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