title: Amphetamine's dose-dependent effects on dorsolateral striatum sensorimotor neuron firing.
abstract: Amphetamine elicits motoric changes by increasing the activity of central neurotransmitters such as dopamine and serotonin, but how these neurochemical signals are transduced into motor commands is unclear. The dorsolateral striatum (DLS), a component of the cortico-subcortical reentrant motor loop, contains abundant neurotransmitter transporters that amphetamine could affect. It has been hypothesized that DLS medium spiny neurons contribute to amphetamine's motor effects. To study striatal activity contributing to amphetamine-induced movements, activity of DLS neurons related to vertical head movement was recorded while tracking head movements before and after acute amphetamine injection. Relative to saline, all amphetamine doses induced head movements above pre-injection levels, revealing an inverted U-shaped dose-response function. Lower doses (1 mg/kg and 2 mg/kg, intraperitoneal) induced a greater number of long (distance and duration) movements than the high dose (4 mg/kg), which induced stereotypy. Firing rates (FR) of individual head movement neurons were compared before and after injection during similar head movements, defined by direction, distance, duration, and apex. Changes in FR induced by amphetamine were co-determined by dose and pre-injection FR of the neuron. Specifically, all doses increased the FRs of slower firing neurons but decreased the FRs of faster firing neurons. The magnitudes of elevation or reduction were greater at lower doses, but less pronounced at the high dose, forming an inverted U function. Modulation of DLS firing may interfere with sensorimotor processing. Furthermore, pervasive elevation of slow firing neurons' FRs may feed-forward and increase excitability in thalamocortical premotor areas, contributing to the increased movement initiation rate.
authors: Department of Psychology, Rutgers, The State University of New Jersey, New Brunswick, NJ 08854, USA. sisima@rci.rutgers.edu
authors: Sisi
authors: S
authors: Ma
authors: Anthony P
authors: AP
authors: Pawlak
authors: Jeiwon
authors: J
authors: Cho
authors: David H
authors: DH
authors: Root
authors: David J
authors: DJ
authors: Barker
authors: Mark O
authors: MO
authors: West
mesh_terms: D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003342:Corpus Striatum / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D019416:Head Movements / Q000187:drug effects / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D013239:Stereotyped Behavior / Q000187:drug effects / Q000502:physiology
chemical_list: D000697:Central Nervous System Stimulants; D000661:Amphetamine
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