Nigella sativa and its chemical constituents: pre-clinical and clinical evidence for their potential anti-SARS-CoV-2 effects.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused over 500 million reported cases of COVID-19 worldwide with relatively high morbidity and mortality. Although global vaccination drive has helped control the pandemic, the newer variant of the virus still holds the world in ransom. Several medicinal herbs with antiviral properties have been reported, and one such promising herb is Nigella sativa (NS). Recent molecular docking, pre-clinical, and clinical studies have shown that NS extracts may have the potential to prevent the entry of coronaviruses into the host cell as well as to treat and manage COVID-19 symptoms. Several active compounds from NS, such as nigelledine, α-hederin, dithymoquinone (DTQ), and thymoquinone (TQ), have been proposed as excellent ligands to target angiotensin-converting enzyme 2 (ACE2 receptors) and other targets on host cells as well as the spike protein (S protein) on SARS-CoV-2. By binding to these target proteins, these ligands could potentially prevent the binding between ACE2 and S protein. Though several articles have been published on the promising therapeutic role of NS and its constituents against SARS-CoV-2 infection, in this review, we consolidate the published information on NS and SARS-CoV-2, focusing on pre-clinical in silico studies as well as clinical trials reported between 2012 and 2023.

Bell Palsy: Facts and Current Research Perspectives.

Bell palsy is a non-progressive neurological condition characterized by the acute onset of ipsilateral seventh cranial nerve paralysis. People who suffer from this type of facial paralysis develop a droop on one side of their face, or sometimes both. This condition is distinguished by a sudden onset of facial paralysis accompanied by clinical features such as mild fever, postauricular pain, dysgeusia, hyperacusis, facial changes, and drooling or dry eyes. Epidemiological evidence suggests that 15 to 23 people per 100,000 are affected each year, with a recurrence rate of 12%. It could be caused by ischaemic compression of the seventh cranial nerve, which could be caused by viral inflammation. Pregnant women, people with diabetes, and people with respiratory infections are more likely to have facial paralysis than the general population. Immune, viral, and ischemic pathways are all thought to play a role in the development of Bell paralysis, but the exact cause is unknown. However, there is evidence that Bell's hereditary proclivity to cause paralysis is a public health issue that has a greater impact on patients and their families. Delay or untreated Bell paralysis may contribute to an increased risk of facial impairment, as well as a negative impact on the patient's quality of life. For management, antiviral agents such as acyclovir and valacyclovir, and steroid treatment are recommended. Thus, early diagnosis accompanied by treatment of the uncertain etiology of the disorder is crucial. This paper reviews mechanistic approaches, and emerging medical perspectives on recent developments that encounter Bell palsy disorder.

The Effect of Statins on Male Reproductive Parameters: A Mechanism Involving Dysregulation of Gonadal Hormone Receptors and TRPV1.

Statins have been shown to cause diverse male reproductive function impairment, and in some cases, orchialgia. Therefore, the current study investigated the possible mechanisms through which statins may alter male reproductive parameters. Thirty adult male Wistar rats (200-250 g) were divided into three groups. The animals were orally administered rosuvastatin (50 mg/kg), simvastatin (50 mg/kg), or 0.5% carboxy methyl cellulose (control), for a 30-day period. Spermatozoa were retrieved from the caudal epididymis for sperm analysis. The testis was used for all biochemical assays and immunofluorescent localization of biomarkers of interest. Rosuvastatin-treated animals presented with a significant decrease in sperm concentration when compared to both the control and simvastatin groups (p < 0.005). While no significant difference was observed between the simvastatin and the control group. The Sertoli cells, Leydig cells and whole testicular tissue homogenate expressed transcripts of solute carrier organic anion transporters (SLCO1B1 and SLCO1B3). There was a significant decrease in the testicular protein expression of the luteinizing hormone receptor, follicle stimulating hormone receptor, and transient receptor potential vanilloid 1 in the rosuvastatin and simvastatin-treated animals compared to the control. The expression of SLCO1B1, SLCO1B2, and SLCO1B3 in the different spermatogenic cells portray that un-bio transformed statin can be transported into the testicular microenvironment, which can subsequently alter the regulation of the gonadal hormone receptors, dysregulate pain-inflammatory biomarkers, and consequently impair sperm concentration.

Statins and Male Fertility: Is There a Cause for Concern?

