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Rats were implanted with stimulating electrodes aimed either at the medial forebrain bundle-lateral hypothalamus (MFB-LH) or the midbrain-central gray (MID-GG), and were trained to lever-press for brain self-stimulation on a fixed ratio: 15 schedule of reinforcement. The dose-dependent effects of morphine (0.1-3.0 mg/kg), naloxone (0.1-30 mg/kg), and(More)
Squirrel monkeys were trained in a two-choice discrete trial avoidance task to discriminate between intramuscular injections of saline and 3.0 mg/kg of morphine. Morphine (0.1-10 mg/kg) produced a dose-related increase in the number of trials completed on the morphine-appropriate lever. The stimulus control produced by the discriminative effects of morphine(More)
These studies were aimed at investigating interactions between alcohol and nicotine on operant behavior and on locomotor activity. Independent groups of rats with electrodes in the lateral hypothalamus were trained to lever press for intracranial self-stimulation (ICSS) on either a fixed-ratio 15 (FR 15), FR 30, fixed-interval 15-second (FI 15-s) or FI 30-s(More)
p-Chloroamphetamine (PCA), a serotonin depletor, was given to rats at least 24 h prior to testing in an open field or a shock avoidance Y-maze task. In the open field PCA groups showed hypoactivity and increased defecation up to 30 days after drug administration. These same animals plus independent groups of PCA animals, showed facilitated avoidance(More)
In order to characterize the discriminative stimulus properties of cyclazocine squirrel monkeys were trained to discriminate between intramuscular injections of 0.1 mg/kg of cyclazocine and drug vehicle in a discrete-trial avoidance paradigm in which a response on one of two levers would prevent or terminate the delivery of a mild electric shock to the(More)
Rats were implanted with stimulating electrodes in the medial forebrain bundle-lateral hypothalamus, and trained in one of two brain self-stimulation (ICSS) procedures. One group of animals was trained in the auto-titration procedure which measured response rates and reinforcement thresholds for ICSS. When trained, the animals were tested with D-amphetamine(More)
Rats were implanted with stimulating electrodes aimed at the midbrain-central gray area (MID-CG) and trained to lever press for brain stimulation (ICSS) on a fixed ratio:30 (FR:30) schedule of reinforcement. When response rates were stable, animals were administered either naloxone hydrochloride, naltrexone hydrochloride, naloxone methobromide or naltrexone(More)
Rats were trained to bar-press in order to obtain electrical stimulation of the medial forebrain bundle through chronically implanted electrodes. Dose-response and time-effect curves were determined for morphine (1.0-30 mg/kg), levorphanol (0.1 to 3.0 mg/kg), methadone (0.1-3.0 mg/kg), meperidine (1.0-30 mg/kg), oxymorphone (0.03-1.0 mg/kg), and(More)