  Prostaglandin E2 (PGE2), is a major prostanoid produced by the activity of
cyclooxygenases (COX) in response to various physiological and pathological
stimuli. PGE2 exerts its effects by activating four specific E-type prostanoid
receptors (EP1, EP2, EP3, and EP4). In the present study, we analyzed the
expression of the PGE2 receptor EP1 (mRNA and protein) in different regions of
the adult rat brain (hippocampus, hypothalamus, striatum, prefrontal cerebral
cortex, parietal cortex, brain stem, and cerebellum) using reverse
transcription- polymerase chain reaction, Western blotting, and
immunohistochemical methods. On a regional basis, levels of EP1 mRNA were the
highest in parietal cortex and cerebellum. At the protein level, we found very
strong expression of EP1 in cerebellum, as revealed by Western blotting
experiments. Furthermore, the present study provides for the first time
evidence that the EP1 receptor is highly expressed in the cerebellum, where the
Purkinje cells displayed very high immunolabeling of their perikaryon and
dendrites, as observed in the immunohistochemical analysis. Results from the
present study indicate that the EP1 prostanoid receptor is expressed in
specific neuronal populations, which possibly determine the region-specific
response to PGE2.
