Neuroscience letters
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Neuroscience letters · Dec 2002
Comparative StudyIntervention with environmental enrichment after experimental brain trauma enhances cognitive recovery in male but not female rats.
Environmental enrichment (EE) has been repeatedly shown to affect multiple aspects of brain function, and is known to enhance cognitive recovery after experimental traumatic brain injury (TBI) in males. However, the impact of gender on how EE affects behavioral performance after experimental TBI have not been studied. Male and normally cycling female Sprague-Dawley rats underwent controlled cortical impact injury or sham surgery and then were placed in either a standard or enriched housing environment. ⋯ Placement in an EE after TBI enhanced spatial memory performance in male but not female rats. EE did not impact motor performance in this setting. These findings have gender specific implications for how to approach and evaluate treatments and interventions after TBI.
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Neuroscience letters · Dec 2002
Comparative StudyCross-tolerance between the different mu-opioid receptor agonists endomorphin-1, endomorphin-2 and morphine at the spinal level in the rat.
In the present study we investigated the development of tolerance to an antinociceptive effect after intrathecal administration of endomorphin-1, endomorphin-2 and morphine in tail-flick and paw pressure tests. We also assessed cross-tolerance between the antinociceptive effects of the two endogenous mu-opioid receptor agonists - endomorphins and morphine. The tolerance developed on day 3 after i.th. injection of both endomorphins, endomorphin-2 (18, 36 nmol), endomorphin-1 (16 nmol). ⋯ In contrast, no cross-tolerance was observed after administration of endomorphin-2 in rats tolerant to endomorphin-1. In rats tolerant to endomorphin-2, the antinociceptive effect of morphine and endomorphin-1 was attenuated in both the tests used. Our results suggest that the three ligands of mu-opioid receptors probably act via different subtypes of the mu-opioid receptor.