Rj. Rodgers et al., MODULATION OF PLUS-MAZE BEHAVIOR IN MICE BY THE PREFERENTIAL D-3-RECEPTOR AGONIST 7-OH-DPAT, Pharmacology, biochemistry and behavior, 54(1), 1996, pp. 79-84
Differences in the behavioural profiles of dopamine D-2 receptor antag
onists (e.g., haloperidol vs. sulpiride) in animal models of anxiety h
ave prompted speculation concerning the importance of their relative a
ffinities for D-2-like receptor populations. In an initial attempt to
investigate the involvement of D-3 receptors in anxiety, the present s
tudy examined the effects of the preferential D-3-receptor agonist, (/-)7-OH-DPAT (0.01-10.0 mg/kg), on behaviours displayed by male mice i
n the elevated plus-maze paradigm. An ethological approach incorporati
ng measurement of a range of defensive acts and postures in addition t
o conventional parameters was used to provide a comprehensive behaviou
ral profile for the compound. Data analysis indicated a significant in
crease in percentage of open-arm entries at 10 mg/kg and an altered te
mporal distribution of behaviour at 1-10 mg/kg. Furthermore, risk-asse
ssment measures (stretched attend postures, closed-arm returns) were d
ose dependently reduced by drug treatment. Although these behavioural
changes would be consistent with anxiety reduction, such an interpreta
tion is negated by dose-dependent decreases in all active behaviours (
arm entries, rearing, and head-dipping) and by marked increases in ent
ry latencies and nonexploratory behaviour at the highest dose tested.
Overall, these effects are remarkably similar to those previously repo
rted for quinpirole, suggesting either that D-2 and D-3 receptors exer
t similar behavioural control or that the agents employed are sufficie
ntly potent at D-2 receptors to prevent a resolution of D-2 and D-3 re
sponses.