According to a tv ad, "because depression is a chemical imbalance, new venlafaxine's extended release can with mood, sleep, arousal, and alertness by working on the two key neurotransmitters involved in depression." the two neurotransmitters are serotonin and:

norepinephrine

Neurotransmitters are chemical messengers in the brain that are the means by which brain cells communicate with each other. New drugs like venlafaxine are called serotonin-norepinephrine reuptake inhibitors, and their function is to target two main neurotransmitters: serotonin and norepinephrine, which are the main neurotransmitters associated with depression.

fir trees are found in areas with cooler climates. fir trees have needles for leaves and remain green year-round.