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Sonnay S, Duarte JMN, Just N, Gruetter R. Energy metabolism in the rat cortex under thiopental anaesthesia measured In Vivo by 13 C MRS. J Neurosci Res 2017; 95:2297-2306. [PMID: 28316083 DOI: 10.1002/jnr.24032] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 01/05/2017] [Accepted: 01/16/2017] [Indexed: 01/05/2023]
Abstract
Barbiturates, commonly used as general anaesthetics, depress neuronal activity and thus cerebral metabolism. Moreover, they are likely to disrupt the metabolic support of astrocytes to neurons, as well as the uptake of nutrients from circulation. By employing 13 C magnetic resonance spectroscopy (MRS) in vivo at high magnetic field, we characterized neuronal and astrocytic pathways of energy metabolism in the rat cortex under thiopental anaesthesia. The neuronal tricarboxylic acid (TCA) cycle rate was 0.46 ± 0.02 µmol/g/min, and the rate of the glutamate-glutamine cycle was 0.09 ± 0.02 µmol/g/min. In astrocytes, the TCA cycle rate was 0.16 ± 0.02 µmol/g/min, accounting for a quarter of whole brain glucose oxidation, pyruvate carboxylase rate was 0.02 ± 0.01 µmol/g/min, and glutamine synthetase was 0.12 ± 0.01 µmol/g/min. Relative to previous experiments under light α-chloralose anaesthesia, thiopental reduced oxidative metabolism in neurons and even more so in astrocytes. Interestingly, total oxidative metabolism in the cortex under thiopental anaesthesia surpassed the rate of pyruvate production by glycolysis, indicating substantial utilisation of substrates other than glucose, likely plasma lactate. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Sarah Sonnay
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland
| | - João M N Duarte
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland
| | - Nathalie Just
- Centre d'Imagerie Biomédicale - Animal and Technology Core, Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland.,Department of Radiology, University of Geneva, Switzerland.,Department of Radiology, University of Lausanne, Switzerland
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2
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Lodge D, Mercier MS. Ketamine and phencyclidine: the good, the bad and the unexpected. Br J Pharmacol 2015; 172:4254-76. [PMID: 26075331 DOI: 10.1111/bph.13222] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 05/29/2015] [Accepted: 06/03/2015] [Indexed: 12/21/2022] Open
Abstract
The history of ketamine and phencyclidine from their development as potential clinical anaesthetics through drugs of abuse and animal models of schizophrenia to potential rapidly acting antidepressants is reviewed. The discovery in 1983 of the NMDA receptor antagonist property of ketamine and phencyclidine was a key step to understanding their pharmacology, including their psychotomimetic effects in man. This review describes the historical context and the course of that discovery and its expansion into other hallucinatory drugs. The relevance of these findings to modern hypotheses of schizophrenia and the implications for drug discovery are reviewed. The findings of the rapidly acting antidepressant effects of ketamine in man are discussed in relation to other glutamatergic mechanisms.
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Affiliation(s)
- D Lodge
- Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - M S Mercier
- Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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3
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Sogawa N, Hazehara Y, Kunitomo M, Morita Y, Yoo B, Ohyama K, Sogawa C, Kitayama S. Age-dependent changes in the susceptibility to thiopental anesthesia in mice: analysis of the relationship to the functional expression of GABA transporter. Pharmacol Biochem Behav 2012; 103:267-72. [PMID: 22963929 DOI: 10.1016/j.pbb.2012.08.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 08/24/2012] [Accepted: 08/28/2012] [Indexed: 11/19/2022]
Abstract
The potency of anesthetics changes during development, probably due not only to pharmacokinetic factors such as differential distribution and/or metabolism, but also to pharmacodynamic factors such as changes to the GABAergic system in the brain. To explore the latter mechanism, we focused on the GABA transporter (GAT), the uptake system for GABA, which participates in the synaptic clearance of GABA. Thiopental-induced anesthesia, as assessed by the onset and duration of loss of the righting reflex, was more pronounced in 3-week-old mice than in 7-week-old mice. Both NO-711 and SKF89976A, selective GAT-1 inhibitors, significantly enhanced the anesthesia in the 7-week-old but not in the 3-week-old mice. In synaptosomes prepared from the cerebral cortex, the kinetics of GABA transport was similar between the two age groups, as assessed by [(3)H]GABA uptake assay. In addition, expression of GAT mRNA was similar between the two age groups, as assessed by quantitative RT-PCR. Thiopental reduced [(3)H]GABA uptake only at high concentrations in a similar manner at both ages. Conversely, the ability of SKF89976A to inhibit [(3)H]GABA uptake was greater in the 7-week-old mice than in the 3-week-old mice. Based on these results, GAT seems unlikely to contribute to the greater susceptibility to thiopental anesthesia in 3-week-old mice, while the increased ability of GABA uptake inhibitors to enhance thiopental-induced anesthesia in 7-week-old mice is at least partly due to higher sensitivity of GAT to the inhibitors.
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Affiliation(s)
- Norio Sogawa
- Department of Dental Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8525, Japan
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Abstract
Anesthesia has broad actions that include changing neuronal excitability, vascular reactivity, and other baseline physiologies and eventually modifies the neurovascular coupling relationship. Here, we review the effects of anesthesia on the spatial propagation, temporal dynamics, and quantitative relationship between the neural and vascular responses to cortical stimulation. Previous studies have shown that the onset latency of evoked cerebral blood flow (CBF) changes is relatively consistent across anesthesia conditions compared with variations in the time-to-peak. This finding indicates that the mechanism of vasodilation onset is less dependent on anesthesia interference, while vasodilation dynamics are subject to this interference. The quantitative coupling relationship is largely influenced by the type and dosage of anesthesia, including the actions on neural processing, vasoactive signal transmission, and vascular reactivity. The effects of anesthesia on the spatial gap between the neural and vascular response regions are not fully understood and require further attention to elucidate the mechanism of vascular control of CBF supply to the underlying focal and surrounding neural activity. The in-depth understanding of the anesthesia actions on neurovascular elements allows for better decision-making regarding the anesthetics used in specific models for neurovascular experiments and may also help elucidate the signal source issues in hemodynamic-based neuroimaging techniques.
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Affiliation(s)
- Kazuto Masamoto
- Center for Frontier Science and Engineering, University of Electro-Communications, Tokyo, Japan.
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Müller CP, Pum ME, Amato D, Schüttler J, Huston JP, De Souza Silva MA. The in vivo neurochemistry of the brain during general anesthesia. J Neurochem 2011; 119:419-46. [DOI: 10.1111/j.1471-4159.2011.07445.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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6
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Benali A, Trippe J, Weiler E, Mix A, Petrasch-Parwez E, Girzalsky W, Eysel UT, Erdmann R, Funke K. Theta-burst transcranial magnetic stimulation alters cortical inhibition. J Neurosci 2011; 31:1193-203. [PMID: 21273404 PMCID: PMC6623597 DOI: 10.1523/jneurosci.1379-10.2011] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 09/24/2010] [Accepted: 11/16/2010] [Indexed: 11/21/2022] Open
Abstract
Human cortical excitability can be modified by repetitive transcranial magnetic stimulation (rTMS), but the cellular mechanisms are largely unknown. Here, we show that the pattern of delivery of theta-burst stimulation (TBS) (continuous versus intermittent) differently modifies electric activity and protein expression in the rat neocortex. Intermittent TBS (iTBS), but not continuous TBS (cTBS), enhanced spontaneous neuronal firing and EEG gamma band power. Sensory evoked cortical inhibition increased only after iTBS, although both TBS protocols increased the first sensory response arising from the resting cortical state. Changes in the cortical expression of the calcium-binding proteins parvalbumin (PV) and calbindin D-28k (CB) indicate that changes in spontaneous and evoked cortical activity following rTMS are in part related to altered activity of inhibitory systems. By reducing PV expression in the fast-spiking interneurons, iTBS primarily affected the inhibitory control of pyramidal cell output activity, while cTBS, by reducing CB expression, more likely affected the dendritic integration of synaptic inputs controlled by other classes of inhibitory interneurons. Calretinin, the third major calcium-binding protein expressed by another class of interneurons was not affected at all. We conclude that different patterns of TBS modulate the activity of inhibitory cell classes differently, probably depending on the synaptic connectivity and the preferred discharge pattern of these inhibitory neurons.
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Affiliation(s)
- Alia Benali
- Institute of Physiology, Department of Neurophysiology
- Department of Cognitive Neurology, Hertie-Institute for Clinical Brain Research and Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany
| | - Jörn Trippe
- Institute of Physiology, Department of Neurophysiology
| | - Elke Weiler
- Institute of Physiology, Department of Neurophysiology
| | - Annika Mix
- Institute of Physiology, Department of Neurophysiology
| | | | - Wolfgang Girzalsky
- Institute of Physiological Chemistry, Department of Systems Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany, and
| | - Ulf T. Eysel
- Institute of Physiology, Department of Neurophysiology
| | - Ralf Erdmann
- Institute of Physiological Chemistry, Department of Systems Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany, and
| | - Klaus Funke
- Institute of Physiology, Department of Neurophysiology
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7
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Theta burst and conventional low-frequency rTMS differentially affect GABAergic neurotransmission in the rat cortex. Exp Brain Res 2009; 199:411-21. [DOI: 10.1007/s00221-009-1961-8] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Accepted: 07/22/2009] [Indexed: 01/16/2023]
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Accorsi-Mendonça D, Leão RM, Aguiar JF, Varanda WA, Machado BH. Urethane inhibits the GABAergic neurotransmission in the nucleus of the solitary tract of rat brain stem slices. Am J Physiol Regul Integr Comp Physiol 2006; 292:R396-402. [PMID: 16946076 DOI: 10.1152/ajpregu.00776.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Because urethane is a widely used anesthetic in animal experimentation, in the present study, we evaluated its effects on neurons of the nucleus of the solitary tract (NTS) in brain stem slices from young rats (25-30 days old). Using the whole cell configuration of the patch-clamp technique, spontaneous postsynaptic currents (sPSCs) and evoked excitatory postsynaptic currents (eEPSCs) were recorded. Urethane (20 mM) decreased by approximately 60% the frequency of GABAergic sPSCs (1.0 +/- 0.2 vs. 0.4 +/- 0.1 Hz) but did not change the frequency, amplitude, or half-width of glutamatergic events or TTX-resistant inhibitory sPSCs [miniature inhibitory postsynaptic currents (IPSCs)]. Miniature IPSCs were measured in the presence of urethane plus 1 mM diazepam (1 mM), and no changes were seen in their amplitude. This suggests that the GABA concentration in the NTS synapses is set at saturating level. We also evaluated the effect of urethane on eEPSCs, and no significant change was observed in the amplitude of N-methyl-d-aspartate [NMDA; 44.2 +/- 11.5 vs. 37.6 +/- 10.6 pA (holding potential = 40 mV)] and non-NMDA currents [204.4 +/- 35.5 vs. 196.6 +/- 31.2 pA (holding potential = -70 mV)]. Current-clamp experiments showed that urethane did not alter the action potential characteristics and passive membrane properties. These data suggest that urethane has an inhibitory effect on GABAergic neurons in the NTS but does not change the spontaneous or evoked excitatory responses.
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Affiliation(s)
- Daniela Accorsi-Mendonça
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, 14049-900 Ribeirão Preto, SP, Brazil
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9
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Whitehead KJ, Rose S, Jenner P. Halothane anesthesia affects NMDA-stimulated cholinergic and GABAergic modulation of striatal dopamine efflux and metabolism in the rat in vivo. Neurochem Res 2004; 29:835-42. [PMID: 15098949 DOI: 10.1023/b:nere.0000018858.64265.e9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Microdialysis of the striatum of halothane-anesthetized rats was used to study the participation of local cholinergic and GABAergic neurotransmission in NMDA receptor-modulated striatal dopamine release and metabolism. Reverse dialysis.of NMDA (1 mM) evoked a 10-fold increase in dopamine efflux and reduced DOPAC and HVA to > 20% of basal values. The effect of NMDA on dopamine efflux was abolished by atropine (10 microM) but unaffected by (+)-bicuculline (50 microM). NMDA-induced decrease in DOPAC (but not HVA) efflux was potentiated by atropine, whereas (+)-bicuculline attenuated the decrease in DOPAC and HVA. Compared to our previous studies in unanesthetised rats, our data suggest that halothane anesthesia alters the balance between NMDA-stimulated cholinergic and GABAergic influences on striatal dopamine release and metabolism. Differential sensitivity to halothane of NMDA receptors expressed by the neurones mediating these modulatory influences, or loss of specific NMDA receptor populations through voltage-dependent Mg2+ block under anesthesia, could underlie these observations.
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Affiliation(s)
- K J Whitehead
- Neurodegenerative Diseases Research Centre, Hodgkin Building, Guy's King's and St. Thomas's School of Biomedical Sciences, King's College, Guy's Campus, London, United Kingdom.
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Westphalen RI, Hemmings HC. Selective depression by general anesthetics of glutamate versus GABA release from isolated cortical nerve terminals. J Pharmacol Exp Ther 2003; 304:1188-96. [PMID: 12604696 DOI: 10.1124/jpet.102.044685] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The role of presynaptic mechanisms in general anesthetic depression of excitatory glutamatergic neurotransmission and facilitation of GABA-mediated inhibitory neurotransmission is unclear. A dual isotope method allowed simultaneous comparisons of the effects of a representative volatile (isoflurane) and intravenous (propofol) anesthetic on the release of glutamate and GABA from isolated rat cerebrocortical nerve terminals (synaptosomes). Synaptosomes were prelabeled with L-[(3)H]glutamate and [(14)C]GABA, and release was determined by superfusion with pulses of 30 mM K(+) or 1 mM 4-aminopyridine (4AP) in the absence or presence of 1.9 mM free Ca(2+). Isoflurane maximally inhibited Ca(2+)-dependent 4AP-evoked L-[(3)H]glutamate release (99 +/- 8% inhibition) to a greater extent than [(14)C]GABA release (74 +/- 6% inhibition; P = 0.023). Greater inhibition of L-[(3)H]glutamate versus [(14)C]GABA release was also observed for the Na(+) channel antagonists tetrodotoxin (99 +/- 4 versus 63 +/- 5% inhibition; P < 0.001) and riluzole (84 +/- 5 versus 52 +/- 12% inhibition; P = 0.041). Propofol did not differ in its maximum inhibition of Ca(2+)-dependent 4AP-evoked L-[(3)H]glutamate release (76 +/- 12% inhibition) compared with [(14)C]GABA (84 +/- 31% inhibition; P = 0.99) release. Neither isoflurane (1 mM) nor propofol (15 microM) affected K(+)-evoked release, consistent with a molecular target upstream of the synaptic vesicle exocytotic machinery or voltage-gated Ca(2+) channels coupled to transmitter release. These findings support selective presynaptic depression of excitatory versus inhibitory neurotransmission by clinical concentrations of isoflurane, probably as a result of Na(+) channel blockade.
