Figure 2

• A : [33P]-labeled cRNA probes specific to exon 2 of TASK-1 or TASK-3 were used to assess transcript presence in sagittal brain sections.

  • TASK-1−/− mice showed no detectable hybridization with the TASK-1 probe, even at twice the probe concentration.

  • TASK-3−/− mice showed no detectable hybridization with the TASK-3 probe under the same conditions.

  • Key Findings :

    • TASK-1 and TASK-3 transcripts are absent in their respective knock-out mice.

    • The alternate TASK transcript ( TASK-3 in TASK-1−/− , and TASK-1 in TASK-3−/− ) is distributed in the brain similarly to wild-type and rat models ,

      • indicating no compensatory expression.

• B : TASK-1 and TASK-3 mRNA levels were quantified in brainstem tissue from controls and knock-out mice.

  • TASK-1 mRNA was undetectable in TASK-1−/- mice , and TASK-3 mRNA was undetectable in TASK-3−/− mice.

  • There was no compensatory upregulation of the alternate TASK transcript in either knock-out mouse model.

  • Key Findings :

    • Gene-specific knock-out was confirmed.

    • TASK-1−/− and TASK-3−/− knock-outs do not trigger increased transcription of the remaining TASK subunit.

• C : Rotarod Test

  • Mice were assessed for motor coordination and balance using an accelerating rotarod test.

  • No significant differences were observed between control mice and TASK-1−/− , TASK-3−/− , or double knock-out ( TASK−/− ) mice.

  • All groups maintained balance equally well across trials.

  • Key Findings :

    • TASK knock-out mice have normal motor coordination and balance, with no gross sensorimotor deficits.

• D : Tail Flick Test

  • Mice were tested for latency to remove their tails from a radiant heat source at low and high intensities.

  • TASK knock-out mice performed similarly to control mice, with no significant difference in response time.

  • Key Findings :

    • TASK knock-out mice show normal thermal nociception at both low and high intensities.

• Summary :

  • TASK-1 and TASK-3 transcripts are absent in their respective knock-out mice, as shown by in situ hybridization and qRT-PCR.

  • No compensatory upregulation of the alternate TASK transcript occurs in either knock-out.

  • Behavioral assessments (rotarod and tail flick tests) show no gross sensorimotor or nociceptive deficits in TASK knock-out mice.

  • These results suggest that TASK-1 and TASK-3 are not critical for the tested aspects of motor coordination, balance, or thermal pain perception.

Figure 5

• A : Effects of Halothane and pH on Holding Current and Conductance

  • Key Findings:

    • Halothane's effect: Halothane (3%) decreased both holding current and conductance in RTN neurons, contrary to what is expected for TASK (tandem pore domain acid-sensitive K⁺) channels, which are typically potentiated by halothane.

    • pH sensitivity: The effects of extracellular pH changes (acidification) on holding current and conductance were similar in magnitude under control conditions and in the presence of halothane. This suggests that halothane does not interfere with the pH-sensitivity of these neurons.

    • Asterisks (*) indicate traces where artifacts in the recording were blanked and corrected.

  • Conclusion:

    • Halothane inhibits a background K⁺ current that contributes to the resting conductance, but it does not affect the neuron’s pH sensitivity. This is inconsistent with TASK channel involvement.

• B : Halothane-Sensitive Current

  • Key Findings:

    • The current-voltage (I–V) relationship of the halothane-sensitive current demonstrates a weakly rectifying profile, with reversal potential near the equilibrium potential for potassium (Eₖ).

    • This finding indicates that halothane inhibits a background K⁺ current.

  • Conclusion:

    • Halothane's action likely involves the inhibition of a non-TASK background K⁺ current, reducing the overall membrane conductance and current.

• C : pH-Sensitive Current

  • Key Findings:

    • The I–V relationships of pH-sensitive currents were unaffected by halothane, as the currents under control conditions and in halothane were essentially identical.

    • This indicates that the pH-sensitive current in RTN neurons is not mediated by TASK channels, which are often implicated in pH sensitivity in other systems.

  • Conclusion:

    • The pH-sensitive current in RTN neurons is mediated by mechanisms or ion channels that are independent of TASK channels and are not modulated by halothane.

Figure 2

Panel A: Ventilatory responses to hypoxia (10% O₂ in inspired air)

A1: Respiratory frequency ($f_R$$f_R$, breaths per minute)

• TASK-3⁻/⁻ mice have a slightly lower baseline $f_R$$f_R$ than TASK⁺/⁺ at 21% O₂.

• Both TASK-3⁻/⁻ and TASK⁺/⁺ mice increase $f_R$$f_R$ in response to hypoxia (10% O₂).

• No significant difference in $f_R$$f_R$ between genotypes under hypoxia.

A2: Tidal volume ($V_T$$V_T$, microliters per gram)

• TASK-3⁻/⁻ mice have slightly higher $V_T$$V_T$ at baseline (21% O₂) compared to TASK⁺/⁺.

• Both groups show a moderate increase in $V_T$$V_T$ under hypoxia (10% O₂).

• No significant genotype-dependent difference in $V_T$$V_T$ at either oxygen level.

A3: Minute ventilation ($V_E$$V_E$, milliliters per minute per gram)

• At baseline (21% O₂), TASK-3⁻/⁻ mice show slightly higher $V_E$$V_E$ than TASK⁺/⁺ mice.

• Both groups increase $V_E$$V_E$ similarly in response to hypoxia.

• No significant difference in $V_E$$V_E$ between genotypes.

A4: Summary of hypoxia results

• "The resting ventilation and the ventilatory response of TASK-3⁻/⁻ and TASK⁺/⁺ mice to hypoxic stimulation were similar."

Panel B: Ventilatory responses to normoxic hypercapnia

B1: Respiratory frequency ($f_R$$f_R$, breaths per minute)

• $f_R$$f_R$ increases in both TASK-3⁻/⁻ and TASK⁺/⁺ as CO₂ levels rise (from <0.3% to 6%).

• TASK-3⁻/⁻ mice have slightly higher $f_R$$f_R$ at 6% CO₂ compared to TASK⁺/⁺, but this difference is not statistically significant.

B2: Tidal volume ($V_T$$V_T$, microliters per gram)

• $V_T$$V_T$ increases in both TASK-3⁻/⁻ and TASK⁺/⁺ as CO₂ levels rise.

• TASK-3⁻/⁻ mice show slightly higher $V_T$$V_T$ at all CO₂ levels, but the differences are not statistically significant.

B3: Minute ventilation ($V_E$$V_E$, milliliters per minute per gram)

• $V_E$$V_E$ increases substantially with rising CO₂ in both TASK-3⁻/⁻ and TASK⁺/⁺ mice.

• TASK-3⁻/⁻ mice have slightly higher $V_E$$V_E$ at 6% CO₂, but no significant difference is detected between genotypes.

B4: Summary of hypercapnia results

• "No significant differences in any measures of ventilation were detected between TASK-3⁻/⁻ and the wild-type control mice when concentration of CO₂ in the inspired air increased to 3% or 6%."

• "Mice lacking TASK-1 or TASK-3 channels were exposed to graded levels of normoxic hypercapnia, which induced profound increases in ventilation in all groups of animals."