Effects of Amphetamine on Locomotor Activity

1 January 2017

Hypothesis Stewart and Badiani (1993) show in their research that tolerance may develop to a particular effect of a drug whilst at the same time also become sensitised to another effect – could be a little more clearer here. The study also found that tolerance and sensitization can be altered when given in different settings, for example the expectation of the drug and the reason for taking the drug.

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Another piece of literature that shows sensitization is the research done by Badiani, Browman, and Robinson (1994). Not only does it look at the sensitization of a drug, but also how when taken in a novel environment compared to a home environment can change how much the body has been sensitized. The study found that when the subjects were administrated the drugs in a novel environment, the rate of sensitization was significantly higher – going slightly off topic here. Perhaps should have focussed a lot more on the effect of increased doses of a drug on sensitisation.

Lastly, Cado, Bjijou and Stinus (1995) did research on evidence of a complete independence of the neurobiological substrates for the induction and expression of behavioural sensitization to amphetamine. They found that repeating the amphetamine administration in rats, the more behavioural sensitization would occur. This was shown in the rats increased locomotor activity after the drug had been administrated. These previous pieces of literature all show some sort of sensitization to a repeated, or increased amount of a drug. What is the aim?

Always state this first before the hypothesis The first hypothesis is that the rat will have less locomotor activity when given dosages of saline then the rats who are given the amphetamine i. e. there will be an interaction between saline and drug groups. The second hypothesis is that the subjects who were pretreated with amphetamine will produce more locomotor activity with the dosage of amphetamine on day 8 of the experiment. This shows that the rats who have been given the amphetamine during day 1-5 (pretreated) will be more sensitized to the drug (in day 8) than the rats who were only given saline.

Method Design Experimental design was used, with a single independent variable, (treated and not treated rats, as well as the dosage given) and dependent variable (the total amount of locomotor actvity made by the rat on each of the days tested). Subjects The subjects were Sprague-Dawley male rats, weighing between 250-350g. The subjects were bred at Victoria Univeristy in Wellington, New Zealand and were initially housed in pairs and then later housed singly in a temperature- (21? C) and humidity- (55%) controlled room.

The colony was maintained on a 12-hr light/dark cycle with lights on at 0700. Food and water were available ad libitum except during testing periods. Laboratory animal care principles of the Victoria University of Wellington Animal Breeding Facility were followed, and the Victoria University of Wellington Animal Ethics Committee approved all protocols Apparatus Eight open field chambers (450mm x 450mm; Med Associates (ENV-515) Vermont, USA) equipped with four banks of 16 photocells on each of the internal walls of the chamber were used to measure horizontal locomotion.

Photocells were set at 25mm above the floor of the chamber and spaced evenly at 25mm centres around the periphery. The open field boxes were interfaced with a computer and data were obtained using Med Associates software. Each activity chamber was enclosed in sound attenuating boxes (Med associates; Vermont USA). A beam ‘box’ was pre-set encompassing a 3 x 3 beam square (50mm x 50mm). Movement outside of this ‘box’ broke the beams and constituted one locomotor count. Procedure All testing was conducted during the light cycle.

A red house light was illuminated during testing and white noise was also continually present to mask extraneous disturbances. Prior to and after each locomotor activity test, the chamber interiors were cleaned and wiped with Virkon ‘S’ disinfectant (Southern Veterinary Supplies, NZ). Rats were housed individually and were weighed and handled daily, one week prior to the commencement of all experiments Days 1-5: Rats were transported daily from their home cages to the locomotor activity room and placed into the middle of the open field chambers.

Locomotor activity was recorded for 30 minutes, recording was then paused while rats were administered drug or saline and activity was recorded for an additional 60 minutes. Day 8 Rats were transported from their home cages to the locomotor activity room and placed into the middle of the open field chambers. Locomotor activity was recorded for 30 minutes, recording was then paused while rats were administered drug or saline. Total locomotor activity counts were used for the remaining 60 minutes of testing. Results This study was a between group test analysis of variance.

ANOVA was used to compare the average amount of locomotor acitivity by the rats who had been given saline as well as amphetamine, and then the average amount of locomotor activity produced by the rats on day 8 to see if the rats had been sensitised to the repeated usage of the drug. The ANOVA showed F(3,64) = 4. 523, p=. 006 with subjects who had been pretreated with saline (M=1876. 71, SD=2065. 86) which had a significantly lower amount of locomotor activity compared to the subjects who had been treated with amphetamine (M=5335. 42, SD=5172. 9). – This sentence could be presented better. Please refer to the SPSS purple text book for a sample.

There’s no mention of the effect of dose nor the effect of pre-treatment. You’ve only mentioned the main interaction between pre-treatment and dose. A Turky post-hoc test was used to find the interactions between the dosages administered. This showed a statistical significance between pretreatment of saline and treatment on day 8 of amphetamine, while the higher the dosage given of amphetamine in the pretreatment, the higher the mean amount of ocomotor activity on day 8. – I’m not sure what you mean by this? It was a strictly between groups design and this sounds like you’re assuming that the rats that were pre-treated with saline were administered with the drug on testing day when they weren’t. What did the post-hoc tests say about the individual doses?? This shows that the hypotheses were both correct. The amount of locomotor activity did increase when the subjects were given amphetamine, this is also shown in the Badiani, Browman, and Robinson (1994) research.

Their data showed a indicated sensitization to the drugs, also the rate of sensitization became higher when put in a novel environment. The results given in the current study, do show the effect of pretreatment using the drug amphetamine, the higher the dosage of amphetamine, the more locomotor activity was recorded on day 8. This shows sensitisation was a factor, on day 1-5 rats were treated with different dosages of the drug and saline. The increased amount of drug showed on day 8 when the locomotor activity was at its highest rate.

Other studies, such as Cador, Bjijou and Stinus (1995) also show that repeated administration of amphetamine increases behavioural sensitization, which is shown by the amount of locomotor activity produced by the rats after the dosage. – The interpretation could have been outlined more clearly. Also there should have been a separate discussion section to discuss the results back to the hypothesis.

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