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Affiliation(s)
- Robert I Westphalen
- Department of Anesthesiology, Weill Medical College of Cornell University, New York, New York, USA
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11
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General Anesthetic Actions on Norepinephrine, Dopamine, and γ-Aminobutyric Acid Transporters in Stably Transfected Cells. Anesth Analg 2002. [DOI: 10.1213/00000539-200210000-00019] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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12
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Shahani SK, Lingamaneni R, Hemmings HC. General anesthetic actions on norepinephrine, dopamine, and gamma-aminobutyric acid transporters in stably transfected cells. Anesth Analg 2002; 95:893-9, table of contents. [PMID: 12351264 DOI: 10.1097/00000539-200210000-00019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED The effects of general anesthetics on neurotransmitter uptake by plasma membrane transporters are controversial. We analyzed the effects of representative volatile and IV general anesthetics on recombinant transporters for norepinephrine (human NET), dopamine (rat DAT), or gamma-aminobutyric acid (rat GAT-1) stably expressed in a porcine kidney cell line (LLC-PK(1)). This approach avoids complicating factors associated with neuronal preparations, such as the involvement of multiple transporters and the indirect effects of membrane potential. At clinical concentrations, human NET was inhibited only by halothane (50% inhibitory concentration [IC(50)] = 0.54 mM), rat DAT was sensitive to both halothane and isoflurane (IC(50) = 0.60 and 0.64 mM, respectively), and rat GAT-1 was insensitive to both volatile anesthetics. Human NET was inhibited in a dose-dependent fashion by propofol (IC(50) = 41 micro M), ketamine (IC(50) = 150 micro M), and etomidate (IC(50) > 200 micro M), but not by pentobarbital. Only propofol inhibited NET at a clinically relevant concentration (5 micro M). Rat DAT was inhibited in a dose-dependent fashion by propofol (IC(50) = 120 micro M), etomidate (IC(50) = 100 micro M), and ketamine (IC(50) = 210 micro M), but not by pentobarbital. None of these anesthetics was predicted to inhibit DAT at concentrations that produce anesthesia. Propofol inhibited rat GAT-1, but only at the largest concentration tested. General anesthetics have drug- and subtype-selective actions on neurotransmitter transporters. We conclude that effects on catecholamine, but not gamma-aminobutyric acid, transporters may contribute to secondary synaptic actions of certain anesthetics but are unlikely to be essential to their anesthetic properties. IMPLICATIONS Previous studies have implicated neurotransmitter transporters as targets for general anesthetic effects on synaptic transmission. Recombinant transporters for norepinephrine and dopamine were sensitive to certain volatile and IV anesthetics, whereas gamma-aminobutyric acid transporters were insensitive. These anesthetic- and neurotransmitter-specific effects may underlie some of the secondary effects of general anesthetics.
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Affiliation(s)
- Saira K Shahani
- Department of Anesthesiology, Weill Medical College of Cornell University, New York, New York 10021, USA
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13
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Richards CD. Anaesthetic modulation of synaptic transmission in the mammalian CNS. Br J Anaesth 2002; 89:79-90. [PMID: 12173243 DOI: 10.1093/bja/aef162] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- C D Richards
- Department of Physiology, University College London, Gower Street, London WC1A 6BT, UK
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Sugimura M, Kitayama S, Morita K, Imai Y, Irifune M, Takarada T, Kawahara M, Dohi T. Effects of GABAergic agents on anesthesia induced by halothane, isoflurane, and thiamylal in mice. Pharmacol Biochem Behav 2002; 72:111-6. [PMID: 11900777 DOI: 10.1016/s0091-3057(01)00728-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The effects of gamma-aminobutyric acid (GABA) receptor modulators and GABA uptake inhibitors on volatile and intravenous anesthetic-induced anesthesia were examined in male ICR mice, as assessed by the loss of righting reflex (LORR). The GABA uptake inhibitors, NO-711 and SKF89976A, which are permeable to the blood-brain barrier (BBB), but not nipecotic acid or guvacine, which poorly permeate BBB, shortened the onset of LORR but did not affect the duration of LORR induced by 1.5% halothane and 2% isoflurane. NO-711 and SKF89976A shortened the onset of and prolonged the duration of LORR induced by thiamylal (45 mg/kg i.p.). The GABA mimetics, muscimol and diazepam, shortened the onset of and prolonged the duration of LORR induced by halothane, isoflurane, and thiamylal. On the other hand, picrotoxin, a GABAA receptor antagonist, prolonged the onset of LORR induced by all anesthetics tested. Another GABAA receptor antagonist, bicuculline, prolonged the onset of LORR induced by halothane, but not by isoflurane or thiamylal. Both antagonists failed to affect the duration of LORR induced by halothane, isoflurane, or thiamylal. Baclofen, a GABAB receptor agonist, enhanced both volatile anesthetics- and thiamylal-induced anesthesia. These results suggest that anesthesia induced by volatile and intravenous anesthetics might be correlated with the modification of the pre- and/or postsynaptic GABAergic activities.
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Affiliation(s)
- Mitsutaka Sugimura
- Department of Anesthesiology, Hiroshima University Faculty of Dentistry, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553, Japan.
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15
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Sugimura M, Kitayama S, Morita K, Irifune M, Takarada T, Kawahara M, Dohi T. Effects of volatile and intravenous anesthetics on the uptake of GABA, glutamate and dopamine by their transporters heterologously expressed in COS cells and in rat brain synaptosomes. Toxicol Lett 2001; 123:69-76. [PMID: 11514107 DOI: 10.1016/s0378-4274(01)00386-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although the neurotransmitter uptake system is considered a possible target for the presynaptic action of anesthetic agents, observations are inconsistent concerning effects on the transporter and their clinical relevance. The present study examined the effects of volatile and intravenous anesthetics on the uptake of GABA, glutamate and dopamine in COS cells heterologously expressing the transporters for these neurotransmitters and in the rat brain synaptosomes. Halothane and isoflurane, but not thiamylal or thiopental, significantly inhibited uptake by COS cell systems of GABA, dopamine and glutamic acid in a concentration-dependent manner within clinically relevant ranges for anesthesia induced by these agents. Similarly, in synaptosomes halothane and isoflurane but not thiopental significantly suppressed the uptake of GABA and glutamic acid, respectively. These results do not support the hypothesis that volatile and intravenous anesthetics exert their action via specific inhibition of GABA uptake to enhance inhibitory GABAergic neuronal activity. Rather, they suggest that presynaptic uptake systems for various neurotransmitters including GABA may be the molecular targets for volatile anesthetic agents.
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Affiliation(s)
- M Sugimura
- Department of Anesthesiology, Faculty of Dentistry, Hiroshima University, 1-2-3 Kasumi, Minami-ku, 734-8553, Hiroshima, Japan
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16
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Xiao Q, Suguihara C, Hehre D, Devia C, Huang J, Bancalari E. Effects of GABA receptor blockade on the ventilatory response to hypoxia in hypothermic newborn piglets. Pediatr Res 2000; 47:663-8. [PMID: 10813594 DOI: 10.1203/00006450-200005000-00018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Hypothermic newborn piglets have a depressed ventilatory response to hypoxia, and this may be due to an increase in CNS gamma-aminobutyric acid (GABA) levels. To evaluate the effects of GABA(A) receptor blockade on the ventilatory response to hypoxia in hypothermic piglets, 31 anesthetized paralyzed mechanically ventilated newborn piglets (2-7 d) were studied at a brain temperature of 38.5 +/- 0.5 degrees C [normothermia (NT), n = 15] or 34 +/- 0.5 degrees C [hypothermia (HT), n = 16]. The central respiratory output was evaluated by measuring burst frequency and moving time average area of phrenic nerve activity. Measurements of minute phrenic output (MPO), arterial blood pressure, heart rate, oxygen consumption, and arterial blood gases were obtained at room air and during 20 min of isocapnic hypoxia [fraction of expired oxygen (FiO2) = 0.10]. After 10 min of hypoxia, a bolus injection of 20 microL of bicuculline methiodide (BM; 10 microg) or Ringer's solution was administered into the cisterna magna over a 1-min period, and the piglets remained in hypoxia for an additional 10 min. There was an initial increase of 50 +/- 6% in MPO during the first minute of hypoxia followed by a decrease to values 24 +/- 8% above baseline at 10 min in the NT group. In contrast, in the HT group, the initial increase in MPO with hypoxia was eliminated, and, at 10 min, there was a decrease to a mean value 35 +/- 4% below baseline level (NT versus HT, p < 0.03). After administration of BM, a significant increase in MPO with hypoxia was observed in both groups compared with their placebo groups (p < 0.002 in NT-BM group, p < 0.0001 in HT-BM group). However, the magnitude of the increase in MPO during hypoxia was significantly greater in the HT group after administration of BM (NT versus HT, p < 0.0001). Changes in oxygen consumption, arterial blood pressure, heart rate, pH, partial pressure of oxygen (PaO2), and base excess with hypoxia were not different between NT and HT groups before and after the administration of BM. The cardiorespiratory response to hypoxia was not modified after administration of Ringer's solution to NT and HT placebo groups. These data suggest that the depression in hypoxic ventilatory response produced by HT is in part modulated by an increased CNS GABA concentration.
