serotonin and norepinephrinemethylphenidate norepinephrinedopamine and norepinephrinenortriptyline norepinephrineguanfacine norepinephrinenorepinephrine depressionnorepinephrine functiontyrosine norepinephrinenorepinephrine hormonecaffeine and norepinephrineashwagandha norepinephrineincrease norepinephrine