the present invention will preferably utilize microfabricated catheters for intravascular injection . the following description and fig1 - 8 provide three representative embodiments of catheters having microneedles suitable for the delivery of a neuromodulating agent into a perivascular space or adventitial tissue . a more complete description of the catheters and methods for their fabrication is provided in u . s . pat . nos . 7 , 141 , 041 ; 6 , 547 , 803 ; 7 , 547 , 294 ; 7 , 666 , 163 and 7 , 691 , 080 , the full disclosures of which have been incorporated herein by reference . the present invention describes methods and kits useful for the delivery of neuromodulating agents into the adventitia around renal arteries in order to reduce blood pressure in the treatment of hypertension . in each kit , a delivery catheter may be combined with instructions for use and a therapeutically effective amount of a neuromodulating agent as defined above . as shown in fig1 a - 2b , a microfabricated intraluminal catheter 10 includes an actuator 12 having an actuator body 12 a and central longitudinal axis 12 b . the actuator body more or less forms a u - shaped or c - shaped outline having an opening or slit 12 d extending substantially along its length . a microneedle 14 is located within the actuator body , as discussed in more detail below , when the actuator is in its unactuated condition ( furled state ) ( fig1 b ). the microneedle is moved outside the actuator body when the actuator is operated to be in its actuated condition ( unfurled state ) ( fig2 b ). the actuator may be capped at its proximal end 12 e and distal end 12 f by a lead end 16 and a tip end 18 , respectively , of a therapeutic catheter 20 . the catheter tip end serves as a means of locating the actuator inside a body lumen by use of a radio opaque coatings or markers . the catheter tip also forms a seal at the distal end 12 f of the actuator . the lead end of the catheter provides the necessary interconnects ( fluidic , mechanical , electrical or optical ) at the proximal end 12 e of the actuator . retaining rings 22 a and 22 b are located at the distal and proximal ends , respectively , of the actuator . the catheter tip is joined to the retaining ring 22 a , while the catheter lead is joined to retaining ring 22 b . the retaining rings are made of a thin , on the order of 10 to 100 microns ( μm ), substantially flexible but relatively non - distensible material , such as parylene ( types c , d or n ), or a metal , for example , aluminum , stainless steel , gold , titanium or tungsten . the retaining rings form a flexible but relatively non - distensible substantially “ u ”- shaped or “ c ”- shaped structure at each end of the actuator . the catheter may be joined to the retaining rings by , for example , a butt - weld , an ultra sonic weld , integral polymer encapsulation or an adhesive such as an epoxy or cyanoacrylate . the actuator body further comprises a central , expandable section 24 located between retaining rings 22 a and 22 b . the expandable section 24 includes an interior open area 26 for rapid expansion when an activating fluid is supplied to that area . the central section 24 is made of a thin , semi - flexible but relatively non - distensible or flexible but relatively non - distensible , expandable material , such as a polymer , for instance , parylene ( types c , d or n ), silicone , polyurethane or polyimide . the central section 24 , upon actuation , is expandable somewhat like a balloon - device . the central section is capable of withstanding pressures of up to about 200 psi upon application of the activating fluid to the open area 26 . the material from which the central section is made of is flexible but relatively non - distensible or semi - flexible but relatively non - distensible in that the central section returns substantially to its original configuration and orientation ( the unactuated condition ) when the activating fluid is removed from the open area 26 . thus , in this sense , the central section is very much unlike a balloon which has no inherently stable structure . the open area 26 of the actuator is connected to a delivery conduit , tube or fluid pathway 28 that extends from the catheter &# 39 ; s lead end to the actuator &# 39 ; s proximal end . the activating fluid is supplied to the open area via the delivery tube . the delivery tube may be constructed of teflon © or other inert plastics . the activating fluid may be a saline solution or a radio - opaque dye . the microneedle 14 may be located approximately in the middle of the central section 24 . however , as discussed below , this is not necessary , especially when multiple microneedles are used . the microneedle is affixed to an exterior surface 24 a of the central section . the microneedle is affixed to the surface 24 a by an adhesive , such as cyanoacrylate . alternatively , the microneedle maybe joined to the surface 24 a by a metallic or polymer mesh - like structure 30 ( see fig2 a ), which is itself affixed to the surface 24 a by an adhesive . the mesh - like structure may be - made of , for instance , steel or nylon . the microneedle includes