Neuroreport
-
We used whole-cell recording to identify, for the first time, GABAergic tonic current in subpopulations of substantia gelatinosa neurons in mouse spinal cord slices. Application of the gamma-aminobutyric acid type A receptor antagonist bicuculline revealed tonic currents in 49 of 73 substantia gelatinosa neurons. These tonic currents were dissected into three groups according to their diverse pharmacological properties. ⋯ In the second group, furosemide blocked the tonic current but midazolam and propofol failed to enhance the current. In the third group, furosemide blocked and 3alpha, 21-dihydroxy-5alpha-pregnan-20-one enhanced the tonic current. The presence of mRNAs for alpha4, alpha5, delta and epsilon subunits in the substantia gelatinosa (reverse-transcriptase polymerase chain reaction) suggest that gamma-aminobutyric acid type A receptors comprising alpha5betaxgamma2, alphaxbetaxepsilon and alpha4betaxdelta subunits are responsible for tonic currents.