Title: Single-dose tolerance to antinociception, and physical dependence oin β-endorphin in mice
Abstract: β-Endorphin (B-EN) injected intracerebroventricularly in mice produced a rapid onset, dose-dependent antinociceptive effect. The median analgesic dose (AD50) 30 min following administration was found to be 270 ng/mouse (3.7 nmoles/kg). B-En produced an acute, single-dose tolerance development was demonstrable with doses twice or more the AD50. Tolerance was maximal at about 12 h following the priming dose and disappeared within 48 h. Tolerance was maximal at about 12 h following the priming dose and disappeared within 48 h. Tolerance was accompanied by some degree of physical dependence as noted by signs of naxolone-precipitated withdrawal similar to those elicitable in the morphine-dependent state. Tolerance development to B-EN was blocked by the simultaneous adminstration of naloxone and also by pretreatment with 0.35 mg/kg actinomycin D or 30mg/kg cycloheximide 30 min before B-EN. It appears that single-dose tolerance to B-En was initiated by processes similar to those involved with tolerance resulting from chronic adminsitration of morphine.
Publication Year: 1978
Publication Date: 1978-11-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 31
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