The well-known 3-hydroxyl 3-methyl glutaryl-Coenzyme A reductase inhibitors, called statins, have been the main medication used in the treatment of hypercholesterolemia and some cases of cardiovascular diseases. The effectiveness of this drug in controlling cholesterol production is impeccable, however, patients often complain of a variety of side effects, such as myalgia, muscle atrophy, and in some cases, rhabdomyolysis. Not only has the use of statins caused the aforementioned side effects, but they are also shown to cause testicular discomfort, erectile dysfunction, altered semen parameters, and modified steroid hormone production. These reported adverse effects on male fertility are not generally agreed upon, as some have shown the use to be beneficial. Hence, this makes the aftermath effect of statin use on male fertility debatable and controversial. The negative effects have been associated with imbalanced or reduced steroid hormones, which are necessary for proper spermatogenesis and other sexual functions. Meanwhile, the beneficial effects are related to statin's anti-inflammatory and cardioprotective properties. These contradictory findings are in part due to the different age of users, concentrations of statins, the type and duration of treatment, and the underlying disease and/or comorbidities. Therefore, the current study aims to analyze the literature and gather evidence as to the effects of statin on male sexual health and reproductive parameters, and subsequently give recommendations for the direction of future studies.

Effect of introducing interprofessional education concepts on students of various healthcare disciplines: a pre-post study in the United Arab Emirates.

BACKGROUND: The value of interprofessional education (IPE) in nurturing healthcare professionals, and in shaping their professional identities, and their attitudes towards interdisciplinary teamwork and collaboration is established in the literature. IPE is an emerging concept in the Middle East and North Africa (MENA) region and is new to the United Arab Emirates (UAE). To date, the applicability and feasibility of IPE and of the corresponding collaborative practice in MENA countries remain largely unexamined. PURPOSE: To investigate the effect of one of the first experiences of IPE in the UAE, which was purposefully designed in alignment with the principles of the Situated Learning Theory (SLT), on the readiness for interprofessional learning and collaboration among students of various healthcare disciplines in the UAE. METHODS: A pre-post intervention quantitative research design was adopted for this study. The intervention focused on communication skills, and consisted of 2 tailor-made case-based scenarios. A total of 90 students (40 medical, 16 nursing, 16 pharmacy, and 18 physiotherapy), spread across two sessions (1 session per academic year across 2 academic years), took part in the IPE intervention. Readiness for Interprofessional Learning Scale (RIPLS) was used as the pre- and post- intervention assessments; aggregate data was analyzed using SPSS. RESULTS: Of those who participated in the intervention (across both rounds), 77 participants responded to the pre-assessment (85. 6%) and 84 responded to the post-assessment (93. 3%). The IPE intervention under investigation significantly increased the level of readiness to engage in cross-disciplinary learning and collaboration among participating health professions' students. In terms of the subscales, the participants' openness to engage in teamwork was raised and their professional identity was fostered. Yet, no statistical significance around clarity of roles and responsibilities was detected. CONCLUSION: The findings of this study encourage other universities in the MENA region to adopt IPE to improve future health professionals' capacity to develop shared understanding and mutual respect within cross-disciplinary teams. This, ultimately, feeds into improved quality of care and patient outcomes.

Pharmaceutical perspective of neuropathic pain management for primary care providers.

Neuropathic pain (NP) is a chronic condition that affects ~ 1% of the general population globally. Several conditions such as chronic diabetes, herpes zoster (HZ), cancer, HIV, stroke, multiple sclerosis, physical compression or damage of nerves and certain surgical procedures can lead to neuropathy and related pain. The condition is difficult to treat with traditional analgesic drugs. Typically, non-traditional analgesics are used in treating pain in this condition such as antidepressants and antiepileptic drugs. Opioids are useful in some patients, but the risk of addiction and the risk of both short-term and long-term adverse effects make it a low priority drug class in the treatment of NP. In the current review we discuss the pharmacology and pharmaceutical care aspects of various classes of drugs used in the treatment of NP, counselling points for these drug classes, and future prospects in the treatment of NP.

Pain in chronic prostatitis and the role of ion channels: a brief overview.

