ANY-maze Help > The ANY-maze reference > The Protocol page > The elements of a protocol > Additional information > Treatment doses > Specifying the concentration of the treatments that you will use

Specifying the concentration of the treatments that you will use

In brief

If you specify that ANY-maze should calculate the volume of the treatment that you should administer to the animals, then you will be asked how ANY-maze should determine the concentration of the treatments.

Details

There are three options for how ANY-maze will determine the concentration of the treatments:

The volume administered should be approximately the same for all treatment groups

This option is the one you're most likely to want to use, as it ensures that the volume administered (usually injected) will be roughly the same for all the animals, irrespective of the treatment they receive.

The easiest way to understand this option is through an example. Let's imagine you have two treatment groups, one will receive 1mg/kg of your drug and the other will receive 5mg/kg. If you made up a solution in which you had dissolved 100mg of your drug in 1 litre of water, then a 100g animal in the first group would need to be injected with 1ml of the solution and a 100g animal in the second group would need to injected with 5ml. Clearly these are not similar volumes and the fact that one group is being injected with 5x the volume of the other group, may confound your results.

So, rather than making up a single solution of your drug, you might choose to make two, one containing 50mg/litre and the other containing 250mg/litre. Now if you injected a 100g animal from the first group with 2ml of the first solution, the animal would receive 0.1g of the drug (i.e. 1mg/kg of its body weight), and if you injected a 100g animal from the second group with 2ml of the second solution, the animal would receive 0.5mg of the drug (i.e. 5mg/kg of its body weight), exactly as we wanted - and both animals would have received the same volume.

If you want to work in this way, then you can simply tell ANY-maze what the target volume you want to inject is (2ml in the above example), and what the approximate weight of the animals is (100g in the example). It will then calculate the concentrations for the drug solutions and show these to you on the Experiment page - see figure 1.

Figure 1. When you want to administer approximately the same volume to all the treatment groups, ANY-maze will calculate the appropriate concentration of each treatment and show it to you in the Treatments spreadsheet on the Experiment page.

Note that this does require that all the animals are roughly the same weight. For example, if in the example above, the animal from the first group actually weighed 150g (not 100g) then we'd have needed to inject it with 3ml of our drug solution. Clearly we could change the solution to be 75mg/litre and then the animal would receive 2ml, but if we had another animal in the group that weighs 100g, it would then need to be injected with 1.33ml!

The point is that all the animals need to be roughly the same weight and then they'll all receive roughly the same volume. For example, if the animals in your experiment actually vary in weight from 90g to 120g and you told ANY-maze that you want to inject them with 5ml and that their average weight is 105g, then they would actually receive something between 4.3ml and 5.7ml, but that's probably close enough to 5ml in all cases that the volume injected would not be sufficiently different between the animals to confound your results.

The concentration will be different for each treatment group

This option is much simpler, as you just enter the concentration of the treatment for each treatment group. You do this on the Experiment page - see figure 2.

Figure 1. When you want to use a different concentration of your treatment for each treatment group, then ANY-maze will include a 'Concentration' column in the Treatments spreadsheet on the Experiment page, where you can enter the concentrations.

The concentration will be the same for all treatment groups

The final option is simpler still. You'll just use a single concentration for all the treatment groups.

Specifying the volume to inject for control groups

If you choose either the second or third option, then there is a small issue to address relating to control groups. Let's imagine that you intend to treat some of your animals with 1mg/Kg of drug, some with 5mg/kg of drug and some with saline. So ANY-maze will calculate the volume to administer for the two drug groups based on the concentration of the solution (which you'll have specified) and the animals' weights. But the saline animals will have no 'concentration' for the solution, so what volume should they receive? A simple answer would be to just specify some fixed volume, perhaps 3ml. This would work, but it would mean that ANY-maze would then tell the experimenter to inject a volume it has calculated, based on the animal's weight, for each animal in the drug groups (so these would be varying numbers, as the animals' weights will vary) and exactly 3ml for all saline animals. If you're trying to run the experiment blind, then the fact that all the animals in one group are being treated with an identical volume, irrespective of the animal's weight, would be a bit of a giveaway that these animals are the controls.

To address this you need to enter the volume you'd like to administer to the control animals, 3ml in my example, and the weight of animal that should receive this volume - for example 100g. Then ANY-maze will adjust the volume based on the animals' actual weights - so an animal weighing 120g would receive 3.6ml. This would mean that the control animals would not all receive an identical volume (unless they all happen to have identical weights) and this would make it much less likely that the experimenter could use the treatment volume to identify the control animals.

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ANY-maze help topic T0600