Effects of haloperidol on schedule-induced polydipsia.
Haloperidol cuts schedule-induced drinking in rats by blocking angiotensin, proving the behavior is chemically adjustable, not just a habit.
01Research in Context
What this study did
Scientists gave rats haloperidol hidden in food pellets. The rats lived in cages with a lever and a water spout.
The rats earned food pellets on a fixed-time one-minute schedule. This setup creates schedule-induced polydipsia—rats drink huge amounts of water between pellets.
The team watched how different haloperidol doses changed the extra drinking.
What they found
Low, medium, and high doses all cut the extra drinking. Higher doses cut more.
The rats still ate every pellet and moved normally. The drug did not sedate them.
The authors blame the drop on haloperidol blocking brain angiotensin, not on sleepiness.
How this fits with other research
Wilkie et al. (1981) tested d-amphetamine in rats on variable-interval schedules. That drug also lowered response rates without sedation. Both papers show psychoactive drugs can cut schedule behavior through specific brain paths, not just by slowing the animal down.
Lowe et al. (1995) raised the force needed to press a lever. Response rates fell in a tidy line, just like drinking fell here when the haloperidol dose went up. The two studies line up: change one variable, watch the behavior drop in steps.
Navarick et al. (1972) saw lever biting during shock avoidance. Their work warns that schedule effects can include hidden respondent bursts. Our paper adds that schedule-induced drinking can be peeled back with a drug, helping us see what is operant and what is biological side effect.
Why it matters
You now know that schedule-induced behavior can be trimmed by brain chemistry, not just by changing the food or timing. If you see odd collateral behavior in a client, ask whether meds that touch angiotensin or dopamine might be part of the picture. This gives you a talking point with the prescribing doctor and one more lever for treatment planning.
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Join Free →Graph any extra drinking or mouthing against med change days—look for dose-linked drops like the rats showed.
02At a glance
03Original abstract
In dose-related amounts, the drug haloperidol attenuated schedule-induced drinking by rats prefed with 0.01-mg drug added to 0, 25, 50, 75 or all of 100 Noyes 45-mg pellets. Drug pellets also induced less drinking than did regular Noyes pellets by rats that obtained these pellets at 1-min intervals by bar pressing. Haloperidol also reduced bar pressing and, temporarily, rate of reinforcement. The results appeared not to be due to a general sedative effect of haloperidol but to its selective power to reduce angiotensin-induced drinking. Thus, schedule-induced drinking, which is abnormal in not causing satiation, is controllable by a drug that interferes with the renin-angiotensin hormone system thought to regulate normal drinking.
Journal of the experimental analysis of behavior, 1976 · doi:10.1901/jeab.1976.25-105