The existence of an endogenous antiopiate system which counteracts endogenous opiate effects has been proposed. The present study set out to seek substance/s with morphine-antagonist activity in the brain and serum of morphine-tolerant rats. Cerebral extracts were partly purified on Sephadex G 25 and serum was ultrafiltered through membranes with pore diameter smaller than 0.005 micron. On the guinea pig ileum myenteric plexus longitudinal muscle a fraction of the cerebral extract and the serum ultrafiltrate in toto did increase electrically induced contractions, and antagonized the depressant effect of morphine. The serum ultrafiltrate also enhanced longitudinal smooth muscle tone. Preliminary findings suggest that levels of endogenous morphine-antagonist substance/s are higher in morphine-tolerant rats than in controls. Only cerebral extract, not serum ultrafiltrate, inhibited [3H]-naloxone binding to cerebral opiate receptors. In the guinea pig bioassay both the cerebral extract and serum ultrafiltrate antagonized, to some extent, the inhibition elicited by morphine, norepinephrine and adenosine. These observations support the existence of endogenous compound/s which may be functional antagonist/s of opiates and play a role in the development of tolerance and dependence.
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http://dx.doi.org/10.1016/s0031-6989(88)80067-5 | DOI Listing |
J Med Internet Res
January 2025
Department of Computer Science and Software Engineering, United Arab Emirates University, Al Ain, United Arab Emirates.
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Key Laboratory of Longevity and Aging-Related Disease of Chinese Ministry of Education, Center for Translational Medicine, School of Basic Medical Sciences, Guangxi Medical University, Nanning, Guangxi, China.
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Deparment of Radiation Oncology, Duke University, Durham, North Carolina, USA.
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January 2025
Department of Surgery, Neurology and Neurosurgery Unit, Federal University of Góias, Góias, Brazil.
Objectives: Balancing oxygen requirements, neurologic outcomes, and systemic complications from transfusions in traumatic brain injury (TBI) patients is challenging. This review compares liberal and restrictive transfusion strategies in TBI patients.
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Senior researcher and lecturer at the Master Specialized Physical Therapy programs at Avans+, Breda, The Netherlands.
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