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Affiliation(s)
- Q Xiao
- University of Miami School of Medicine, Department of Pediatrics, Florida 33101, USA
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17
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Liachenko S, Tang P, Somogyi GT, Xu Y. Concentration-dependent isoflurane effects on depolarization-evoked glutamate and GABA outflows from mouse brain slices. Br J Pharmacol 1999; 127:131-8. [PMID: 10369465 PMCID: PMC1566008 DOI: 10.1038/sj.bjp.0702543] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The synaptic concentrations of glutamate and gamma-aminobutyric acid (GABA) are modulated by their release and re-uptake. The effects of general anaesthetics on these two processes remain unclear. This study evaluates the effects of isoflurane, a clinically important anaesthetic, on glutamate and GABA release and re-uptake in superfused mouse cerebrocortical slices. Experiments consisted of two 1.5-min exposures to 40 mM KCl in 30 min intervals. During the second exposure, different concentrations of isoflurane with and without 0.3 mM L-transpyrrolidine-2,4-dicarboxylic acid (PDC, a competitive inhibitor of glutamate uptake transporter) or 1 mM nipecotic acid (a competitive inhibitor of GABA uptake transporter) were introduced. The ratios of the second to first KCl-evoked increases in glutamate and GABA were used to determine the isoflurane concentration-response curves. The results can be described as a sum of two independent processes, corresponding to the inhibitions of release and re-uptake, respectively. The EC50 values for the inhibitions of release and re-uptake were 295+/-16 and 805+/-43 microM for glutamate, and 229+/-13 and 520+/-25 microM for GABA, respectively. Addition of PDC did not significantly affect glutamate release but shifted the re-uptake curve to the left (EC50= 315+/-20 microM). Nipecotic acid completely blocked GABA uptake, rendering isoflurane inhibition of GABA re-uptake undetectable. Our data suggest that isoflurane inhibits both the release and re-uptake of neurotransmitters and that the inhibitions occur at different EC50's. For GABA, both EC50's are within the clinical concentration range. The net anaesthetic effect on extracellular concentrations of neurotransmitters, particularly GABA, depends on the competition between inhibition of release and that of re-uptake.
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Affiliation(s)
- Serguei Liachenko
- Department of Anaesthesiology and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, U.S.A
| | - Pei Tang
- Department of Anaesthesiology and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, U.S.A
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, U.S.A
| | - George T Somogyi
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, U.S.A
| | - Yan Xu
- Department of Anaesthesiology and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, U.S.A
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, U.S.A
- Author for correspondence:
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Richards CD. What the actions of anaesthetics on fast synaptic transmission reveal about the molecular mechanism of anaesthesia. Toxicol Lett 1998; 100-101:41-50. [PMID: 10049173 DOI: 10.1016/s0378-4274(98)00163-5] [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: 11/26/2022]
Abstract
1. Synapses with the brain are important components of the networks responsible for higher nervous function and current evidence suggests that general anaesthetics modulate synaptic transmission in the brain. 2. Analysis of anaesthetic action on these synapses not only defines the cellular mechanisms involved in anaesthesia but also reveals much about the molecular targets of anaesthetic action. 3. It appears that while anaesthetics affect a wide variety of processes, the most sensitive are those which are directly linked to the activity of ligand-gated ion channels. Moreover, both single channel patch clamp studies and the molecular biological investigations of the sub-unit specificity of the sensitivity to anaesthetics indicate that anaesthetics interact directly with these functional proteins.
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Affiliation(s)
- C D Richards
- Department of Physiology, Royal Free Hospital School of Medicine, London, UK.
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Liachenko S, Tang P, Somogyi GT, Xu Y. Comparison of anaesthetic and non-anaesthetic effects on depolarization-evoked glutamate and GABA release from mouse cerebrocortical slices. Br J Pharmacol 1998; 123:1274-80. [PMID: 9559915 PMCID: PMC1565278 DOI: 10.1038/sj.bjp.0701728] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
1. Investigation with substances that are similar in structure, but different in anaesthetic properties, may lead to further understanding of the mechanisms of general anaesthesia. 2. We have studied the effects of two cyclobutane derivatives, the anaesthetic, 1-chloro-1,2,2-trifluorocyclobutane (F3), and the non-anaesthetic, 1,2-dichlorohexafluorocyclobutane (F6), on K+-evoked glutamate and gamma-aminobutyric acid (GABA) release from isolated, superfused, cerebrocortical slices from mice, by use of h.p.l.c. with fluorescence detection for quantitative analysis. 3. At clinically relevant concentrations, the anaesthetic, F3, inhibited 40 mM K+-evoked glutamate and GABA release by 72% and 47%, respectively, whereas the structurally similar non-anaesthetic, F6, suppressed evoked glutamate release by 70% but had no significant effects on evoked GABA release. A second exposure to 40 mM KCl after a approximately 30 min washout of F3 or F6 showed recovery of K+-evoked release, suggesting that F3 and F6 did not cause any non-specific or irreversible changes in the brain slices. 4. Our findings suggest that suppression of excitatory neurotransmitter release may not be directly relevant to the primary action of general anaesthetics. A mechanism involving inhibitory postsynaptic action is implicated, in which a moderate suppression of depolarization-evoked GABA release by the anaesthetic may be consistent with the enhancement of postsynaptic GABAergic activities.
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Affiliation(s)
- S Liachenko
- Department of Anaesthesiology and Critical Care Medicine, University of Pittsburgh, Pennsylvania 15261, USA
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20
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Rao RS, Greenberg HE, Sica AL, Scharf SM. gamma-Aminobutyric acid contributes to modulation of cardiorespiratory control after chronic ventilatory loading. RESPIRATION PHYSIOLOGY 1997; 108:35-44. [PMID: 9178375 DOI: 10.1016/s0034-5687(97)02533-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Diseases imposing chronic ventilatory loads may depress ventilation and cause chronic hypercapnia. This may be a result of mechanical loading imposed on pre-existing decreased respiratory drive or functional alteration of neural circuits involved in ventilatory control. To evaluate these possibilities, chronic resistive airway loading was imposed in rats via a circumferential tracheal band which tripled tracheal resistance (obstructed group). Sham surgery was performed in controls. After 8 weeks, animals were anesthetized (urethane) and tracheostomy performed relieving increased tracheal resistance. The ventral medullary surface (VMS) was exposed and the intermediate area (IA) identified. The integrated diaphragm EMG (EMGDI) was recorded. The obstructed group was hypercapnic while controls were eucapnic (PCO2, 45.1 +/- 7.9 vs. 37.6 +/- 3.4 Torr; P < 0.001). Respiratory rate (RR) remained lower in obstructed than in control animals despite relief of the resistive load by tracheostomy (58.5 +/- 5.1 vs. 75.4 +/- 5.4 bpm; P < 0.05). Application of 1 mM bicuculline soaked pledgets (BIC) to the IA of the VMS significantly increased EMGDI in obstructed but not in control animals (27.5 +/- 5.5 vs. 5.2 +/- 4.4%; P < 0.006). RR was unaffected. Mean arterial pressure increased with BIC in obstructed but not control animals (23.0 +/- 6.5 vs. 4.5 +/- 3.5%; P < 0.02). These data suggest that alteration of cardiorespiratory control occurs during chronic resistive hypercapnic loading and that GABAergic neurons in the VMS participate in this adaptive response.