a sharp tip 14 a and a shaft 14 b . the microneedle tip can provide an insertion edge or point . the shaft 14 b can be hollow and the tip can have an outlet port 14 c , permitting the injection of a neuromodulating or drug into a patient . the microneedle , however , does not need to be hollow , as it may be configured like a neural probe to accomplish other tasks . as shown , the microneedle extends approximately perpendicularly from surface 24 a . thus , as described , the microneedle will move substantially perpendicularly to an axis of a lumen into which has been inserted , to allow direct puncture or breach of body lumen walls . the microneedle further includes a neuromodulating or drug supply conduit , tube or fluid pathway 14 d which places the microneedle in fluid communication with the appropriate fluid interconnect at the catheter lead end . this supply tube may be formed integrally with the shaft 14 b , or it may be formed as a separate piece that is later joined to the shaft by , for example , an adhesive such as an epoxy . the microneedle 14 may be bonded to the supply tube with , for example , an adhesive such as cyanoacrylate . the needle 14 may be a 30 - gauge , or smaller , steel needle . alternatively , the microneedle may be microfabricated from polymers , other metals , metal alloys or semiconductor materials . the needle , for example , may be made of parylene , silicon or glass . microneedles and methods of fabrication are described in u . s . application ser . no . 09 / 877 , 653 , filed jun . 8 , 2001 , entitled “ microfabricated surgical device ”, the entire disclosure of which is incorporated herein by reference . the catheter 20 , in use , is inserted through an opening in the body ( e . g . for bronchial or sinus treatment ) or through a percutaneous puncture site ( e . g . for artery or venous treatment ) and moved within a patient &# 39 ; s body passageways 32 , until a specific , targeted region 34 is reached ( see fig3 ). the targeted region 34 may be the site of tissue damage or more usually will be adjacent the sites typically being within 100 mm or less to allow migration of the therapeutic or diagnostic agent . as is well known in catheter - based interventional procedures , the catheter 20 may follow a guide wire 36 that has previously been inserted into the patient . optionally , the catheter 20 may also follow the path of a previously - inserted guide catheter ( not shown ) that encompasses the guide wire . during maneuvering of the catheter 20 , well - known methods of x - ray fluoroscopy or magnetic resonance imaging ( mri ) can be used to image the catheter and assist in positioning the actuator 12 and the microneedle 14 at the target region . as the catheter is guided inside the patient &# 39 ; s body , the microneedle remains furled or held inside the actuator body so that no trauma is caused to the body lumen walls . after being positioned at the target region 34 , movement of the catheter is terminated and the activating fluid is supplied to the open area 26 of the actuator , causing the expandable section 24 to rapidly unfurl , moving the microneedle 14 in a substantially perpendicular direction , relative to the longitudinal central axis 12 b of the actuator body 12 a , to puncture a body lumen wall 32 a . it may take only between approximately 100 milliseconds and five seconds for the microneedle to move from its furled state to its unfurled state . the microneedle aperture , may be designed to enter body lumen tissue 32 b as well as the adventitia , media , or intima surrounding body lumens . additionally , since the actuator is “ parked ” or stopped prior to actuation , more precise placement and control over penetration of the body lumen wall are obtained . after actuation of the microneedle and delivery of the agents to the target region via the microneedle , the activating fluid is exhausted from the open area 26 of the actuator , causing the expandable section 24 to return to its original , furled state . this also causes the microneedle to be withdrawn from the body lumen wall . the microneedle , being withdrawn , is once again sheathed by the actuator . various microfabricated devices can be integrated into the needle , actuator and catheter for metering flows , capturing samples of biological tissue , and measuring ph . the device 10 , for instance , could include electrical sensors for measuring the flow through the microneedle as well as the ph of the neuromodulating being deployed . the device 10 could also include an intravascular ultrasonic sensor ( ivus ) for locating vessel walls , and fiber optics , as is well known in the art , for viewing the target region . for such complete systems , high integrity electrical , mechanical and fluid connections are provided to transfer power , energy , and neuromodulatings or biological agents with reliability . by way of example , the microneedle may have an overall length of between about 200 and 3 , 000 microns ( μm ). the interior cross - sectional dimension of the shaft 14 b and supply tube 14 d may be on the order of 20 to 250 um , while the tube &# 39 ; s and shaft &# 39 ; s exterior cross - sectional dimension may be between about 100 and 500 μm . the overall length of the actuator body may be between about 5 and 50 millimeters ( mm ), while the exterior and interior cross - sectional dimensions of the actuator body can be between about 0 . 