GABAergic pathways

There is evidence that the histaminergic tract that passes from the posterior hypothalamus to the cortex via the thalamus is inhibited by a GABAergic pathway. It is now known that H3 receptors act as autoreceptors on histaminergic neurons and that agonists of H3 receptors augment slow-wave sleep. In addition, histamine can increase cortical arousal by enhancing excitatory cholinergic neurons from the basal forebrain and also inhibits the hypothalamic pre-optic area which normally promotes sleep. With respect to the control of the circadian rhythm, histamine has... 

Fig. 10 Regulation of the striatopallidal indirect GABAergic pathway A2A receptor-mediated dual excitatory modulation of the indirect pathway. Presumed action of the nondopamineigic adenosine receptor ligand in the basal ganglia circuit. Adenosine A(2A) receptors are localized to the indirect striatal output function (courtesy of Mori and Shindou, 2003)...

The tremorigenic properties of ibogaine and related compounds have been attributed to an action on GABAergic pathways (98-100) and to the blockade of voltage-dependent sodium channels. 

Central nervous system changes are the most frequently observed systemic toxicities of lidocaine. The initial manifestations are restlessness, vertigo, tinnitus, slurred speech, and eventually, seizures. Subsequent manifestations include CNS depression with a cessation of convulsions and the onset of unconsciousness and respiratory depression or cardiac arrest. This biphasic effect occurs because local anesthetics initially block the inhibitory GABAergic pathways, resulting in stimulation, and eventually block both inhibitory and excitatory pathways... 

This is the case when the excitatory Dx receptors on these striatal GABAergic projection neurons are no longer activated since the transmitter dopamine is reduced (green broken arrows at 2). The indirect pathway is... 

Figure 10.3 Possible cellular pathways involved in the physiological modulation of GABAergic function by melatonin via the MTi receptor. See text for explanation. (See also Plate 2.)...

GABA is the predominant intrinsic transmitter of the basal ganglia. Inhibition and disinhibition are considered to be the most important modes of information transfer in the basal ganglia. Ninety-five percent of all neurons in the striatum are GABAergic medium spiny neurons. These neurons are the striatal output neurons. The medium spiny neurons which give rise to the direct pathway also contain substance P or dynorphin as a co-transmitter, while those striatal output neurons that give rise to the indirect pathway contain enkephalin as a co-transmitter. Most striatal interneurons, as well as neurons in GPe, GPi and SNr are also GABAergic. Because striatal and GPe... 

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