Figure 1. Intrinsic chemosensitive responses of serotonergic DRN neurons are greatly decreased in Htr1a^RO mice.

A, B, Representative loose-seal cell-attached voltage-clamp recordings performed in the presence of synaptic blockers (see results) showing time-courses of serotonergic neuron firing in response to bath application of 9% and 3% CO₂ in slices from control (A) and Htr1a^RO (B) mice. Each panel reports three time-courses from different neurons. In B, one neuron with basal firing rate higher than the average of Htr1a^RO group is shown to illustrate that the lack of responses to CO₂ changes did not depend on basal firing rate of the recorded neuron (see results). Lines show firing rate calculated over 10 s bins. Traces illustrate recorded action currents for each experiment. C, Bar graph of baseline firing rate in the two groups. D, Summary bar graph comparing the effects of 9% and 3% CO₂ in control and Htr1a^RO mice. * p<0.05; *** p<0.001 (Mann-Whitney test). Number of recorded neurons is indicated in parentheses.