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Affiliation(s)
- R S Rao
- Division of Pulmonary and Critical Care Medicine, Long Island Jewish Medical Center, Albert Einstein College of Medicine, New Hyde Park, NY 11040, USA
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21
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Capsius B, Leppelsack HJ. Influence of urethane anesthesia on neural processing in the auditory cortex analogue of a songbird. Hear Res 1996; 96:59-70. [PMID: 8817307 DOI: 10.1016/0378-5955(96)00038-x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Functional maps of auditory response areas were derived from multi-unit recordings in the caudal telencephalon of the starling (Sturnus vulgaris L.). A regular grid of recording sites with distances of 200 microns horizontally and 100 microns vertically was placed over the auditory cortex analogue. Within one plane, mapping of auditory responses was first performed in the awake bird and then repeated under urethane anesthesia. The data from both experimental approaches differ considerably. Urethane reduces the spontaneous discharge rate significantly. Under anesthesia, inhibition decreases in all auditory subunits. Excitation is less affected. Eight auditory subcenters were divided into three groups according to the changes in their excitatory responses. In the first group 'on' and sustained excitation changed only weakly. These areas are thought to receive direct inputs from the diencephalon. In the second group, 'on' and sustained excitation are substantially reduced. These subcenters seem to receive projections from other forebrain areas. In subunits of the third group, an increase in sustained excitation is correlated to a decrease in inhibition. Within some specific centers, distinct natural calls, for example the bird's own song, elicit stronger responses under anesthesia than other stimuli.
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Affiliation(s)
- B Capsius
- Institut für Zoologie TU München, Garching, Germany
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Patel PM, Goskowicz RL, Drummond JC, Cole DJ. Etomidate Reduces Ischemia-Induced Glutamate Release in the Hippocampus in Rats Subjected to Incomplete Forebrain Ischemia. Anesth Analg 1995. [DOI: 10.1213/00000539-199505000-00013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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23
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Patel PM, Goskowicz RL, Drummond JC, Cole DJ. Etomidate reduces ischemia-induced glutamate release in the hippocampus in rats subjected to incomplete forebrain ischemia. Anesth Analg 1995; 80:933-9. [PMID: 7726435 DOI: 10.1097/00000539-199505000-00013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Etomidate and thiopental reduce ischemic neuronal injury but the mechanism by which they do so is not clear. Ischemia-induced release of the excitatory neurotransmitters glutamate and glycine is thought to play a major role in the pathophysiology of ischemic injury. To determine how etomidate and thiopental modulate excitatory transmitter release, their effect on the release of glycine and glutamate during ischemia was evaluated by microdialysis in the hippocampus and cortex of rats. Three groups of Wistar-Kyoto rats (n = 5/group) were studied. In the etomidate and thiopental groups, electroencephalogram (EEG) burst-suppression was achieved and maintained by a continuous infusion of either etomidate (0.6 mg.kg-1.min-1) or thiopental (3 mg.kg-1.min-1) 40 min prior to ischemia. Halothane anesthetized (1 minimum alveolar anesthetic concentration [MAC]) rats served as controls. Ischemia was induced in all three groups by bilateral carotid artery occlusion with simultaneous hypotension to 35 mm Hg for 10 min. Pericranial temperature was controlled at 38 degrees C. Dialysate was collected before, during, and after ischemia. The levels of glutamate and glycine in the dialysate were measured by high-performance liquid chromatography. Within the hippocampus, both glutamate and glycine levels increased significantly in the thiopental and control groups. By contrast, in the etomidate group, glutamate and glycine levels did not increase during ischemia, and peak levels were significantly less than those in the thiopental group. Peak glutamate levels in the thiopental group were significantly larger than in the control group, whereas the peak glycine levels were not different among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P M Patel
- Department of Anesthesiology, University of California, San Diego, USA
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Dringenberg HC, Vanderwolf CH, Hamilton JT. Urethane reduces contraction to 5-hydroxytryptamine (5-HT) and enhances the action of the 5-HT antagonist ketanserin on the rat thoracic aortic ring. J Neural Transm (Vienna) 1995; 101:183-93. [PMID: 8695048 DOI: 10.1007/bf01271555] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The general anesthetic urethane (ethyl carbamate) is widely used in electrophysiological in vivo experiments. However, its pharmacological effects are poorly understood. Here, the effects of urethane on in vitro contractile responses of the rat thoracic aortic ring preparation were investigated. Bath application of 5-HT produced a concentration-dependent contractile response (EC50 = 4.3 x 10(-6) M). Urethane (11.2 mM = 1 mg/ml) shifted the concentration-response curve (CRC) for 5-HT to the right (EC50 = 1.7 x 10(-5) M) and decreased the maximal contraction by 30.8%. The CRC for NA (EC50 = 7.2 X 10(-9)M) was also shifted to the right by urethane (EC50 = 1.4 X 10(-8)M), but the shift of the 5-HT-CRC was twice that of the NA-CRC (3.95 vs. 1.95). The CRC to KCl was shifted rightwards only slightly by urethane (ratio 1.27) and the maximal contraction to KCl was not affected. The CRC to replacement of CaCl2 (0.1-10 mM) to KCl-depolarized vessels in a Ca(2+)-free Krebs solution was unaffected by urethane. Ketanserin (10(-9)M) antagonized the contraction to 5-HT, and a combination of ketanserin and urethane was markedly more effective than either drug alone, decreasing the maximal contraction by 58%. Antagonism of NA contraction by prazosin (5 X 10(-8)M) was not increased by addition of urethane. The urethane dose used here approximates blood and brain concentrations required to produce anesthetic effects in mammals. It is possible that reductions in 5-HT transmission and, to a lesser extent, in NA transmission, but not blockade of Ca2+ or K+ channels, may contribute to the anesthetic effect of urethane. In addition, the action of the selective 5-HT2 antagonist ketanserin is clearly altered by urethane. These findings are important to consider when urethane is used for in vivo neurophysiological investigations, particularly when 5-HT mechanisms are involved.
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25
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Lecharny JB, Salord F, Henzel D, Desmonts JM, Mantz J. Effects of thiopental, halothane and isoflurane on the calcium-dependent and -independent release of GABA from striatal synaptosomes in the rat. Brain Res 1995; 670:308-12. [PMID: 7743195 DOI: 10.1016/0006-8993(94)01350-q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effects of the anesthetic agents thiopental, halothane and isoflurane on the release of GABA induced by depolarization and/or reversal of the GABA carrier were investigated in a synaptosomal preparation obtained from the rat striatum. Veratridine (1 microM) and KCl (9 mM) elicited a significant, Ca(2+)-dependent release of [3H]GABA. The KCl-evoked release was not significantly modified in the presence of nipecotic acid (10(-5) M), a selective blocker of the neuronal GABA carrier. The [3H]GABA release was significantly decreased by omega-conotoxin (10(-7) M, a blocker of the N voltage-dependent Ca2+ channels, but was affected by neither nifedipine (10(-4) M) nor omega-Aga-IVA (10(-7) M which block the L and P Ca2+ channels, respectively. Thiopental application (10(-5) to 10(-3) M) was followed by a dose-related, significant, decrease in both the veratridine and KCl-induced releases, whether nipecotic acid was present or not. In contrast, halothane and isoflurane (1-3%) failed to alter [3H]GABA release. Altogether, these results suggest that reduction of the depolarization-evoked GABA release might contribute to thiopental anesthesia, but this seems unlikely for volatile anesthetics.
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Affiliation(s)
- J B Lecharny
- Institut National de la Santé et de la Recherche Médicale (INSERM U408), Faculté de Médecine Xavier Bichat, Paris, France
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26
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Abstract
General anaesthetics are much more selective than is usually appreciated and may act by binding to only a small number of targets in the central nervous system. At surgical concentrations their principal effects are on ligand-gated (rather than voltage-gated) ion channels, with potentiation of postsynaptic inhibitory channel activity best fitting the pharmacological profile observed in general anaesthesia. Although the role of second messengers remains uncertain, it is now clear that anaesthetics act directly on proteins rather than on lipids.
