Pharmacokinetic and pharmacodynamic studies of (R)-8-hydroxy-2-(di-n-propylamino)tetralin in the rat.
Racemic 8-OH-DPAT, (R,S)-8-hydroxy-2-(di-n-propylamino)tetralin, has become the prototype 5-HT1A receptor agonist. The enantiomers of 8-OH-DPAT have similar affinities to the 5-HT1A receptor, but the (R)-enantiomer is a full agonist, whereas the (S)-enantiomer is a partial agonist. This communication describes the dose- and time-response relationships of behavioural (5-HT behavioural syndrome, cage-leaving response), physiological (body temperature) and biochemical (5-HT turnover, 5-hydroxytryptophan accumulation) effects of (R)-8-OH-DPAT in rats. A high-performance liquid chromatography (HPLC)-UV method for determination of plasma and brain concentrations of (R)-8-OH-DPAT was developed, permitting studies of the pharmacokinetics of the drug. The concentrations of 8-OH-DPAT in brain were several fold higher than in plasma, and there were large variations in (R)-8-OH-DPAT concentrations between brain regions (highest in the hippocampus). (R)-8-OH-DPAT peaked in plasma at 5 min and in brain at 15 min after subcutaneous administration. The 5-HT1A behavioural syndrome peaked within 5 min after administration and disappeared after 30 min, when brain concentrations were still high. The hypothermic and biochemical responses developed gradually and were maximal at 45-60 min post injection, when both plasma and brain concentrations were declining. Thus, there was not a simple relationship between the kinetics and the dynamics of (R)-8-OH-DPAT. These results prompt further studies on the pharmacokinetics of 8-OH-DPAT within the central nervous system.
Yu
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Department of Psychiatry, Uppsala University, Sweden.
Lewander
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D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000493:pharmacokinetics* / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D007279:Injections, Subcutaneous; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000096:biosynthesis / Q000378:metabolism; D017366:Serotonin Receptor Agonists / Q000493:pharmacokinetics* / Q000494:pharmacology*; D013056:Spectrophotometry, Ultraviolet; D014018:Tissue Distribution
D017366:Serotonin Receptor Agonists; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin