Locus coeruleus, noradrenergic neurons

Figure 4.1 Effect of an iontophoretic injection of bicuculline, a GABAa antagonist, on a locus coeruleus noradrenergic neuron. With reduced activity during slow wave sleep, this neuron then becomes silent during paradoxical sleep (PS). The application of bicuculline reversibly restores tonic discharge, indicating the role of GABA in the cessation of activity of this neuron during PS.

Verret, L Fort, P., Gervasoni, D., Leger, L. Luppi, P. H. (2006). Localization of the neurons active during paradoxical (REM) sleep and projecting to the locus coeruleus noradrenergic neurons in the rat. J. Comp. Neurol. 495, 573-86. 

Srinivasan J, Schmidt WJ (2004c) Functional recovery of locus coeruleus noradrenergic neurons after DSP-4 lesion effects on dopamine levels and neuroleptic induced-parkinsonian symptoms in rats. J. Neural Transm. 111 13-26. 

Adult Locus coeruleus Noradrenergic neurons Substantia nigra 80% 6-OHDA in adult Arenas and Persson, 1994... 

The inhibition of firing of catecholamine neurons resulting from amphetamine administration is likely due to activation of somatodendritic autoreceptors. This causes a hyperpolarization of the somatodendritic membrane of both locus coeruleus noradrenergic and substantia nigra dopamine neurons, probably as a consequence of an increase in potassium conductance (Lacey et al. 1987 Williams et al. 1985). 

Other hand, the locus coeruleus is known to be richly innervated with CRH im-munoreactive fibers (Valentino et al. 1993). Stress- or CRH-induced increases in locus coeruleus neuronal firing are blocked by CRH receptor antagonists and chronic antidepressant treatment (e.g., Valentino et al. 1990 Schulz et al. 1996), suggesting that anxiogenic effects of CRH are mediated through its actions on the locus coeruleus noradrenergic system (Butler et al. 1990). 

NET (SLC6A2) Noradre-naline, dopamine 1 CNS noradrenergic neurons (emanate from locus coeruleus and lateral tegmental area), sympathetic nervous system Clearance of interstitial neuro-transmitter, reuptake into neurons... 

Figure 8.2 The distribution of noradrenergic neurons in the brain. The cell bodies are clustered in nuclei (A1 A7) in the pons/medulla regions of the brainstem and their axons project both rostrally and caudally to most regions of the neuraxis. The major nucleus is the locus coeruleus...

Figure 8.3 Brain areas receiving a prominent noradrenergic innervation. Most brain regions are innervated by neurons projecting from both the locus coeruleus and the lateral tegmental system. However, the frontal cortex, hippocampus and olfactory bulb are innervated exclusively by neurons with cell bodies in the locus coeruleus. With the exception of the paraventricular nucleus (and possibly the suprachiasmatic nucleus) hypothalamic nuclei are innervated by neurons projecting from the lateral tegmental system...

Many electrophysiological studies have shown that single-unit activity of noradrenergic neurons in the locus coeruleus is increased by sensory stimuli. Effective stimuli range from those causing physical discomfort (e.g. footshock) and interoceptive... 

Cederbaum, JM and Aghajanian, GK (1976) Noradrenergic neurons of the locus coeruleus inhibition by epinephrine and activation by the alpha-antagonist piperoxane. Brain Res. 112 413-419. 

Gervasoni, D Darracq, L., Fort, P. et al. (1998). Electrophysiological evidence that noradrenergic neurons of the rat locus coeruleus are tonically inhibited by GABA during sleep. Eur. J. Neurosci. 10, 964-70. 

---