Inward-rectifying membrane currents activated by hyperpolarization in immature rat olfactory cortex neurones in vitro

Sciancalepore, M. and Constanti, A. (1998) Inward-rectifying membrane currents activated by hyperpolarization in immature rat olfactory cortex neurones in vitro. Brain Research, 814 (1-2). pp. 133-142. 10.1016/S0006-8993(98)01067-1.

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DOI: 10.1016/S0006-8993(98)01067-1

Abstract

The properties of inward-rectifying membrane currents in immature rat olfactory cortex neurones (postnatal day (P) 10-22) were analysed using whole-cell patch-clamp recordings. In 78% of cells (40/51), injection of hyperpolarizing current pulses elicited graded electrotonic potentials showing a slowly developing sag in the membrane potential. Under voltage clamp, negative commands from -50 mV activated slow inward current (I(Slow)) relaxations whose amplitude and exponential rate of onset increased with increasing hyperpolarization (n = 40); the I(Slow) activation time constant (τ(on)) ranged from 650 ± 116 (mean ± S.E.M.) ms at -70 mV to 177 ± 18 ms at - 120 mV; n = 34). By contrast, in 11/51 neurones, similar negative commands revealed only fast-type inward rectification (I(IR)) with either rapid (n = 9) or 'instantaneous' onset kinetics (n = 2). I(Slow) activation threshold was at ~ -60 mV, with full activation at - 120 mV; the half- maximal voltage (V0.5) and slope factor (k) of activation were: -85 ± 0.4 mV and 11 ± 0.5, respectively (n = 13). The estimated reversal potential for I(Slow was -28 ± 2 mV (n = 5). No obvious age-dependent changes in maximal I(Slow) current amplitude or density (at - 120 mV) or in the proportion of cells showing I(IR) were found between P10 and P22. I(slow) was blocked by Cs+ (5 mM, n = 6) or the specific h-current blocker ZD 7288 (50 μM, n = 11) but not Ba2+ (500 μM, n = 7); in contrast, I(IR) was blocked by Cs+ or Ba2+ but not ZD 7288. It is concluded that unlike adult olfactory cortical cells, immature olfactory neurones can exhibit both slow and fast-types of inward rectification: the more predominant I(Slow) component, resembled the h-current (I(h)) previously identified in other central neurones.

Item Type:Article
Uncontrolled Keywords:Brain slice; Development; Fast inward rectification; Hyperpolarization-activated current; Rat olfactory cortex neurone; Slow h-current (I(h)); Specific I(h) blocker; Whole-cell patch clamp; ZD 7288
Departments, units and centres:Department of Pharmacology > Department of Pharmacology
ID Code:3290
Journal or Publication Title:Brain Research
Deposited By:Library Staff
Deposited On:24 May 2012 17:51
Last Modified:24 May 2012 17:51

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