Description

Dermorphin Peptide

 

 

CAS Number	77614-16-5
Other Names	Tyrosyl-alanyl-phenylalanyl-glycyl-tyrosyl-prolyl-serinamide
IUPAC Name	(2S)-N-[(2S)-1-amino-3-hydroxy-1-oxopropan-2-yl]-1-[(2S)-2-[[2-[[(2S)-2-[[(2R)-2-[[(2S)-2-amino-3-(4-hydroxyphenyl)propanoyl]amino]propanoyl]amino]-3-phenylpropanoyl]amino]acetyl]amino]-3-(4-hydroxyphenyl)propanoyl]pyrrolidine-2-carboxamide
Molecular Formula	C₄₀H₅₀N₈O₁₀
Molecular Weight	802.88
Purity	≥99% Pure (LC-MS)
Liquid Availability	N/A
Powder Availability	10 milligrams vial (lyophilized/freeze-dried)
Storage Condition	Store cold, keep refrigerated. Do NOT freeze.
Terms	All products are for laboratory developmental research USE ONLY. Products are not for human consumption.

**Important Information: Each peptide comes lyophilized/freeze-dried and must be reconstituted with Bacteriostatic Water in order to be dispensable in liquid form.

 

What is Dermorphin?

Dermorphin is a naturally occurring opioid peptide originally isolated from the secretions of South American Phyllomedusa tree frogs. Composed of seven amino acids, dermorphin is notable for its potent and selective agonist activity at the μ-opioid receptor, exhibiting strong analgesic effects at lower doses. Its unique structure featuring a D-alanine residue at the second position, confers enhanced receptor affinity and resistance to enzymatic degradation, distinguishing it from most endogenous opioids. Although primarily studied in experimental and pharmacological contexts, dermorphin has attracted interest for its potential therapeutic applications in pain management and neuroscience research.

 

Main Research

1) The presence of the N-terminal of the tripeptide dermorphin facilitates intrinsic opioid-like antinociceptive activity.

2) Dermorphin alleviates frostbite-induced pain through the regulation of TRP channel-mediated microglial activation and neuroinflammation.

 

