D. Feifel et K. Priebe, The effects of subchronic haloperidol on intact and dizocilpine-disrupted sensorimotor gating, PSYCHOPHAR, 146(2), 1999, pp. 175-179
Rationale: Reversal of deficits in prepulse inhibition (PPI) of the startle
reflex in rats is considered a preclinical screen for potential antipsycho
tics, Whereas acutely administered antipsychotics consistently reverse apom
orphine-induced deficits in PPI, some antipsychotics, including haloperidol
, are unable to reverse deficits in PPI produced by non-competitive NMDA an
tagonists such as phencyclidine or dizocilpine (MK-801). Acute administrati
on of antipsychotics tends to facilitate baseline PPI. However, the effect
is generally not large enough in magnitude nor reliable enough to be consid
ered a useful preclinical screen for antipsychotic activity. Objective: Bec
ause the clinical effects of antipsychotics typically require subchronic ad
ministration, this study tested the hypothesis that reversal of NMDA antago
nist-induced deficits in PPI by antipsychotics require subchronic administr
ation. A second aim of this study was to determine if subchronic administra
tion of an antipsychotic produces a more potent facilitation of baseline PP
I than acute administration. Methods: Rats received a subcutaneous injectio
n of 0, 0.025, 0.1 or 0.5 mg/kg haloperidol for 16 consecutive days. On day
16, half the rats in each haloperidol dose group received a second subcuta
neous injection consisting of either dizocilpine (0.1 mg/kg) or saline. Res
ults: None of the haloperidol doses tested had a significant effect on base
line PPI. The 0.1 mg/kg dose of haloperidol diminished but did not complete
ly reverse dizocilpine-induced disruption of PPI. The other doses had no si
gnificant effect. Conclusions: These results suggest that time course facto
rs may partially modify the effects of haloperidol on dizocilpine-induced d
isruption of PPI but not its effect on baseline PPI.