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Conditioned apomorphine-induced turning in 6-OHDA-lesioned rats
J L Hudson1, C S Fong, S J Boyson
1Department of Pharmacology, University of Colorado Health Sciences Center, Denver 80262.
Pharmacology, Biochemistry, and Behavior
|September 1, 1994
Summary
The first peak in apomorphine-induced turning behavior in rats may stem from a conditioned response, not solely the nigrostriatal dopamine system. This conditioned turning behavior emerges with repeated testing, independent of dopaminergic input.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Parkinson's Disease Research
Background:
- Apomorphine-induced turning is a model for assessing nigrostriatal denervation and graft reinnervation.
- The first peak of turning behavior is resistant to dopaminergic treatments, suggesting non-dopaminergic origins.
Purpose of the Study:
- To investigate if the first peak of apomorphine-induced turning is a conditioned response.
- To differentiate between dopaminergic and conditioned factors influencing rotational behavior.
Main Methods:
- Unilateral 6-hydroxydopamine (6-OHDA) lesions in Fisher 344 rats.
- Repeated apomorphine administration in freely moving and restrained conditions.
- Quantification of rotational behavior.
Main Results:
- The first peak of turning was absent in the initial unrestrained apomorphine trial.
- The first peak appeared in subsequent trials, supporting a conditioned response.
- Restrained rats and controls also developed the first peak upon subsequent unrestrained trials.
Conclusions:
- The first peak of apomorphine-induced turning behavior is likely a conditioned response.
- This finding has implications for interpreting rotational behavior in models of Parkinson's disease.
- Conditioning plays a significant role in drug-induced behavioral responses.