral actions. This lack of overt behavioral effects most likely reflects the modulatory nature of the receptor action. Nevertheless, two separate behavioral studies have recently reported an enhancement of cognitive performance in several different animal species following blockade of GABAB receptors (Mondadori et al., 1992; Carletti et al., 1993). Because of their small number of side effects, GABAB receptor antagonists may represent effective therapeutic tools for modulation of cognition. Alternatively, the lack of overt behavioral effects of GABAB receptors may indicate that these receptors are more important in pathologic rather than normal physiological states (Wojcik et al., 1989). For example, a change in receptor affinity or receptor number brought on by the pathology could enhance the effectiveness of GABAB receptors. Of significance, CGP 35348 has been shown to block absence seizures in genetically seizure prone animals, while inducing no seizures in control animals (Hosford et al., 1992; Liu et al., 1992). Thus, GABAB receptors may represent effective sites for pharmacological regulation of absence seizures. Perhaps further behavioral effects of these receptors will become apparent only after additional studies have been performed using the highly potent antagonists that have been recently introduced.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- D D Mott
- Department of Pediatrics (Neurology), Duke University Medical Center, Durham, North Carolina 27710
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Ronken E, Mulder AH, Schoffelmeer AN. Interacting presynaptic kappa-opioid and GABAA receptors modulate dopamine release from rat striatal synaptosomes. J Neurochem 1993; 61:1634-9. [PMID: 8228982 DOI: 10.1111/j.1471-4159.1993.tb09797.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The presynaptic regulation of stimulated dopamine release from superfused rat striatal synaptosomes by opioids and gamma-aminobutyric acid (GABA) was studied. It was found that in addition to dopamine D2 autoreceptors, calcium-dependent K(+)-stimulated [3H]dopamine release was inhibited through activation of a homogeneous population of kappa-opioid receptors in view of the potent inhibitory effect of the kappa-selective agonist U69,593 (EC50 0.2 nM) and its antagonism by norbinaltorphimine. Neither mu- nor delta-selective receptor agonists affected release of [3H]-dopamine. In addition, GABA potently inhibited the evoked [3H]dopamine release (EC50 0.4 nM) through activation of GABAA receptors in view of the GABA-mimicking effect of muscimol, the sensitivity of its inhibitory effect to picrotoxin and bicuculline, and the absence of an effect of the GABAB receptor agonist baclofen. In the presence of a maximally effective concentration of GABA, U69,593 did not induce an additional release-inhibitory effect, indicating that these receptors and the presynaptic D2 receptor are colocalized on the striatal dopaminergic nerve terminals. The excitatory amino acid agonists N-methyl-D-aspartate and kainate, as well as the cholinergic agonist carbachol, stimulated [3H]dopamine release, which was subject to kappa-opioid receptor-mediated inhibition. In conclusion, striatal dopamine release is under regulatory control of multiple excitatory and inhibitory neurotransmitter by activation of colocalized presynaptic receptors for excitatory amino acids, acetylcholine, dopamine, dynorphins, and GABA within the dopaminergic nerve terminals. Together, these receptors locally control ongoing dopamine neurotransmission.
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Affiliation(s)
- E Ronken
- Department of Pharmacology, Faculty of Medicine, Vrije Universiteit, Amsterdam, The Netherlands
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Herdeis C, Lütsch K. Enantiopure DAVA-derivatives-part III. Synthesis of all 4 stereoisomers of 2-methyl-4-hydroxy-5-aminopentanoic acid (2-Me-4-OH-DAVA). ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s0957-4166(00)86022-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Schwarz M, Block F, Sontag KH. N-methyl-D-aspartate (NMDA)-mediated muscle relaxant action of memantine in rats. Neurosci Lett 1992; 143:105-9. [PMID: 1436651 DOI: 10.1016/0304-3940(92)90243-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The present study examined in vivo whether memantine exerts muscle relaxant activity via an antagonistic action at N-methyl-D-aspartate (NMDA) receptors. Intraperitoneal (i.p.) administration of memantine, 50-100 mumol/kg, reduced the tonic activity in the electromyogram recorded from the gastrocnemius muscle of spastic mutant rats. This effect was prevented by coadministration of NMDA. Memantine, while not affecting monosynaptic Hoffmann (H)-reflexes, depressed polysynaptic flexor reflexes in anaesthetized rats following i.p. (6.25-100 mumol/kg) or intrathecal (i.t., 10-500 nmol) administration. The latter effect was prevented by i.t. coadministration of NMDA, but not of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). These observations suggest that NMDA receptors might be involved in the mediation of the muscle relaxant activity of memantine.
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Affiliation(s)
- M Schwarz
- Department of Neurology, University of Essen, FRG
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Yamasaki K, Goto Y. Direct evidence for central action of PCPGABA to stimulate gastric acid secretion by intracisternal injection. JAPANESE JOURNAL OF PHARMACOLOGY 1990; 54:7-12. [PMID: 2177122 DOI: 10.1254/jjp.54.7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
PCPGABA, injected into the cisterna magna, significantly stimulated gastric acid secretion in the perfused rat stomach preparation. This secretagogue action was dose-dependent (0.5-2 micrograms/rat). The peak response occurred within 60 min and lasted up to 100 min. The secretagogue action by PCPGABA was completely reduced by truncal vagotomy. Intracisternal injection of 5-aminovaleric acid, a GABAB-receptor antagonist, did not alter basal gastric acid output, and it also failed to antagonize the acid secretory response to intracisternal PCPGABA. These results demonstrate that intracisternal PCPGABA caused hypersecretion of acid through vagal dependent mechanisms partially independent of GABAB-receptors.
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Affiliation(s)
- K Yamasaki
- Department of Pharmacology, Tokushima Bunri University, Japan
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17
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Wüllner U, Klockgether T. Is the antispastic action of baclofen mediated by GABAB receptors? GABAB receptors and spasticity. Trends Pharmacol Sci 1990; 11:103. [PMID: 1966568 DOI: 10.1016/0165-6147(90)90193-c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Robinson TN, Cross AJ, Green AR, Toczek JM, Boar BR. Effects of the putative antagonists phaclofen and delta-aminovaleric acid on GABAB receptor biochemistry. Br J Pharmacol 1989; 98:833-40. [PMID: 2556202 PMCID: PMC1854788 DOI: 10.1111/j.1476-5381.1989.tb14612.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
1. Phaclofen and delta-aminovaleric acid (delta-AVA) have been reported to be antagonists at gamma-aminobutyric acidB (GABAB) receptors. Phaclofen, delta-AVA and related compounds were examined for potency and specificity at GABAB and GABAA receptors in rat cortical membranes labelled with [3H]-(-)-baclofen and [3H]-muscimol, respectively. Additionally phaclofen and delta-AVA were examined in two functional tests of central GABAB activity in rat cortical slices, namely the inhibition of forskolin-stimulated cyclic AMP accumulation, and the potentiation of isoprenaline-stimulated cyclic AMP accumulation. 2. delta-AVA (IC50 = 11.7 microM) was 20 fold more potent than phaclofen (IC50 = 229 microM) on GABAB receptor binding. All compounds possessing a phosphonic acid group, including phaclofen, which were active at GABAB receptors were inactive at GABAA receptors, while delta-AVA was equally potent at both receptors. Several compounds exhibited Hill coefficients of less than unity in displacing [3H]-(-)-baclofen binding. 3. (-)-Baclofen inhibited forskolin-stimulated cyclic AMP accumulation (IC50 = 7.9 microM) but this effect was not stereospecific. Phaclofen (1 mM) was inactive against this inhibition but produced a potentiation of the forskolin effect. delta-AVA (1 mM) failed to antagonize the effect of baclofen; rather it mimicked baclofen. 4. (-)-Baclofen (10 microM) potentiated isoprenaline-stimulated cyclic AMP accumulation, an effect antagonized by phaclofen (1 mM). delta-AVA (1 mM) may be a weak antagonist but also potentiated basal cyclic AMP accumulation. 5. We conclude that neither delta-AVA nor phaclofen are potent specific GABAB receptor antagonists.
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Wüllner U, Klockgether T, Sontag KH. Phaclofen antagonizes the depressant effect of baclofen on spinal reflex transmission in rats. Brain Res 1989; 496:341-4. [PMID: 2804645 DOI: 10.1016/0006-8993(89)91085-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The action of phaclofen, the phosphonic acid derivative of baclofen, on baclofen-induced suppression of spinal reflex transmission was tested in anaesthetized rats. Intrathecal (i.th.) injection of phaclofen, 100 nmol, antagonized the depressant effect of baclofen, 2 nmol, on spinal Hoffmann (H)-reflexes and polysynaptic flexor reflexes but ha on the action of muscimol, 20 nmol. The antagonistic effect of phaclofen on baclofen-induced depression of H-reflexes was dose-dependent in doses ranging from 1 to 100 nmol. When administered alone, phaclofen, 100 nmol, was devoid of stimulatory or depressant effects on spinal reflexes. These results indicate that phaclofen specifically antagonizes the reflex suppressant action of baclofen. The lack of intrinsic action of phaclofen suggests that there is no endogenous tonic inhibition mediated by GABAB receptors under the present experimental conditions.
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Affiliation(s)
- U Wüllner
- Max-Planck-Institute for Experimental Medicine, Göttingen, F.R.G
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