CO2-sensitivity of GABAergic neurons in the ventral medullary surface of GAD67-GFP knock-in neonatal mice.
We investigated the CO2 responsiveness of GABAergic neurons in the ventral medullary surface (VMS), a putative chemoreceptive area using a 67-kDa isoform of GABA-synthesizing enzyme (GAD67)-green fluorescence protein (GFP) knock-in neonatal mouse, in which GFP is specifically expressed in GABAergic neurons. The slice was prepared by transversely sectioning at the level of the rostral rootlet of the XII nerve and the rostral end of the inferior olive in mock cerebrospinal fluid (CSF). Each medullary slice was continuously superfused with hypocapnic CSF. GFP-positive neurons in the VMS were selected by using fluorescent optics and their membrane potentials and firing activities were analyzed with a perforated patch recording technique. Thereafter, superfusion was changed from hypocapnic to hypercapnic CSF. In 4 out of 8 GABAergic neurons in the VMS, perfusion with hypercapnic CSF induced more than a 20% decrease in the discharge frequency and hyperpolarized the neurons. The remaining 4 GFP-positive neurons were CO2-insensitive. GABAergic neurons in the VMS have chemosensitivity. Inhibition of chemosensitive GABAergic neural activity in the VMS may induce increases in respiratory output in response to hypercapnia.
Kuribayashi
Junya
J
Department of Anesthesiology, Keio University School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan. j_kuriba0416@yahoo.co.jp
Sakuraba
Shigeki
S
Hosokawa
Yuki
Y
Hatori
Eiki
E
Tsujita
Miki
M
Takeda
Junzo
J
Yanagawa
Yuchio
Y
Obata
Kunihiko
K
Kuwana
Shun-ichi
S
D000818:Animals; D000831:Animals, Newborn; D002245:Carbon Dioxide / Q000494:pharmacology*; D005968:Glutamate Decarboxylase / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics; D066298:In Vitro Techniques; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D012143:Respiratory Physiological Phenomena; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D002245:Carbon Dioxide; D049452:Green Fluorescent Proteins; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1