4 and 4 mm , and 0 . 5 and 5 mm , respectively . the gap or slit through which the central section of the actuator unfurls may have a length of about 4 - 40 mm , and a cross - sectional dimension of about 50 μm to 4 mm . the diameter of the delivery tube for the activating fluid may be between 100 and 500 μm . the catheter size may be between 1 . 5 and 15 french ( fr ). referring to fig4 a - 4d , an elastomeric component is integrated into the wall of the intraluminal catheter of fig1 - 3 . in fig4 a - d , the progressive pressurization of such a structure is displayed in order of increasing pressure . in fig4 a , the balloon is placed within a body lumen l . the lumen wall w divides the lumen from periluminal tissue t , or adventitia a *, depending on the anatomy of the particular lumen . the pressure is neutral , and the non - distensible structure forms a u - shaped involuted balloon 12 similar to that in fig1 in which a needle 14 is sheathed . while a needle is displayed in this diagram , other working elements including cutting blades , laser or fiber optic tips , radiofrequency transmitters , or other structures could be substituted for the needle . for all such structures , however , the elastomeric patch 400 will usually be disposed on the opposite side of the involuted balloon 12 from the needle 14 . actuation of the balloon 12 occurs with positive pressurization . in fig4 b , pressure (+ δp 1 ) is added , which begins to deform the flexible but relatively non - distensible structure , causing the balloon involution to begin its reversal toward the lower energy state of a round pressure vessel . at higher pressure + δp 2 in fig4 c , the flexible but relatively non - distensible balloon material has reached its rounded shape and the elastomeric patch has begun to stretch . finally , in fig4 d at still higher pressure + δp 3 , the elastomeric patch has stretched out to accommodate the full lumen diameter , providing an opposing force to the needle tip and sliding the needle through the lumen wall and into the adventitia a . typical dimensions for the body lumens contemplated in this figure are between 0 . 1 mm and 50 mm , more often between 0 . 5 mm and 20 mm , and most often between 1 mm and 10 mm . the thickness of the tissue between the lumen and adventitia is typically between 0 . 001 mm and 5 mm , more often between 0 . 01 mm and 2 mm and most often between 0 . 05 mm and 1 mm . the pressure + δp useful to cause actuation of the balloon is typically in the range from 0 . 1 atmospheres to 20 atmospheres , more typically in the range from 0 . 5 to 20 atmospheres , and often in the range from 1 to 10 atmospheres . as illustrated in fig5 a - 5c , the dual modulus structure shown in fig4 a - 4d provides for low - pressure ( i . e ., below pressures that may damage body tissues ) actuation of an intraluminal medical device to place working elements such as needles in contact with or through lumen walls . by inflation of a constant pressure , and the elastomeric material will conform to the lumen diameter to provide full apposition . dual modulus balloon 12 is inflated to a pressure + δp 3 in three different lumen diameters in fig5 a , 5 b , and 5 c for the progressively larger inflation of patch 400 provides optimal apposition of the needle through the vessel wall regardless of diameter . thus , a variable diameter system is created in which the same catheter may be employed in lumens throughout the body that are within a range of diameters . this is useful because most medical products are limited to very tight constraints ( typically within 0 . 5 mm ) in which lumens they may be used . a system as described in this invention may accommodate several millimeters of variability in the luminal diameters for which they are useful . the above catheter designs and variations thereon , are described in published u . s . pat . nos . 6 , 547 , 803 ; 6 , 860 , 867 ; 7 , 547 , 294 ; 7 , 666 , 163 and 7 , 691 , 080 , the full disclosures of which are incorporated herein by reference . co - pending application ser . no . 10 / 691 , 119 , assigned to the assignee of the present application , describes the ability of substances delivered by direct injection into the adventitial and pericardial tissues of the heart to rapidly and evenly distribute within the heart tissues , even to locations remote from the site of injection . the full disclosure of that co - pending application is also incorporated herein by reference . an alternative needle catheter design suitable for delivering the therapeutic or diagnostic agents of the present invention will be described below . that particular catheter design is described and claimed in u . s . pat . no . 