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Affiliation(s)
- N P Franks
- Biophysics Section, Blackett Laboratory, Imperial College of Science, Technology & Medicine, London, UK
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27
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Jones CA, Silvers KM. K+ concentration influences methohexitone inhibition of K(+)-stimulated release of [3H]noradrenaline from minislices of rat cerebral cortex. J Pharm Pharmacol 1993; 45:234-7. [PMID: 8097785 DOI: 10.1111/j.2042-7158.1993.tb05542.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This study investigated the effect of methohexitone, a barbiturate anaesthetic, with variation of the K+ concentration used to stimulate [3H]noradrenaline release from superfused minislices of rat cerebral cortex. The amount of [3H]noradrenaline released by K(+)-stimulation depended on the concentration of K+ used (increasing release was seen at 10-50 mM K+). Methohexitone (10(-7)-3 x 10(-4) M) added to the superfusing medium did not alter the basal efflux of [3H]noradrenaline, but high concentrations inhibited K(+)-stimulated release. Using 12.5 mM K+, inhibition of release was observed only at 10(-4) M methohexitone (48% inhibition); the effect of 25 mM K+ was reduced by 3 x 10(-5) M (72% inhibition) and higher concentrations while release stimulated by 50 mM K+ was inhibited by 10(-5) M methohexitone (30% inhibition) and higher concentrations.
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Affiliation(s)
- C A Jones
- Department of Biomedical Science, University of Sheffield, UK
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28
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Charlesworth P, Pocock G, Richards CD. The action of anaesthetics on stimulus-secretion coupling and synaptic activity. GENERAL PHARMACOLOGY 1992; 23:977-84. [PMID: 1487133 DOI: 10.1016/0306-3623(92)90275-o] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
1. Anaesthetics are known to depress excitatory synaptic transmission and the mechanism of this inhibition has been investigated using bovine adrenal chromaffin cells as an experimental model. 2. These cells are homologous with post-ganglionic sympathetic neurons and have well characterized receptor and secretory mechanisms. They are amenable both to the direct measurement of evoked secretion with its associated ion fluxes, and to electrophysiological investigation using the patch clamp technique. 3. These approaches have been used to study the influence of anaesthetics on pre- and post-synaptic mechanisms involved in stimulus-secretion coupling. 4. A variety of agents inhibited secretion evoked by direct depolarization, and this was shown to be due to a reduction in calcium influx. 5. Direct inhibition of voltage-gated calcium currents was confirmed by whole-cell patch clamp measurements. 6. In addition, anaesthetics powerfully modulated nicotinic receptor mediated events: carbachol-evoked secretion was more sensitive to anaesthetics than that stimulated by high potassium. 7. The mechanism of anaesthetic action on the nAChR was examined in more detail with patch-clamp experiments. 8. These showed that anaesthetics reduced the probability of channels being in the open state, largely as a result of reduction in mean channel open time. 9. The data are discussed in relation to excitatory synaptic transmission.
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Affiliation(s)
- P Charlesworth
- Department of Physiology, Royal Free Hospital School of Medicine, London, England
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29
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Mantz J. Effets des anesthésiques intraveineux sur les neurones du système nerveux central : mécanismes d'action cellulaires et moléculaires. ACTA ACUST UNITED AC 1992; 11:540-57. [PMID: 1362044 DOI: 10.1016/s0750-7658(05)80761-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The mechanisms of action of intravenous anaesthetics are not yet completely elucidated. Until recently, most of the studies had focused on the interactions between anaesthetics and lipid bilayers. It has been proposed that loss of consciousness is produced by disorganization of the lipid phase of nerve membranes, which impairs the action potential propagation. However, new data obtained with sophisticated neuropharmacological tools such as the patch clamp technique have recently contributed to challenge this hypothesis. Indeed, several lines of evidence suggest that intravenous anaesthetics are thought to induce loss of consciousness by blocking the excitatory synaptic transmission. This can be achieved presynaptically, by inhibiting glutamate release from nerve endings via alterations in the gating properties of voltage-dependent calcium channels. Blockade of excitatory synaptic transmission can also occur at the postsynaptic level by antagonizing the glutamate receptors of the N-methyl D-aspartate subtype. Some anaesthetic agents including ketamine also block the nicotinic receptors, however the relevance of this finding with respect to clinical anaesthesia requires further investigation. Preliminary data also suggest that propofol and etomidate elicit uncoupling of gap junctions between astrocytes, which represent a major nonneuronal cell population in the central nervous system. This phenomenon might indirectly contribute to the hypnotic action of these compounds. Whether loss of consciousness involves preferential target structures within the brain remains to be delineated. A better understanding of the mechanisms of action of general anaesthetics might contribute to generate new agents with more pharmacological selectivity and less undesirable side-effects.
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Affiliation(s)
- J Mantz
- Département d'Anesthésie et de Réanimation Chirurgicale, Hôpital Bichat-Claude-Bernard, Paris
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30
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31
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Affiliation(s)
- G Pocock
- Department of Physiology, Royal Free Hospital School of Medicine, University of London, United Kingdom
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Pollard CE, Angel A. Spontaneous single cell discharge in rat somatosensory cortical slices and its relationship to discharge in the urethane-anaesthetized rat. Brain Res 1990; 518:120-6. [PMID: 2390717 DOI: 10.1016/0006-8993(90)90962-b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A slice preparation of rat somatosensory cortex has been used to observe the nature of spontaneous single cell discharge in layer V. On the basis of their discharge pattern, cells recorded using extracellular microelectrodes fell in to one of two categories: 70% of cells discharged single action potentials separated by relatively constant time intervals, while the remainder discharged in bursts of 2-7 action potentials. The firing patterns and the range of discharge frequencies observed were similar to those recorded in the same region and layer of the cortex in urethane-anaesthetized rats. However, unlike cells recorded in vivo, the majority of cells in slices never changed their discharge pattern. This suggests that while these layer V cells in cortical slices have the basic ability to discharge spontaneously, the potential for switching between discharge patterns requires circuitry absent from this isolated preparation. Urethane, over the dose range 6-24 mM, caused a dose-dependent decrease in the discharge frequency of cells with a regular firing pattern but did not affect their basic pattern of discharge.
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Affiliation(s)
- C E Pollard
- Department of Biomedical Sciences, The University, Sheffield, U.K
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33
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POSTER COMMUNICATIONS. Br J Pharmacol 1990. [DOI: 10.1111/j.1476-5381.1990.tb16988.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Arai T, Hatano Y, Mori K. Effects of halothane on the efflux of [3H]D-aspartate from rat brain slices. Acta Anaesthesiol Scand 1990; 34:267-70. [PMID: 2343726 DOI: 10.1111/j.1399-6576.1990.tb03083.x] [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: 12/31/2022]
Abstract
The in vitro effects of halothane on the potassium-stimulation-induced efflux of [3H]D-aspartate in rat cerebral cortex slices were studied. The slices were initially incubated with Krebs-Ringer's solution containing [3H]D-aspartate, a putative excitatory transmitter. The slices were then stimulated with high concentrations of K+ in the presence and absence of halothane, and the efflux was measured using a scintillation counter. Halothane, 1% and 2%, had little effect on the potassium-stimulation-induced efflux, but that of 4 and 8% increased the efflux significantly. The spontaneous efflux was unaffected by all concentrations of halothane studied. The control study of pentobarbital, in the concentration of 0.05 to 1.00 mmol/l, reduced the efflux in a dose-related manner. These findings indicate that the release of an excitatory transmitter, aspartate, may not be involved in the mechanism of halothane anaesthesia.
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Affiliation(s)
- T Arai
- Department of Anesthesia, Kyoto University Hospital, Japan
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35
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Abstract
Light evoked neuronal responses of urethane anaesthetized rats were compared with those recorded in freely moving animals. The results demonstrate that urethane reduces the firing frequency, the response probability as well as the number of excitatory light evoked response phases. These changes are combined with a prolongation of the postexcitatory inhibitory phases. The latencies to diffuse flashes are increased in geniculate neuronal responses as well as in evoked potentials recorded from the visual cortex. A similar relation exists between diminution of late geniculate excitations and suppression of cortical photic afterdischarges.
