MUTUAL POTENTIATION OF AMPHETAMINE AND AMYLOBARBITONE MEASURED BY ACTIVITY IN RATS

Rat gestation during space flight: outcomes for dams and their offspring born after return to Earth

Sprague-Dawley rats were studied to learn whether gestation in the near-zero gravity, high radiation environment of space impacts selected mammalian postnatal events. Ten rats spent days nine to twenty of pregnancy aboard the space shuttle orbiter Atlantis (STS-66). Their movement was studied shortly after return to Earth; subsequently, several of their offspring were cross-fostered and examined through postnatal day 81 (P81) for whole body growth and somatic motor development. Values for the flight animals were compared to ground-based control groups. Relative to controls, the pregnant flight rats showed a marked paucity of locomotion during the first few hours after returning to Earth. There was greater likelihood of perinatal morbidity for the offspring of flight dams when compared to the control groups. Whole body weight of surviving offspring, averaged for each group separately, showed typical sigmoidal growth curves when plotted against postnatal age. The flight group for our study had a larger ratio of female to male pups, and that was sufficient to account for the lower average daily weight gained by the flight animals when compared to the control groups. Walking was universally achieved by P13 and preceded eye opening, which was complete in all pups by P17. Thus, both of these developmental horizons were attained on schedule in the flight as well as the control rats. Characteristic changes were observed in hind limb step length and gait width as the pups grew. These patterns occurred at the same time in each group of rats. Therefore, prenatal space flight from days nine to twenty of gestation did not interfere with the establishment of normal patterns for hind paw placement during walking.

Functional relationships, previous history and the discrimination of a drug mixture in rats

These experiments aim to probe the role of different functional relationships between drugs, responses and reinforcers in studies on the discrimination of drug mixtures. Two-lever discriminations based on mixtures of (+)-amphetamine (0.4 mg/kg) plus pentobarbitone (10 mg/kg) have been compared in three groups of rats (n = 8) trained to discriminate: (i) the mixture from saline, called the AND-discrimination; (ii) either the mixture, amphetamine or pentobarbitone from saline, the OR-discrimination; (iii) the mixture from either amphetamine or pentobarbitone, the AND-OR-discrimination. The rats were trained in a two-bar operant conditioning procedure with a tandem schedule of food reinforcement. The rats trained on the AND procedure acquired the discrimination more rapidly than the rats trained on the other two procedures, but after 60 training sessions, all discriminations were performed with similar (90-94%) accuracy. In rats trained under the AND and the OR procedures, there was full generalization from the mixture to the largest doses used of either amphetamine or pentobarbitone. In contrast, in rats trained under the AND-OR procedure, there was no generalization from the mixture to any dose of either drug separately. The training procedures for the OR and the AND-OR groups were changed to AND-discrimination training; the effects of the different previous histories were found to persist for a prolonged period, despite the fact that training conditions were now the same in all groups. The effects of the drugs on rates of responding were also influenced by the previous training history. Thus, using different training procedures to alter functional relationships can substantially and persistently influence the major characteristics of a discrimination based on a mixture of drugs.

Discrimination of an amphetamine-pentobarbitone mixture by rats in an AND-OR paradigm

Rats were trained to discriminate a mixture of amphetamine plus pentobarbitone from either drug separately in a two-bar procedure with food reinforcement. Discrimination was 86% accurate after 48 sessions, and no dose of amphetamine or pentobarbitone alone produced mixture-appropriate responding. Some mixtures increased response rates whereas the same doses of each drug separately had little effect. The same rats were then trained to discriminate a mixture from saline. There was a continuing lack of discriminative response to amphetamine and only a partial response to pentobarbitone, and under these conditions mixtures did not increase overall response rates. Thus, the way rats are trained, and their previous history, can determine the characteristics of the cue obtained.

