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Liu C, Zhou X, Zhu Q, Fu B, Cao S, Zhang Y, Zhang L, Zhang Y, Yu T. Dopamine neurons in the ventral periaqueductal gray modulate isoflurane anesthesia in rats. CNS Neurosci Ther 2020; 26:1121-1133. [PMID: 32881314 PMCID: PMC7564192 DOI: 10.1111/cns.13447] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 06/10/2020] [Accepted: 06/29/2020] [Indexed: 12/14/2022] Open
Abstract
Aims General anesthesia has been applied in surgery for more than 170 years, and there is little doubt that GABAA receptors have an important role as anesthetic molecular targets, but its neural mechanisms remain unclear. Increasing researchers have shown that dopaminergic pathways in the brain are crucial for sleep and wake. General anesthesia‐induced unconsciousness and natural sleep share some neural correlates. However, the role of GABAA receptors in ventral periaqueductal gray (vPAG) dopamine (DA) neurons in the isoflurane‐induced unconsciousness has yet to be identified. Methods In the present study, we used calcium fiber photometry recording to explore that the activity of ventral periaqueductal gray (vPAG) neurons. Then, rats were unilaterally microinjected with 6‐hydroxydopamine into the vPAG area to determine the role of vPAG‐DA neurons in isoflurane‐induced‐anesthesia. Furthermore, thirty SD rats were divided into three groups: a GABAAR agonist‐muscimol group, a GABAAR antagonist‐gabazine group, and a control group. Finally, whole‐cell patch clamp was used to examine the effects of isoflurane and GABAA receptor agonist/antagonist on vPAG‐DA neurons. Results The vPAG neurons were markedly inhibited during isoflurane anesthesia induction and that these neurons were activated during emergence from isoflurane anesthesia. Lesion to the vPAG‐DA neurons shortened the induction time and prolonged the emergence time while increasing δ power in isoflurane anesthesia. Intracerebral injection of the GABAA receptor agonist (muscimol) into the vPAG accelerated the induction of anesthesia and delayed recovery from isoflurane anesthesia, with a decrease of δ power and an augment of β power. Injection of GABAA receptor antagonist gabazine generated the opposite effects. Isoflurane enhanced GABAergic transmission, and GABAA receptor agonist partly increased isoflurane‐induced inhibition of vPAG‐DA neurons, while GABAA receptor antagonist evidently attenuated GABAergic transmission. Conclusion Our results suggest that vPAG‐DA neurons are involved in isoflurane anesthesia through activation of the GABAA receptor.
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Affiliation(s)
- Chengxi Liu
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, China.,Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, China
| | - Xiao Zhou
- Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, China
| | - Qiuyu Zhu
- Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, China
| | - Bao Fu
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, China.,Department of Critical Care Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Song Cao
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, China
| | - Yu Zhang
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, China.,Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, China
| | - Lin Zhang
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, China.,Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, China
| | - Yi Zhang
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, China.,Department of Anesthesiology, The Second Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Tian Yu
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, China.,Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, China
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Piao MH, Liu Y, Wang YS, Qiu JP, Feng CS. Volatile anesthetic isoflurane inhibits LTP induction of hippocampal CA1 neurons through α4β2 nAChR subtype-mediated mechanisms. ACTA ACUST UNITED AC 2013; 32:e135-41. [PMID: 24011619 DOI: 10.1016/j.annfar.2013.05.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Accepted: 05/21/2013] [Indexed: 11/17/2022]
Abstract
BACKGROUND AND PURPOSE Volatile anesthetic isoflurane contributes to postoperative cognitive dysfunction and inhibition of long-term potentiation (LTP), a synaptic model of learning and memory, but the mechanisms are uncertain. Central neuronal α4β2 subtype nicotinic acetylcholine receptors (nAChRs) are involved in the induction of LTP in the hippocampus. Isoflurane inhibits α4β2 nAChRs at concentrations lower than those used for anesthesia. Therefore, we hypothesized that isoflurane-inhibited LTP induction of hippocampal CA1 neurons via α4β2 nAChRs subtype inhibition. METHODS Transverse hippocampal slices (400μm thick) were obtained from male rats (6-8 weeks old). Population spikes were evoked using extracellular electrodes by electrical stimulation of the Schaffer collateral-commissural pathway of rat hippocampal slices. LTP was induced using high frequency stimulation (HFS; 100Hz, 1s). Clinically relevant concentrations (0.125-0.5mM) of isoflurane with or without nicotine (nAChRs agonist), mecamylamine (nAChRs antagonist), 3-[2(S)-2-azetidinylmethoxy] pyridine (A85380) and epibatidine (α4β2 nAChRs agonist), dihydro β erythroidine (DHβE) (α4β2 nAChRs antagonist) were added to the perfusion solution 20min before HFS to test their effects on LTP by HFS respectively. RESULTS A brief HFS induced stable LTP in rat hippocampal slices, but LTP was significantly inhibited in the presence of isoflurane at concentrations of 0.125-0.5mM. The inhibitive effect of isoflurane on LTP was not only reversible and could be prevented by nAChRs agonist nicotine and α4β2 nAChRs agonist A85380 and epibatidine, but also mimicked and potentiated by nAChRs antagonist mecamylamine and α4β2 nAChRs antagonist DHβE. CONCLUSIONS Inhibition of α4β2 nAChRs subtype of hippocampus participates in isoflurane-mediated LTP inhibition.
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Affiliation(s)
- M-H Piao
- Department of anesthesiology, the first hospital of Jilin university, n(o) 71, Xinmin St, 130021 Changchun, China; School of public health, Jilin university, Changchun 130021, China
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Central and Peripheral GABA(A) Receptor Regulation of the Heart Rate Depends on the Conscious State of the Animal. Adv Pharmacol Sci 2011; 2011:578273. [PMID: 22162673 PMCID: PMC3226329 DOI: 10.1155/2011/578273] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 09/05/2011] [Indexed: 12/29/2022] Open
Abstract
Intuitively one might expect that activation of GABAergic inhibitory neurons results in bradycardia. In conscious animals the opposite effect is however observed. GABAergic neurons in nucleus ambiguus hold the ability to control the activity of the parasympathetic vagus nerve that innervates the heart. Upon GABA activation the vagus nerve will be inhibited leaving less parasympathetic impact on the heart. The picture is however blurred in the presence of anaesthesia where both the concentration and type of anaesthetics can result in different effects on the cardiovascular system. This paper reviews cardiovascular outcomes of GABA activation and includes own experiments on anaesthetized animals and isolated hearts. In conclusion, the impact of changes in GABAergic input is very difficult to predict in these settings, emphasizing the need for experiments performed in conscious animals when aiming at determining the cardiovascular effects of compounds acting on GABAergic neurons.
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Wang X, Gorini C, Sharp D, Bateman R, Mendelowitz D. Anaesthetics differentially modulate the trigeminocardiac reflex excitatory synaptic pathway in the brainstem. J Physiol 2011; 589:5431-42. [PMID: 21930602 DOI: 10.1113/jphysiol.2011.215392] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The trigeminocardiac reflex (TCR) occurs upon excitation of the trigeminal nerve with a resulting bradycardia and hypotension. While several anaesthetics and analgesics have been reported to alter the incidence and strength of the TCR the mechanisms for this modulation are unclear. This study examines the mechanisms of action of ketamine, isoflurane and fentanyl on the synaptic TCR responses in both neurones in the spinal trigeminal interpolaris (Sp5I) nucleus and cardiac vagal neurones (CVNs) in the Nucleus Ambiguus (NA). Stimulation of trigeminal afferent fibres evoked an excitatory postsynaptic current (EPSC) in trigeminal neurones with a latency of 1.8 ± 0.1 ms, jitter of 625 μs, and peak amplitude of 239 ± 45 pA. Synaptic responses further downstream in the reflex pathway in the CVNs occurred with a latency of 12.1 ± 1.1 ms, jitter of 0.8-2 ms and amplitude of 57.8 ± 7.5 pA. The average conduction velocity to the Sp5I neurones was 0.94 ± 0.18 mm ms(-1) indicating a mixture of A-δ and C fibres. Stimulation-evoked EPSCs in both Sp5I and CVNs were completely blocked by AMPA/kainate and NMDA glutamatergic receptor antagonists. Ketamine (10 μm) inhibited the peak amplitude and duration in Sp5I as well as more distal synapses in the CVNs. Isoflurane (300 μm) significantly inhibited, while fentanyl (1 μm) significantly enhanced, EPSC amplitude and area in CVNs but had no effect on the responses in Sp5l neurones. These findings indicate glutamatergic excitatory synaptic pathways are critical in the TCR, and ketamine, isoflurane and fentanyl differentially alter the synaptic pathways via modulation of both AMPA/kainate and NMDA receptors at different synapses in the TCR.
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Affiliation(s)
- Xin Wang
- Department of Pharmacology and Physiology, and Department of Anesthesiology and Critical Care Medicine, The George Washington University, 2300 Eye Street, NW, Washington, DC 20037, USA
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