Time-dependent actions of D2 family agonist quinpirole on spontaneous behavior in the rat: dissociation between sniffing and locomotion.
BACKGROUND
Dopamine agonists elevate locomotion, sniffing, grooming, and a number of other behaviors. However, the D2 family (D2/D3/D4) agonist quinpirole, across a wide dose range, produces a period of locomotor inhibition that precedes the drug's locomotor excitatory effects.


OBJECTIVE
The present study asked whether the suppressive actions of quinpirole also extend to other aspects of spontaneous behavior, such as sniffing, rearing and grooming, or whether this suppression of locomotion occurs while the frequency of other behaviors is increased or unaffected.


METHODS
Locomotion, sniffing, rearing and grooming were observed over a 150-min test session in rats treated with 0, 0.1, 0.5, 1.0, or 10.0 mg/kg quinpirole.


RESULTS
At 0.1 mg/kg, quinpirole suppressed locomotion. Higher doses (0.5-10.0 mg/kg) produced locomotor suppression followed by locomotor excitation. During the period of locomotor suppression, quinpirole also reduced the frequency of rearing and grooming. However, animals under high doses (1 and 10 mg/kg) of quinpirole showed elevated sniffing during the period of locomotor, rear and groom suppression.


CONCLUSIONS
These results demonstrate that the well-documented locomotor suppression that precedes quinpirole's excitatory locomotor actions occurs in the midst of active sniffing. These results suggest that the suppressive effects of quinpirole on locomotion do not reflect a state of general behavioral suppression.
Horvitz
J C
JC
Department of Psychology, Columbia University, 1190 Amsterdam Avenue, Room 406, New York, NY 10027, USA. jon@psych.columbia.edu
Williams
G
G
Joy
R
R
D000818:Animals; D018491:Dopamine Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006120:Grooming / Q000187:drug effects* / Q000502:physiology; D008124:Locomotion / Q000187:drug effects* / Q000502:physiology; D008297:Male; D019257:Quinpirole / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000819:agonists* / Q000502:physiology*; D013997:Time Factors
D018491:Dopamine Agonists; D017448:Receptors, Dopamine D2; D019257:Quinpirole