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Repetitive firing properties of neurons in the ventral region of nucleus tractus solitarius. In vitro studies in adult and neonatal rat.

Abstract：

:1. A brain stem slice preparation and intracellular techniques were used to examine the cellular properties of neurons within the ventral and ventrolateral region of the nucleus tractus solitarius (v-NTS) in adult and neonatal (3-12 days old) rats. These neurons are believed to be involved in the control of respiratory function. 2. On the basis of their active and passive electrophysiologic properties, cells in the v-NTS of adult rats were categorized into type A and type B neurons. Type A neurons fired spontaneously with rates ranging from 0.5 to 5 spikes/s at resting potential (-59.0 +/- 6 mV, mean +/- SD). When depolarized, type A cells responded with an initial high rate of firing, which rapidly declined to a steady state level. Spike-frequency adaptation (SFA) index (defined as steady state firing divided by peak activity x 100) was 40%, with a time constant for adaptation of 100-280 ms. When depolarized from membrane potentials more negative than resting, these neurons exhibited a silent period (up to 900 ms) before any spiking was observed (delayed excitation). The delay depended on the duration and magnitude of the hyperpolarizing prepulse that preceded depolarization. The action potentials of type A cells had a shoulder on the repolarization phase, measured 2-3 ms at one-half height, and increased in duration during repetitive firing. 3. At resting potential, type B neurons fired three to five times faster than type A. Although both type A and type B neurons showed spike-frequency adaptation, type B neurons adapted at a much faster rate than type A. The time constant for adaptation was 2-14 ms in type B cells. These cells displayed no delayed excitation on depolarization from membrane potentials more negative than rest. Some type B cells exhibited postinhibitory rebound (PIR) and depolarizing afterpotentials (DAPs). Both types A and B v-NTS neurons had comparable input resistance and showed inward rectification. 4. Neonatal v-NTS cells, in contrast to adult cells, belonged to a single population of neurons. Their resting membrane potential was -58 +/- 6.3 mV (mean +/- SD). The majority of these cells (30/34) were active (5-10 spikes/s) at rest. When depolarized, they showed an immediate increase in firing rate, which gradually slowed down to reach a steady state. Spike-frequency adaptation index was 59%, with a time constant for adaptation of 300-750 ms.(ABSTRACT TRUNCATED AT 400 WORDS)

journal_name

J Neurophysiol

journal_title

Journal of neurophysiology

authors

Haddad GG,Getting PA

doi

10.1152/jn.1989.62.6.1213

subject

Has Abstract

pub_date

1989-12-01 00:00:00

pages

1213-24

issue

eissn

0022-3077

issn

1522-1598

journal_volume

pub_type

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Repetitive firing properties of neurons in the ventral region of nucleus tractus solitarius. In vitro studies in adult and neonatal rat.