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Repeated treatments with 7-OH-DPAT: context-independent behavioral sensitization and conditioned hyperactivity
B A Mattingly1, L L Rice, M Langfels
1Department of Psychology, Morehead State University, KY 40351-1689, USA.
Pharmacology, Biochemistry, and Behavior
|February 15, 2000
Summary
Behavioral sensitization to dopamine D3 receptor agonist 7-OH-DPAT is not context-dependent in rats. This suggests that conditioned hyperactivity from dopamine agonists may involve different mechanisms than previously thought.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Behavioral sensitization, a form of neuroplasticity, is often context-dependent with dopamine agonists.
- Previous studies indicated context dependency for D2-type dopamine agonists like bromocriptine and quinpirole.
Purpose of the Study:
- To investigate whether behavioral sensitization to the dopamine D3 receptor agonist 7-OH-DPAT is context-dependent.
- To differentiate the mechanisms of sensitization to D3 agonists from those of D2 agonists.
Main Methods:
- Male Wistar rats received repeated injections of 7-OH-DPAT or vehicle in a paired or unpaired manner relative to activity testing.
- Locomotor activity was measured in photocell arenas.
- Sensitization was assessed via a challenge injection of 7-OH-DPAT.
Main Results:
- The paired 7-OH-DPAT group showed progressively increased locomotor activity.
- The paired group exhibited significantly higher activity than controls or the unpaired group during vehicle tests, indicating some conditioning.
- Both paired and unpaired 7-OH-DPAT groups showed equal, significant sensitization after a challenge injection, irrespective of context.
Conclusions:
- The expression of behavioral sensitization to 7-OH-DPAT is not context-dependent.
- Conditioned hyperactivity observed with dopamine agonists may not rely on the same associative mechanisms responsible for sensitization.