Yuya Hasegawa

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In this study we investigated whether κ-opioid receptor stimulation by dynorphin A (1-13), a potent fragment of endogenous peptide, attenuated repeated stress-induced behavioral impairments in mice. In order to reduce the motivation to escape, mice were preexposed to inescapable electric footshock (day 0), and then dynorphin A (1-13) was administered to(More)
The reinforcing effects of two enkephalin analogs, Tyr-D-Ala-Gly-MePhe-NHNHCOCH2CH3.AcOH (EK-209) and Tyr-D-Met(O)-Gly-EtPhe-NHNHCOCH3.AcOH (EK-399), were assessed by means of a self-administration technique with rats. The animals were trained to self-administer an intravenous dose of morphine by a lever-press response. A test drug was substituted for(More)
The discriminative stimulus effects of two enkephalin analogs, Tyr-D-Ala-Gly-MePhe-NHNHCOCH2CH3.AcOH (EK-209) and Tyr-D-Met(O)-Gly-EtPhe-NHNHCOCH3.AcOH (EK-399), were assessed in a drug discrimination experiment with rats. The animals were trained to discriminate between the effect of morphine (3 mg/kg s.c.) and saline in a two-lever choice, water(More)
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