Acupuncture and Parasympathetic Activity and Enkephalins, Longhurst

Readers of this blog are familiar with Dr. Longhurst. I’ve blogged about his work on acupuncture and hypertension and his recent conference here, here, and here. I also mentioned how he is convinced that electro acupuncture is necessary, indeed in this study his control is manual acupuncture. This is a study looking at electro acupuncture in cats at PC 5 and 6, showing that stimulation in the neurons of the nucleus ambiguous may be responsible for the increase in parasympathetic activity induced by acupuncture. This area of inquiry is of keen interest to me since my research concerns the autonomic nervous system and acupuncture effectiveness. More info on my practice here.

Nucleus ambiguus cholinergic neurons activated by acupuncture: Relation to enkephalin.
Brain Res. 2012 Jan 12.
Guo ZL, Li M, Longhurst JC.

Acupuncture regulates autonomic function. Our previous studies have shown that electroacupuncture (EA) at the Jianshi-Neiguan acupoints (P5-P6, underlying the median nerve) inhibits central sympathetic outflow and attenuates excitatory cardiovascular reflexes, in part, through an opioid mechanism. It is unknown if EA at these acupoints influences the parasympathetic system. Thus, using c-Fos expression, we examined activation of nucleus ambiguus (NAmb) neurons by EA, their relation to cholinergic (preganglionic parasympathetic) neurons and those containing enkephalin. To enhance detection of cell bodies containing enkephalin, colchicine (90-100μg/kg) was administered into the subarachnoid space of cats 30h prior to EA or sham-operated controls for EA. Following bilateral barodenervation and cervical vagotomy, either EA for 30min at P5-P6 acupoints or control stimulation (needle placement at P5-P6 without stimulation) was applied. While perikarya containing enkephalin were observed in some medullary nuclei (e.g., raphé), only enkephalin-containing neuronal processes were found in the NAmb. Compared to controls (n=4), more c-Fos immunoreactivity, located principally in close proximity to fibers containing enkephalin was noted in the NAmb of EA-treated cats (n=5; P<0.01). Moreover, neurons double-labeled with c-Fos and choline acetyltransferase in the NAmb were identified in EA-treated, but not control animals. These data demonstrate for the first time that EA activates preganglionic parasympathetic neurons in the NAmb. Because of their close proximity, these EA-activated neurons likely interact with nerve fibers containing enkephalin. These results suggest that EA at the P5-P6 acupoints has the potential to influence parasympathetic outflow and cardiovascular function, likely through an enkephalinergic mechanism.