Regulation of granule cell excitability by a low-threshold calcium spike in turtle olfactory bulb
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Regulation of granule cell excitability by a low-threshold calcium spike in turtle olfactory bulb. / Pinato, Giulietta; Midtgaard, Jens.
In: Journal of Neurophysiology, Vol. 90, No. 5, 01.11.2003, p. 3341-51.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Regulation of granule cell excitability by a low-threshold calcium spike in turtle olfactory bulb
AU - Pinato, Giulietta
AU - Midtgaard, Jens
PY - 2003/11/1
Y1 - 2003/11/1
N2 - Granule cells excitability in the turtle olfactory bulb was analyzed using whole cell recordings in current- and voltage-clamp mode. Low-threshold spikes (LTSs) were evoked at potentials that are subthreshold for Na spikes in normal medium. The LTSs were evoked from rest, but hyperpolarization of the cell usually increased their amplitude so that they more easily boosted Na spike initiation. The LTS persisted in the presence of TTX but was antagonized by blockers of T-type calcium channels. The voltage dependence, kinetics, and inactivation properties of the LTS were characteristic of a low-threshold calcium spike. The threshold of the LTS was slightly above the resting potential but well below the Na spike threshold, and the LTS was often evoked in isolation in normal medium. Tetraethylammonium (TEA) and 4-aminopyridine (4-AP) had only minimal effects on the LTS but revealed the presence of a high-threshold Ca2+ spike (HTS), which was antagonized by Cd2+. The LTS displayed paired-pulse attenuation, with a timescale for recovery from inactivation of about 2 s at resting membrane potential. The LTS strongly boosted Na spike initiation; with repetitive stimulation, the long recovery of the LTS governed Na spike initiation. Thus the olfactory granule cells possess an LTS, with intrinsic kinetics that contribute to sub- and suprathreshold responses on a timescale of seconds. This adds a new mechanism to the early processing of olfactory input.
AB - Granule cells excitability in the turtle olfactory bulb was analyzed using whole cell recordings in current- and voltage-clamp mode. Low-threshold spikes (LTSs) were evoked at potentials that are subthreshold for Na spikes in normal medium. The LTSs were evoked from rest, but hyperpolarization of the cell usually increased their amplitude so that they more easily boosted Na spike initiation. The LTS persisted in the presence of TTX but was antagonized by blockers of T-type calcium channels. The voltage dependence, kinetics, and inactivation properties of the LTS were characteristic of a low-threshold calcium spike. The threshold of the LTS was slightly above the resting potential but well below the Na spike threshold, and the LTS was often evoked in isolation in normal medium. Tetraethylammonium (TEA) and 4-aminopyridine (4-AP) had only minimal effects on the LTS but revealed the presence of a high-threshold Ca2+ spike (HTS), which was antagonized by Cd2+. The LTS displayed paired-pulse attenuation, with a timescale for recovery from inactivation of about 2 s at resting membrane potential. The LTS strongly boosted Na spike initiation; with repetitive stimulation, the long recovery of the LTS governed Na spike initiation. Thus the olfactory granule cells possess an LTS, with intrinsic kinetics that contribute to sub- and suprathreshold responses on a timescale of seconds. This adds a new mechanism to the early processing of olfactory input.
KW - Animals
KW - Calcium Channel Blockers
KW - Calcium Signaling
KW - Olfactory Bulb
KW - Sensory Thresholds
KW - Turtles
U2 - 10.1152/jn.00560.2003
DO - 10.1152/jn.00560.2003
M3 - Journal article
C2 - 12867531
VL - 90
SP - 3341
EP - 3351
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
SN - 0022-3077
IS - 5
ER -
ID: 33291190