Abrupt changes in pentobarbital sensitivity in preBötzinger complex region, hypoglossal motor nucleus, nucleus tractus solitarius, and cortex during rat transitional period (P10–P15)

• Pentobarbital sensitivity changed during P10–P15 in rat medullary and cortical slices.
• Pentobarbital resistance in preBötC-region neurons increased on P14.
• Pentobarbital resistance in hypoglossal nucleus decreased with nadir at P14.
• Pentobarbital resistance in nucleus tractus solitarius decreased on P14.
• Abrupt changes may compensate for increased GABAergic inhibition during P11–P14.

On postnatal days P10–P15 in rat medulla, neurotransmitter receptor subunit composition shifts toward a more mature phenotype. Since medullary GABAARs regulate cardiorespiratory function, abrupt alterations in GABAergic synaptic inhibition could disrupt homeostasis. We hypothesized that GABAARs on medullary neurons become more resistant to positive allosteric modulation during P10–P15. Medullary and cortical slices from P10 to P20 rats were used to record spontaneous action potentials in pre-Botzinger Complex (preBötC-region), hypoglossal (XII) motor nucleus, nucleus tractus solitarius (NTS), and cortex during exposure to pentobarbital (positive allosteric modulator of GABAARs). On P14, pentobarbital resistance abruptly increased in preBötC-region and decreased in NTS, but these changes in pentobarbital resistance were not present on P15. Pentobarbital resistance decreased in XII motor nucleus during P11–P15 with a nadir at P14. Abrupt changes in pentobarbital resistance indicate changes in GABAergic receptor composition and function that may compensate for potential increased GABAergic inhibition and respiratory depression that occurs during this key developmental transitional period.