H super(+)-Sensitivity of cultured neurons from the dorsomedial and ventrolateral medulla of neonate rats

The H super(+)-sensitivity of neonate rat cultured neurons derived from the dorsomedial medulla (DMM) containing the nucleus tractus solitarii and the ventrolateral medulla (VLM) was determined by H super(+)-sensitive fluorescent probe BCECF-AM and immunohistochemical methods. Against an extracellular pH as low as 7.2-7.3, H super(+)-sensitivity was verified in 2.6% of the DMM neurons (46/1800) and 2.1% of the VLM neurons (38/1800). This H super(+)-sensitive neurons of the DMM were immunoreactive to glutamate (52.4%) and glutamic acid decarboxylase (GAD) (28.6%), while those of the VLM were immunoreactive to glutamate (66.7%) and GAD (33.3%). There was no immunoreactivity to tyrosine hydroxylase, phenylethanolamine-N-methyltransferase or choline acetyltransferase in the H super(+)-sensitive neurons are present in the DMM and VLM besides the ventral medullary surface, the site of the central chemoreceptors.