Selected Data
1) This study performed by Kisara et al evaluated the antinociceptive activity and opioid receptor specificity of dermorphin and several of its synthetic analogues using both behavioral and in vitro assays in mice and guinea pigs. Male Std-ddy mice weighing between 22 and 25 grams and Hartley guinea pigs weighing between 250 and 300 grams were used for the experiments. The animals were housed in standardized temperature- and light-controlled conditions with free access to food and water, except during testing. Experimental procedures were conducted between 10:00 a.m. and 6:00 p.m. [1].
Antinociceptive activity in mice was measured using the tail-pressure method. In this assay, mechanical pressure was applied to the base of the tail at a rate of 20 mmHg per second, and the mouse’s biting or struggling behavior was recorded as an indication of the pain response threshold. The pressure was not allowed to exceed 200 mmHg to avoid tissue injury. The mean pressure value at which the animal responded was recorded. To evaluate drug efficacy, dose-response curves were generated by plotting administered peptide dose against the percent of maximum possible effect (%MPE). The %MPE was calculated using the formula: %MPE = [(P₂ − P₁) / (200 − P₁)] × 100, where P₁ represents the baseline response pressure before peptide injection and P₂ represents the pressure after peptide administration [1].
Peptides were dissolved in Ringer’s solution and administered intracerebroventricularly to unanaesthetized mice using a Hamilton syringe, in a total injection volume of 10 microliters. To determine whether the analgesic effects of the peptides were mediated by opioid receptors, the opioid antagonist naloxone, at a dose of 0.5 mg/kg, was administered intraperitoneally five minutes prior to intracerebroventricular peptide injection. Naloxone was prepared in 0.9% saline (w/v) and administered in a volume of 0.1 mL per 10 g of body weight.
In addition to the in vivo assay, the study also evaluated the pharmacological effects of the peptides on isolated guinea pig ileum tissue. After humane euthanasia by a blow to the head, a section of the ileum was removed from the terminal portion, excluding the 10 cm segment nearest the ileocecal junction. Ileum segments approximately 2–3 cm long were mounted longitudinally in a 10 mL tissue bath containing Krebs-Henseleit solution with the following composition: NaCl 117.56 mM, KCl 5.36 mM, MgSO₄ 0.57 mM, CaCl₂ 1.90 mM, NaHSO₄ 0.90 mM, NaHCO₃ 23.81 mM, and glucose 11.10 mM. The bath was maintained at 37°C and continuously aerated with a gas mixture of 95% O₂ and 5% CO₂ [1].
The tissues were electrically stimulated at a frequency of 0.1 Hz, with a pulse duration of 0.5 milliseconds and a voltage of 10 V, delivered by an electronic stimulator. The peptides were added to the tissue bath in a non-cumulative manner to assess their inhibitory effects on the twitch response induced by electrical field stimulation. The magnitude of the ileum twitch contraction was recorded before and after peptide administration, and the percentage inhibition of twitch height was calculated. A minimum of three concentrations of each peptide was tested on every ileum preparation to generate reliable dose-response data.
The compounds tested included dermorphin, [D-Arg²]dermorphin, and a series of truncated [D-Arg²]dermorphin fragments, namely [D-Arg²]dermorphin(1–6), (1–5), (1–4), (1–3), and (1–2). For comparison, morphine hydrochloride and naloxone hydrochloride were also included in the assays. Dermorphin and its analogues were synthesized in the laboratory using conventional liquid-phase peptide synthesis methods. Data analysis for the antinociceptive tests involved Duncan’s multiple comparison procedure to assess overall differences among treatment groups. Where appropriate, individual t-tests or analyses of variance were performed to determine specific differences between experimental conditions [1].
In summary, this study combined behavioral and tissue-based pharmacological assays to examine the potency and receptor specificity of dermorphin and its analogues. The use of naloxone allowed the researchers to confirm that the observed antinociceptive effects were mediated through opioid receptor activation. Through both central nervous system testing in mice and smooth muscle assays in guinea pig ileum, the research provided a comprehensive evaluation of the analgesic and pharmacodynamic properties of dermorphin and its modified peptides [1].
2) This study performed by Ummadisetty et al investigated the behavioral and molecular effects of the peptide dermorphin [D-Arg2, Lys4] (1–4) amide (DALDA) in a rat model of frostbite-induced neuropathic pain. Healthy adult male Sprague–Dawley rats were used for the experiments. The animals were housed in standard laboratory conditions, with four to five rats per cage, under a 12-hour light–dark cycle at a controlled temperature of 21 ± 2 °C. They had free access to food and water at all times [2].
