Actions of noradrenaline recorded intracellularly in rat hippocampal CA1 pyramidal neurones, in vitro.

Abstract

SUMMARY1. CA1 pyramidal neurones were studied in rat in vitro hippocampal slices using standard intracellular and single-electrode voltage-clamp recording techniques to examine the actions of noradrenaline (NA).2. NA had two different effects on the resting membrane potential of pyramidal neurones; either a hyperpolarization accompanied by a decrease in membrane input resistance, or less commonly, a depolarization accompanied by an increase in input resistance. In many cells, both effects, a hyperpolarization followed by a depolarization were observed. The depolarization was mediated by a noradrenergic f-receptor.The hyperpolarization was more difficult to characterize, but may result from a-receptor activation.3. NA reduced the amplitude and duration ofthe slow calcium-activated potassium after-hyperpolarization (a.h.p.) that follows depolarization-induced action potentials. This action of NA was mediated by ,l1-noradrenergic receptors.

An Examination of Calcium Current Function on Heterotopic Neurons in Hippocampal Slices from Rats Exposed to Methylazoxymethanol

“…Because hippocampal heterotopic neurons in the MAM model receive excessive innervation by catecholaminergic fibers (25)(26)(27), and it is well established that catecholamines modulate Ca 2+ channel activity (40) or hippocampal neuronal excitability (28,40,41,42), we investigated adrenergic modulation of VDCC on heterotopic neurons. Bath application of norepinephrine (NE, 10-100 M), a potent agonist at ␣ 1, ␣ 2 , and ␤-adrenergic receptors, significantly reduced VDCC peak current amplitude in a dose-dependent manner on both CA1 pyramidal control neurons and heterotopic cells (Fig.…”

Effects of DAU 6215, a novel 5‐hydroxytryptamine3 (5‐HT3) antagonist on electrophysiological properties of the rat hippocampus

“…These compounds were perfused for at least 30min before testing 5-HT. Under these conditions, injections of positive current pulses (100ms) through the recording electrode elicited a calcium spike, followed by a large calcium-dependent K+-activated AHP (Schwartzkroin & Slawsky, 1977;Madison & Nicoll, 1986, Andrade & Nicoll, 1987. This procedure was used, as opposed to examining the AHP following a burst of spikes, because the large amplitude, reproducible AHP produced by the calcium spike, enables the systematic examination of the effects of 5-HT and its antagonists (Chaput et al, 1990).…”

Protein kinase A-independent modulation of ion channels in the brain by cyclic AMP.

“…A possible candidate for such an unconventional cAMP effect is the depolarization of the membrane potential that accompanies the suppression of IAHP in response to cAMP and monoamine transmitters (8,11,12). We found that the depolarizing action of cAMP and 13-adrenergic agonists was due to an enhancement of the cation current IQ (also called Ih;refs.…”

“…In CAl hippocampal neurons, cAMP and the monoamine transmitters activating cAMP production-norepinephrine, serotonin, histamine, and dopamine-are all known to increase excitability by suppressing the Ca2+-activated K+ current, IAHP (8)(9)(10)(11)(12)(13)(14)(15)(16), which is a current underlying the slow afterhyperpolarization (sAHP) and spike frequency adaptation (17). The suppression of IAHP has previously been shown to be mediated by PKA for each of these monoamine transmitters (10,16).…”