7 , 141 , 041 , the full disclosure of which is incorporated herein by reference . referring now to fig6 , a needle injection catheter 310 constructed in accordance with the principles of the present invention comprises a catheter body 312 having a distal end 314 and a proximal 316 . usually , a guide wire lumen 313 will be provided in a distal nose 352 of the catheter , although over - the - wire and embodiments which do not require guide wire placement will also be within the scope of the present invention . a two - port hub 320 is attached to the proximal end 316 of the catheter body 312 and includes a first port 322 for delivery of a hydraulic fluid , e . g ., using a syringe 324 , and a second port 326 for delivering the neuromodulating agent , e . g ., using a syringe 328 . a reciprocatable , deflectable needle 330 is mounted near the distal end of the catheter body 312 and is shown in its laterally advanced configuration in fig6 . referring now to fig7 , the proximal end 314 of the catheter body 312 has a main lumen 336 which holds the needle 330 , a reciprocatable piston 338 , and a hydraulic fluid delivery tube 340 . the piston 338 is mounted to slide over a rail 342 and is fixedly attached to the needle 330 . thus , by delivering a pressurized hydraulic fluid through a lumen 341 tube 340 into a bellows structure 344 , the piston 338 may be advanced axially toward the distal tip in order to cause the needle to pass through a deflection path 350 formed in a catheter nose 352 . as can be seen in fig8 , the catheter 310 may be positioned in a blood vessel bv , over a guide wire gw in a conventional manner . distal advancement of the piston 338 causes the needle 330 to advance into tissue t surrounding the lumen adjacent to the catheter when it is present in the blood vessel . the therapeutic or diagnostic agents may then be introduced through the port 326 using syringe 328 in order to introduce a plume p of agent in the cardiac tissue , as illustrated in fig8 . the plume p will be within or adjacent to the region of tissue damage as described above . the needle 330 may extend the entire length of the catheter body 312 or , more usually , will extend only partially into the therapeutic or diagnostic agents delivery lumen 337 in the tube 340 . a proximal end of the needle can form a sliding seal with the lumen 337 to permit pressurized delivery of the agent through the needle . the needle 330 will be composed of an elastic material , typically an elastic or super elastic metal , typically being nitinol or other super elastic metal . alternatively , the needle 330 could be formed from a non - elastically deformable or malleable metal which is shaped as it passes through a deflection path . the use of non - elastically deformable metals , however , is less preferred since such metals will generally not retain their straightened configuration after they pass through the deflection path . the bellows structure 344 may be made by depositing by parylene or another conformal polymer layer onto a mandrel and then dissolving the mandrel from within the polymer shell structure . alternatively , the bellows 344 could be made from an elastomeric material to form a balloon structure . in a still further alternative , a spring structure can be utilized in , on , or over the bellows in order to drive the bellows to a closed position in the absence of pressurized hydraulic fluid therein . after the therapeutic material is delivered through the needle 330 , as shown in fig8 , the needle is retracted and the catheter either repositioned for further agent delivery or withdrawn . in some embodiments , the needle will be retracted simply by aspirating the hydraulic fluid from the bellows 344 . in other embodiments , needle retraction may be assisted by a return spring , e . g ., locked between a distal face of the piston 338 and a proximal wall of the distal tip 352 ( not shown ) and / or by a pull wire attached to the piston and running through lumen 341 . the perivascular space is the potential space over the outer surface of a “ vascular wall ” of either an artery or vein . referring to fig9 , a typical arterial wall is shown in cross - section where the endothelium e is the layer of the wall which is exposed to the blood vessel lumen l . underlying the endothelium is the basement membrane bm which in turn is surrounded by the intima i . the intima , in turn , is surrounded by the internal elastic lamina iel over which is located the media m . in turn , the media is covered by the external elastic lamina ( eel ) which acts as the outer barrier separating the arterial wall , shown collectively as w , from the adventitial layer a . usually , the perivascular space will be considered anything lying beyond the external elastic lamina eel , including regions within the adventitia and beyond . turning now to fig1 a - c , the renal arterial location and structure are shown . in fig1 a , the aorta ( ao ) is shown as the central artery of the body , with the right renal artery ( rra ) and left renal artery ( lra ) branching from the aorta to lead blood into the kidneys . for example , the right renal artery leads oxygenated blood into the right kidney ( rk ). in fig1 b , the nerves ( n ) that lead from the aorta to the kidney are displayed . the nerves are shown to surround the renal artery , running roughly parallel but along a somewhat tortuous and