Biomedical subjects

P Schnur

Publications and source records attributed to P Schnur.

29 records · Page 2Linked to original sources

PubMed1986

Effects of naloxone on morphine induced sedation and hyperactivity in the hamster.

Three experiments investigated the effects of naloxone on morphine elicited changes in hamster locomotor activity. In Experiment 1, a prior subcutaneous injection of naloxone (0.4 mg/kg) converted morphine (15 mg/kg) elicited hypoactivity into hyperactivity: Compared with saline controls, naloxone pretreated animals were hyperactive following a subcutaneous injection of morphine. Experiment 2 investigated the effects of four doses of naloxone (0, 0.04, 0.1, 0.4 mg/kg) on morphine elicited hyperactivity. Results indicated that naloxone reversal of morphine elicited hyperactivity is directly related to dose of naloxone. In Experiment 3, naloxone (0.4 mg/kg) was administered one and two hours after a morphine injection. Compared with saline controls, morphine treated animals were hypoactive for approximately 40 minutes after each of the naloxone injections. Results are discussed in terms of a modified dual-action hypothesis.

Animals↗

PubMed1985

Morphine tolerance and sensitization in the hamster.

The effects of morphine on hamster locomotor activity were studied. Repeated administration of morphine in doses from 5 to 40 mg/kg produced systematic changes in morphine's biphasic time effect pattern: morphine's sedative effects decreased (tolerance) while morphine's excitatory effects increased (sensitization). These results extend findings of behavioral tolerance and sensitization in the hamster to a range of higher doses than those used previously.

Animals↗

PubMed1984

Locomotor activity and opiate effects in male and female hamsters.

Locomotor activity of golden Syrian hamsters was investigated in three experiments. In Experiment 1, running wheel activity of male and female hamsters was compared under the following conditions: no injection, saline injection, morphine injection (15 mg/kg) and naltrexone injection (1 mg/kg). During two hour test sessions, females maintained high levels of activity, whereas males slowed down considerably during the second hour. The difference between males and females was evident under all conditions except following morphine which produced a biphasic time-effect pattern in both sexes. Naltrexone, however, had no detectable effects on either males or females. Experiment 2 investigated the effects of four doses of naltrexone (0.3, 1, 3, 10 mg/kg) on hamster locomotion. Results indicated that none of the doses tested had an effect. Experiment 3 demonstrated that a 1 mg/kg dose of naltrexone antagonizes two of morphine's (15 mg/kg) effects on activity. First, naltrexone partially blocked morphine elicited sedation. Second, naltrexone blocked the increase in activity that characterizes recovery from morphine.

Analysis of Variance↗

PubMed1983

Tolerance and sensitization to the biphasic effects of low doses of morphine in the hamster.

Two experiments investigated the dose and time related effects of morphine sulfate on wheel running behavior in golden Syrian hamsters. In Experiment 1, within-subject comparisons were made of the acute effects of 5, 20, and 40 mg/kg doses of morphine sulfate on running wheel activity. Compared with saline, morphine produced a dose related decrease in activity followed by a dose related recovery. At the lowest dose, the time effect curve was biphasic, with sustained hyperactivity following the recovery. In Experiment 2, the effects of low doses of morphine sulfate (0.5, 1.0, 2.5, 5.0 mg/kg) on running wheel activity were monitored for three days. Biphasic time effect patterns were evident at each dose: An initial period of hypoactivity was followed by recovery and subsequent hyperactivity. Moreover, repeated administration produced both tolerance and sensitization to morphine's effects on activity. Implications for mechanisms underlying the biphasic response pattern are discussed.

Animals↗

PubMed1983

Biphasic effects of morphine on locomotor activity in hamsters.

Two experiments investigated the dose and time related effects of morphine sulfate on the running wheel activity of golden Syrian hamsters. Compared with saline controls, a low dose (5 mg/kg) increased locomotor activity, whereas high doses (10, 20 and 40 mg/kg) produced an initial dose-related depression in activity, a gradual dose-related recovery and finally a period of hyperactivity. The results are discussed in terms of similar biphasic effects of morphine observed in rats.

Animals↗

PubMed1978

Comments on "Studies of the interaction of psychological and pharmacological determinants of smoking" by Schachter et al.

The work by Schachter and his colleagues on the psychological and pharmacological determinants of smoking is reviewed. The experiemental procedures are critically examined, and some are judged to be in violation of ethical standards for the conduct of research with human participants. Questions are raised concerning matters of informed consent, the description of debriefing procedures, and use of the college classroom as a psychological laboratory.

Behavioral Research↗

PubMed1975

The number of trials of compound conditioning: its effect on latent inhibition in rats.

Two experiments interspersed nonreinforced tests for the strength of the preexposed and nonpreexposed elements of a compound CS throughout conditioning. The nonreinforced exposures and the conditioning trials were superimposed on an appetitive operant baseline, and conditioned suppression of the rats' bar pressing was the dependent variable. In both experiments, the preexposed element failed to suppress responding and failed to gain strength over trials. The nonpreexposed element at first suppressed responding completely but gradually lost control of responding, even while the compound continued to suppress responding asymptotically. The results are discussed in terms of 'loss of salience' and 'discrimination' hypotheses.

Animals↗

PubMed1971