BACKGROUND: Prostatitis is the third most common urologic condition affecting more than half the male population at some point in their lives. There are different categories of prostatitis, of which approximately 90% of cases can be classified under the National Institute of Health (NIH) type III category (chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS)) with no causative agents identified. CP/CPPS is associated with several symptoms, of which the most prominent being chronic pain. Despite its high incidence, pain management in patients with CP/CPPS has been poor, possibly due to the lack of understanding of aetiological factors and mechanisms underlying pain development. METHODS: An extensive literature search of published articles on the molecular mechanisms of pain in CP/CPPS was conducted using PubMed and Google Scholar search engines (https://pubmed.ncbi.nlm.nih.gov and https://scholar.google.com). The terms used for the search were: prostatitis, pain mechanism in CP/CPPS, prostatitis pain models, acid-sensing ion channels (ASICs), transient receptor potential vanilloid type 1 (TRPVs), purinergic channels (P2X) in prostatitis pain mechanism and inflammatory mediators in CP/CPPS. The papers were identified based on the title and abstract, and after excluding the articles that did not emphasize the pain mechanism in CP/CPPS. Ninety-five articles (36 review and 59 original research papers) met our criteria and were included in the review. RESULTS: A number of inflammatory mediator molecules and pain channels, including ASICs, transient receptor potential vanilloid channels (TRPVs) and P2Xs have been investigated for their role in prostatitis pain pathology using various animal models. CONCLUSION: This review summarizes the pain mechanisms in CP/CPPS focusing on the inflammatory mediators, neurotransmitters, pain-transducing ion channels and small animal models developed for studying prostatitis.

Mechanisms of pain in sickle cell disease.

OBJECTIVES: The hallmark of sickle cell disease (SCD) is acute and chronic pain, and the pain dominates the clinical characteristics of SCD patients. Although pharmacological treatments of SCD targeting the disease mechanisms have been improved, many SCD patients suffer from pain. To overcome the pain of the disease, there have been renewed requirements to understand the novel molecular mechanisms of the pain in SCD. METHODS: We concisely summarized the molecular mechanisms of SCD-related acute and chronic pain, focusing on potential drug targets to treat pain. RESULTS: Acute pain of SCD is caused by vaso-occulusive crisis (VOC), impaired oxygen supply or infarction-reperfusion tissue injuries. In VOC, inflammatory cytokines include tryptase activate nociceptors and transient receptor potential vanilloid type 1. In tissue injury, the secondary inflammatory response is triggered and causes further tissue injuries. Tissue injury generates cytokines and pain mediators including bradykinin, and they activate nociceptive afferent nerves and trigger pain. The main causes of chronic pain are from extended hyperalgesia after a VOC and central sensitization. Neuropathic pain could be due to central or peripheral nerve injury, and protein kinase C might be associated with the pain. In central sensitization, neuroplasticity in the brain and the activation of glial cells may be related with the pain. DISCUSSION: In this review, we summarized the molecular mechanisms of SCD-related acute and chronic pain. The novel treatments targeting the disease mechanisms would interrupt complications of SCD and reduce the pain of the SCD patients.

Current methodologies to refine bioavailability, delivery, and therapeutic efficacy of plant flavonoids in cancer treatment.

Over the last two decades, several advancements have been made to improve the therapeutic efficacy of plant flavonoids, especially in cancer treatment. Factors such as low bioavailability, poor flavonoid stability and solubility, ineffective targeted delivery, and chemo-resistance hinder the application of flavonoids in anti-cancer therapy. Many anti-cancer compounds failed in the clinical trials because of unexpected altered clearance of flavonoids, poor absorption after administration, low efficacy, and/or adverse effects. Hence, the current research strategies are focused on improving the therapeutic efficacy of plant flavonoids, especially by enhancing their bioavailability through combination therapy, engineering gut microbiota, regulating flavonoids interaction with adenosine triphosphate binding cassette efflux transporters, and efficient delivery using nanocrystal and encapsulation technologies. This review aims to discuss different methodologies with examples from reported dietary flavonoids that showed an enhanced anti-cancer efficacy in both in vitro and in vivo models. Further, the review discusses the recent progress in biochemical modifications of flavonoids to improve bioavailability, solubility, and therapeutic efficacy.

Natural compound catechol induces DNA damage, apoptosis, and G1 cell cycle arrest in breast cancer cells.

