Abnormal involuntary movement (AIM) expression following D2 dopamine agonist challenge is determined by the nature of prior dopamine receptor stimulation (priming) in 6-hydroxydopamine lesioned rats

Rats with unilateral 6-hydroxydopamine (6-OHDA) lesions show sensitization (priming) of rotational behavior upon repeated treatment with dopamine agonists. To relate these observations to dyskinesias exhibited by Parkinson's Disease patients, we assessed abnormal involuntary movements (AIMs) in 6-OHDA rats, which were primed with three injections of either the following: water, D1/D2 agonist apomorphine (Apo) (0.5 mg/kg), D1 agonist SKF38393 (SKF) (10 mg/kg) or D2 agonist quinpirole (Quin) (1 or 2.5 mg/kg). The rats were challenged one week later with Quin (0.25 mg/kg). Axial, limb, orolingual, locomotor, and grooming AlMs were scored (0-4) every 5 min. Priming with water did not produce AIMs. Priming with Quin (1 mg/kg) produced axial and locomotor AlMs, while priming with Apo, SKF or Quin (2.5 mg/kg) produced axial, locomotor, limb, and grooming AlMs. The disparity in AIM profiles between Quin (1 mg/kg) and (2.5 mg/kg) was not the result of D1 receptor stimulation since there was little striatal Fos expression following the third priming injection with Quin (1 or 2.5 mg/kg) compared to following SKF, which led to robust striatal Fos expression. Challenge with Quin (0.25 mg/kg) essentially reproduced the categories of AlMs exhibited during priming, with no AlMs in water-primed 6-OHDA rats, mild, non-significant, axial and locomotor AlMs in Quin (1 and 2.5 mg/kg)-primed 6-OHDA rats, and axial, limb, locomotor, and grooming AlMs in Apo- and SKF-primed 6-OHDA rats. These data suggest that the types of AlMs expressed following challenge with Quin depend on the dopamine receptor subtype and dose of dopamine agonist used during priming. (C) 2013 Elsevier Inc. All rights reserved.