ABSTRACT
Each of four doses of intravenous morphine and four of intravenous heroin was tested for reinforcing efficacy, and comparisons were made among the four morphine doses, among the four heroin doses, and between morphine and heroin. Rats with venous catheters performed one daily forced run for 75 s to one of the two compartments of a spatial choice apparatus, with compartments and doses or drugs alternating over days. In each trial, the accessible compartment depended on which dose (including zero dose) or drug a rat was to receive. After 18-28 forced trials and 0 or 4 reinforced choice trials, efficacies of the different doses and drugs were measured by subsequent compartment choices. Increasing dose effects on choice were found for morphine (0.32, 1.0, 3.2, and 10.0 mg/kg intravenously) and for heroin (0.032, 0.10, 0.32, and 1.0 mg/kg intravenously). A 32:1 morphine:heroin dose ratio produced nearly equal choice. Dose effects were more evident in within-subjects experiments (each rat received two doses or two drugs) than in between-subjects experiments (each rat received one dose of one drug.
Subject(s)
Analgesics, Opioid/pharmacology , Conditioning, Operant/drug effects , Heroin/pharmacology , Morphine/pharmacology , Analgesics, Opioid/administration & dosage , Animals , Dose-Response Relationship, Drug , Heroin/administration & dosage , Injections, Intravenous , Male , Morphine/administration & dosage , Rats , Rats, Sprague-Dawley , Reinforcement, PsychologyABSTRACT
Detection of water and social play reinforcers by a place conditioning method based on instrumental conditioning was investigated in rats and compared to detection by conditioned place preference, a method currently used primarily to measure drug reinforcement. Operant place conditioning measures of reinforcement were choices between the reward and nonreward chambers during an apparatus exploration test and during a discrete-trials choice test and also, in some experiments, choices and latencies of chamber entry during training. Three of these four measures showed larger reinforcement effects than did the conditioned place preference measure of relative time spent in the reward chamber. By all reinforcement measures, conditioned place preference training was effective with water reinforcement but was ineffective with social reinforcement. Operant place conditioning was effective with both reinforcers by all measures.
Subject(s)
Conditioning, Operant , Reinforcement, Psychology , Reinforcement, Social , Animals , Male , Play and Playthings , Rats , Rats, Inbred Strains , Reaction Time , WaterABSTRACT
A new place conditioning procedure for assessing drug reinforcement, based on drug administration following chamber entry, was examined in rats and compared to conditioned place preference (which is based on chamber exposure of drugged animals). Besides relative time subsequently spent in the morphine chamber, choices between the drug and nondrug chambers were recorded during the time test and during a discrete-trials choice test. In some experiments, either choices or latencies of chamber entry were recorded during training. Most choice and latency measures showed larger reinforcement effects than did time spent. Placement training was somewhat less effective than operant place conditioning overall, but produced significant time differences and discrete-trial choices in four of five groups. With intravenous morphine, the lengthy chamber exposures generally used in conditioned place preference were unnecessary.
Subject(s)
Conditioning, Operant , Morphine , Reinforcement, Psychology , Animals , Male , Rats , Rats, Inbred StrainsABSTRACT
Studies of the audiograms of a sample of male aerospace workers to establish the relationship between hearing level and occupational exposure indicate that hearing levels at 4000 Hz of the sample are essentially the same as the general U. S. male population under age 45 but show a greater loss over age 45. Partial correlation studies relating hearing level changes to duration of employment, with age effects held constant, attribute this difference to factors other than occupational exposure. The correlation studies of the overall sample show a slight trend for increasing loss with longer durations of employment. The net effect is of no practical significance. Detailed age group correlation studies indicate that this age-related change occurs primarily in the under age 35 group, a factor of significance to hearing conservation activities.
