yup a completely different set of brain chemicals (always thought they were endorphins but it probably a comlpex cascade of many reactions) gets activated when its long term. it stops being about attraction/fucking and more about companionship. Explains why swingers feel the need to fuck around yet still love their spouses
Still even with all the science saying this I wouldnt say there is no such thing as love...probably because I'm a sap

but also because I'm a firm believer in a soul/inner personality that brain chemistry cannot define. just because your brain uses certain chemicals to communicate with each other it doesnt mean it didnt have to somehow decide to fall in love. Like how electrical impulses down a phone wire dont mean thats the reason someone made a telephone call, there had to be a person on one end who needed to call someone for a specific reason. Neurology yet doesnt know why the brain can determine the reason, just the reigon of the brain responsible for wanting to call.