Before the experiments, animals were acclimated to the laboratory environment for one week. Baseline behavioral measurements were recorded prior to inducing injury. Frostbite injury (FBI) was created by applying deep-frozen magnets maintained at –20 °C to the sub-plantar surface of the left hind paw for three minutes. Following injury, the rats were allowed to recover for seven days. On day eight post-injury, treatment with DALDA or a reference drug began, and pain-related behaviors were recorded from day eight through day thirteen. The study included six experimental groups with six to eight rats per group, including: naïve or uninjured, vehicle control, frostbite-injured rats treated with DALDA at three doses ranging from 1, 3, and 10 mg/kg, subcutaneously, and a standard treatment group receiving 100 mg/kg ibuprofen, intraperitoneally [2].
A battery of behavioral assays was used to assess various pain modalities, including thermal, mechanical, and cold hypersensitivity. Thermal hyperalgesia was evaluated using the Hargreaves test, which measures paw withdrawal latency (PWL) in response to a focused infrared (IR) heat source applied to the plantar surface of the hind paw. Rats were placed in transparent acrylic chambers for acclimation, and an automated IR device applied the stimulus. A 20-second cutoff was imposed to prevent tissue damage. Each paw (ipsilateral and contralateral) was tested three times per session, and the average PWL was used as the measure of thermal sensitivity [2].
Mechanical allodynia was assessed using the von Frey hair test, which determines the threshold at which the rat withdraws its paw in response to a series of calibrated filaments of increasing force. After acclimation in testing chambers, filaments were applied perpendicularly to the paw until a withdrawal or flinching response occurred, marking the allodynia threshold. Mechanical hyperalgesia was further examined using the pinprick test, in which a fine 22-gauge needle was lightly applied to the hind paw through the mesh floor. Positive responses included rapid withdrawal or licking.
Cold sensitivity was evaluated through two complementary assays. The ice floor test measured cold hyperalgesia by placing rats in transparent plexiglass chambers on a surface maintained at 4 ± 2 °C. The number of paw lifts during a one-minute trial was recorded from video footage by a blinded observer. The acetone drop test assessed cold allodynia, where 100 μL of acetone was gently applied to the dorsal surface of the hind paw through a mesh floor. Behavioral responses such as paw withdrawal, licking, or shaking were recorded in three one-minute trials, also scored by a blinded observer.
After behavioral testing, animals were euthanized via an overdose of ketamine and xylazine, followed by cervical decapitation. The spinal cord was exposed through a dorsal incision and removal of the vertebral column. The lumbar region of the spinal cord (segments L4–L5), dorsal root ganglia (DRGs), and sciatic nerve were dissected for molecular and biochemical analyses. All tissue samples were rapidly frozen and stored at –80 °C until further processing [2].
For biochemical assays, the sciatic nerve samples were washed with saline, homogenized on ice, and centrifuged at 12,000 rpm for 20 minutes at 4 °C. The supernatant was used for assays assessing oxidative stress. Lipid peroxidation (LPO), an indicator of oxidative membrane damage, was quantified by mixing the sample with acetic acid, sodium dodecyl sulfate (SDS), and thiobarbituric acid, heating at 100 °C for one hour, and measuring absorbance at 532 nm. Reduced glutathione (GSH), a key antioxidant marker, was measured using 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB), with absorbance recorded at 412 nm. Nitrite levels, an indicator of nitrosative stress and inflammation, were determined by reacting the samples with Griess reagent and reading absorbance at 540 nm [2].
Western blotting was conducted to quantify protein expression in DRG tissue. Tissues were homogenized in the RIPA buffer, and protein concentration was determined using the Bradford method. Equal amounts of protein were separated on SDS-PAGE gels, transferred to PVDF membranes, and blocked with 3% bovine serum albumin (BSA). Membranes were incubated overnight at 4 °C with primary antibodies targeting ICAM-1, TNF-α, Iba1, TRPV1, TRPA1, and β-actin as a loading control. After washing, membranes were exposed to secondary antibodies for two hours at room temperature. Protein bands were visualized using an enhanced chemiluminescence (ECL) substrate and imaged on Bio-Rad’s ChemiDoc TM system, and intensities were quantified using ImageJ software.
In summary, this experimental design comprehensively combined behavioral pain assays and molecular analyses to evaluate the therapeutic potential of DALDA in mitigating frostbite-induced neuropathic pain and its associated oxidative and inflammatory responses in rats [2].

