Hello all!

Recently I ran a two-chamber conditioned place preference (CPP) test with rats, activating specific neurons through an excitatory DREADD (with surgery-naive rats as controls). The CNO was paired with the more-preferred chamber as determined by a pretest. They received 6 days of 30 min alternating treatment (CNO-saline) in a counterbalanced design. These rats had previously been conditioned with CNO in the opposite (less-preferred) chamber, and did not receive any extinction training in between. However, there was a gap of 3 days, 1 of which involved the pretest. CPP scores were ascertained by manually scoring 15 minute videos of how long the rats spent in each chamber.

The CPP results were all over the place, with a huge amount of variation. The amount of variation was not seen in these rats after CNO-with-less-preferred-side testing, nor METH testing.

I can think of only two explanations for this:

1- My scoring methods are wrong, or

2- The lack of extinction between tests threw everything off

To address 1, I am rescoring the videos digitally. As to 2, I am not sure if the lack of extinction would cause the variation in data.

Any insight you guys have would be great!

UPDATE 11/13/18-

The rats seem to have an intrinsic preference for the grid, as opposed to metal bar, floor. Does anyone else have experience with that? It seems we didn't notice the preference because we had initially done tests using METH, which was a powerful enough incentive to overcome any inclination towards grid flooring. We'll do CPP tests for experimentally naive rats and get back to you.