Pharmacology, biochemistry, and behavior
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Pharmacol. Biochem. Behav. · Jul 1990
Scopolamine produces locomotor stereotypy in an open field but apomorphine does not.
Both dopaminergic and nondopaminergic drugs produce hyperlocomotion in rats. Dopaminergic drugs also produce focused stereotypy (absence of locomotion and intense sniffing or licking/biting of a restricted area of the environment). Some drugs produce repetitive routes of locomotion; this phenomenon might represent a combination of hyperlocomotion and stereotypy. ⋯ Scopolamine (0.5 and 2.0 mg/kg) produced locomotor stereotypy at both doses. Apomorphine (1.0, 2.0, and 3.0 mg/kg) failed to reliably produce locomotor stereotypy. Thus, there is not necessarily a relationship between the ability of a drug to produce focused stereotypy and the ability of the drug to produce locomotor stereotypy.
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Pharmacol. Biochem. Behav. · Jul 1990
Butorphanol's efficacy at mu and kappa opioid receptors: inferences based on the schedule-controlled behavior of nontolerant and morphine-tolerant rats and on the responding of rats under a drug discrimination procedure.
The purpose of the present investigation was to characterize the mu agonist and kappa antagonist effects of the mixed opioid agonist/antagonist butorphanol. To this end, the effects of butorphanol were examined: 1) alone and in combination with the kappa agonist bremazocine in nontolerant and morphine-tolerant rats responding under a fixed-ratio 30 (FR30) schedule of food presentation, and 2) in rats trained to discriminate 10 mg/kg morphine from saline. Prior to the induction of morphine tolerance, morphine, bremazocine and butorphanol produced dose-dependent decreases in rate of responding under the FR30. ⋯ In these morphine-tolerant rats, butorphanol produced a dose-dependent antagonism of bremazocine's rate-decreasing effects. In rats trained to discriminate morphine from saline, butorphanol substituted completely for the morphine stimulus. Unlike morphine, which produced its stimulus effects only at doses that decreased rate of responding, butorphanol substituted for the morphine stimulus at doses that had little or no effect on rate of responding.(ABSTRACT TRUNCATED AT 250 WORDS)
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Pharmacol. Biochem. Behav. · Jun 1990
Potentiating effect of morphine upon d-methamphetamine-induced hyperthermia in mice. Effects of naloxone and haloperidol.
We have examined changes in rectal temperature of mice after subcutaneous administrations of d-methamphetamine alone or methamphetamine plus morphine. Methamphetamine 5 mg/kg produced slight hyperthermia, while simultaneous administration of morphine (25-100 mg/kg), which alone produces hypothermia, potentiated markedly the increase in body temperature by methamphetamine. ⋯ When animals were pretreated with 2.5 mg/kg haloperidol, hyperthermia due to methamphetamine alone was completely abolished, while that due to methamphetamine plus morphine was still observed. These results showed that dopamine may be implicated in methamphetamine hyperthermia and a haloperidol-nonsensitive mechanism may be involved in the methamphetamine-morphine hyperthermia.
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Pharmacol. Biochem. Behav. · Jul 1989
Characteristics of radiation-induced performance changes in bar-press avoidance with and without a preshock warning cue.
Rats were trained to perform one of three tasks in which responses on a lever delayed the onset of footshock for 20 sec. One task provided a warning tone beginning 15 sec after the last response on the lever and lasting for 5 sec just prior to the presentation of a shock (fixed-interval signalled avoidance), while a second task provided no external cues (unsignalled avoidance). The third task was similar to the fixed-interval signalled avoidance task, except that the warning tone preceding shock began at varying intervals after the last response on the lever (variable-interval signalled avoidance). ⋯ The animals not provided cues also experienced more shocks during the first 10 min after irradiation but were relatively less affected in performing the task. Response rates on the bar and the patterns of responding on these tasks were not significantly different after irradiation, except that animals responded after the onset of shock more often after irradiation than before. These results suggest that rats will continue to effectively use task related cues after irradiation, but that the relative degree of behavioral decrement may depend on the initial level of performance or possibly the complexity of the task.
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Pharmacol. Biochem. Behav. · Feb 1989
Stressor predictability and rat brain noradrenaline metabolism.
This study examined the effects of stressor predictability on regional rat brain noradrenaline (NA) turnover, by measuring levels of a principal metabolite of NA (3-methoxy-4-hydroxyphenylethyleneglycol sulfate, MHPG-SO4). Male Wistar rats were exposed to one of three shock conditions for 19 hr: nonshock, signalled, and unsignalled shocks. Rats in the shock conditions received shock (1.2 mA intensity, 2 sec duration) on a 2.5 min variable time (VT) either preceded by a 12-sec, 10-W light signal (signal-shock interval of 10 sec) or not preceded by this signal. ⋯ Moreover, the unpredictably shocked rats exhibited greater elevations in MHPG-SO4 levels in the hypothalamus, amygdala, and thalamus, as well as in plasma corticosterone levels, when compared to the predictably shocked rats. These results are consistent with previous reports showing that unsignalled shock induced extensive somatic effects in comparison to signalled shock. The present study suggests that the presence of a signal attenuates the extent of NA release in some brain regions resulting from irregular inescapable shock stress.