Discussion
1) This study performed by Kisara et al investigated the antinociceptive properties of dermorphin, a potent opioid peptide, and its synthetic analogue [D-Arg²]dermorphin, along with a series of shortened N-terminal fragments derived from the latter. The experiments examined the dose-response relationships, time course of action, and opioid receptor specificity of these compounds using intracerebroventricular administration in mice, as well as their inhibitory effects on electrically stimulated contractions of isolated guinea pig ileum tissue [1].
When administered intracerebroventricular at doses of 4.8, 6.5, and 8.4 picomoles per mouse, dermorphin produced a clear dose-dependent antinociceptive effect, as measured by the tail-pressure test. The analgesic effect of dermorphin peaked approximately 10 minutes after injection and then gradually diminished over the following 90 minutes. The median effective dose for dermorphin was calculated to be 5.7 picomoles per mouse, with 95% confidence limits ranging from 4.8 to 6.8 picomoles. Control injections of Ringer’s solution produced no measurable analgesic effect, confirming that the response was due to the active peptide.
The structural modification of dermorphin through the substitution of D-arginine at position 2 resulted in a significant reduction in potency. The analogue [D-Arg²]dermorphin had an ED₅₀ value of 23.0 picomoles per mouse, indicating that dermorphin was roughly four times more potent than its modified form. Despite this difference in potency, both compounds showed a similar time to peak effect around 10 minutes post-injection. However, the duration of analgesia was longer for dermorphin than for [D-Arg²]dermorphin when each was given at its maximally effective dose. Pretreatment with naloxone, a specific opioid receptor antagonist, completely abolished the antinociceptive effects of both peptides, demonstrating that their actions were mediated through opioid receptors [1].
A series of N-terminal fragments of [D-Arg²]dermorphin were then tested to determine how peptide length influenced analgesic potency. The hexapeptide fragment, [D-Arg²]dermorphin(1–6), produced a higher level of antinociception than the full-length [D-Arg²]dermorphin, though the difference was not statistically significant based on their ED₅₀ values. The pentapeptide fragment, [D-Arg²]dermorphin(1–5), showed nearly the same analgesic potency as the parent heptapeptide. Interestingly, the tetrapeptide fragment, [D-Arg²]dermorphin(1–4), was approximately twice as potent as [D-Arg²]dermorphin, though again the difference was not statistically significant [1].
The activity declined sharply with further shortening of the peptide chain. The tripeptide fragment exhibited significantly less analgesic effect than the hepta-, penta-, and tetrapeptides, yet it still demonstrated higher potency than morphine, highlighting the inherent strength of this peptide sequence. The dipeptide Tyr–D-Arg amide, formed by the removal of phenylalanine from position 3 of the tripeptide, showed a marked loss of analgesic activity, indicating that this residue plays a crucial role in receptor binding or efficacy.
When animals were pretreated with 0.5 mg/kg naloxone intraperitoneally, the antinociceptive effects of all [D-Arg²]dermorphin fragments, except the dipeptide, were almost completely antagonized. In the case of the dipeptide, naloxone at doses of 0.5 and 1.0 mg/kg reduced the analgesic response, but only partially; even at the higher dose, inhibition did not exceed 50%. This partial antagonism suggested that the dipeptide’s action might involve a less specific or weaker interaction with opioid receptors compared to the longer fragments [1].
The study also assessed the effects of [D-Arg²]dermorphin and its N-terminal fragments on contractions of the guinea pig ileum, a classic model for opioid receptor-mediated inhibition of smooth muscle contractions. [D-Arg²]dermorphin significantly inhibited the field-stimulated twitch response in a concentration-dependent manner. The hexapeptide and pentapeptide fragments showed somewhat lower inhibitory potency than [D-Arg²]dermorphin, though their half-maximal inhibitory concentration values were not statistically different. Notably, the tetrapeptide fragment displayed the highest potency among all tested derivatives, being approximately nine times more active than the hexapeptide fragment. The tripeptide fragment, however, exhibited only about 40% of the potency of [D-Arg²]dermorphin and showed an inhibitory effect roughly equivalent to that of morphine.
In summary, dermorphin was shown to be a highly potent opioid peptide with strong, dose-dependent antinociceptive effects, superior to both its D-Arg-modified analogue and morphine. The introduction of D-Arg at position 2 significantly decreased potency, although the analogue and its fragments retained measurable activity mediated by opioid receptors. The shortening of the peptide sequence progressively reduced analgesic potency, with the tetrapeptide retaining the highest activity among the truncated forms. Parallel experiments on the guinea pig ileum confirmed that these peptides exerted strong opioid-like inhibitory effects on smooth muscle contractions, with relative potency trends similar to those observed in the behavioral assays. Overall, the results demonstrated a clear structure–activity relationship, where peptide length and specific amino acid residues critically determined the analgesic strength and opioid receptor affinity of dermorphin analogues [1].
2) This study conducted by Ummadisetty et al examined the analgesic and anti-inflammatory effects of dermorphin [D-Arg2, Lys4] (1–4) amide (DALDA), a selective μ-opioid receptor (MOR) agonist, in a rat model of frostbite-induced neuropathic pain. The results demonstrated that DALDA effectively alleviated multiple pain modalities, such as thermal, mechanical, and cold hypersensitivity, while also reducing oxidative stress and neuroinflammatory responses in the peripheral and central nervous systems [2].
Thermal hyperalgesia was evaluated using the Hargreaves test, which measures PWL to a heat stimulus. Frostbite-injured rats showed a significant decrease in PWL of the ipsilateral paw compared to their pre-injury baseline, indicating increased thermal sensitivity. Treatment with DALDA at various doses, as well as ibuprofen, significantly increased PWL at 0.5, 1, 2, and 4 hours post-administration, suggesting a marked attenuation of thermal hyperalgesia. In contrast, no significant change in PWL was observed in the contralateral paw, indicating that the analgesic effect of DALDA was localized to the site of injury. These findings support the hypothesis that activation of peripheral MORs by DALDA produces a potent analgesic effect against thermal hypersensitivity induced by frostbite injury [2].
Mechanical allodynia and hyperalgesia were assessed using the von Frey and pinprick tests, respectively. In the von Frey assay, frostbite-injured rats exhibited a reduced mechanical threshold, consistent with heightened sensitivity to touch. Subcutaneous administration of DALDA at doses of 1, 3, and 10 mg/kg significantly increased mechanical thresholds in a dose-dependent manner, comparable to ibuprofen. The effect was observed at 0.5, 1, and 2 hours post-treatment, with statistical analysis revealing significant group differences. Similarly, in the pinprick test, DALDA and ibuprofen treatments significantly reduced PWF in the ipsilateral paw at multiple time points. No significant effects were detected in the contralateral paw. These results indicate that DALDA effectively mitigates both mechanical allodynia and hyperalgesia following frostbite injury.
Cold allodynia and hyperalgesia were assessed using the acetone drop and ice floor tests. Frostbite injury led to increased behavioral responses to cold stimuli, as indicated by higher response scores and paw lift frequencies compared to uninjured controls. Treatment with DALDA and ibuprofen significantly reduced cold allodynia assessed through the acetone test, and hyperalgesia assessed through the ice floor test, at 0.5, 1, and 2 hours after administration. Statistical analyses confirmed significant decreases in pain-related behaviors in the ipsilateral paw, while contralateral responses remained unchanged. These results further demonstrate that DALDA exerts broad-spectrum analgesic effects against thermal, mechanical, and cold modalities of frostbite-induced pain [2].
In addition to behavioral improvements, DALDA treatment attenuated biochemical markers of oxidative and nitrosative stress in the sciatic nerve. Frostbite injury caused a significant decrease in glutathione (GSH) levels and increases in malondialdehyde (MDA) and nitrite levels, indicating heightened oxidative damage. Treatment with DALDA (particularly at higher doses) and ibuprofen significantly restored GSH levels and reduced MDA and nitrite concentrations, suggesting that DALDA possesses antioxidant properties that contribute to its neuroprotective effects [2].

