Quote (Balla @ 31 Jan 2015 19:34)

Hmm.. Interesting question.
Many studies have indeed corroborated your sentiment here that a nap improves mood, vigilance, etc. I think much of it is probably due to that - the increase in wakefulness, vigilance, attention, etc.

For instance: most people and studies attribute an increase in mood overall when drinking coffee/caffeine. This is mostly due to promoting wakefulness. One of the main aspects that promotes sleepiness is the accretion of adenosine. Caffeine antagonizes adenosine receptors to induce its wakeful promoting effects.. so it could ostensibly be that adenosine and its subsequent somnogen action attenuates mood by the mere process of being sleepy. I know that I get very moody and very irritable when I'm sleepy/lethargic in the middle of the day. Coffee immediately boosts my mood to its usual good ponit.

With that, from a neurochemical perspective, adenosine mitigates excitatory neurotransmission, which either sleep or coffee would impede. So a nap/coffee would effectively INCREASE excitatory neurotransmission, ie glutamate mainly through AMPA & NMDARs, both of which have an antidepressant effect through their transmission being able to induce LTP --> CREB --> BDNF synthesis --> neurogenesis/synaptogenesis, etc. This also increases some dopamine and perhaps norepi signaling too, though I don't think to the same degree, and those could potentially enhance mood but not nearly as overt. Though there are a few mechanistic details that may paint a picture here.

Also, hopefully you don't think I'm lying to you because the A2A receptor technically is opposite to the above but its not as robust. Technically the A2a causes sleepiness but is "excitatory" in that it increases bdnf, creb, and DA & glutatmate tranmission. But its effects don't seem to be so global is the likely disparity. It's more-so permissive and slightly modulatory.