Neuromodulation of ganglia
Modulation of neural activity of a ganglion, by applying a signal to a sympathetic nerve adjacent to the ganglion, results in preferential reduction of sympathetic signals to an effector, thereby providing ways of treating and preventing conditions associated with exacerbated sympatho-excitation.
1. A system for reversibly modulating neural activity of a sympathetic nerve, wherein the system comprises:
at least two neural interfacing elements suitable for placement on or around the sympathetic nerve adjacent to a ganglion, wherein the ganglion transmits sympathetic signals between the ganglion and an effector; and
at least one voltage or current source configured to generate at least one electrical signal with a charge density per phase to be applied to the sympathetic nerve, via the at least two neural interfacing elements, to modulate the neural activity of the sympathetic nerve to reduce sympatho-excitation in the effector,
wherein the at least two neural interfacing elements are arranged such that the electrical signal incites action potentials in the sympathetic nerve that propagate away from the effector, towards the ganglion, wherein a first neural interfacing element is positioned along a nerve axis adjacent to a second neural interfacing element, and arranged such that the second neural interfacing element is closer to the effector along the nerve axis than the first neural interfacing element and either (i) a surface area of the first neural interfacing element is larger than a surface area of the second neural interfacing element or (ii) the first neural interfacing element is radially recessed away from the sympathetic nerve relative to the second neural interfacing element or (iii) the surface area of the first neural interfacing element is larger than the surface area of the second neural interfacing element and the first neural interfacing element is radially recessed away from the sympathetic nerve relative to the second neural interfacing element,
wherein the charge density per phase applied to the sympathetic nerve by the electrical signal is below a predetermined threshold,
the predetermined threshold defined as a minimum charge density per phase required to produce a response associated with sympatho-excitation in the effector by modulating the neural activity of the sympathetic nerve.
2. The system of claim 1 , wherein the at least two neural interfacing elements comprises at least a first electrode and a second electrode, the first electrode being positioned, in use, along the nerve axis adjacent to the second electrode, and arranged such that the first electrode is closer to the ganglion than the second electrode along the nerve axis, and wherein the first electrode is configured to be a cathode and the second electrode is configured to be an anode.
3. The system of claim 2 , wherein the first electrode has a greater width than the second electrode, the width defined as the distance an electrode spans along a longitudinal axis of the sympathetic nerve.
4. The system of claim 2 , wherein the first electrode is recessed away from the sympathetic nerve and the second electrode is in contact with the sympathetic nerve.
5. The system of claim 1 , wherein the at least one electrical signal to be applied to the sympathetic nerve has a pulse train waveform.
6. The system of claim 5 , wherein the pulse train waveforms are charged-balanced biphasic pulses.
7. The system of claim 5 , wherein the pulse train waveforms have a pulse duration of ≤2 ms.
8. The system of claim 5 , wherein the pulse train waveform is a charge-balanced DC waveform.
9. The system of claim 5 , wherein the at least one electrical signal has a frequency of ≤10 Hz.
10. The system of claim 5 , wherein the at least one electrical signal has an average current intensity of ≤10 mA.
11. The system of claim 1 , wherein the charge density per phase applied to the sympathetic nerve by the electrical signal is between 0.1τ and 0.9τ, where τ is the predetermined threshold.
12. The system of claim 1 , wherein the predetermined threshold is ≤80 μC/cm 2 /phase.
13. The system of claim 1 , wherein the sympathetic nerve is a branch of a greater splanchnic nerve, the effector is a foregut, wherein the response associated with sympatho-excitation of foregut comprises an increase in blood pressure, an increase in heart rate and/or an increase in myocardial contractility.
14. The system of claim 13 , wherein the ganglion is a suprarenal ganglion, and at least two neural interfacing elements suitable are configured to be placed on the sympathetic nerve between the suprarenal ganglion and a celiac ganglion.
15. The system of claim 13 , wherein the ganglion is the celiac ganglia, and the first and second electrodes are configured to be placed on the sympathetic nerve between the celiac ganglion and the foregut.
16. The system of claim 13 , for use in treating conditions associated with impaired glucose control.
17. A method of reversibly modulating neural activity in a sympathetic nerve, comprising:
(i) implanting in the subject a system of claim 1 ;
(ii) positioning the at least two neural interfacing elements of the system at the nerve adjacent to a ganglion; and optionally
(iii) activating the system.
18. The method of claim 17 , wherein the method is for treating or preventing a condition associated with impaired glucose control, wherein the effector is an organ in a foregut, further comprising assessing a change in a response associated with sympatho-excitation of the organ in a foregut, the response comprising an increase in blood pressure, an increase in heart rate or an increase in myocardial contractility.
19. A method for reversibly modulating neural activity of a sympathetic nerve, comprising:
placing at least two neural interfacing elements on or around the sympathetic nerve adjacent to a ganglion, wherein the ganglion transmits sympathetic signals between the ganglion and an effector; and
applying, by at least one voltage or current source, at least one electrical signal with a charge density per phase to the sympathetic nerve, via the at least two neural interfacing elements, to modulate the neural activity of the sympathetic nerve to reduce sympatho-excitation in the effector, wherein the at least two neural interfacing elements are arranged such that the electrical signal incites action potentials in the sympathetic nerve which propagate away from the effector, towards the ganglion, wherein a first neural interfacing element is positioned along a nerve axis adjacent to a second neural interfacing element, and arranged such that the second neural interfacing element is closer to the effector along the nerve axis than the first neural interfacing element and either (i) a surface area of the first neural interfacing element is larger than a surface area of the second neural interfacing element or (ii) the first neural interfacing element is radially recessed away from the sympathetic nerve relative to the second neural interfacing element or (iii) the surface area of the first neural interfacing element is larger than the surface area of the second neural interfacing element and the first neural interfacing element is radially recessed away from the sympathetic nerve relative to the second neural interfacing element, wherein the charge density per phase applied to the sympathetic nerve by the electrical signal is below a predetermined threshold, the predetermined threshold defined as a minimum charge density per phase required to produce a response associated with sympatho-excitation in the effector by modulating the neural activity of the sympathetic nerve.
20. The method of claim 19 , wherein the effector is a foregut, and the method for use in treating conditions associated with impaired glucose control.