Pharmacology, biochemistry, and behavior
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Pharmacol. Biochem. Behav. · Jan 1989
The effects of amphetamine on a multitrial partial reinforcement extinction effect (PREE) in an operant chamber.
Two experiments investigated the effects of d-amphetamine (1 mg/kg) on the partial reinforcement extinction effect (PREE) in an operant chamber using a discrete multitrial procedure. Experiment 1 used a random 50% partial reinforcement (PRF) schedule. Experiment 2 used two 40% PRF schedules: one schedule maximized the number of nonreinforced trials preceding any given reinforced trial (maximum N-length of four) and the second maximized the number of N-R transitions (N-length of one). ⋯ The PREE, i.e., increased resistance to extinction of PRF as compared to CRF animals, was obtained in the random 50% PRF and the schedule maximizing N-length in both the placebo and amphetamine-treated animals. Both drug and no-drug animals failed to exhibit PREE on the schedule maximizing N-R transitions. These results show that on a PRF schedule with short intertrial intervals, amphetamine-treated animals are not impaired in their capacity to learn sequences of events and to associate the outcomes of preceding trials with subsequent consequences.
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Pharmacol. Biochem. Behav. · Oct 1988
Tolerance to tobacco smoke- and nicotine-induced analgesia in rats.
Acute exposure of male Sprague-Dawley rats to either nicotine or tobacco smoke results in analgesia as measured by tail-flick latencies. A second treatment, 24 hr after the first, failed to produce analgesia, thereby demonstrating the rapid development of tolerance. The restraint which was a necessary part of the tobacco smoke exposure also produced analgesia, although of a more transient nature and lesser magnitude than that resulting from tobacco smoke exposure. ⋯ Additionally, long-term tobacco smoke exposure resulted in an increased tail-flick latency when the animals had been withdrawn from tobacco smoke for 24 hr, suggesting the development of tolerance. The data also suggest a differential time course for the development of tolerance and dependence. This is the first report that addresses the effect of acute and chronic tobacco smoke exposure on pain sensitivity.
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Pharmacol. Biochem. Behav. · Jan 1987
Determination of cross tolerance in rat spinal cord using intrathecal infusion via sequential mini-osmotic pumps.
Continuous intrathecal (IT) infusion via ALZET mini-osmotic pumps was used to induced spinal tolerance to morphine in the rat. Naloxone (1 mg/kg IP), injected on day 3 of continuous IT morphine (10 micrograms/hr), produced mild withdrawal symptoms in all morphine-treated animals. In rats pretreated with continuous IT morphine (10 micrograms/hr) or saline, systemic morphine (2, 4, 8, 10 and 15 mg/kg IP) produced equivalent, dose-dependent antinociception using the tail-flick and paw pressure tests. ⋯ A sequential, double mini-osmotic pump technique for cross tolerance studies in rat spinal cord is described. In rats pretreated with continuous IT norepinephrine for 4 days, the antinociceptive actions of continuous IT morphine were reduced but not significantly different from saline-pretreated animals. These data suggest that morphine, injected into the spinal cord, does not produce behavioural analgesia by activation of local adrenergic systems.
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Pharmacol. Biochem. Behav. · Jan 1987
Interactions of clonidine with phencyclidine and ketamine: studies of radial maze performance and righting reflex in rats.
Rats were trained to obtain food pellets in an 8-arm radial maze until a criterion of 89% efficiency, i.e., all arms entered within 9 arm entries, was reached in 5 consecutive sessions. Decreases in efficiency caused by phencyclidine (PCP; 4 to 9 mg/kg, IP, 15 min before testing) or ketamine (25 mg/kg, IP, 5 min) were attenuated when subjects were pretreated with clonidine (0.05 mg/kg, IP, 30 min). However, significant improvements in performance in the maze were not observed when clonidine (0.05 to 0.4 mg/kg, IP) was administered 15 min after PCP (9 mg/kg, IP, 45 min). ⋯ When clonidine (0.05 mg/kg, IP) was administered 15 minutes before [3H]PCP (40 microCi/kg, IP), brain levels of tritium were reduced by 42 to 55%. The present findings do not support the suggestion that clonidine may be useful in the treatment of PCP intoxication. The data does indicate that pretreatment of surgical patients with clonidine may reduce the dose of ketamine required for anesthesia.
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Pharmacol. Biochem. Behav. · Dec 1986
Cigarette filter vent blocking: effects on smoking topography and carbon monoxide exposure.
Two studies were conducted using smokers of unventilated cigarettes to determine the effects of filter vent blocking on smoke exposure (Experiment 1) and smoking topography (Experiment 2). In both studies, subjects were exposed to ultra low yield cigarettes that had 0%, 50%, and 100% of their filter vents blocked with tape. ⋯ In Experiment 2, when puff and inhalation parameters were allowed to vary, subjects took significantly more puffs, and larger puffs from unblocked cigarettes than from completely blocked cigarettes, but CO exposure from the completely blocked cigarette was double that from the unblocked cigarette (8.96 ppm vs. 4.32 ppm). The increased number and volume of puffs taken from ultra low yield cigarettes with unblocked filter vents may be due to changes in physical characteristics of the cigarette, and not to smokers actively compensating for reduced smoke constituent yields.