The Modulatory Effect of Acupuncture on the Activity of Locus Coeruleus Neuronal Cells: A Review

The Locus Coeruleus (LC) is a small collection of noradrenergic neurons located in the pons. In the brain, noradrenaline (NE) is primarily produced by noradrenergic cell groups in the LC, which is the largest group of noradrenergic neurons in the central nervous system. Acupuncture, including the electroacupuncture which is a modified acupuncture method, is known to be effective in various kinds of diseases, and the involvement of noradrenergic system in the central nervous system has been reported by previous studies. However, on whether acupuncture can modulate the LC neuronal cells activities, results vary from studies to studies. In this paper, we included twelve articles, which observed the effect of acupuncture on the activities of LC in humans and animals. Our study shows that, among twelve included studies, six reported decrease of LC activities, whereas six showed increase of LC activities after acupuncture treatment. Although it is difficult to draw a firm conclusion, the authors suggest that the difference of frequencies may play an important role in the modulatory effect of acupuncture on LC. Further studies are needed to clarify the precise mechanism of acupuncture on LC, as it can lead to a new therapeutic method for various LC-NE related diseases.

Allergic lung inflammation affects central noradrenergic control of cholinergic outflow to the airways in ferrets

Brain stem noradrenergic cell groups mediating autonomic responses to stress project to airway-related vagal preganglionic neurons (AVPNs). In ferrets, their activation produces withdrawal of cholinergic outflow to the airways via release of norepinephrine and activation of α2A-adrenergic receptors (α2A-AR) expressed by AVPNs. In these studies, we examined the effects of allergen exposure of the airway (AE) with ovalbumin on noradrenergic transmission regulating the activity of AVPNs and, consequently, airway smooth muscle tone. Experiments were performed in vehicle control (Con) and AE ferrets. Microperfusion of an α2A-AR agonist (guanabenz) in close proximity to AVPNs elicited more pronounced effects in Con than AE ferrets, including a decrease in unit activity and reflexly evoked responses of putative AVPN neurons with a corresponding decrease in cholinergic outflow to the airways. Although no differences were found in the extent of noradrenergic innervation of the AVPNs, RT-PCR and Western blot studies demonstrated that AE and repeated exposure to antigen significantly reduced expression of α2A-ARs at message and protein levels. These findings indicate that, in an animal model of allergic asthma, sensitization and repeated challenges with a specific allergen diminish central inhibitory noradrenergic modulation of AVPNs, possibly via downregulation of α2A-AR expression by these neurons.