Properties of a Ca2+-activated K+ conductance in acutely isolated pyramidal-like neurons from the rat basolateral amygdaloid complex.

A calcium (Ca2+)-activated potassium (K+) conductance was studied in large pyramidal-like neurons acutely dissociated from the rat basolateral amygdaloid complex. Neurons were immunoreactive to anti-alpha(913-926), a sequence-directed antibody directed against the pore-forming alpha-subunit of the BK(Ca) channel, also termed slo. Whole cell current-voltage (I-V) relationships obtained on application of slow (46.7 mV/s) voltage ramps from -110 to +100 mV were N shaped positive to -30 mV. Maximal current activation occurred at +9.8 +/- 2.7 (SE) mV, with a mean current density of 404.8 +/- 25.0 pA/pF. Substitution of extracellular Ca2+ with manganese (Mn2+), or with magnesium (Mg2+) and addition of 5 mM ethyleneglycol-bis (beta-aminoethylether)-N,N,N',N'-tetraacetic acid, abolished the N-shaped I-V relationship with a reduction in maximal outward current to 15.3 +/- 2.3% of the control value. The Ca2+-sensitive K+ current component, as revealed by voltage step protocols, activated at depolarizations positive to -30 mV with a slow time course (time constant 430.7 +/- 78.6 ms). The current was reduced by 80.4 +/- 4.6% through 1 mM tetraethyammonium chloride and by 66.8 +/- 3.4% through 100 nM iberiotoxin, whereas apamin up to 1 microM had no effect. It is concluded that pyramidal-like neurons of the basolateral amygdaloid complex possess BK(Ca) channels and the corresponding macroscopic Ca2+-sensitive K+ conductance, activation of which will substantially contribute to the Ca2+-dependent regulation of electrogenic behavior in these neurons.