title: Regulation of dopamine D2 receptors in the guinea pig cochlea.
abstract: CONCLUSIONS
  Our study demonstrates that the regulation of D2 receptors may be frequency specific. The reduction in cochlear microphonics (CM) and distortion product otoacoustic emission (DPOAE) amplitudes after perfusion with a D2 antagonist suggests that this receptor plays a role in the regulation of cochlear hair cell activation.
  
  
  OBJECTIVE
  Dopaminergic terminals are subject to negative feedback from dopamine D2 receptors. In the present study we investigated whether the regulation of dopamine D2 receptor is frequency specific and evaluated changes in CM in guinea pig cochlea.
  
  
  METHODS
  A total of 30 male guinea pigs were randomly assigned to 3 groups and perfused with artificial perilymph (AP), AP containing ethanol (0.1%), or a D2 antagonist (L741626) for 2 h. In each group, compound action potentials (CAPs) evoked by a 1, 2, 4, 8, 16 or 24 kHz tone pip, CM evoked by 4 kHz tone bursts, and DPOAEs were measured before and 2 h after perilymphatic perfusion.
  
  
  RESULTS
  Perfusion with the D2 antagonist resulted in increased CAP thresholds compared with the other two groups at high frequencies (4, 8, 16, 24 kHz, p < 0.05); however, no significant increase was observed at low frequencies (1, 2 kHz, p > 0.05). There was a significant reduction in DPOAEs and CM amplitudes after the 2 h perfusion with the D2 antagonist. A CM input/output (I/O) function curve plotted with the stimulating level as input and the CM relative amplitude as output indicated obvious nonlinearity after the 2 h perfusion in all three groups.
authors.affiliation: Department of Otolaryngology, Peking University People's Hospital , Beijing.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.forename: Jingjing
authors.initials: J
authors.lastname: Li
authors.forename: Lisheng
authors.initials: L
authors.lastname: Yu
authors.forename: Xingqi
authors.initials: X
authors.lastname: Li
mesh_terms: D000161:Acoustic Stimulation; D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D003051:Cochlea / Q000187:drug effects*; D003055:Cochlear Microphonic Potentials / Q000187:drug effects*; D065127:Dopamine D2 Receptor Antagonists / Q000494:pharmacology*; D006168:Guinea Pigs; D006198:Hair Cells, Auditory; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous / Q000187:drug effects*; D010498:Perilymph; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000502:physiology*
chemical_list: D065127:Dopamine D2 Receptor Antagonists; D017448:Receptors, Dopamine D2
keywords: Dopamine; cochlear microphonics; compound action potential; distortion product otoacoustic emissions