Journal of Neuroscience, Vol 7, 3687-3694, Copyright © 1987 by Society for Neuroscience
Membrane properties and adrenergic responses in locus coeruleus neurons of young rats
JT Williams and KC Marshall
Neuropharmacology Laboratory, Massachusetts Institute of Technology, Cambridge 02139.
Intracellular recordings were made from locus coeruleus neurons in slices
taken from rats 8-26 d of age. Neurons from these animals exhibited
spontaneous action potentials, which were superimposed on slow (0.3-3 Hz)
rhythmic depolarizations. The frequency of these potentials was closely
related to the age of the animals from which the slice was taken, the
slowest frequencies being observed in tissues from the youngest animals. In
adult animals, such rhythmic activity was only rarely observed under normal
recording conditions. The rhythmic depolarizations had a slow rate of rise
and fall, were 3-15 mV in amplitude, were not affected by tetrodotoxin, and
were abolished in solutions that contained elevated magnesium content. When
the membrane potential was hyperpolarized by passing current through the
recording electrode, the depolarizing rhythmic activity persisted even at
very negative potentials (-120 mV). These depolarizations appear to be
generated by the inward movement of calcium ions, probably in dendritic
regions of the neuron. Superfusion of phenylephrine caused membrane
depolarizations, increased the frequency of action potentials and of the
slow, rhythmic depolarizations in about 80% of the cells from young rats,
whereas it had no effect or a depressant action on cells from adults.
Noradrenaline hyperpolarized the cells through an alpha 2- adrenoceptor and
abolished the slow depolarizations. In cells from young rats, the
hyperpolarization produced by noradrenaline reached a maximum and then
declined, such that there was a "sag" in the membrane potential toward the
resting potential following the peak of the hyperpolarization. Following
the washout of noradrenaline, the membrane potential repolarized before
moving toward the resting level.(ABSTRACT TRUNCATED AT 250 WORDS)
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