caa a22 4500 465737145 CHVBK 20180323111758.0 cr unu---uuuuu 170327e19901101xx s 000 0 eng 10.1007/BF02244095 doi (NATIONALLICENCE)springer-10.1007/BF02244095 Acute morphine lowers brain stimulation reward thresholds in rats with depressed or elevated response rates [Elektronische Daten] [B. Hine, M. Lopez] The positively-reinforcing effect of acute morphine sulfate (MS) administration was assessed by concurrent rate-dependent and rate-independent measures of brain stimulation reward in male rats. An acute 4 mg/kg MS injection produced a rapid, statistically-significant decrease in reward threshold of 28.5%, when compared with saline control values, 45 min after injection. Response rates for brain stimulation delivery decreased by 60.6%, when compared with saline values during the period of maximum threshold change. Other animals, injected with an acute 1 mg/kg MS dose, exhibited significant threshold decreases (21.5%), relative to changes in saline values that occurred in a prior session, and response-rate increases of 23.1%, relative to saline-session changes, when the data were recorded 40 min after injection. The findings reported here demonstrate that the decreases in reward threshold produced by acute morphine administration are independent of the response-rate changes that occur and also support the idea that morphine's rewarding effect may be independent of the behavioral inhibition or activation that can result from the effects of different morphine doses. Springer-Verlag, 1990 Morphine nationallicence Brain stimulation reward nationallicence Reward threshold nationallicence Intracranial self-stimulation nationallicence Response rate nationallicence Hine B. Department of Pharmaceutical Sciences, School of Pharmacy, University of Puerto Rico, Medical Sciences Campus, GPO Box 5067, 00936, San Juan, PR, USA aut Lopez M. Department of Pharmaceutical Sciences, School of Pharmacy, University of Puerto Rico, Medical Sciences Campus, GPO Box 5067, 00936, San Juan, PR, USA aut Psychopharmacology Springer-Verlag 102/3(1990-11-01), 309-311 0033-3158 102:3<309 1990 102 213 https://doi.org/10.1007/BF02244095 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02244095 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Hine B. Department of Pharmaceutical Sciences, School of Pharmacy, University of Puerto Rico, Medical Sciences Campus, GPO Box 5067, 00936, San Juan, PR, USA aut NATIONALLICENCE 700 1- Lopez M. Department of Pharmaceutical Sciences, School of Pharmacy, University of Puerto Rico, Medical Sciences Campus, GPO Box 5067, 00936, San Juan, PR, USA aut NATIONALLICENCE 773 0- Psychopharmacology Springer-Verlag 102/3(1990-11-01), 309-311 0033-3158 102:3<309 1990 102 213 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer