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Neurotransmitters and Receptors, Ion Channels, G Proteins and Second Messengers
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
GABA, an amino acid, is a major inhibitory neurotransmitter in the brain. Two types of GABA receptors have been identified. GABAA receptors have a pentameric (2α, 2β and 1γ subunit) structure and inhibit the CNS cells by opening chloride channels, resulting in membrane hyperpolarization. Several anaesthetic drugs such as the volatile anaesthetics, barbiturates, intravenous anaesthetics except ketamine and benzodiazepines bind to the GABAA receptor and increase the inhibitory effect of GABA (Figure 3.6).
Central Nervous System Effects of Essential Oil Compounds
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
Elaine Elisabetsky, Domingos S. Nunes
GABA receptors play a crucial role in sleep. GABAA α1 subunit is associated with sedation, the α2/3 subunits with anxiety, and the α5 with temporal and spatial memory (Draguhn et al., 1990). Benzodiazepines promote the binding of GABA to the GABAA subtype of GABA receptors. Novel receptor agonists, referred to as Z compounds, are agonists on the benzodiazepine site of the GABAA receptor, selective to GABAA receptors that contain the α1 subunit.
Pharmacotherapy of Neurochemical Imbalances
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
Rupali Patil, Aman Upaganlawar, Suvarna Ingale
GABA receptors are two types—GABAA and GABAB receptors. GABAA receptors (Hosie et al., 2003) are ligand-gated ion channel whereas the other, GABAB receptors, is G-protein-coupled (Barnard et al., 1998).
Stimulatory and inhibitory effects of morphine on pentylenetetrazol-induced epileptic activity in rat
Published in International Journal of Neuroscience, 2021
Samrand Rashan, Yousef Panahi, Emad Khalilzadeh
According to Sesack and Pickel, in the ventral tegmental area of rats, approximately 20% of axon terminals immunoreactive for leu-enkephalin are labeled for GABA. In the locus ceruleus, a high proportion (38%) of leu-enkephalin immunoreactive axon terminals is found labeled for GABA. In other studies, single cells received afferents from both encephalin-ergic and GABAergic afferents without the two substances coexisting in the same terminal [11]. The mechanism of this action may be mediated by inhibitory effects on GABAergic activity, not triggering the excitatory glutamate pathways [23]. Some studies report that the number of active GABA receptors on the postsynaptic membrane decreases gradually during prolonged seizures, whereas the number of inactive GABA-A receptors increases. These changes result in a significant reduction in the efficacy of anticonvulsant drugs, such as clonazepam, diazepam, valproic acid, phenobarbital, propofol, and midazolam, which target the GABAergic system [24].
Lilium davidii extract alleviates p‑chlorophenylalanine‑induced insomnia in rats through modification of the hypothalamic-related neurotransmitters, melatonin and homeostasis of the hypothalamic-pituitary-adrenal axis
Published in Pharmaceutical Biology, 2020
Yanpo Si, Lili Wang, Jinxu Lan, Hanwei Li, Tao Guo, Xiaohui Chen, Chunhong Dong, Zhen Ouyang, Sui-qing Chen
GABA, as a main inhibitory neurotransmitter in the mammalian brain, may inhibit arousal systems to promote sleep by binding to the GABAA receptor. There are generally 2 types of GABA receptors: GABAA and GABAB. The most important receptor concerning sleep is the GABAA receptor (Gottesmann 2002). It is well-known that activation of GABAA receptors is beneficial for sleep (Abdou et al. 2006). Hence GABAA receptors are key targets in the search for natural resist sleep disorders compounds (Trauner et al. 2008). The results showed that LD extract upregulated the expression of the GABAA receptor (Figure 6(A)). In several studies, it was revealed that exogenous melatonin supplementation increased the GABA content in the hypothalamus, thereby indicating that the sleep regulation effect of melatonin was related to the GABA content in the hypothalamus (Wang et al. 2000), which is also consistent with our findings after LD extract administration. Besides, studies have shown that GABAA receptors (GABAARs) are of greater relevance to activation of the HPA axis (Brickley and Mody 2012), and a role of GABA in the regulation of the HPA axis in response to stress has been also well established (Decavel and Van den Pol 1990; Cullinan et al. 2008).
Novel investigational therapeutics for generalized anxiety disorder (GAD)
Published in Expert Opinion on Investigational Drugs, 2019
Bella Schanzer, Ana Maria Rivas-Grajales, Aamir Khan, Sanjay J Mathew
GAD is a common disorder that causes immeasurable disability to those suffering from it. To provide reliable relief, alternative options and new novel mechanisms must be developed. Unfortunately, there are few drugs with novel mechanisms of action in the pipeline. Current Phase II and III clinical trials are focused on several targets; GABA and glutamate modulators are well-known targets, but treatments acting on the GABA/glutamate system are associated with sedation, memory issues and potential for misuse. Current investigational drugs are focused on specific aspects of the GABA receptor or pathway to enhance the anxiolytic effect while minimizing the deleterious side effects associated with the benzodiazepine class of drugs. Unfortunately, these studies have so far been yielded negative results but investigations continue. Glutamate modulation is also being investigated as an option to decrease excitation without the sedation or cognitive impairment associated thus far with GABA receptor targets. Monoamine neurotransmitters are also of interest given their role in the fear response; Tandospirone, a 5HT1A receptor agonist, is used in China and Japan. A relatively novel target for investigation had been the neuropeptide corticotropin-releasing factor (CRF); however, a large RCT was negative when compared to placebo. Finally, a treatment that might work through anti-oxidant and anti-inflammatory activity is also being explored. Effective and low-risk non-benzodiazepine treatments for GAD are needed and further investigation is required.