How do you feel today, yompf? The ol' septicemia acting up, or are you doing better?
Meanwhile, I found that invertebrates absolutely have opioid signaling in their "brains", and
a study where researchers got ants hooked on morphine. So you may be right about those cockroaches.
They had to "train" them to go after morphine by spiking sugar first, so I don't know how close it matches. But, the ants get a dopamine kick same as humans.
When you're feeling better, try to kick out the junkie bugs before you shoot up again.