Targeting cell cycle and inducing DNA damage by activating cell death pathways are considered as effective therapeutic strategy for combating breast cancer progression. Many of the naturally known small molecules target these signaling pathways and are effective against resistant and/or aggressive types of breast cancers. Here, we investigated the effect of catechol, a naturally occurring plant compound, for its specificity and chemotherapeutic efficacies in breast cancer (MCF-7 and MDA-MB-231) cells. Catechol treatment showed concentration-dependent cytotoxicity and antiproliferative growth in both MCF-7 and MDA-MB-231 cells while sparing minimal effects on noncancerous (F-180 and HK2) cells. Catechol modulated differential DNA damage effects by activating ATM/ATR pathways and showed enhanced γ-H2AX expression, as an indicator for DNA double-stranded breaks. MCF-7 cells showed G1 cell cycle arrest by regulating p21-mediated cyclin E/Cdk2 inhibition. Furthermore, activation of p53 triggered a caspase-mediated cell death mechanism by inhibiting regulatory proteins such as DNMT1, p-BRCA1, MCL-1, and PDCD6 with an increased Bax/Bcl-2 ratio. Overall, our results showed that catechol possesses favorable safety profile for noncancerous cells while specifically targeting multiple signaling cascades to inhibit proliferation in breast cancer cells.

Role of flavonoids in thrombotic, cardiovascular, and inflammatory diseases.

The failure of mechanisms of natural anti-coagulation either due to genetic impairment or due to severe external injuries may result in a condition called thrombosis. This is believed to be the primary cause for a variety of life-threatening conditions such as: heart attack, stroke, pulmonary embolism, thrombophlebitis, and deep venous thrombosis (DVT). The growing number of these incidents requires an alternative anti-coagulant or anti-thrombotic agent that has minimal side effects and improved efficiency. For decades, plant polyphenols, especially flavonoids, were known for their vital role in preventing various diseases such as cancer. Mitigating excessive oxidative stress caused by reactive oxygen species (ROS) with anti-oxidant-rich flavonoids may reduce the risk of hyper-activation of platelets, cardiovascular diseases (CVD), pain, and thrombosis. Furthermore, flavonoids may mitigate endothelial dysfunction (ED), which generally correlates to the development of coronary artery and vascular diseases. Flavonoids also reduce the risk of atherosclerosis and atherothrombotic disease by inhibiting excessive tissue factor (TF) availability in the endothelium. Although the role of flavonoids in CVD is widely discussed, to the best of our knowledge, their role as anti-thrombotic lead has not been discussed. This review aims to focus on the biological uses of dietary flavonoids and their role in the treatment of various coagulation disorders, and may provide some potential lead to the drug discovery process in this area.

Penetration and pharmacokinetics of non-steroidal anti-inflammatory drugs in rat prostate tissue.

BACKGROUND: Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) involves inflammation of the prostate and affects the quality of life of men of all ages. It is well reported in clinical studies that the treatment for CP/CPPS using nonsteroidal anti-inflammatory drugs (NSAIDs) produced favorable outcomes. However, currently, there are no guidelines on choice of the NSAIDs for the treatment of CP/CPPS. Therefore, in the current research study, we evaluated the prostate tissue penetration of four NSAIDs in rats to provide guidance on choice of NSAIDs for the treatment of CP/CPPS. METHODS: Male Sprague-Dawley rats were administered orally with four NSAIDs viz. celecoxib, diclofenac, ibuprofen, and naproxen at 500 mg/kg dose. The animals were then sacrificed at various time points, and their prostate tissues were harvested. The NSAIDs were then extracted from the prostate tissues using liquid extraction technique, and their concentration in prostate tissue was quantified using high-performance liquid chromatography (HPLC). The prostate tissue penetration and related pharmacokinetic parameters were evaluated by non-compartmental analysis. RESULTS: The HPLC method for quantifying NSAIDs in prostate tissue resulted in single, sharp peaks without any interference and all validation parameters were within limits. Celecoxib showed the highest area under the curve (AUC) [146.50 ± 2.75 µg/mL*h] of all NSAID's. A two-factor analysis of variance (ANOVA) with replication indicated an overall statistically significant difference in the pharmacokinetic parameters for celecoxib, diclofenac, ibuprofen, and naproxen. CONCLUSIONS: This study for the first time reported the relative prostate tissue penetration of four NSAIDs. The pharmacokinetic data indicated that celecoxib has the highest penetration and retention in rat prostate tissues. Therefore, celecoxib may be considered as a better choice for the treatment CP/CPPS involving NSAIDs.

A Critical Approach to Evaluating Clinical Efficacy, Adverse Events and Drug Interactions of Herbal Remedies.

