caa a22 4500 465739288 CHVBK 20180323111804.0 cr unu---uuuuu 170327e19900401xx s 000 0 eng 10.1007/BF02243995 doi (NATIONALLICENCE)springer-10.1007/BF02243995 Tolerance and dependence after continuous morphine infusion from osmotic pumps measured by operant responding in rats [Elektronische Daten] [Jill Adams, Stephen Holtzman] Food-deprived rats were trained to lever-press on a fixed interval 3-min schedule of food presentation. Using a cumulative dosing procedure, morphine and naltrexone were tested weekly for effects on rates of responding. A separate group of subjects was tested weekly for morphine analgesia using the tail-flick assay. Chronic morphine infusion (10 mg/kg/day, SC, from a 4-week osmotic pump) induced tolerance to the rate-decreasing and analgesic effects of morphine as demonstrated by a more than 4-fold increase in the morphine ED50s for both of these effects, relative to those of predependent rats. Physical dependence was evidenced in the operant procedure by increased sensitivity to the rate-decreasing effects of the opioid antagonist, naltrexone, such that the ED50 for naltrexone was 5000 times lower than it was in predependent animals. In addition, marked weight loss was observed over the 2-h naltrexone test session. The degree of tolerance was a function of both the length of chronic administration and of the maintenance dose and was of a similar magnitude for operant responding and analgesia. Further, the degree of tolerance and dependence was comparable to that observed in other studies that used different methods of chronic drug administration. Thus, osmotic pumps provide a convenient and effective alternative for chronic drug administration in behavioral studies. Springer-Verlag, 1990 Opioid nationallicence Morphine nationallicence Tolerance nationallicence Physical dependence nationallicence Analgesia nationallicence Osmotic pump nationallicence Naltrexone nationallicence Operant behavior nationallicence Adams Jill Department of Pharmacology, Emory University School of Medicine, 30322, Atlanta, GA, USA aut Holtzman Stephen Department of Pharmacology, Emory University School of Medicine, 30322, Atlanta, GA, USA aut Psychopharmacology Springer-Verlag 100/4(1990-04-01), 451-458 0033-3158 100:4<451 1990 100 213 https://doi.org/10.1007/BF02243995 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02243995 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Adams Jill Department of Pharmacology, Emory University School of Medicine, 30322, Atlanta, GA, USA aut NATIONALLICENCE 700 1- Holtzman Stephen Department of Pharmacology, Emory University School of Medicine, 30322, Atlanta, GA, USA aut NATIONALLICENCE 773 0- Psychopharmacology Springer-Verlag 100/4(1990-04-01), 451-458 0033-3158 100:4<451 1990 100 213 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer