A GABA with analgesic activity A Receptor targeting peptide DZ2 and its synthesis method and application

Abstract

This invention belongs to the field of biomedical technology and discloses a method for targeting GABA. A The receptor-dependent cyclic peptide analgesic DZ2 has the following amino acid sequence: Cys-Asn-Thr-Glu-Arg-Pro-Gly-Met-Leu-Asp-Phe-Lys-Gly-Lys-Ala-Lys-Trp-Asp-Ala-Trp-Cys, where the N-terminal Cys and C-terminal Cys are cyclically linked by a disulfide bond, and the molecular weight is 2454.81 g / mol. This cyclic peptide can be obtained through classic Fmoc-solid-phase synthesis, using GABA... A Receptor-targeting drugs play an important role in drug development. The compounds provided in this invention can activate GABA. A The receptor generates a GABA-like inward current. Furthermore, DZ2 exhibits excellent analgesic effects in a mouse pain model, providing a potential alternative for GABA-based analgesics. A This provides new ideas and theoretical basis for the development of receptor-based analgesics.

Description

Technical Field

[0001] The present invention belongs to the field of biomedical technology and relates to a GABA having analgesic activity. A Receptor targeting peptide DZ2 and its synthesis method and application. Background Art

[0002] Pain is an unpleasant feeling, both physical and emotional, and many diseases are accompanied by pain. Under normal circumstances, pain is a protective response of the body to external noxious stimuli, but chronic pain (pain that persists or recurs for more than three months) can affect the normal physiological functions of the organism, and severe pain may cause physiological dysfunction or even death (Lancet. 2015, 386, 743-800). Current analgesics mainly include opioids (such as morphine), nonsteroidal anti-inflammatory drugs (such as aspirin), capsaicin, antidepressants and anti-epileptic drugs, etc., but these drugs have limited analgesic effects and are often accompanied by a series of adverse reactions such as drug tolerance, dependence, gastrointestinal disorders, respiratory depression and hyperalgesia. Therefore, it is of great significance to study the pathological mechanisms related to pain and develop related analgesics.

[0003] DRG neurons are located in front of the dorsal horn of the spinal cord and are responsible for transmitting sensory information (including somatic and visceral sensations) from the periphery to the central nervous system. They are an important processing site for sensory information (Pain. 1999, Suppl 6, S27-35). Under pathological conditions, sensory neurons in DRG can generate spontaneous electrical activity and can be used as a target area for chronic pain treatment (Anesthesiology and pain medicine. 2021, 11(2):e113020). Studies have shown that there is a complete GABA circuit in DRG, and DRG neuron cell bodies can release GABA under excitatory stimulation, thereby activating the inhibitory regulation of induced neurons and relieving chronic pain in animals (JClin Invest. 2017, 127, 1741-56). Therefore, the GABAergic inhibitory system in DRG can be used as a target area for pain treatment, and the development of targeted GABA in DRG is needed. A Drugs that target receptors are of great significance. Summary of the invention

[0004] The purpose of the present invention is to provide a GABA having analgesic activity A Receptor targeting peptide DZ2 and its synthesis method and application.

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical solutions:

[0006] A type of GABA AThe GABA receptor targeting peptide DZ2 A The receptor targeting peptide DZ2 is a cyclic peptide with the following structural formula:

[0007] ;

[0008] The GABA A The amino acid sequence of the receptor targeting peptide DZ2 is:

[0009] Cys-Asn-Thr-Glu-Arg-Pro-Gly-Met-Leu-Asp-Phe-Lys-Gly-Lys-Ala-Lys-Trp-Asp-Ala-Trp-Cys, as shown in SEQ ID NO.1, wherein the N-terminal Cys and the C-terminal Cys form a ring through a disulfide bond.

[0010] GABA A The synthetic method of receptor targeting peptide DZ2 comprises the following steps:

[0011] (a) Solid phase synthesis of linear peptides: Using CTC resin as a solid phase carrier, the Fmoc solid phase synthesis method was used to synthesize a linear peptide having the amino acid sequence of the target product, and its structure is as follows:

[0012] H-Cys-Asn-Thr-Glu-Arg-Pro-Gly-Met-Leu-Asp-Phe-Lys-Gly-Lys-Ala-Lys-Trp-Asp-Ala-Trp-Cys-OH;

[0013] (b) Disulfide bond formation: The linear peptide is dissolved in a solution and oxidized to form disulfide bonds, thereby obtaining a cyclic GABA with disulfide bonds. A Receptor targeting peptide DZ2.

