We studied the CO2-sensitivity of neurons from LC, NTS and RTN. Firing rate and intracellular pH (pHi) responses to hypercapnic acidosis (HA) were studied in neurons from neonatal rat brainstem slices (300 µm) using whole cell patch and fluorescence imaging techniques. In response to HA, >90% of LC, 46% of NTS and 42% of RTN neurons increased their firing rate. The magnitude of the HA-induced increase in firing rate, calculated as the chemosensitivity index (CI), was 137±5% (n=17), 153±6% (52), and 248±30% (18) for LC, NTS and RTN neurons, respectively. Upon exposure to synaptic block medium (SNB) (11.4 mM Mg2+; 0.2 mM Ca2+), the spontaneous firing rate of LC neurons increased from 0.9±0.1 to 2.2±0.5 Hz (10) (p2-sensitive neurons are intrinsically chemosensitive. Since pHi responses to HA are similar in neurons from these areas, the differences in their intrinsic chemosensitivity must reside in differences in their ion channels.
[Supported by NIH grants RO1 HL56683 and F32 HL80877.]
Available at: http://works.bepress.com/nick_ritucci/34/