Chadbury et al and Tye et al

I found this articles a bit challenging to read but both articles displayed many methods of observing ventral tegmental area (VTA) dopamine neurons and its relationship to depression related behaviors.  Chadbury et al begins explaining how he targets specific VTA dopamine neurons by expressing channelrhodopsin-2 (CHR2) with enhanced yellow fluorescent protein (eYFP). Using optogenetics, they test by using methods of sucrose preference and social interaction tests. I think Chadbury et al. shows a clear and concise way of displaying groups of tonic ChR2, phasic CHR2 and phasic eYFP. We see that for social interaction,  target neurons with ChR2 (tonic)  group had a much higher time for social interaction than the other groups. However, it was interesting to see that the target group with ChR2 (phasic) had a decrease time in social interaction.  The sucrose preference test also showed similar results with the group with neurons with ChR2 (phasic)  having a decrease in sucrose water compared to the other groups.  All  tests that used the method in this article showed very similar results, validating that using phasic stimulation expressing ChR2 has some causal relationship with increase of firing VTA dopamine neurons.  Tye. et al, however finds some interesting results when looking at similar models. Instead of social interactions, they implemented chronic mild stress for a longer period of time and the amount of snuggling time that mice encountered when turning on the light stimulation increased with CHR2 and chronic mild stress.  Sucrose preference in the same group has also increased percentage when the stimulation was turned on.  Tye et al. also adds in the forced swim test measuring amounts of kicks per minute, showing us how each time the mouse is stimulated, there was an increase in amount of kicks.  Overall, I felt Tye et al. added more stimulation effects, which validated the increase in VTA dopamine neurons.