branching route from the aorta to the kidney . the cross - section along line 10 c - 10 c of fig1 b is then shown in fig1 c . as seen in this cross - sectional representation of a renal artery , the nerves ( n ) that lead from aorta to kidney run through the arterial adventitia ( a ) and in close proximity but outside the external elastic lamina ( eel ). the entire arterial cross section is shown in this fig1 c , with the lumen ( l ) surrounded by , from inside to outside , the endothelium ( e ), the intima ( i ), the internal elastic lamina ( iel ), the media ( m ), the external elastic lamina ( eel ), and finally the adventitia ( a ). as illustrated in fig1 a - f , the methods of the present invention may be used to place an injection or infusion catheter similar to those illustrated by fig1 - 5 into a vessel as illustrated in fig1 c and to inject a plume ( p ) of neuromodulating agent into the adventitia ( a ) such that the agent comes in contact with the nerves ( n ) that innervate the adventitia of the renal artery . as can be seen in fig1 a , a catheter in the same state as fig4 a , wherein an actuator is shielding a needle so that the actuator can be navigated through the vessels of the body without scraping the needle against the vessel walls and causing injury , is inserted into an artery that has a media ( m ), an adventitia ( a ), and nerves ( n ) within the adventitia and just outside the media . a cross - section along line 11 d - 11 d from fig1 a is shown in fig1 d . it can be seen from this cross section that a therapeutic instrument comprised similarly to those in fig1 - 3 , with an actuator ( 12 ) attached to a catheter ( 20 ) and a needle ( 14 ) disposed within the actuator . turning to fig1 b and 11e , we see the same system as that in fig1 a and 11d , again where fig1 e is a view of the cross - section along line 11 e - 11 e from fig1 b . in fig1 b and 11e , however , the actuator that has been filled with a fluid , causing the actuator to unfurl and expand , and the needle aperture to penetrate the media and into the adventitia where nerves are located . after the needle penetrates to the adventitia , a plume ( p ) that consists of either diagnositic agent such as radio - opaque contrast medium or neuromodulating agent such as botulinum toxin or guanethidine or a combination of the diagnostic and therapeutic agents is delivered beyond the eel and into the adventitia . the plume ( p ) begins to migrate circumferentially and longitudinally within the adventitia and begins to come into contact with the nerve fibers that run through the adventitia . at this point , the physician may begin to notice the therapeutic effects . usually , the plume p that is used to diagnose the presence of the injection and the location of the injection is in the range from 10 to 100 μa , more often around 50 ia . the plume will usually indicate one of four outcomes : ( 1 ) that the needle has penetrated into the adventitia and the plume begins to diffuse in a smooth pattern around and along the outside of the vessel , ( 2 ) that the plume follows the track of a sidebranch artery , in which case the needle aperture has been located into the sidebranch rather than in the adventitia , ( 3 ) that the plume follows the track of the artery in which the catheter is located , indicating that the needle has not penetrated the vessel wall and fluid is escaping back into the main vessel lumen , or ( 4 ) that a tightly constricted plume is forming and not diffusing longitudinally or cyndrically around the vessel , indicating that the needle aperture is located inward from the eel and inside the media or intima . the plume is therefore useful to the operating physician to determine the appropriateness of continued injection versus deflation and repositioning of the actuator at a new treatment site . in fig1 c and 11f , where fig1 f is a cross - sectional view across the line 11 f - 11 f from fig1 c , one can see that after the plume is used to diagnose the appropriate tissue location of injection , further injection can be performed to surround the vessel with the neuromodulating agent . the extent of the final plume p * is usually fully circumferential around the artery and usually travels longitudinally by at least 1 cm when the injection volume is between 300 μl and 1 ml . in many cases , less than these volumes may be required in order to observe a therapeutic benefit to the patient &# 39 ; s hypertension . at this point , the neuromodulating agent has penetrated the nerves around the entire artery , blocking the transmission of nerve signals and thereby creating chemical , neuromodulating , or biological denervation . fig1 illustrates the process by which botulinum toxin interrupts the transmission of nerve signals . in fig1 , it is seen that the toxin , here labeled “ botulinum neurotoxin ”, is comprised of a “ light chain ” and a “ heavy chain ”. the heavy chain is critical to bind the botulinum neurotoxin receptors and allow the botulinum neurotoxin to enter the cell by endocytosis . once in the cell , the light chain of botulinum neurotoxin separates from the heavy chain in this illustration and cleaves snare