Stimulation of δ1- and δ2-opioid receptors produces amnesia in mice

• Published in: European journal of pharmacology 1997-10, Vol.338 (1), p.1-6
• Main Authors: Ukai, Makoto, Takada, Akio, Sasaki, Yusuke, Kameyama, Tsutomu
• Format: Article
• Language: English
• Subjects: [ d-Ala 2]deltorphin II; [ d-Pen 2, l-Pen 5]enkephalin; Biological and medical sciences; Disorders of higher nervous function. Focal brain diseases. Central vestibular syndrome and deafness. Brain stem syndromes; Elevated plus-maze behavior; Medical sciences; Mouse; Nervous system (semeiology, syndromes); Neurology; Passive avoidance learning; Spontaneous alternation performance; δ-Opioid receptor
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(97)01310-1

The effects of intracerebroventricular administration of δ 1- and δ 2-selective opioid receptor agonists on spontaneous alternation performance, elevated plus-maze behavior and passive avoidance learning including step-down and step-through types were examined in mice. Although the δ 1-selective opioid receptor agonist, [ d-Pen2, l-Pen5]enkephalin (DPLPE) (1–10 μg) or the δ 2-selective opioid receptor agonist, [ d-Ala 2]deltorphin II (deltorphin) (1–10 μg) did not markedly affect spontaneous alternation performance or elevated plus-maze behavior, DPLPE (1, 3 and/or 10 μg) and deltorphin (3 and 10 μg) inhibited passive avoidance learning including step-down and step-through types. The δ 1-selective opioid receptor antagonist, 7-benzylidenenaltrexone (3.5 ng), and the δ 2-selective opioid receptor antagonist, naltriben (19 ng), significantly antagonized the inhibitory effects of DPLPE (3 μg) and deltorphin (3 μg) on passive avoidance learning, respectively. In contrast, DPLPE (3 μg) or deltorphin (3 μg) did not markedly influence behavioral responses induced by electroshocks during training of passive avoidance learning. Moreover, DPLPE (0.3–3 μg) or deltorphin (0.3–3 μg) failed to significantly affect the radiant heat-induced nociceptive responses. These results suggest that stimulation of δ 1- and δ 2-opioid receptors produces amnesia, depending on the learning tasks used.