[0014] Furthermore, step (a) specifically includes the following steps:

[0015] (a-1) reacting the C-terminal protected amino acid Fmoc-Cys(Mmt)-OH with CTC resin to prepare Fmoc-Cys(Mmt)-CTC resin;

[0016] (a-2) Under inert gas atmosphere, with the participation of Fmoc solid phase synthesis condensation agent, starting from the first amino acid at the C-terminus of the DZ2 sequence, Fmoc-Ala-OH, Fmoc-Asp(OtBu)-OH, Fmoc-Trp(Boc)-OH, Fmoc-Lys(Boc)-OH, Fmoc-Ala-OH, Fmoc-Lys(Boc)-OH, Fmoc-Gly ... moc-Phe-OH, Fmoc-Asp(OtBu)-OH, Fmoc-Leu-OH, Fmoc-Met-OH, Fmoc-Gly-OH, Fmoc-Pro-OH, Fmoc-Arg(Pbf)-OH, Fmoc-Glu(OtBu)-OH, Fmoc-Thr(OtBu)-OH, Fmoc-Asn(Trt)-OH, and Fmoc-S-(Mmt)-L-Cys to obtain the target peptide resin;

[0017] (a-3) Add the target peptide resin to the cleavage reagent and react at room temperature; after the reaction, combine the filtered cleavage reagents, pour them into the pre-cooled MTBE solvent, filter out the precipitated solid, redissolve the solid with DCM solvent, and wash with an equal volume of NaHCO3 aqueous solution; after washing, concentrate the cleavage reagent by rotary evaporation to obtain the precipitated linear peptide crude product;

[0018] (a-4) Purify the crude linear peptide by preparative RP-HPLC, collect the corresponding fractions, and obtain the linear peptide.

[0019] The Fmoc solid phase synthesis condensing agent is one of DIC / HOBt, DIC / HOAt, EDC•HCl / HOBt / DIPEA, HATU / HOAt / DIPEA, HBTU / HOBt / DIPEA or TBTU / HOBt / DIPEA, and the amount used is 2-3 times the amount of the peptide resin substance.

[0020] The cleavage reagent is an aqueous solution of trifluoroacetic acid (TFA) and triethylsilane (TIS), wherein the volume fraction of TFA is 95% and the volume fraction of TIS is 1-5%. Its function is to cleave the target polypeptide from the resin and remove the side chain protecting groups.

[0021] The concentration of the NaHCO3 aqueous solution is 0.1-2 mol / L, and the criterion for judging the completion of washing is that the aqueous phase p H = 7-8.

[0022] The substitution degree of the CTC resin is 0.5-1.0 mmol / g.

[0023] Furthermore, step (b) specifically includes the following steps:

[0024] (b-1) Dissolving the linear peptide obtained in step (a) in a solvent and adjusting the solution p H is neutral, add an oxidant to react for 20-30 hours, and use analytical RP-HPLC to detect the progress of the reaction; or dissolve the linear peptide obtained in (a) in an acetic acid aqueous solution of AcOH, slowly add an AcOH solution of I2 under stirring, the equivalent of the oxidant I2 is 20-50 times that of the linear peptide, stir and react for 1-3 hours, and use analytical RP-HPLC to detect the progress of the reaction; after the reaction is completed, slowly add V equivalent to I2 to the reaction solution C The solution is heated until the brown color completely fades to reduce the excess I2 to terminate the reaction; the solvent is any one of water, methanol, ethanol, acetonitrile, DCM, DMF or a mixture of several thereof;

[0025] (b-2) After the above reaction is completed, the reaction solution is concentrated by low-temperature rotary evaporation, purified by preparative RP-HPLC, and the corresponding components are collected. After vacuum cooling and drying, a cyclic peptide with a disulfide bond is obtained. The purity is analyzed by analytical HPLC, and the molecular weight is confirmed by ESI-MS to ensure that its structure is consistent with the target molecule DZ2.

[0026] Wherein, the oxidant is H2O 2、 Air or DMSO, among which, when 30% H2O2 is used as an oxidant, its dosage is 0.5%-1% of the solution volume; when air is used as an oxidant, an air pump is used to introduce it; when DMSO is used as an oxidant, the dosage is 30%-40% of the solution volume.

[0027] In the acetic acid aqueous solution of AcOH, the volume fraction of AcOH is 20%-30%.

[0028] The conditions of the preparative RP-HPLC are as follows: the chromatographic filler is 5 μm reverse phase C18 silica gel with a pore size of 100Å, and the size of the chromatographic column is 30×250 mm; the mobile phase A is a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA is 0.05% and the volume percentage of MeCN is 5%; the mobile phase B is a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA is 0.05% and the volume percentage of MeCN is 90%; the flow rate is 25 mL / min; and the ultraviolet detection wavelength is 214 nm.

[0029] The conditions of the analytical RP-HPLC are as follows: the chromatographic filler is 5 μm reverse phase C18 silica gel, the pore size is 100Å, and the chromatographic column size is 4.6×250 mm; the mobile phase A is a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA is 0.05% and the volume percentage of MeCN is 5%; the mobile phase B is a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA is 0.05% and the volume percentage of MeCN is 90%; the flow rate is 1 mL / min; and the ultraviolet detection wavelength is 214 nm, 230 nm or 280 nm.

[0030] The present invention also provides the above-mentioned GABA A Application of receptor targeting peptide DZ2 in the preparation of analgesic drugs.

[0031] GABA of the present invention A The receptor-targeting peptide DZ2 can specifically bind to GABA A The α1β2 interface of the receptor directly activates GABA A The receptors generate an inhibitory inward current, which significantly relieves pain.

[0032] Preferably, the analgesic drugs include drugs for treating chronic inflammatory pain, neuropathic pain and nerve damage.

[0033] Preferably, the analgesic drug contains the targeting peptide DZ2 as an active ingredient and further comprises a pharmaceutically acceptable carrier or additive.

[0034] The beneficial effects of the present invention are:

[0035] (1) This invention uses molecular docking technology for the first time to A The GABA receptor and its endogenous ligand DBI were simulated and composited to obtain the analgesic cyclic peptide DZ2. A The receptor targeting peptide DZ2 is easy to synthesize, easy to purify, and can be synthesized in large quantities. A The amino acids of the receptor targeting peptide DZ2 are all common amino acids, which are easy to purchase and inexpensive, and the synthesis cost is low.

[0036] (2) GABA disclosed in the present invention A The receptor targeting peptide DZ2 targets GABA A Receptors, avoiding the risks of a series of adverse reactions of existing analgesics such as tolerance, dependence, gastrointestinal disorders, respiratory depression and hyperalgesia, with good safety and better clinical application prospects.

[0037] (3) The present invention shows through patch clamp experiments that GABA AThe receptor-targeting peptide DZ2 can activate GABA A The receptor generates an inward current similar to GABA, which then relieves pain. DZ2 shows good analgesic effect in mouse pain models such as the chronic inflammatory pain model (CFA model), the sciatic nerve chronic ligation (CCI) model in neuropathic pain animal models, and the sciatic nerve branch selective injury (SNI) model. The present invention will be based on GABA A It provides new ideas and theoretical basis for the research and development of receptor drugs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 GABA A Structure diagram of the receptor targeting peptide DZ2.

[0039] Figure 2 DBI and GABA A Receptor molecule docking results.

[0040] Figure 3 GABA of the present invention A Mass spectrometry chromatogram of receptor targeting peptide DZ2.

[0041] Figure 4 GABA of the present invention A The receptor targeting peptide DZ2 A The direct activation of the receptor (i.e., generating an inward current), where Figure A shows the activation of DZ2 and GABA to GABA A Figure 1 is the activation current diagram of the receptor, and Figure B is the current size statistics diagram.

[0042] Figure 5 GABA of the present invention A A diagram showing the analgesic effect of the receptor targeting peptide DZ2 on the CFA pain model.

[0043] Figure 6 GABA of the present invention A A diagram showing the analgesic effect of the receptor targeting peptide DZ2 on the SNI pain model.

[0044] Figure 7 GABA of the present invention A A diagram showing the analgesic effect of the receptor targeting peptide DZ2 on the CCI pain model. DETAILED DESCRIPTION

[0045] The specific embodiments used below are for detailed description of the present invention, but are not intended to limit the present invention; modifications to the sequence and structure of the polypeptide compound shown, and changes to the feed ratio of raw materials or the reaction solvent and condensing agent according to the present invention are all within the scope of protection of the present invention.

[0046] In order to make the technical problems to be solved, technical solutions and functional features of the present invention clearer, they are described in detail below in conjunction with specific embodiments.

[0047] GABA of the present invention A The receptor targeting peptide DZ2 is based on GABA A The receptor and its endogenous ligand DBI were independently designed and obtained. The amino acid sequence of DZ2 is CNTERPGMLDFKGKAKWDAWC, i.e., Cys-Asn-Thr-Glu-Arg-Pro-Gly-Met-Leu-Asp-Phe-Lys-Gly-Lys-Ala-Lys-Trp-Asp-Ala-Trp-Cys, as shown in SEQ ID NO.1, and the molecular weight is 2454.81 g / mol; the structural formula is as follows Figure 1 shown.

[0048] The amino acid abbreviations of DZ2 of the present invention are shown in Table 1:

[0049] Table 1 List of amino acid abbreviations of DZ2

[0050] .

[0051] The meanings of the English abbreviations of the reagents used in the synthesis and preparation of DZ2 of the present invention are shown in Table 2:

[0052] Table 2 Meaning of the abbreviations of reagents used in the DZ2 synthesis method of the present invention

[0053] .

[0054] Example 1 Targeting GABA A Design of short peptide drugs for receptors

[0055] Download GABA from the PDB database A The crystal structures of the receptor (PDB ID: 7QNE) and DBI (PDB ID: 1HB6) were obtained from Schrodinger ® In the Protein Preparation Wizard module of 2021-1 Suite, crystal water molecules were deleted, energy minimization and other structural preprocessing were performed as receptor and ligand protein structures respectively; Schrodinger ® 2021-1Suite's Protein-Protein Docking module (Piper) is used for docking. Ligand DBI and receptor GABA A The protein advantage docking results are as follows Figure 2 As shown, it can be seen that a loop in DBI is embedded in GABA AThe α1+ / β2- interface of the receptor retains the main structure of the loop and is cyclized by cyclizing two Cys at the terminal to maintain its fixed secondary structure, thus obtaining the cyclic peptide DZ2.

[0056] Example 2 Targeting GABA A Synthesis of Cyclic Peptide Drug DZ2 for Targeting TNF-α Receptor

[0057] GABA of the present invention A The receptor DZ2 was synthesized using the classical Fmoc-solid phase synthesis method, which specifically includes the following steps:

[0058] (1) Preparation of Fmoc-Cys(Mmt)-CTC resin: Weigh 10 mmol of CTC resin and place it in a peptide resin synthesizer. Add 100 mL of DCM and swell for 3 hours. After swelling, wash the resin with 100 mL of DMF for 3 times. Weigh 20 mmol of Fmoc-Cys(Mmt)-OH, 20 mmol of HOBt, 20 mmol of EDC•HCl and 24 mmol of DIPEA, dissolve them in 100 mL of DMF, add them to the container and react for 4 hours. After the reaction, wash it with DMF 3 times, then add 100 mL of the end-capping reagent DIPEA-methanol-DCM (3:2:25L) and react for 1 hour. After the reaction is completed, wash it with DMF, DCM and methanol 3 times, 100 mL each time, and then vacuum dry to obtain Fmoc-Cys(Mmt)-CTC resin.

[0059] (2) Preparation of peptide resin: Weigh 10 mmol of the Fmoc-Cys(Mmt)-CTC resin and place it in a peptide synthesis reactor. Add 100 mL of DCM and swell for 2 h. After swelling, wash the resin with 100 mL of DMF for 3 times. Add 100 mL of 20% piperidine in DMF solution and perform two 10-min deprotection reactions. After the reaction, wash the resin with 100 mL of DMF for 6 times. Weigh 20 mmol of Fmoc-Trp(Boc)-OH, HOBt, EDC•HCl and 24 mmol of DIPEA respectively, dissolve them in 100 mL of DMF, add them to the reactor and react for 4 h. Use Kaiser test or ESI-MS mass spectrometry to monitor the reaction endpoint. After the reaction, wash the resin with DMF 6 times, then deprotect and couple the next protected amino acid. Repeat the above steps, sequentially proceed to Fmoc-Ala-OH, Fmoc-Asp(OtBu)-OH, Fmoc-Trp(Boc)-OH, Fmoc-Lys(Boc)-OH, Fmoc-Ala-OH, Fmoc-Lys(Boc)-OH, Fmoc-Gly-OH, F moc-Lys(Boc)-OH, Fmoc-Phe-OH, Fmoc-Asp(OtBu)-OH, Fmoc-Leu-OH, Fmoc-Met-OH, Fmoc-Gly-OH, Fmoc-Pro-OH, Fmoc-Arg(Pbf)-OH, Fmoc-G Lu (OtBu) -OH, Fmoc-Thr (OtBu) -OH, Fmoc-Asn (Trt) -OH, N-Fmoc-S- (Mmt) -L-Cys coupling, prepare H-Cys (Mmt) -Asn (Trt) -Thr (OtBu) -Glu (OtBu) -Arg (Pbf) -Pro-Gly-Met-Leu-Asp (OtBu) -Phe-Lys (Boc) -Gly-Lys (Boc) -Ala-Lys (Boc) -Trp (Boc) -Asp (OtBu) -Ala-Trp (Boc) -Cys (Mmt) -CTC resin. The prepared peptide resin was washed with DCM and methanol three times, 100 mL each time, and vacuum dried to obtain the peptide resin.

[0060] (3) Preparation of linear peptides: Place the peptide resin in a peptide synthesis tube, add 150 mL of cleavage reagent TFA-TIS-H2O (90:5:5) and react at room temperature for 5 minutes. After the reaction is completed, filter the cleavage reagent into a filtration bottle, repeat the cleavage reaction 3 times, and collect the filtrate. Wash the resin with TFA 5 times, 10 mL each time. Combine the filtrate and washing liquid, pour into 500 mL of pre-cooled MTBE, place in an ice room for 2 hours, filter to obtain a solid, and wash 5 times with cold MTBE to obtain a solid. Add 200 mL of DCM to dissolve the solid, and add an equal volume of 0.1N NaHCO3 aqueous solution to wash until the solution p H is 7-8, concentrated by rotary evaporation at room temperature, collected by filtration, and dried in vacuo to obtain a crude linear peptide, which was then purified by preparative RP-HPLC, and the corresponding components were collected and freeze-dried in vacuo to obtain a linear peptide.

[0061] (4) Formation of disulfide bonds: 5 mmol of a linear peptide was weighed and placed in a reaction vessel, dissolved in a 2.5 L AcOH:water (1:4) solution, and 5 mL of a 0.1 M I2 AcOH solution was slowly added dropwise under stirring. The reaction was stirred for 1 h, and the experimental process was monitored using analytical RP-HPLC. At the end of the experiment, an amount of V equivalent to I2 was slowly added dropwise to the reaction solution. C The solution was stirred until the brown color completely faded. The reaction solution was concentrated by rotary evaporation at low temperature, purified by preparative RP-HPLC, and the corresponding components were collected. After vacuum cooling and drying, a cyclic peptide with two sulfur bonds was obtained. The purity was analyzed by analytical HPLC, and the molecular weight was confirmed by ESI-MS. The mass of the cyclic peptide DZ2 was confirmed by ESI-MS mass spectrometry. Figure 3 shown.

[0062] The conditions of the above-mentioned preparative RP-HPLC are as follows: the chromatographic filler is 5 μm reverse phase C18 silica gel with a pore size of 100Å and a chromatographic column size of 30×250 mm; the mobile phase A is a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA is 0.05% and the volume percentage of MeCN is 5%; the mobile phase B is a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA is 0.05% and the volume percentage of MeCN is 90%; the flow rate is 25 mL / min; and the ultraviolet detection wavelength is 214 nm.

[0063] The conditions for analytical RP-HPLC were as follows: the chromatographic packing material was 5 μm reverse phase C18 silica gel with a pore size of 100 Å and a chromatographic column size of 4.6×250 mm; mobile phase A was a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA was 0.05% and the volume percentage of MeCN was 5%; mobile phase B was a mixed aqueous solution of TFA and MeCN, wherein the volume percentage of TFA was 0.05% and the volume percentage of MeCN was 90%; the flow rate was 1 mL / min; and the UV detection wavelength was 214 nm, 230 nm or 280 nm.

