Biomaterial Database

Suppression of Harmaline Tremor by Activation of an Extrasynaptic GABAA Receptor: Implications for Essential Tremor. 2018

Adrian Handforth, and Pournima A Kadam, and Hovsep P Kosoyan, and Pirooz Eslami

Neurology Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA.

Metabolic imaging has revealed excessive cerebellar activity in essential tremor patients. Golgi cells control cerebellar activity by releasing gamma-aminobutyric acid (GABA) onto synaptic and extrasynaptic receptors on cerebellar granule cells. We postulated that the extrasynaptic GABAA receptor-specific agonist THIP (gaboxadol; 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) would suppress tremor in the harmaline model of essential tremor and, since cerebellar extrasynaptic receptors contain α6 and δ subunits, would fail to do so in mice lacking either subunit. Digitally measured motion power, expressed as 10-16 Hz power (the tremor bandwidth) divided by background 8-32 Hz motion power, was accessed during pre-harmaline baseline, pre-THIP harmaline exposure, and after THIP administration (0, 2, or 3 mg/kg). These low doses were chosen as they did not impair performance on the straight wire test, a sensitive test for psychomotor impairment. Littermate δ wild-type and knockout (Gabrd+/+, Gabrd-/-) and littermate α6 wild-type and knockout (Gabra6+/+, Gabra6 ) mice were tested. Gabrd+/+ mice displayed tremor reduction at 3 mg/kg THIP but not 2 mg/kg, and Gabra6+/+ mice showed tremor reduction at 2 and 3 mg/kg. Their respective subunit knockout littermates displayed no tremor reduction compared with vehicle controls at either dose. The loss of anti-tremor efficacy with deletion of either δ or α6 GABAA receptor subunits indicates that extrasynaptic receptors containing both subunits, most likely located on cerebellar granule cells where they are highly expressed, mediate tremor suppression by THIP. A medication designed to activate only these receptors may display a favorable profile for treating essential tremor.

UI	MeSH Term	Description	Entries
D007555	Isoxazoles	Azoles with an OXYGEN and a NITROGEN next to each other at the 1,2 positions, in contrast to OXAZOLES that have nitrogens at the 1,3 positions.	Isoxazole
D008297	Male		Males
D008810	Mice, Inbred C57BL	One of the first INBRED MOUSE STRAINS to be sequenced. This strain is commonly used as genetic background for transgenic mouse models. Refractory to many tumors, this strain is also preferred model for studying role of genetic variations in development of diseases.	Mice, C57BL,Mouse, C57BL,Mouse, Inbred C57BL,C57BL Mice,C57BL Mice, Inbred,C57BL Mouse,C57BL Mouse, Inbred,Inbred C57BL Mice,Inbred C57BL Mouse
D011963	Receptors, GABA-A	Cell surface proteins which bind GAMMA-AMINOBUTYRIC ACID and contain an integral membrane chloride channel. Each receptor is assembled as a pentamer from a pool of at least 19 different possible subunits. The receptors belong to a superfamily that share a common CYSTEINE loop.	Benzodiazepine-Gaba Receptors,GABA-A Receptors,Receptors, Benzodiazepine,Receptors, Benzodiazepine-GABA,Receptors, Diazepam,Receptors, GABA-Benzodiazepine,Receptors, Muscimol,Benzodiazepine Receptor,Benzodiazepine Receptors,Benzodiazepine-GABA Receptor,Diazepam Receptor,Diazepam Receptors,GABA(A) Receptor,GABA-A Receptor,GABA-A Receptor alpha Subunit,GABA-A Receptor beta Subunit,GABA-A Receptor delta Subunit,GABA-A Receptor epsilon Subunit,GABA-A Receptor gamma Subunit,GABA-A Receptor rho Subunit,GABA-Benzodiazepine Receptor,GABA-Benzodiazepine Receptors,Muscimol Receptor,Muscimol Receptors,delta Subunit, GABA-A Receptor,epsilon Subunit, GABA-A Receptor,gamma-Aminobutyric Acid Subtype A Receptors,Benzodiazepine GABA Receptor,Benzodiazepine Gaba Receptors,GABA A Receptor,GABA A Receptor alpha Subunit,GABA A Receptor beta Subunit,GABA A Receptor delta Subunit,GABA A Receptor epsilon Subunit,GABA A Receptor gamma Subunit,GABA A Receptor rho Subunit,GABA A Receptors,GABA Benzodiazepine Receptor,GABA Benzodiazepine Receptors,Receptor, Benzodiazepine,Receptor, Benzodiazepine-GABA,Receptor, Diazepam,Receptor, GABA-A,Receptor, GABA-Benzodiazepine,Receptor, Muscimol,Receptors, Benzodiazepine GABA,Receptors, GABA A,Receptors, GABA Benzodiazepine,delta Subunit, GABA A Receptor,epsilon Subunit, GABA A Receptor,gamma Aminobutyric Acid Subtype A Receptors
D002531	Cerebellum	The part of brain that lies behind the BRAIN STEM in the posterior base of skull (CRANIAL FOSSA, POSTERIOR). It is also known as the "little brain" with convolutions similar to those of CEREBRAL CORTEX, inner white matter, and deep cerebellar nuclei. Its function is to coordinate voluntary movements, maintain balance, and learn motor skills.	Cerebella,Corpus Cerebelli,Parencephalon,Cerebellums,Parencephalons
D005260	Female		Females
D006246	Harmaline	A beta-carboline alkaloid isolated from seeds of PEGANUM.	3H-Pyrido(3,4-b)indole, 4,9-dihydro-7-methoxy-1-methyl-,Dihydroharmine,Harmidine
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014202	Tremor	Cyclical movement of a body part that can represent either a physiologic process or a manifestation of disease. Intention or action tremor, a common manifestation of CEREBELLAR DISEASES, is aggravated by movement. In contrast, resting tremor is maximal when there is no attempt at voluntary movement, and occurs as a relatively frequent manifestation of PARKINSON DISEASE.	Action Tremor,Intention Tremor,Resting Tremor,Coarse Tremor,Continuous Tremor,Darkness Tremor,Fine Tremor,Intermittent Tremor,Involuntary Quiver,Massive Tremor,Passive Tremor,Persistent Tremor,Pill Rolling Tremor,Rest Tremor,Saturnine Tremor,Senile Tremor,Static Tremor,Tremor, Limb,Tremor, Muscle,Tremor, Neonatal,Tremor, Nerve,Tremor, Perioral,Tremor, Semirhythmic,Action Tremors,Coarse Tremors,Continuous Tremors,Darkness Tremors,Fine Tremors,Intention Tremors,Intermittent Tremors,Involuntary Quivers,Limb Tremor,Limb Tremors,Massive Tremors,Muscle Tremor,Muscle Tremors,Neonatal Tremor,Neonatal Tremors,Nerve Tremor,Nerve Tremors,Passive Tremors,Perioral Tremor,Perioral Tremors,Persistent Tremors,Pill Rolling Tremors,Quiver, Involuntary,Rest Tremors,Resting Tremors,Saturnine Tremors,Semirhythmic Tremor,Semirhythmic Tremors,Senile Tremors,Static Tremors,Tremor, Action,Tremor, Coarse,Tremor, Continuous,Tremor, Darkness,Tremor, Fine,Tremor, Intention,Tremor, Intermittent,Tremor, Massive,Tremor, Passive,Tremor, Persistent,Tremor, Pill Rolling,Tremor, Rest,Tremor, Resting,Tremor, Saturnine,Tremor, Senile,Tremor, Static,Tremors
D057507	Mice, 129 Strain	Strains of mice arising from a parental inbred stock that was subsequently used to produce substrains of knockout and other mutant mice with targeted mutations.	129 Mice,129 Mouse,129 Strain Mice,129 Strain Mouse,Bar Harbor 129 Mice,Bar Harbor 129 Mouse,Mice, 129,Mice, Strain 129,Mouse, 129,Mouse, 129 Strain,Strain 129 Mice,Strain Mice, 129