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Affiliation(s)
- D Albrecht
- Institute of Physiology, Medical School (Charite), Humboldt University Berlin, G.D.R
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36
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Pavlides C, Greenstein YJ, Winson J. Comparative extracellular current flow at dendrites and soma of dentate granule cells during long-term potentiation. Neurosci Lett 1988; 92:177-81. [PMID: 3185988 DOI: 10.1016/0304-3940(88)90056-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In the study of long-term potentiation (LTP) in the dentate gyrus, the magnitude of the initial slope of the evoked synaptic potential (ESP) in the region of the granule cell layer, is commonly used as a measure of synaptic efficacy at the site of the perforant path (PP) input. To investigate the viability of this assumption, in rats anesthetized with either chloropent or urethane, LTP was induced by tetanic stimulation of the PP and ESPs were measured simultaneously at both the soma and dendritic site of the PP input. Following LTP, the two responses were decoupled, the somal response being greater than the dendritic in rats anesthetized with chloropent, the opposite being true in urethanized animals. We conclude that in investigating changes in synaptic efficacy following LTP, measurements should be taken at the site of the PP input.
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Affiliation(s)
- C Pavlides
- Rockefeller University, New York, NY 10021
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37
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Erecińska M, Nelson D, Silver IA. Interactions of benztropine, atropine and ketamine with veratridine-activated sodium channels: effects on membrane depolarization, K+-efflux and neurotransmitter amino acid release. Br J Pharmacol 1988; 94:871-81. [PMID: 2902895 PMCID: PMC1854019 DOI: 10.1111/j.1476-5381.1988.tb11599.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
1. The effect of benztropine, atropine and ketamine on veratridine-induced efflux of K+, membrane depolarization and release of amino acid neurotransmitters was investigated in the preparation of rat brain synaptosomes. 2. All three drugs inhibited in a concentration-dependent manner the processes measured: the most effective compound was benztropine which exhibited an approximate Kd of 2 microM. The inhibition was not competitive in nature. 3. The veratridine titration curves in the presence of drugs were sigmoid with Hill coefficients of about 1.4. 4. At higher concentrations, benztropine, atropine and ketamine blocked uptake of amino acid neurotransmitters into synaptosomes. 5. It is postulated that benztropine, atropine and ketamine interfere with the veratridine-activated influx of sodium into synaptosomes through voltage-dependent channels by acting at the same site as local anaesthetics. Interactions at this site alter allosterically binding and action of veratridine. In addition, at higher concentrations the drugs interact with the carrier proteins for amino acid neurotransmitters and block their transport.
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Affiliation(s)
- M Erecińska
- Department of Pharmacology, University of Pennsylvania, School of Medicine, Philadelphia 19104
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38
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Pocock G, Richards CD. The action of pentobarbitone on stimulus-secretion coupling in adrenal chromaffin cells. Br J Pharmacol 1987; 90:71-80. [PMID: 2434179 PMCID: PMC1917282 DOI: 10.1111/j.1476-5381.1987.tb16826.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The action of pentobarbitone on stimulus-secretion coupling was studied in bovine isolated adrenal medullary cells. Pentobarbitone inhibited catecholamine release evoked by 500 microM carbachol with half maximal inhibition (IC50) around 50 microM. It also inhibited catecholamine release induced by depolarization with 77 mM potassium (IC50 100 microM). These effects of pentobarbitone were observed with concentrations that lie within the range encountered during general anaesthesia. Evoked secretion required the presence of calcium in the extracellular medium and was associated with an influx of Ca2+ through voltage-sensitive channels. Pentobarbitone inhibited 45Ca influx in response to both carbachol (IC50 50 microM) and K+-depolarization (IC50 150 microM). The action of pentobarbitone on the relationship between intracellular free Ca and exocytosis was examined using electropermeabilised cells which were suspended in solutions containing a range of concentrations of ionised calcium between 10(-8) and 10(-4)M. Catecholamine secretion was measured in the presence of 0, 50, 200 or 500 microM pentobarbitone. The anaesthetic had no effect on the activation of exocytosis by intracellular free calcium. When catecholamine secretion in response to potassium or carbachol was modulated by varying extracellular calcium or by adding pentobarbitone to the incubation medium, the amount of catecholamine secretion for a given Ca2+ entry was the same. Pentobarbitone inhibited the secretion and 45Ca uptake induced by carbachol in a non-competitive manner. The secretion evoked by nicotinic agonists was associated with an increase in 22Na influx. Pentobarbitone inhibited this influx with an IC50 of 100 microM. We concluded that: (a) Pentobarbitone inhibits the catecholamine secretion from bovine adrenal chromaffin cells induced by nicotinic agonists by non-competitive inhibition of the nicotinic receptor. (b) The decrease in Ca influx caused by pentobarbitone accounts fully for the decrease in secretion in response to depolarization with potassium.
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39
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Halsey MJ, Wardley-Smith B, Wood S. Pressure reversal of alphaxalone/alphadolone and methohexitone in tadpoles: evidence for different molecular sites for general anaesthesia. Br J Pharmacol 1986; 89:299-305. [PMID: 3096406 PMCID: PMC1917003 DOI: 10.1111/j.1476-5381.1986.tb10260.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Tadpoles were used to study quantitative interactions between high pressure and two intravenous anaesthetics, alphaxalone/alphadolone and methohexitone. The potencies of the two agents were decreased by high pressure but to different extents. The maximum effect was seen in the pressure range 70-130 atmospheres absolute (ATA). The increases in the normobaric anaesthetizing concentration (ED50) required at 100 ATA were alphaxalone/alphadolone:405 +/- 5 (s.d.)%; methohexitone:658 +/- 80 (s.d.)%. For both alphaxalone/alphadalone and methohexitone, the curves obtained when the increase in ED50 was plotted against increasing pressure showed plateaux at pressures above 70 ATA. These data support the concept of the two intravenous drugs causing general anaesthesia by the occupation of separate molecular 'sites' with different but finite capacities.
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Maggi CA, Meli A. Suitability of urethane anesthesia for physiopharmacological investigations in various systems. Part 1: General considerations. EXPERIENTIA 1986; 42:109-14. [PMID: 2868911 DOI: 10.1007/bf01952426] [Citation(s) in RCA: 302] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The suitability of urethane anesthesia for physiopharmacological investigations is reviewed. Total dose administered and route of administration are recognized as factors having a great influence on both resting parameters and biological responses to drugs. A peculiar characteristic of urethane is represented by its ability to induce a surgical plane of anesthesia without affecting neurotransmission in various subcortical areas and the peripheral nervous system. This makes urethane a suitable general anesthetic for studying neural function in both central and peripheral nervous systems and accounts for the preservation of a number of reflex responses in urethane-anesthetized animals.