[0064] Example 3 Identification of GABA by Patch Clamp Electrophysiology A The receptor targeting peptide DZ2 A Receptor activation

[0065] GABA was confirmed by patch clamp electrophysiology A Receptor targeting peptide DZ2 for GABA A The activation of the receptor includes the following steps:

[0066] GABA transfection in HEK293 cells A The expression plasmid of (α1β2γ2 subunit combination) was used for patch clamp recording 24 hours after transfection. Patch clamp recording was performed at room temperature of about 20 ℃. In this experiment, the voltage clamp Gap-free mode was used, the sampling rate was 1000 Hz, holding at -60mV, and the current size was recorded. The specific operation process is as follows:

[0067] A thick-walled borosilicate glass electrode with an outer diameter of 1.50 mm and an inner diameter of 0.84 mm was pulled by an electrode puller for 4 cycles and polished by a polisher to make the electrode's liquid resistance 2-4 MΩ. The internal solution with a punching agent was injected from the tail end of the electrode for later use. The cell was found under a microscope and its size was recorded. The tip of the electrode was adsorbed on the cell membrane and negative pressure was applied to form a high resistance seal. After the membrane was broken, the current size was recorded according to the above conditions.

[0068] The experimental results are as follows Figure 4 As shown, GABA A The receptor-targeting peptide DZ2 can directly activate GABA A The receptor generates a GABA-like inward current.

[0069] Example 4 Establishment of CFA-induced inflammatory pain model

[0070] The establishment of CFA-induced inflammatory pain model, the specific steps are as follows:

[0071] Complete Freund's adjuvant (CFA) (25 μL) was injected subcutaneously into the right hind paw of mice, and the mechanical pain threshold was measured before administration and on days 1, 3, 5, 7, 10, and 14 after administration.

[0072] Example 5 Establishment of the sciatic nerve branch selective injury model (SNI)

[0073] The mice were anesthetized by intraperitoneal injection of sodium pentobarbital and placed in a prone position on the operating table. After skin preparation and disinfection, the skin along the surface of the sciatic nerve was cut open, the biceps brachii was bluntly separated, the sciatic nerve was exposed, and the sciatic nerve and its three branches, the common peroneal nerve, the sural nerve and the tibial nerve were separated and found. The common peroneal nerve and the tibial nerve were tightly ligated with 5-0 silk thread and their distal nerves were cut off. About 4 mm of the distal nerve was removed, and the sural nerve was retained. The muscle layer and skin layer were sutured, and iodine was evenly applied to the suture.

[0074] Example 6 Establishment of chronic sciatic nerve ligation model (CCI)

[0075] The mice were anesthetized and placed in a prone position on the operating table. After shaving and disinfection, the skin and superficial fascia along the surface of the sciatic nerve were cut open, the biceps brachii was bluntly separated, the sciatic nerve was exposed and separated, 4 knots were tied on the sciatic nerve with a 40-gait catgut, the muscle layer and the skin layer were sutured, iodine was evenly applied to the suture, penicillin was injected into the left hind leg muscle, and sufficient water and food were given in the mouse cage. The control group underwent a sham operation (suture was performed after the sciatic nerve was exposed).

[0076] Example 7

[0077] The mechanical pain threshold was determined by local DRG cannula administration, with saline as a negative control. The specific method is that in the animal behavior room, the mice that have adapted to the environment in the pain model described in Examples 4-6 are placed on a metal wire mesh, and each mouse is separated by a transparent organic glass box to keep it quiet for at least 30 min. A standard Von Frey fiber needle is placed against the sole of the right hind foot of the mouse and slightly bent, and it stays for more than 3 s. If the mouse suddenly lifts its foot or licks its foot, it is recorded as a positive reaction. Repeat the measurement 5 times, with an interval of at least 1 min each time, and those with positive reactions three or more times are recorded as positive results. Starting from the 1 g fiber needle, the up-and-down method is used to determine the mechanical pain threshold (in g).

[0078] The results of the test are as follows Figure 5-7 As shown, GABA was administered through a local cannula in the DRG. A The receptor-targeting peptide DZ2 can significantly relieve chronic pain.

[0079] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A type of GABA A The receptor targeting peptide DZ2 is characterized in that The GABA A The receptor targeting peptide DZ2 is a cyclic peptide with the following structural formula: ； The GABA A The amino acid sequence of the receptor targeting peptide DZ2 is: Cys-Asn-Thr-Glu-Arg-Pro-Gly-Met-Leu-Asp-Phe-Lys-Gly-Lys-Ala-Lys-Trp-Asp-Ala-Trp-Cys, wherein the N-terminal Cys and the C-terminal Cys form a ring through a disulfide bond.

2. GABA according to claim 1 A The use of receptor targeting peptide DZ2 in the preparation of analgesic drugs is characterized in that: The analgesic drug is a drug for treating chronic inflammatory pain, neuropathic pain and nerve damage.

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