Animal Studies

Psychopharmacology

, Volume 47, Issue 3, pp 217-223

First online:

Effects of apomorphine and haloperidol on the acoustic startle response in rats

  • Michael DavisAffiliated withYale University School of MedicineConnecticut Mental Health Center
  • , George K. AghajanianAffiliated withYale University School of MedicineConnecticut Mental Health Center

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Abstract

A series of 3 experiments tested the effects of 0.01, 0.04, 0.19, 0.75, 3.00, and 6.00 mg/kg apomorphine and 0.13, 0.25, and 0.50 haloperidol on the acoustic startle response in rats. Apomorphine markedly facilitated startle amplitude for about 40 min after injection and then depressed startle over the next 40 min. Both the early facilitory and later inhibitory effects were directly related to the dose. Haloperidol (0.5 mg/kg — given 30 min before) completely blocked both the early facilitory and the later depressant effect of apomorphine (3 mg/kg). Haloperidol alone had only a slight depressant effect on startle. The data support the conclusion that DA receptor stimulation enhances acoustic startle amplitude and indicate that a previous report failed to find an effect of apomorphine on startle because startle was only measured 40 min after injection.

Key words

Startle Apomorphine Haloperidol