proteins “ syntaxin ”, “ synaptobrefin ”, and “ snap 25 ”. when these snare proteins are cleaved , vesicles containing acetylchonine cannot be released from the nerve into the synaptic cleft . while this is shown in fig1 for the neuromuscular junction , this is merely illustrative of the mechanism by which botulinum neurotoxin interacts with nerve cells , as it has also been shown that botulinum neurotoxins prohibit the release of acetylcholine and noradrenaline from other nerve junctions . the following experiments are offered by way of illustration , not by way of limitation . studies were performed in a normal porcine model to determine if adventitial delivery of guanethidine could reduce kidney norepinephrine ( ne ), a marker for successful denervation . successful denervation is well known to reduce blood pressure in hypertensive patients . renal denervation evidenced by ne reduction : guanethidine monosulfate was diluted in 0 . 9 % nacl to a concentration of 12 . 5 mg / ml , then further diluted in iodinated contrast medium to a final concentration of 10 mg / ml . this solution was injected using a mercator medsystems bullfrog micro - infusion catheter ( further described in this application and detailed in fig1 a - f ) into the adventitia of both renal arteries , approximately halfway between the aorta and the hilum of the kidney . the injection was monitored with x - ray visualization of contrast medium to confirm adventitial distribution , which was confirmed to carry the injectate longitudinally and circumferentially around the artery , as well as transversely into the perivascular tissue . no injection was made into control animals , and historical controls from connors ( connors et al , “ renal nerves mediate changes in contralateral renal blood flow after extracorporeal shockwave lithotripsy ,” nephron physiology 2003 ; 95 : 67 - 75 ) were used as comparators . twenty - eight days after injection , kidneys and renal arteries were harvested . kidney samples were taken using the method established by connors ( connors et al , “ renal nerves mediate changes in contralateral renal blood flow after extracorporeal shockwave lithotripsy ,” nephron physiology 2003 ; 95 : 67 - 75 ). briefly , cortex tissue samples from the poles of the kidneys were removed and sectioned into approximately 100 mg segments . from each kidney , samples from each pole were pooled for analysis . renal arteries were perfusion fixed in 10 % neutral buffered formalin and submitted for histopathology . histology : arteries appeared normal at 28 days , with no signs of vascular toxicity . perivascular indications of denervation were apparent from lymphocyte , macrophage and plasma cell infiltration into adventitial nerve bodies , with nerve degeneration characterized by hypervacuolization and eosinophilia . radio - immunoassay : ne levels in renal cortex tissue revealed average levels of 64 nanograms ( ng ) ne per gram ( g ) of renal cortex . when compared to normal controls of 450 ng / g , this represents a reduction in renal cortex ne of 86 %. these data are shown in fig1 . additional comparison can be made to the reduction in renal cortex ne from surgical denervation , which connors ( connors et al , “ renal nerves mediate changes in contralateral renal blood flow after extracorporeal shockwave lithotripsy ,” nephron physiology 2003 ; 95 : 67 - 75 ) reported as 97 % and krum ( krum h , et al ., “ catheter - based renal sympathetic denervation for resistant hypertension : a multicentre safety and proof - of - principle cohort study ,” lancet 2009 ; 373 ( 9671 ): 1228 - 1230 ) reported as 94 %. furthermore , the reduction in kidney ne reported with the use of radiofrequency catheter ablation of the renal nerves has been reported as 86 %. the radiofrequency method has since been used in clinical trials and evidence has been shown that the ablation of the nerves , resulting in reduced ne by 86 %, directly translates to reduced hypertension in patients , with reports of systolic pressure reduction of 27 mmhg and diastolic reduction of 17 mmhg , twelve months after treatment . while the above is a complete description of the preferred embodiments of the invention , various alternatives , modifications , and equivalents may be used . therefore , the above description should not be taken as limiting the scope of the invention which is defined by the appended claims .
sympathetic nerves run through the adventitia surrounding renal arteries and are critical in the modulation of systemic hypertension . hyperactivity of these nerves can cause renal hypertension , a disease prevalent in 30 - 40 % of the adult population . hypertension can be treated with neuromodulating agents , but requires adherence to strict medication regimens and often does not reach target blood pressure threshold to reduce risk of major cardiovascular events . a minimally invasive solution is presented here to reduce the activity of the sympathetic nerves surrounding the renal artery by locally delivering neurotoxic or nerve - blocking agents into the adventitia . extended elution of these agents may also be accomplished in order to tailor the therapy to the patient .