Yamatsu Kiyomi

High performance liquid chromatography (HPLC) determination of endogenous serotonin released from aggregating platelets.

High performance liquid chromatography with electrochemical detection was developed for the determination of serotonin (5-hydroxytryptamine) in rabbit platelet and plasma. A peak from tissue extract (peak a) was identified as serotonin based on retention time on the chromatogram, using a potential that gave limiting current on both a current-potential curve and gas chromatography-mass spectrum, as compared with that of authentic serotonin. For the assay of serotonin, 5-hydroxy-N-methyltryptamine was used as an internal standard and the extraction recovery of the serotonin added to the platelet-rich plasma was almost total. Furthermore, using this highly sensitive method, it has been demonstrated that the release of endogenous serotonin from rabbit platelets occurs during collagen-induced platelet aggregation but not during adenosine diphosphate-induced platelet aggregation. The procedures described should prove to be simple and useful for pharmacological and physiological investigations on the relationship between platelet aggregation and release reaction.

Physical dependence liability of dynorphin A analogs in rodents

Abstract To assess the physical dependence liability of dynorphin A analogs, mice were given repeated injections of various dynorphin A analogs twice daily for 5 days, and rats were given repeated administration of [N-methyl-Tyr 1 ,N-methyl-Arg 7 ,D-Leu 8 ] dy-norphin-A-(1–8) ethylamide (E-2078) twice daily for up to 7 weeks. Mice that had received repeated [D-Cys 2 ,Cys 5 ,N-methyl-Arg 7 , D-Leu 8 ]dynorphin-A-(1–9) amide displayed jumping behavior after subcutaneous injection of naloxonc. an opioid receptor antagonist. In contrast, the animals that had received repeated E-2078 or [N-methyl-Tyr 1 .Phe 4 (p-NO 2 ),N-methyl-Arg 7 , D-Leu 8 ]dynorphin-A-(1–8) ethylamide displayed very few jumps after naloxonc administration. Rats that had received repeated E-2078 administration did not display withdrawal signs, such as weight loss, after either abrupt withdrawal or naloxone administration. These results indicate that E-2078 and [N-methyl-Tyr 1 ,Phe 4 (p-NO 2 ),N-methyl-Arg 7 ,D-Leu 8 ]dynorphin-A-(1–8) ethylamidc may have little dependence liability and that [D-Cys 2 ,Cys 5 ,N-methyl-Arg 7 ,D-Leu 8 ]dynorphin-A-(1–9) amide can cause physical dependence.