Tyrosine Pretreatment Alleviates Suppression of Schedule-Controlled Responding Produced by Corticotropin Releasing Factor (CRF) in Rats
NAVAL MEDICAL RESEARCH INST BETHESDA MD
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Disruption of performance observed when animals are exposed to physical stressors which deplete brain catecholamines can be alleviated by pretreatment with the catecholamine precursor tyrosine. Central administration of the stress hormone corticotropin releasing factor CRF has been shown to affect a variety of behaviors and also to potentially increase the release of central catecholamines. Since CRF-induced distruption of behavior may involve CRF-induced depletion of brain catecholamines, the present study examined whether tyrosine would alleviate suppression of schedule-controlled responding in rats resulting from ICV administration of CRF. Administration of CRF 1.0 mirco produced dose-dependent suppression of response rate and total number of earned reinforcers in rats responding on a multiple fixed-interval 60 sfixed- ratio 20 schedule for food reinforcement. Pretreatment with 200 mgkg tyrosine IP administered with ICV saline decreased response rate but did not lower total reinforcers, whereas 400 mgkg of tyrosine decreased both. Injection of 400 mgkg tyrosine reduced, but did not completely restore, CRF-induced suppression of behavior. The 200 mgkg tyrosine dose was less effective in alleviating CRF-induced suppression of performance. These data indicate that pretreatment with the catecholamine precursor tyrosine can partially ameliorate performance decrements resulting from CRF administration.
- Medicine and Medical Research