Central nervous system inhibitory

Potent central nervous system inhibitory effects and GABA antagonism were reported for muscimol [5], and this alkaloid was synthesized [4,6,7]. On the other hand, it was shown that ibotenic acid, like kainic acid (see Section 6.2), possessed more potent neuronal excitement eflbcts than glutamic acid, and the activities of these alkaloids were 2-7 times and 8-80 times that of glutamic acid, respectively [8]. It can be considered that these alkaloids are derivatives of glutamic acid in which the conformation was fixed. These alkaloids are used as biological tools in neuroexcitatory experiments [9]. 

GABA (y-aminobutyric acid) is an amino acid with mostly inhibitory functions in the mammalian central nervous system. Structures involved in releasing or binding GABA as a neurotransmitter constitute the GABAergic system. The GABAergic system is involved... 

The amino acid glycine, a neurotransmitter at inhibitory synapses throughout the central nervous system (CNS),... 

Histamine produces its pharmacological actions by three subtypes of receptors the postsynaptic Hi and H2 receptors and the presynaptic H3 receptor. The H3 receptor is mainly located in the central nervous system (CNS), where it acts as an inhibitory autoreceptor in the central histaminergic neuronal pathways [176]. A number of therapeutic applications have been proposed for selective H3 receptor antagonists, including several CNS disorders such as Alzheimer s disease. Attention Deficit Hyperactivity Disorder, Schizophrenia, or for enhancing memory or obesity control. 

Ginseng Rg2 has shown inhibitory effects on platelet aggregation similar to aspirin, and R0 reportedly inhibits the conversion of fibrinogen to fibrin [27]. The amount of ginseng administered may also influence the effect(s) produced. In rats and mice, small doses of ginseng extract result in increased spontaneous motor activity, whereas larger doses produce an inhibitory effect on the central nervous system [28]. 

A[ adenosine receptors are inhibitory in the central nervous system 313... 

A1 adenosine receptors are inhibitory in the central nervous system. A receptors were originally characterized on the basis of their ability to inhibit adenylyl cyclase in adipose tissue. A number of other G-protein-mediated effectors of A receptors have subsequently been discovered these include activation of K+ channels, extensively characterized in striatal neurons [13], and inhibition of Ca2+ channels, extensively characterized in dorsal root ganglion cells [14]. Activation of A receptors has been shown to produce a species-dependent stimulation or inhibition of the phosphatidylinositol pathway in cerebral cortex. In other tissues, activation of A receptors results in synergistic activation of the phosphatidylinositol pathway in concert with Ca2+-mobilizing hormones or neurotransmitters [15]. The effectors of A adenosine receptors and other purinergic receptor subtypes are summarized in Table 17-2. 

Many lines of evidence. .. make it seem probable that GABA is a major inhibitory transmitter in the vertebrate central nervous system . 

Gephyrin was initially found in the central nervous system, where it is essential for the clustering of inhibitory neuroreceptors in the postsynaptic membrane. 

Glycine is in a class by itself. It is the only protein amino acid that is not chiral. It is neither hydrophilic nor hydrophobic. With the exception of proline, all other protein amino acids are derived from it by substituting various groups on the oi carbon atom. Glycine is an important inhibitory neurotransmitter in the central nervous system. 

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