| 1. |
The Cl– current (I
Cl) in -aminobutyric acid (GABA)-sensitive frog sensory neuron was separated from other Na+, Ca2+, and K+ currents using a suction pipette technique which allows internal perfusion under a single-electrode voltage clamp.
|
| 2. |
Diazepam (DZP) itself evoked no response but facilitated the dose- and time-dependently GABA-inducedI
Cl without changing the GABA equilibrium potential (E
GABA) at concentrations ranging widely, from 3 × 10–9 to 10–4
M.
|
| 3. |
In the presence of DZP, the GABA dose-response curve shifted to the left without changing the maximum current, indicating that DZP modifies the interaction between GABA and its receptor rather than affecting directly the channel activation step.
|
| 4. |
The enhancement of the GABA-inducedI
Cl by DZP depended neither on the membrane voltage nor on the inward or outward direction of theI
Cl.
|
| 5. |
DZP also potentiated theI
Cl elicited by GABA agonists such as -alanine, taurine, homotaurine, 5-aminovaleric acid,l-GABOB,d-GABOB, glycine, and muscimol.
|
| 6. |
The GABA response enhanced by pentobarbital (PB) was further enhanced by adding DZP, indicating that DZP and PB do not act in the same way.
|
| 7. |
Ro5-3663, a diazepam analogue, enhanced the GABA-inducedI
Cl only in a narrow range of the concentrations but inhibited the current at concentrations higher than 2 × 10–6
M.
|
Key words frog sensory neuron - internal perfusion - diazepam -
-aminobutyric acid (GABA) - chloride current - facilitation