Tentative Role of the Na+/H+ Exchanger Type 3 in Central Chemosensitivity of Respiration

In vitro studies by Wiemann et al. (1999, 2001) have shown cultured CO2/H+ sensitive neurons from the ventrolateral medulla oblongata of newborn rats to enhance their bioelectric activity upon intracellular acidification induced by selective inhibition of the Na+/H+ exchanger type 3 (NHE-3). Recently, Kiwull- Schone et al. (2001) demonstrated the presence of NHE-3 mRNA in the adult rabbit brainstem, and likewise found NHE-3 immunoreactive neurons in brain-stem areas, which have prevalence for central chemosensitivity. The same study revealed that NHE-3 inhibition by the brain-permeant substance S8218 (Aventis Pharma) also significantly modified the central respiratory CO2-response of brain-stem in vivo.