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New pharmacological treatments for periferic neuropathic pain
Universidad Nacional de la Rioja
Instituto de Biotecnología – Centro de Investigación e Innovación Tecnológica (CENIIT) – Universidad Nacional de La Rioja Avenida Luis Vernet y Apóstol Felipe 5300 – La Rioja La Rioja, Argentina
Dr Carlos Laino
Dr Carlos Laino
Type of Research Project
- Basic science
What is the background of the project?
Neuropathic pain may be associated with traumatic injury to the spinal cord and brain or due to lumbar disc syndrome, the entrapment of the ulnar nerve (ulnar tunnel syndrome) and phantom limb pain. It may also be present in various diseases, including diabetes, cancer, herpes zoster infection and human immunodeficiency virus infection. Neuropathic pain is a major clinical problem, as it is a debilitating condition that seriously compromises the quality of life. In addition, neuropathic pain and associated syndromes share an important pharmacological feature as they respond poorly, or only partially, to the available therapies, which often have significant adverse effects. Consequently, there is still a need to explore new therapeutic strategies to identify effective and safer drugs with minimal or at least reduced adverse effects.
What is the aim of the project?
The aim of this project is to evaluate the potential effects of new treatment, as omega-3 fatty acids, using different experimental models of peripheral neuropathic pain models, as a chronic constriction injury (CCI), partial sciatic nerve ligation (Seltzer Model) and diabetes-induced neuropathy (Streptozotocin-induced).
What techniques and methods are used?
Behavioural studies: Heat hyperalgesia Test The thermal nociceptive threshold, as an index of thermal hyperalgesia, is assessed by the hot plate. The plate is pre-heated and maintained at a temperature of 52.5 ± 2.0ºC. The rat is placed on the hot plate and nociceptive threshold, with regards to licking of the hind paw, is recorded in seconds. The cut-off time is of 20 sec. Tail Cold Hyperalgesia test (Tail immersion test): The Tail Cold Hyperalgesia is noted by immersing a terminal part of the rat-tail (one cm) in the water maintained at temperature of 0.4°C (mixed with Ethylene Glycol) for each rat. The tail withdrawal latency is recorded (Seconds) and a cut off time of 20 sec is maintained. Hot plate test, The hot plate test is commonly used for evaluating thermal pain sensitivity and also, it is used to investigate sensory functional recovery. The Hot Plate test performs rapid and precise screening of analgesic drug properties on small-laboratory animals. During the experiment, the rat is introduced into an open-ended cylindrical space with a floor consisting of a heated plate. The plate heated to a constant temperature (45 ± 0.2°C) produces two behavioral components that can be measured in terms of their reaction times (latency time), namely paw licking and jumping. Both are considered to be supraspinally integrated responses. Maximal latency accepted is 45 sec. Cold Allodynia test Cold allodynia is assessed using the acetone drop method. Cold allodynia is measured as the number of foot withdrawal responses after application of cold stimuli (acetone) to the plantar surface of the paw. A brisk foot withdrawal response after the spread of acetone over the plantar surface of the paw was considered a sign of cold allodynia. Control rats either ignore the stimulus or occasionally respond with a small and brief withdrawal. Allodynic rats respond with prompt and intense paw withdrawal or escape behaviour to acetone application. The duration of withdrawal response is recorded with an arbitrary minimum value of 0.5 sec and a maximum value of 20 sec. Walking track test The analysis of a rat’s walking pattern by recording their footprints is a well-established and widely employed method for the assessment of motor nerve recovery after nerve injury. Walking track analysis is performed after surgery. The lengths of the third toe to its heel, the first to the fifth toe, and the second toe to the fourth toe are measured on the experimental side and the contralateral normal side in each rat. The Sciatic Function Index in each animal is calculated calculated using Bain's formula. Open field test, Open Field Test is used to determine the net motor activity of an animal over a given time period. The apparatus for the open field test consisted of a black, square open field (60 x 60 cm) with the floor divided in squares (15 × 15 cm) by means of white lines. The animal is placed gently in the center of the open field arena, and allowed to explore freely; their locomotion is measured by the number of squares entered with all four paws (counts) during a period of 5 min. Von Freys Hairs, A valuable and widely used tool for investigating chronic pain uses so-called von Frey fibers to apply pressure to the skin of test animals. Fibers of defined diameters are applied which when made to bend produce a constant pressure which increases with increasing diameter of the applied fiber. The preferred sites for applying nociceptive mechanical stimuli are the hind paw and the tail. Chronic Constriction Injury (CCI): The CCI model is a tool to study pharmacotherapy for chronic neuropathic pain. The model is used to identify experimental compounds with analgesic properties that are palliative for chronic neurophatic pain. The surgical procedure involves ligation on the sciatic nerve rat to create chronic peripheral pain.
What is the role of the student?
- The tasks will be done under supervision
What are the tasks expected to be accomplished by the student?
All the following methods will be done under supervision: Knowledge of and ability to basic rat handling Knowledge of and ability to methods of administration drugs in rats Knowledge of and ability to different pharmacological treatments Knowledge of behavioral studies Knowledge of and ability to functional analysis of regenerated sciatic nerve Skill in using protocols of anesthesia for surgical procedures Skill in using cci surgery Knowledge of and ability to dissection of sciatic nerve and dorsal root ganglia Ability to analyze the neuropathological and histomorphometric results Ability to analyze results and draw conclusion
Will there be any theoretical teaching provided (preliminary readings, lectures, courses, seminars etc)
Preliminary readings Lectures
What is expected from the student at the end of the research exchange? What will be the general outcome of the student?
- The student will prepare a scientific report - The student will have the opportunity to present the results together with the supervisor at a conference
What skills are required of the student? Is there any special knowledge or a certain level of studies needed?
Are there any legal limitations in the student’s involvement
Type of students accepted
This project accepts: - Medical students - Graduated students (less than 6 months)
- Analgesia Enhancement and Prevention of Tolerance to Morphine: Beneficial Effects of Combined Therapy with Omega 3 Fatty Acids Graciela E Escudero; Carolina B Romañuk; Maria E Toledo ; Ruben H Manzo ; María E Olivera; Carlos H Laino. J Pharm Pharmacol.(2015) Volume 67; Issue 9; 1251–1262.
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