Combined action of diazepam and d-amphetamine on fixed-interval performance in cats.
Mixing diazepam with amphetamine can either magnify or reverse amphetamine's effect on schedule-controlled behavior, so dose changes need close watching.
01Research in Context
What this study did
Researchers gave cats both diazepam and d-amphetamine. They watched how the drug mix changed lever pressing on a fixed-interval schedule. Each cat served as its own control, so dose effects were compared within the same animal.
What they found
The drug pair did not simply add up. Low diazepam plus amphetamine could double the cat's response rate. Higher diazepam could later cancel or reverse that boost. The final pattern depended on the exact dose of each drug.
How this fits with other research
Hymowitz (1981) extends these results. That team gave rats diazepam alone after shock had slowed their pressing. Diazepam restored the lost responses, showing the drug can raise rates even without amphetamine.
McMillan (1979) seems to disagree. Rats given only d-amphetamine pressed less and licked less on the same FI schedule. Sanders (1969) shows that adding diazepam can flip that decrease into an increase, so the papers clash only until you factor in the second drug.
Goldman et al. (1979) saw methamphetamine plus scopolamine increase lever switching while overall rate fell. The 1969 cat data mirror that complexity: stimulant–sedative mixes can re-shape, not just depress, operant output.
Why it matters
If you consult on cases where clients take both a stimulant and a benzodiazepine, expect non-linear behavior change. A small dose tweak might swing a client from lethargic to hyperactive. Track response patterns session-by-session and share the data with the prescribing doctor.
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Join Free →Graph each session's response rate separately for morning and afternoon if the med schedule changes—look for sudden rate shifts after dose adjustments.
02At a glance
03Original abstract
Cats trained under a fixed-interval 5-min schedule of milk presentation were injected with diazepam, amphetamine, and combinations of amphetamine and diazepam. Diazepam increased overall response rate as a function of the dose and disrupted the temporal pattern of responding. Low doses of amphetamine (0.5 mg/kg) usually increased the response rate; higher doses (1 to 2 mg/kg) either decreased the response rate or had little effect. Amphetamine always disrupted the temporal pattern of responding, even though it did not affect the overall rate. When doses of amphetamine that increased the response rate or left it unchanged were combined with diazepam, a potentiated increase in response rate occurred. When doses of amphetamine that decreased the response rate were combined with diazepam, the amphetamine-induced rate decreases were reversed at least partially. Less clear potentiation of disruption of the temporal pattern of responding was observed when amphetamine and diazepam were combined.
Journal of the experimental analysis of behavior, 1969 · doi:10.1901/jeab.1969.12-989