P. Kloppenburg et al., Voltage-activated currents from adult honeybee (Apis mellifera) antennal motor neurons recorded in vitro and in situ, J NEUROPHYS, 81(1), 1999, pp. 39-48
Voltage-activated currents from adult honey bee antennal motor neurons were
characterized with in vitro studies in parallel with recordings taken from
cells in situ. Two methods were used to ensure unequivocal identification
of cells as antennal motor neurons: 1) selective backfilling of the neurons
with fluorescent markers before dissociation for cell culture or before re
cording from cells in intact brains, semiintact brains, or in brain slices
or 2) staining with a fluorescent marker via the patch pipette during recor
dings and identifying antennal motor neurons in situ on the basis of their
characteristic morphology. Four voltage-activated currents were isolated in
these antennal motor neurons with pharmacological, voltage, and ion substi
tution protocols. The neurons expressed at least two distinct K+ currents,
a transient current (I-A) that was blocked by 4-aminopyridine (4-5 x 10(-3)
M), and a sustained current (I-K(V)) that was partially blocked by tetraet
hylammonium(2-3 x 10(-2) M) and quinidine (5 x 10(-5) M). I-A activated abo
ve -40 to -30 mV and the half-maximal voltages for steady-state activation
and inactivation were -8.8 and -43.2 mV, respectively. I-K(V) activated abo
ve -50 to -40 mV and the midpoint of the steady-state activation curve was
+11.2 mV. I-K(V) did not show steady-state inactivation. Additionally, two
inward currents were isolated: a tetrodotoxin (10(-7) M)-sensitive, transie
nt Na+ current (I-Na) that activated above -35 mV, with a maximum around -5
mV and a half-maximal voltage for inactivation of -72.6 mV, and a CdCl2 (5
x 10(-5) M)-sensitive Ca2+ current that activated above -45 to -40 mV, wit
h a maximum around -15 mV. This study represents the first step in our effo
rt to analyze the cellular and ionic mechanisms underlying the intrinsic pr
operties and plasticity of antennal motor neurons.