Figure 1: Effects of DALDA administration on frostbite-induced oxidative stress in the sciatic nerve.
At the molecular level, RT-PCR analysis of spinal cord tissue revealed that frostbite injury upregulated the mRNA expression of TRPM8, TNF-α, and IL-1β—key mediators of neuroinflammation and nociceptive sensitization. DALDA treatment significantly downregulated these genes in the ipsilateral spinal cord, comparable to ibuprofen, indicating suppression of inflammatory signaling pathways.
Western blot analysis of DRG tissue further confirmed that frostbite injury elevated the expression of proteins associated with neuroinflammation and nociceptor activation, including ICAM1, IBA1, TRPV1, TRPA1, and TNF-α. DALDA treatment significantly reduced ICAM1, IBA1, TRPA1, and TNF-α protein levels, while ibuprofen decreased IBA1, TNF-α, and TRPA1 expression. Notably, neither DALDA nor ibuprofen significantly altered TRPV1 expression. These findings suggest that DALDA alleviates frostbite-induced pain by inhibiting glial activation and inflammatory responses in the peripheral nervous system, thereby reducing nociceptor excitability [2].
Overall, the study demonstrates that DALDA exerts potent multimodal analgesic effects through peripheral MOR activation. Its actions include attenuation of thermal, mechanical, and cold hypersensitivity, reduction of oxidative stress, and suppression of inflammatory and nociceptive signaling in both the sciatic nerve and spinal cord. Together, these findings highlight the potential of DALDA to act as a promising therapeutic candidate for the management of frostbite-induced neuropathic pain and related inflammatory disorders [2].

 

Disclaimer

**LAB USE ONLY**
*This information is for educational purposes only and does not constitute medical advice. THE PRODUCTS DESCRIBED HEREIN ARE FOR RESEARCH USE ONLY. All clinical research must be conducted with oversight from the appropriate Institutional Review Board (IRB). All preclinical research must be conducted with oversight from the appropriate Institutional Animal Care and Use Committee (IACUC) following the guidelines of the Animal Welfare Act (AWA).

 

Citations

[1] Kisara K, Sakurada S, Sakurada T, et al. Dermorphin analogues containing D-kyotorphin: structure-antinociceptive relationships in mice. Br J Pharmacol. 1986;87(1):183-189. doi:10.1111/j.1476-5381.1986.tb10170.x

[2] Ummadisetty O, Akhilesh, Gadepalli A, et al. Dermorphin [D-Arg2, Lys4] (1-4) Amide Alleviates Frostbite-Induced Pain by Regulating TRP Channel-Mediated Microglial Activation and Neuroinflammation. Mol Neurobiol. 2024;61(8):6089-6100. doi:10.1007/s12035-024-03949-4

 

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