Penicillin blocks human alpha(1)beta(1) and alpha(1)beta(1)gamma(2S) GABA(A) channels that open spontaneously.

• We used the open-channel blocker, penicillin (10 mM), as a tool to investigate if the human α1β1 or α1β1γ2S γ-aminobutyric acid type A (GABAA) receptor channels opened in the absence of GABA. Application of penicillin to cells expressing the receptors resulted in a transient inward whole-cell current, the off-current, upon penicillin removal. The amplitude of the off-current was dependent on the duration of the penicillin application, it reversed in polarity at depolarized potentials and exhibited “run-down” similar to the GABA-activated currents. Bicuculline (100 μM) blocked the off-current response. Pentobarbital (50 μM) enhanced the peak off-current amplitude by 2.8 and 3.4 in α1β1 and α1β1γ2S receptors, respectively. Diazepam (1 μM) only enhanced the off-current peak response in α1β1γ2S receptors (1.6) and induced the development of an inward current when applied alone. The results are consistent with that the α1β1 or α1β1γ2S GABAA receptors can open in the absence of GABA and raise the question of what role spontaneous channel openings have in the function of GABAA receptors.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Farmakologi och toxikologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Pharmacology and Toxicology (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

Nyckelord

γ-aminobutyric acid

Spontaneous activity

Channel block

Tonic current

Inhibition

Barbiturate

Benzodiazepine

GABAA receptor

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