Effects of two diketopiperazines, cyclo (His-Pro) and cyclo (Asp-Phe), on striatal dopamine: a microdialysis study.
The effects of two diketopiperazines, Cyclo (His-Pro) (CHP) and Cyclo (Asp-Phe) (CAP), on striatal extracellular levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were examined using in vivo microdialysis in anaesthetized rats. Treatment with neither CHP (0.1-10 mg/kg IP and 0.3 mg/kg i.v.) nor CAP (0.1-10 mg/kg IP and 10 mg/kg PO) significantly changed the efflux of DA, DOPAC, HVA, or 5-HIAA when compared to the effects of treatment with saline. Our results suggest that systemic administration of CHP or CAP alone does not modify striatal dopaminergic neurotransmission. The previous findings of enhanced DA release by systemic administration of thyrotropin releasing hormone (TRH) are probably not explained by formation of CHP from TRH.
Kaakkola
S
S
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139.
Wurtman
R J
RJ
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006719:Homovanillic Acid / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007700:Kinetics; D008297:Male; D017551:Microdialysis / Q000379:methods; D010456:Peptides, Cyclic / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D010456:Peptides, Cyclic; D010879:Piperazines; D015102:3,4-Dihydroxyphenylacetic Acid; C084152:cyclo(aspartyl-phenylalanyl); D006897:Hydroxyindoleacetic Acid; C015924:histidyl-proline diketopiperazine; D004298:Dopamine; D006719:Homovanillic Acid