title: Pharmacological characterization of harmaline-induced tremor activity in mice.
abstract: Harmaline-induced tremor in rodents is a model of essential tremor. We utilized a novel assay to quantify tremor activity in mice and found that tremor activity was dependent on harmaline dose. The first-line clinical essential tremor treatments propranolol, primidone and gabapentin and gamma-hydroxybutyrate (GHB) significantly attenuated harmaline-induced tremor. The anticonvulsants valproate and carbamazepine and the mood stabilizer lithium suppressed harmaline-induced tremor. The gamma-amino-butyric acid (GABA) receptor subtype A receptor agonist muscimol attenuated harmaline-induced tremor. By contrast, the GABA(B) receptor agonist R-baclofen increased tremor at the lowest dose tested, but had no effects at higher doses. Administration of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists phencyclidine or 5R,10S-(+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine hydrogen maleate (MK-801) attenuated harmaline-induced tremor. The competitive NMDA antagonist D-4-[(2E)-3-phosphono-2-propenyl]-2-piperazinecarboxylic acid (d-CPPene) dose-dependently blocked harmaline-induced tremor, as did the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide disodium salt (NBQX). The metabotropic glutamate subtype 5 (mGlu5) receptor antagonist 6-methyl-2-(phenylethynyl)pyridine (MPEP) was inactive against tremor. The dopamine reuptake inhibitor GBR12909 and the dopamine D(1)/D(2) receptor agonist apomorphine attenuated harmaline-induced tremor. Follow-up studies indicated that dopamine D(2)/D(3) but not dopamine D(1) receptor activation likely mediates the effects of apomorphine and GBR12909. Administration of compounds with sedative side-effects had no effect on tremor activity. In summary, the present data confirm the pharmacological validity of harmaline-induced tremor in mice, quantified via a novel assay, as an animal model of essential tremor. Further, these data provide additional evidence for the roles of ionotropic glutamate, GABA(A) and dopamine D(2)/D(3) receptors in the neurobiology of harmaline-induced tremor.
authors.affiliation: Behavioral Pharmacology, PsychoGenics, Inc., Tarrytown, NY 10591, USA.
authors.forename: Neil E
authors.initials: NE
authors.lastname: Paterson
authors.forename: Sam A
authors.initials: SA
authors.lastname: Malekiani
authors.forename: Mark M
authors.initials: MM
authors.lastname: Foreman
authors.forename: Berend
authors.initials: B
authors.lastname: Olivier
authors.forename: Taleen
authors.initials: T
authors.lastname: Hanania
mesh_terms: D000339:Affect / Q000187:drug effects; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D001418:Baclofen / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects; D001552:Benzazepines / Q000494:pharmacology; D002243:Carbolines / Q000494:pharmacology; D002707:Chlordiazepoxide / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005971:Glutamates / Q000378:metabolism; D006246:Harmaline / Q000494:pharmacology*; D018021:Lithium Chloride / Q000494:pharmacology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009118:Muscimol / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D020891:Raclopride / Q000494:pharmacology; D017470:Receptors, Glutamate / Q000378:metabolism; D012978:Sodium Oxybate / Q000494:pharmacology; D014202:Tremor / Q000139:chemically induced*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D000927:Anticonvulsants; D001552:Benzazepines; D002243:Carbolines; D005971:Glutamates; D018377:Neurotransmitter Agents; D010879:Piperazines; D017470:Receptors, Glutamate; D009118:Muscimol; D020891:Raclopride; D005680:gamma-Aminobutyric Acid; D002707:Chlordiazepoxide; D012978:Sodium Oxybate; C071262:SK&F 82958; C043425:vanoxerine; D011433:Propranolol; D006246:Harmaline; D018021:Lithium Chloride; D001418:Baclofen; D004298:Dopamine