Capsaicin

Capasaicin is the active ingredient in hot peppers of the New World.

Some stubs to fill out:

chemical structure and related compounds (including antagonist)

acts on vanilloid receptor (Julius paper), which is a heat sensitive receptor

mammals sensitive but not birds

production by hot peppers appears to select for seed dispersal by birds, and discourages mammals because mammalian digestive system destroys seeds

aposematic coloration by hot peppers -- relies on predators ability to learn association of color with ingestive effect (positive for birds, aversive for mammals)

also produced by some tarantuallas for use in venom

why humans like to eat hot peppers (Paul Rozin work)

PBN lesion blocks acquisition of sucrose/LiCl-mediated CTA, but not capsaicin/LiCl CTA -- capsaicin works through trigeminal somatosensory nerves, not gustatory nerves