Stimulation Of Nucleus Locus Coeruleus Research Articles

Lumbar dorsal root potentials elicited by stimulation of nucleus locus coeruleus

Lumbar dorsal root potentials (DRP) were elicited by nucleus locus coeruleus (LC) stimulation in the cat. Inhibition, by LC stimulation, of dorsal horn cells responding to noxious inputs corresponded in time with the DRPs evoked by LC stimulation. Comparing cutaneous stimulation-evoked DRPs with LC stimulation-evoked DRPs and their respective effects on dorsal horn single-unit activity suggested a shared segmental underlying mechanism and the possible involvement of the coeruleospinal system with that of a diffuse noxious inhibitory suprasegmental loop.

Evidence against specificity of electrical stimulation of the nucleus locus coeruleus in activating the sympathetic nervous system in the rat

Electrical stimulation of the central nucleus locus coeruleus (LC) was previously shown to increase activity of the peripheral sympathetic nervous system (SNS) as measured by increases in plasma levels of the norepinephrine (NE) metabolite 3-methoxy-4-hydroxyphenethyleneglycol (MHPG) in the rat. Four experimental approaches were designed to test the specificity of the LC cell group in activating the SNS in the stimulation paradigm. Varying the stimulation current amplitude, varying the site of stimulating electrode placement, and electrolytic lesions of the LC yielded results consistent with the hypothesis that the site of SNS activation was within the anatomical region of the LC cell group. Neurochemical lesioning with intraventricular 6-hydroxydopamine, however, did not effectively block the plasma MHPG increase observed after stimulation of the LC region. The possibility that non-noradrenergic cells, fibers of passage, or terminals in the LC region of the midbrain may be responsible for SNS activation when the LC is electrically stimulated is discussed. These studies are pertinent to all studies of LC function which employ electrical stimulation of the LC nucleus, including investigations of the role of the LC in social behavior, intracranial self-stimulation, and blood pressure regulation.

The action of norepinephrine in the rat hippocampus. II. Activation of the input pathway

The electrical activity of single pyramidal cells in the hippocampus was monitored extracellularly during electrical stimulation of nucleus locus coeruleus (LC) in anesthetized rats. Stimulation of the LC produced long-lasting inhibition of spontaneous activity of pyramidal cells. This inhibition was reversibly blocked during iontophoretic administration of MJ-1999, a beta adrenergic blocking agent, potentiated during administration of DMI and was absent in 6-OHDA treated rats. The inhibition was not apparently mediated by extraneuronal mechanisms nor by a GABA containing synapse. It was potentiated by papaverine and antagonized by prostaglandin E 1, substances which affect cAMP metabolism. It is suggested that the inhibitory synapses of the fibers from LC to the hippocampus utilize NE as a transmitter.