Journal of Neurophysiology, Vol 67, Issue 5 1367-1374, Copyright © 1992 by APS
gamma-Aminobutyric acid-induced response in rat dissociated paratracheal ganglion cells
S. Itabashi, K. Aibara, H. Sasaki and N. Akaike
Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
1. The pharmacologic properties of gamma-aminobutyric acid (GABA)-induced
Cl- current (ICl) were studied in the paratracheal ganglion cells freshly
dissociated from 7- to 10-day-old rat trachea in a whole-cell recording
mode by the use of a conventional patch-clamp technique. 2. GABA- and
muscimol-induced currents increased sigmoidally in a
concentration-dependent manner, and both currents reversed at approximately
-3 mV, which was close to the Cl- equilibrium potential (ECl). 3.
Strychnine (STR) at low concentration and bicuculline (BIC) inhibited GABA
response competitively, whereas STR at the higher concentrations,
benzylpenicillin (PCG), or picrotoxin (PTX) inhibited noncompetitively.
Inhibition of GABA response by PCG but not other antagonists was voltage
dependent, indicating that PCG acts as a Cl- channel blocker. 4. The
concentration-response curve of pentobarbital sodium (PB)-induced ICl was
bell shaped. At concentrations higher than 10(-3) M, both the peak and
plateau currents decreased, and a transient "hump" current appeared
immediately after washing out PB. In the presence of PB, the
concentration-response curve of GABA shifted toward left without changing
the maximum response. 5. Although diazepam (DZP) at concentration used did
not induce a response, it potentiated the GABA response in a
concentration-dependent manner between 10(-8) and 10(-6) M. DZP also caused
a parallel shift toward left in the concentration-response curve of GABA.
6. PB or DZP further enhanced the GABA response in the presence of the
other agent. 7. It is concluded that the properties of GABAA receptors in
the paratracheal ganglion cells are essentially similar to those reported
in other preparations.