Systematic reviews and meta-analyses represent the uppermost ladders in the hierarchy of evidence. Systematic reviews/meta-analyses suggest preliminary or satisfactory clinical evidence for agnus castus (Vitex agnus castus) for premenstrual complaints, flaxseed (Linum usitatissimum) for hypertension, feverfew (Tanacetum partenium) for migraine prevention, ginger (Zingiber officinalis) for pregnancy-induced nausea, ginseng (Panax ginseng) for improving fasting glucose levels as well as phytoestrogens and St John's wort (Hypericum perforatum) for the relief of some symptoms in menopause. However, firm conclusions of efficacy cannot be generally drawn. On the other hand, inconclusive evidence of efficacy or contradictory results have been reported for Aloe vera in the treatment of psoriasis, cranberry (Vaccinium macrocarpon) in cystitis prevention, ginkgo (Ginkgo biloba) for tinnitus and intermittent claudication, echinacea (Echinacea spp.) for the prevention of common cold and pomegranate (Punica granatum) for the prevention/treatment of cardiovascular diseases. A critical evaluation of the clinical data regarding the adverse effects has shown that herbal remedies are generally better tolerated than synthetic medications. Nevertheless, potentially serious adverse events, including herb-drug interactions, have been described. This suggests the need to be vigilant when using herbal remedies, particularly in specific conditions, such as during pregnancy and in the paediatric population. Copyright © 2016 John Wiley & Sons, Ltd.

Perceptions of tenure and tenure reform in academic pharmacy.

OBJECTIVES: To determine the academic pharmacy community's perceptions of and recommendations for tenure and tenure reform. METHODS: A survey instrument was administered via either a live interview or an online survey instrument to selected members of the US academic pharmacy community. RESULTS: The majority of respondents felt that tenure in academic pharmacy was doing what it was intended to do, which is to provide academic freedom and allow for innovation (59.6%). Respondents raised concern over the need for faculty mentoring before and after achieving tenure, whether tenure adequately recognized service, and that tenure was not the best standard for recognition and achievement. The majority (63%) agreed that tenure reform was needed in academic pharmacy, with the most prevalent recommendation being to implement post-tenure reviews. Some disparities in opinions of tenure reform were seen in the subgroup analyses of clinical science vs basic science faculty members, public vs private institutions, and administrators vs nonadministrators. CONCLUSIONS: The majority of respondents want to see tenure reformed in academic pharmacy.

An integrated course in pain management and palliative care bridging the basic sciences and pharmacy practice.

OBJECTIVE: To describe the development of an integrated pain and palliative care course and to investigate the long-term effectiveness of the course during doctor of pharmacy (PharmD) students' advanced pharmacy practice experiences (APPEs) and in their practice after graduation. DESIGN: Roseman University College of Pharmacy faculty developed a 3-week elective course in pain and palliative care by integrating relevant clinical and pharmaceutical sciences. Instructional strategies included lectures, team and individual activities, case studies, and student presentations. ASSESSMENT: Students who participated in the course in 2010 and 2011 were surveyed anonymously to gain their perception about the class as well as the utility of the course during their APPEs and in their everyday practice. Traditional and nontraditional assessment of students confirmed that the learning outcomes objectives were achieved. CONCLUSIONS: Students taking the integrated course on pain management and palliative care achieved mastery of the learning outcome objectives. Surveys of students and practicing pharmacists who completed the course showed that the learning experience as well as retention was improved with the integrated mode of teaching. Integrating basic and clinical sciences in therapeutic courses is an effective learning strategy.

The ß4 nicotinic receptor subunit modulates the chronic antidepressant effect mediated by bupropion.

The objective of the current study is to investigate the role of the nicotinic receptor ß4 subunit in the antidepressant activity of bupropion. Wild-type (ß4+/+) and knockout (ß4-/-) mice were intraperitoneally administered with normal saline (control) or bupropion (40mg/kg) daily for the first two weeks. Forced swim tests were performed on day 1 to determine the acute effect of bupropion at 0, 15, 30, 45, or 60min after the injection, and after two weeks of daily treatment to determine the chronic effects. To examine the remnant effects of bupropion after withdrawal, forced swim tests were performed one and two weeks after the last day of treatment with bupropion. Our results indicate that: (1) the acute treatment with bupropion increases the swimming time (i.e., antidepressant effect) in ß4+/+ and ß4-/- mice from both genders, (2) the antidepressant effect after the chronic treatment is seen only in female ß4+/+ mice, and (3) the residual antidepressant effect of bupropion persists only in male ß4+/+ mice after one week withdrawal. We conclude that the ß4 subunit plays a modulatory role in the chronic antidepressant effect mediated by bupropion, and that its effect is gender-specific.

TRPV1 is important for mechanical and heat sensitivity in uninjured animals and development of heat hypersensitivity after muscle inflammation.

Inflammatory thermal hyperalgesia is principally mediated through transient receptor potential vanilloid 1 (TRPV1) channels, as demonstrated by prior studies using models of cutaneous inflammation. Muscle pain is significantly different from cutaneous pain, and the involvement of TRPV1 in hyperalgesia induced by muscle inflammation is unknown. We tested whether TRPV1 contributes to the development of mechanical and heat hypersensitivity of the paw in TRPV1(-/-) mice after muscle inflammation. Because TRPV1(-/-) mice lack TRPV1 at the site of inflammation (muscle) and at the testing site (paw), we do not know whether TRPV1 is important as a mediator of nociceptor sensitization in the muscle or as a heat sensor in the paw. Using recombinant herpesviruses, we reexpressed TRPV1 in TRPV1(-/-) mice in primary afferents innervating skin, muscle, or both to determine which sites were important for the behavioral deficits. Responses to repeated application of noxious mechanical stimuli to the hind paw were enhanced in TRPV1(-/-) mice; this was restored by reexpression of TRPV1 into skin. Withdrawal latencies to noxious heat were increased in TRPV1(-/-) mice; normal latencies were restored by reexpression of TRPV1 in both skin and muscle. Heat hypersensitivity induced by muscle inflammation did not develop in TRPV1(-/-) mice; mechanical hypersensitivity was similar between TRPV1(-/-) and TRPV1(+/+) mice. Heat hypersensitivity induced by muscle inflammation was restored by reexpression of TRPV1 into both muscle and skin of TRPV1(-/-) mice. These results suggest that TRPV1 serves as both a mediator of nociceptor sensitization at the site of inflammation and as a heat sensor at the paw.

Increased glutamate and decreased glycine release in the rostral ventromedial medulla during induction of a pre-clinical model of chronic widespread muscle pain.

Two injections of acidic saline into the gastrocnemius muscle produce long-lasting hyperalgesia that is initiated and maintained by changes in the rostroventromedial medulla (RVM). Potential underlying mechanisms could be increased release of excitatory neurotransmitters and/or reduced release of inhibitory neurotransmitters, in the RVM. We tested this hypothesis by measuring concentrations of aspartate, glutamate and glycine in response to the first and second injection of acidic saline and compared to intramuscular injections of normal saline using microdialysis with HPLC analysis. We show a significant increase in aspartate and glutamate during the second acidic saline injection compared to normal saline injections or the first injection of acidic saline. There were also long-lasting decreases in glycine concentrations in the RVM in response to both the first and second injection of acidic saline. It is possible that disinhibition after the first injection leads to long-lasting neuronal changes that allow a greater release of excitatory neurotransmitters after the second injection. We hypothesize that increased release of excitatory neurotransmitters in the RVM drives the release of excitatory neurotransmitters in the spinal cord, central sensitization and the consequent hyperalgesia.

Transcutaneous electrical nerve stimulation at both high and low frequencies reduces primary hyperalgesia in rats with joint inflammation in a time-dependent manner.

BACKGROUND AND PURPOSE: Clinical studies of transcutaneous electrical nerve stimulation (TENS) have used a variety of outcome measures to assess its effectiveness, with conflicting results. It is possible that TENS is effective on some measures of pain and not on others. The purpose of this study was to test the hypothesis that TENS reduces primary hyperalgesia of the knee induced by joint inflammation. SUBJECTS: Male Sprague-Dawley rats were used in this study. METHODS: Inflammation of the knee joint was induced by intra-articular injection of a mixture of 3% kaolin and 3% carrageenan. Primary hyperalgesia was measured as the compression withdrawal threshold of the knee joint before and after the induction of inflammation (4 hours, 24 hours, and 2 weeks) and after sham TENS treatment, treatment with high-frequency TENS (100 Hz), or treatment with low-frequency TENS (4 Hz). RESULTS: The compression withdrawal threshold was significantly reduced at 4 hours, 24 hours, and 2 weeks after the induction of inflammation. Either high-frequency TENS or low-frequency TENS completely reversed the compression withdrawal threshold when applied at 24 hours or 2 weeks after the induction of inflammation but not when applied at 4 hours after the induction of inflammation. DISCUSSION AND CONCLUSION: These data suggest that TENS inhibits primary hyperalgesia associated with inflammation in a time-dependent manner after inflammation has already developed during both acute and chronic stages.