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41
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Lerner J. Effectors of amino acid transport processes in animal cell membranes. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1985; 81:713-39. [PMID: 2863064 DOI: 10.1016/0300-9629(85)90903-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Various effectors, which act upon ion gradients, protein synthesis, membrane components or cellular functional groups, have been employed to provide insights into the nature of amino acid-membrane transport processes in animal cells. Such effectors, for example, include ions, hormones, metabolites and various organic reagents and their judicious use has allowed the following list of conclusions. Sodium ion has been found to stimulate amino acid transport in a wide variety of cell systems, although depending on the tissue and/or substrate, this ion may have no effect on such transport, or even inhibit it. Amino acid transport can be stimulated in some cell systems by other ions such as K+, Li+, H+ or Cl-. Both H+ and K+ have been found to be inhibitory in other systems. Amino acid transport is dependent in many cell systems upon an inwardly directed Na+ gradient and is stimulated by a membrane potential (negative cell interior). In some cell systems an inwardly directed Cl- and H+ gradient or an outwardly directed K+ gradient can energize transport. Structurally dissimilar effectors such as ouabain, Clostridium enterotoxin, aspirin and amiloride inhibit amino acid transport presumably through dissipation of the Na+ gradient. Inhibition by certain sugars or metabolic intermediates of the tricarboxylic acid cycle may compete with the substrate for the energy of the Na+ gradient or interact with the substrate at the carrier level either allosterically or at a common site. Stimulation of transport by other sugars or intermediates may result from their catabolism to furnish energy for transport. Insulin and glucagon stimulate transport of amino acids in a variety of cell systems by a mechanism which involves protein synthesis. Microtubules may be involved in the regulation of transport by insulin or glucagon. Some reports also suggest that insulin has a direct effect on membranes. In addition, a number of growth hormones and factors have stimulatory effects on amino acid transport which are also mediated by protein synthesis. Steroid hormones have been noted to enhance or diminish transport of amino acids depending on the nature of the hormone. These agents appear to function at the level of protein synthesis. While stimulation may involve increased carrier synthesis, inhibition probably involves synthesis of a labile protein which either decreases the rate of synthesis or increases the rate of degradation of a component of the transport system.(ABSTRACT TRUNCATED AT 400 WORDS)
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42
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Little HJ, Atkinson HD. Ketamine potentiates the responses of the rat superior cervical ganglion to GABA. Eur J Pharmacol 1984; 98:53-9. [PMID: 6714303 DOI: 10.1016/0014-2999(84)90108-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The responses of the rat superior cervical ganglion to gamma-aminobutyric acid (GABA) were recorded in vitro using extracellular electrodes. Ketamine was found to increase the amplitude of these responses by up to 100%. This potentiation was seen at ketamine concentrations as low as 18 microM, reached maximum at 180 microM and then declined as the concentration was raised further. Ketamine (90 microM and over) depressed the nicotinic responses of the ganglia. The log concentration-effect curve to GABA was shifted to the left, and the maximum response increased, by ketamine. Inhibition of glial uptake of GABA did not prevent the effect of ketamine. The effects of 3-aminopropane sulphonic acid, which has a very low affinity for this GABA uptake mechanism, were also increased by ketamine. We conclude that ketamine, at concentrations which are found during general anaesthesia, potentiates the responses of the ganglion to GABA, by a mechanism other than inhibition of uptake, and suggest this may be due to action at the GABA receptor site.
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Anis NA, Berry SC, Burton NR, Lodge D. The dissociative anaesthetics, ketamine and phencyclidine, selectively reduce excitation of central mammalian neurones by N-methyl-aspartate. Br J Pharmacol 1983; 79:565-75. [PMID: 6317114 PMCID: PMC2044888 DOI: 10.1111/j.1476-5381.1983.tb11031.x] [Citation(s) in RCA: 1007] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The interaction of two dissociative anaesthetics, ketamine and phencyclidine, with the responses of spinal neurones to the electrophoretic administration of amino acids and acetylcholine was studied in decerebrate or pentobarbitone-anaesthetized cats and rats. Both ketamine and phencyclidine selectively blocked excitation by N-methyl-aspartate (NMA) with little effect on excitation by quisqualate and kainate. Ketamine reduced responses to L-aspartate somewhat more than those of L-glutamate; the sensitivity of responses to these two putative transmitters was between that to NMA on one hand and that to quisqualate or kainate on the other. On Renshaw cells, ketamine and phencyclidine reduced responses to acetylcholine less than those to NMA but more than those to quisqualate or kainate. Dorsal root-evoked synaptic excitation of Renshaw cells was reduced to a greater extent than that following ventral root excitation. Intravenous ketamine, 2.5-20 mg/kg, and phencyclidine, 0.2-0.5 mg/kg, also selectively blocked excitation of neurones by NMA. Ketamine showed no consistent or selective effect on inhibition of spinal neurones by electrophoretically administered glycine or gamma-aminobutyricacid (GABA). The results suggest that reduction of synaptic excitation mediated via NMA receptors contributes to the anaesthetic/analgesic properties of these two dissociative anaesthetics.
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Cullen KD, Martin RJ. Dissimilar influences of some injectable anaesthetics on the responses of reticulo-spinal neurones to inhibitory transmitters in the lamprey. Br J Pharmacol 1982; 77:493-504. [PMID: 7139199 PMCID: PMC2044617 DOI: 10.1111/j.1476-5381.1982.tb09323.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
1 Intracellular recordings were made from identified bulbar reticulo-spinal neurones in the medulla of lamprey ammocoetes. Responses to iontophoretically applied inhibitory transmitters were measured as changes in membrane potential and input resistance. 2 Dose-dependent alterations in the responses to gamma-aminobutyric acid (GABA) and glycine during bath application of injectable anaesthetic drugs were measured; the compounds used were pentobarbitone, ketamine, metomidate and the steroid mixture alphaxalone/alphadolone (Saffan). 3 GABA responses were potentiated by pentobarbitone (1-3 X 10(-4) M) and prolonged by ketamine (3.7 X 10(-5) M); but depressed by high concentrations (10(-3) M) of all drugs, as well as by anaesthetic concentrations of alphaxalone (1-3 X 10(-5) M). 4 Glycine responses were depressed by alphaxalone (1-3 X 10(-5) M) and by supra-anaesthetic concentrations of ketamine (3.7 X 10(-4) M) and metomidate (1.8 X 10(-3) M). No drug potentiated the glycine responses. 5 In the absence of an effect common to the 4 anaesthetics, it is concluded that neither potentiation nor inhibition of all GABA or glycine responses is an essential feature of anaesthesia. However, effects comparable to those described here may contribute to the overall clinical picture during anaesthesia of higher vertebrates. The findings do not support the notion that all anaesthetic agents act on biological membranes by a single mechanism.
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Kendall TJ, Minchin MC. The effects of anaesthetics on the uptake and release of amino acid neurotransmitters in thalamic slices. Br J Pharmacol 1982; 75:219-27. [PMID: 6122480 PMCID: PMC2071461 DOI: 10.1111/j.1476-5381.1982.tb08776.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
1 The effect of thiopentone, methohexitone, urethane and ketamine on the uptake and release of gamma-aminobutyric acid (GABA) and D-aspartate by rat thalamic slices has been investigated. 2 A high, supra-anaesthetic concentration of methohexitone increased the uptake of both D-aspartate and GABA. 3 None of the anaesthetics used had any detectable effect upon the spontaneous release of either amino acid. 4 Urethane and ketamine had no effect upon the K+-stimulated release of either amino acid. 5 Methohexitone and thiopentone produced a biphasic dose-response on the K+-stimulated release of both amino acids; low concentrations enhanced release, high concentrations depressed release. 6 Bicuculline hydrochloride and picrotoxin both significantly reduced the barbiturate-induced enhancement of K+-stimulated amino acid release, but did not significantly alter the depression of K+-stimulated release at higher barbiturate concentrations. 7 Baclofen, either alone (1 microM to 1 mM), or tested against the barbiturates, had no detectable effect.
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Minchin MC, Pearson G. The effect of the convulsant agent, catechol, on neurotransmitter uptake and release in rat brain slices. Br J Pharmacol 1981; 74:715-21. [PMID: 6117345 PMCID: PMC2071764 DOI: 10.1111/j.1476-5381.1981.tb10483.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
1 The effect of catechol on uptake and K+-stimulated release of gamma-aminobutyric acid (GABA), D-aspartate, noradrenaline and acetylcholine has been studied in slices of cerebral cortex and thalamus. 2 Low concentrations of catechol did not influence the uptake of any of the neurotransmitters in either brain area. 3 Noradrenaline release was unaffected by catechol. 4 Acetylcholine release from both cortical and thalamic slices was inhibited by high concentrations of catechol. This phenomenon is unlikely to be related to catechol-induced convulsions. 5 Catechol (100 microM) inhibited GABA release from cortical slices by 28%. However, at a concentration of 10 microM catechol enhanced the release of D-aspartate from thalamic slices by over 100%. 6 Potentiated release of excitatory amino acid transmitters may contribute to the enhanced excitability of thalamic cells which occurs during sensory myoclonus induced by low doses of catechol.
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