Name: Video: Surgical Disruption of Sympathetic Neurons in Mice for Peripheral Nerve Study
Uploaded: 2024-07-05T13:40:00
Description: 348 Views. Surgical Disruption of Sympathetic Neurons in Mice for Peripheral Nerve Study

surgical disruption of sympathetic neurons in mice for peripheral nerve study

Targeting Mouse Sympathetic Neurons: A Lumbar Sympathectomy Approach

Peripheral nerve injuries (PNIs) can lead to motor, sensory, and sympathetic deficits in distal tissue targets that rarely fully functionally recover1. PNI research has often focused on the&#160;motor and sensory regeneration; however, nearly one-quarter of the rat sciatic nerve consists of unmyelinated sympathetic axons2.&#160;The role of sympathetic innervation in the peripheral tissues, nevertheless, is not fully understood3. The sympathetic nervous system plays a major role in maintaining bodily homeostasis, participating in immune regulation, thermoregulation, vascular tone, mitochondrial biogenesis, and more4,5,6,7,8,9,10,11. When sympathetic innervation at the neuromuscular junction is lost, persistent muscle weakness and synaptic instability are observed despite the maintenance of motoneuron innervation12. This sympathetic regulation of synaptic transmission at the neuromuscular junction has been shown to decline with aging13,14, which contributes to sarcopenia, defined as the age-dependent reduction in muscle mass, force, and power15. A better understanding of the role of sympathetic innervation of peripheral tissues is necessary for the development of therapies that will optimize functional outcomes for patients with PNIs and other forms of sympathetic dysfunction.
A sympathectomy is a powerful experimental tool that will allow for investigations of the role of sympathetic innervation in distal target tissues. Specifically, removal of the L2-L5 level sympathetic ganglia removes a majority of the sympathetic innervation to the lower limbs, which is especially useful for investigators interested in the sciatic nerve.
This protocol details the removal of L2-L5 level postganglionic sympathetic neurons from a mouse as a survival surgery. This procedure requires rodent microsurgical skills and familiarity with mouse anatomy, and when performed effectively, does not cause any visible phenotypic differences. A surgical lumbar sympathectomy has been used in rodent research, more so in rats than in mice16,17,18,19,20,21; however, a detailed protocol describing the protocol does not currently exist. Previous studies utilizing the lumbar sympathectomy have primarily focused on the role of sympathetic innervation in the pain response, which is generally attenuated by sympathectomy in various nerve injury models. Fewer studies have used this technique in mice22, likely due to the smaller size of anatomic landmarks, as the use of surgical sympathectomy was believed to be &#34;virtually not practicable&#34; in small animals23,24. Localized sympathectomies in the form of microsympathectomies have also been utilized in rodent models, also mostly in the context of pain behaviors25,26,27. The microsympathectomy, in contrast to the total lumbar sympathectomy, utilizes a dorsal approach through which a segment of the gray ramus to a specific spinal nerve is disconnected and removed, allowing for a very targeted sympathectomy that will avoid wider spread side effects.
Because mouse models are critical for many studies requiring genetic manipulation, this procedure will have versatile applications beyond the breadth of peripheral nerve injuries as well. Using a transabdominal approach, the lumbar sympathetic ganglia can be reliably visualized and resected from the mouse with no apparent adverse effects. Although protocols for the chemical destruction of postganglionic sympathetic neurons are available, such as the use of 6-hydroxydopamine (6-OHDA)23,24, this surgical procedure allows for anatomically specific targeting of the postganglionic lumbar sympathetic ganglia. The use of a surgical sympathectomy also avoids the nonspecific and dose-dependent concerns related to pharmacological methods28,29.
The use of chemical sympathectomies via administration of 6-OHDA was described in 1967 as a simple way to achieve selective destruction of adrenergic nerve endings since surgical sympathectomies in small animals were not favored23,24. 6-OHDA is a catecholaminergic neurotoxin that is endogenously formed in patients with Parkinson&#39;s disease, and its toxicity is derived from its ability to form free radicals and inhibit the electron transport chain in mitochondria30,31. Through norepinephrine uptake-1 transport mechanisms, 6-OHDA is able to accumulate within noradrenergic neurons, such as postganglionic sympathetic neurons28. Eventually, the neuron is destroyed by 6-OHDA; however, terminals in the peripheral nervous system do regenerate, with the restoration of functional activity even when the amine levels are still reduced. Different dosage thresholds are also present for different organs in response to 6-OHDA, and higher doses of 6-OHDA have been shown to exhibit more nonspecific effects, extending its neurotoxic consequences to non-catecholamine-containing neurons and even non-neuronal cells. Aside from noradrenergic neurons, dopaminergic neurons are affected by 6-OHDA as well29, making the chemical sympathectomy ultimately less specific to postganglionic sympathetic neurons than the surgical sympathectomy.
Therefore, a surgical lumbar sympathectomy enables the targeted ablation of the sympathetic innervation to the lower limbs, which can be combined with a variety of experimental techniques and genetic manipulations in the mouse to study how the sympathetic nervous system contributes to various injury and disease states.

Author Spotlight: Exploring Plasticity of Sympathetic Neurons

Surgical Lumbar Sympathectomy in Mice

Surgical Disruption of Sympathetic Neurons in Mice for Peripheral Nerve Study

surgical-disruption-sympathetic-neurons-mice-for-peripheral-nerve

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348 Views. Surgical Disruption of Sympathetic Neurons in Mice for Peripheral Nerve Study

Video: Surgical Disruption of Sympathetic Neurons in Mice for Peripheral Nerve Study

Peripheral nerve injuries are common, and full functional recovery after injury is achieved in only 10% of patients. The sympathetic nervous system plays many critical roles in maintaining bodily homeostasis, but it has rarely been studied in the context of peripheral nerve injury. The extent of postganglionic sympathetic neuronal functions in distal targets in the periphery is currently unclear. To better explore the role of sympathetic innervation of peripheral targets, a surgical &#34;knock-out&#34; model provides an alternative approach. Although this can be achieved chemically, chemical destruction of postganglionic sympathetic neurons can be nonspecific and dose-dependent. The use of a surgical lumbar sympathectomy in mice, once thought to be &#34;virtually not practicable&#34; in small animals, allows for specific targeting of postganglionic sympathetic neurons that innervate the hind limbs. This manuscript describes how to surgically remove the L2-L5 lumbar sympathetic ganglia from a mouse as a survival surgery, which reliably decreases the hind paw sweat response and the number of sympathetic axons in the sciatic nerve.

This manuscript presents a protocol for surgically removing the postganglionic lumbar sympathetic neurons from a mouse. This procedure will facilitate a multitude of studies aimed at investigating the role of sympathetic innervation in distal tissue targets.

Peripheral nerve injuries are common, and full functional recovery after injury is achieved in only 10% of patients. The sympathetic nervous system plays ...