Interaction between d-amphetamine and ethanol with respect to locomotion, stereotypies, ethanol sleeping time, and the kinetics of drug elimination

The interaction between d-amphetamine and ethanol with respect to locomotor activity, stereotyped behavior, and sleeping time was investigated in rats. Ethanol 0.8 g/kg i.p. enhanced and prolonged locomotor activity produced by d-amphetamine 1 mg/kg s.c. The increased motility after 5 mg/kg d-amphetamine was not influenced by alcohol 0.8 g/kg i.p. or 3.2 g/kg orally, but slightly protracted. Stereotyped head and paw movements, as well as stereotyped licking, were distinctly strengthened and protracted by 3.2 g/kg ethanol orally. The modified d-amphetamine motility and stereotypies can be explained by alcohol-induced proloneation of the life of d-amphetomine. The effect is produced by alcohol's inhibition d-amphetamine p-hydroxylation in rat liver. After 3.2 g/kg ethanol i.p., the sleeping time of male rats amounted to 153 min. Simultaneous administration of 5 mg/kg d-amphetamine s.c. reduced the sleeping time to 84 min. This is obviously based on a central antagonism.

Interaction of cocaine with chlordiazepoxide assessed by motor activity in mice

1 Effects of a range of doses of cocaine and chlordiazepoxide given separately and as mixtures were determined on the spontaneous locomotor activity of mice. 2 Cocaine increased locomotor activity (walking) during 3 or 5 min trials in a dose-related manner. 3 Chlordiazepoxide had little effect on the total amount of locomotor activity except for depression at very high doses. A lower dose of chlordiazepoxide increased activity at the beginning of the trials only. 4 Mixtures containing certain doses of cocaine and chlordiazepoxide increased locomotor activity ot a much greater extent than cocaine alone. This high level of activity was manifested throughout 5 min trials. 5 This action of cocaine is similar to that of amphetamine.

The effects of a dexamphetamine-amylobarbitone sodium mixture on the reward value of different sensory changes

The effect of a dexamphetamine-amylobarbitone mixture (1;6.5 by weight) on a sensory-contingent bar pressing (SCBP) for different sensory changes was investigated. The aim was to examine the role of (a) reward value of contingent change per se (non drug) and (b) stimulus properties in enhanced SCBP under the drug mixture. The sensory reinforcers used were light Onset, light Offset, and sound offset combined with the light changes contemporaneously. In the first two phases the sensory stimuli were given as continuous reinforecement and in the third phase on an FR2 schedule. The results from the first two phases were consistent with the notion that the drug mixture responding under the drug was enhanced was not significantly related to the kind of sensory change. Instead, responding under the mixture was enhanced in proportion to the level of non drug responding, especially in Phase 1. However, in Phase 3, SCBP was enhanced proportionately more, to a significant extent, in those treatments receiving the combined light and sound change. It was concluded that properties of the sensory stimuli other than their reward value per se (non drug) may also be related to the extent of SCBP enhancement under the drug mixture. In particular, properties of the sound offset reinforcer appear to make it more amenable to enhancement under the drug than the two light reinforcers.

The effects of hallucinogenic drugs on maze exploration in the rat over a 24 hour period

1. The variation with clock-hour in the behaviour of naive rats in a Y-maze has been recorded.2. The number of entries recorded was highest during the light period while the number of faecal boluses was highest during the dark period. Rearing showed a biphasic periodicity.3. The responses to LSD, mescaline and amphetamine also showed significant variation with clock-hour.4. In general, amphetamine, 1.25 mg/kg, increased the number of entries and the number of rears, the effect being greatest at the end of the light period. LSD, 100 mug/kg, and mescaline, 12.5 mg/kg, decreased the number of entries and the number of rears.5. All three drugs decreased the number of faecal boluses. The possible significance of these responses in terms of an effect on the emotional state of the animals is discussed.

The effect of benzodiazepines and atropine on exploratory behaviour and motor activity of mice

1. Male albino mice were watched in red light on a tunnel board to test exploration and their motor activity was assessed in an open cage, 30 min after intraperitoneal injection of drugs.2. Atropine and methylatropine 5 or 10 mg/kg did not alter the motor activity of the mice, while chlordiazepoxide 25 or 50 mg/kg and diazepam 10 or 20 mg/kg increased the activity, especially at the lower of the two doses used.3. All the compounds used except methylatropine adversely affected the exploratory behaviour.4. When atropine 10 mg/kg was given with the benzodiazepines, the activity of the mice was reduced and exploratory behaviour was further impaired. Methylatropine did not have this effect.