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Eddy Hot Plate Analgesiometer - Standard Operating Procedure and Apparatus.pptx

Almost all relevant procedural details covered in appropriate depth and step by step fashion along with videos. Brief Outlook on other screening methods, neurophysiological pathway and viva questions also have been covered. We will also take a look at some significant researches done on the subject and overview of study designs according to rodent grouping and the best suited statistical approach suited to analysing them. Side by side comparison of various drugs have been manually tabulated by researching various credible sources on Experimental pharmacology and pubmed articles. Alternative models for Eddy hot plate Analgesiometer have also been mentioned. The ppt has been systematically organised with slides titled contents, specific learning objectives achieved, summary for academic purposes. References have also been added. Overall a wholesome slideset covering wide aspects of the subject from multiple angles. Perfect for MD pharmacology post graduate level presentation, conferences as well as revision.

Health & Medicine◦
1 Eddy’s Hot Plate Analgesiometer apparatus Presenter - Dr. Kaustubh Bhardwaj (JR-2) Peer Support - Dr. Kamal Akhtar (JR-2) Department of Pharmacology & Therapeutics King George’s Medical University, Lucknow, U.P. India Mail ID : kaustubhbhardwajkgmu@gmail.com 20-09-2025 Dr Kaustubh Bhardwaj
Contents • Introduction • Principle • Apparatus • Drugs Used • Procedure • Data Analysis • Alternate Models • Summary 20-09-2025 Dr Kaustubh Bhardwaj 2
Specific learning objectives At the end of this teaching-learning session, co-learners will be able to: • Understand the principle of Eddy’s Hot Plate experiment • Describe the procedure to evaluate analgesic activity in rodents • Identify apparatus, cut-off times, and precautions • Analyze drug-induced analgesia using reaction time 20-09-2025 Dr Kaustubh Bhardwaj 3
Abbreviations • IP - Intraperitoneal • SC - Subcutaneous • mg/kg - milligram per kilogram 20-09-2025 Dr Kaustubh Bhardwaj 4
Introduction • The hot plate analgesiometer is used to assess the response of animals against thermal stimulus to evaluate the analgesic effects of drugs on somatic pain. • Discovered by N.B. Eddy in 1953. 20-09-2025 Dr Kaustubh Bhardwaj 5
Animal Models for Screening of Analgesic Drugs A) Pain-state models using Thermal stimuli 1. Eddy’s Hot Plate Analgesiometer 2. The tail-flick model using radiant heat/Immersion of the tail in hot water 3. Paw withdrawal test 4. Pain-state models using Cold-stimuli 20-09-2025 Dr Kaustubh Bhardwaj 6 C) Pain-state models using Electrical stimuli 1. Electrical stimulation of the tail 2. Grid-shock test 3. Stimulation of the tooth pulp 4. Stimulation of the limbs B) Pain-state models using Mechanical stimuli 1. Strain gauges 2. Von-Frey filaments D) Pain-state models using Chemical stimuli 1. Formalin test 2. Acetic acid induced writhing test 3. Stimulation of hollow organs
Dr Kaustubh Bhardwaj 7 20-09-2025
Dr Kaustubh Bhardwaj 8 20-09-2025 Supraspinal (Hot Plate) Spinal (Tail Flick, Hargreaves) Peripheral (Writhing, Formalin, Randall-Selitto) Opioids Strong effect Strong effect Moderate effect NSAIDs Minimal / negligible effect Weak effect Strong effect Sedatives False ↑ latency due to drowsiness / motor suppression Can appear to ↑ reflex latency Little/no effect Muscle relaxants False ↑ latency May slow reflex responses Minimal effect
9 20-09-2025 Dr Kaustubh Bhardwaj 1st Order Neurons 2nd Order Neurons 3rd Order Neurons Spinothalamic Pain Conduction Pathway
Dr Kaustubh Bhardwaj 10 Principle 20-09-2025 • Rodents will show aversion effect to thermal stimulus by chaotic defensive movements after placing onto the hot surface • Source of pain: Contact heat • Endpoint: Paw licking and jumping • Cut off time:  Mouse - 15 – 20 sec  Rat - 20 – 30 sec
Dr Kaustubh Bhardwaj 11 Eddy’s Hot Plate 20-09-2025 Perspex glass (acrylic sheet, which is a transparent thermoplastic) Cover Lid Lid sensor Aluminium Plate • Orchid Eddy’s hot plate analgesiometer • Model: EH 01
Dr Kaustubh Bhardwaj 12 Length Breadth Height Base Dimensions 30 cm 33.5 cm 15 cm Plate Dimensions 20.4 cm 20.4 cm 1.2 cm 20-09-2025 Dimensions of Eddy’s Hot Plate Analgesiometer
Dr Kaustubh Bhardwaj 13 Front View : 20-09-2025
Dr Kaustubh Bhardwaj 14 Lid Sensor : 20-09-2025
Dr Kaustubh Bhardwaj 15 20-09-2025
Dr Kaustubh Bhardwaj 16 Start New Experiment/Continue Previous Experiment/View Logs/PC connectivity Sequence Number Cut off time Temperature 20-09-2025
Dr Kaustubh Bhardwaj 17 Back View : 20-09-2025
Dr Kaustubh Bhardwaj 18 20-09-2025 Most commonly used Drugs in Eddy’s Hot Plate Experiment Drugs Dose Morphine 5-10 mg/kg (IP or SC) Codeine 10-30 mg/kg (IP) Tramadol 10-30 mg/kg (IP)
Dr Kaustubh Bhardwaj 19 20-09-2025 Drugs used in Eddy’s Hot Plate Experiment Other Drugs : 1. Antidepressants with analgesic action - TCAS and SNRIS 2. Anticonvulsants with analgesic action - Gabapentin, Pregabalin 3. NMDA receptor antagonists – Ketamine, Dextromethorphan 4. Cannabinoids
Dr Kaustubh Bhardwaj 20 20-09-2025 Ensure the hot plate is clean and in proper working condition Weigh the animals and administer drug dose accordingly. Acclimatise the animal by placing home cage in laboratory. Set the hot plate sequence number, temperature (50-55°C), cut off time using the control panel Preheat the hot plate and check temperature stability Standard Operating Procedure
Dr Kaustubh Bhardwaj 21 20-09-2025 Place the animal gently on the preheated hot plate Start the digital timer Observe the animal for the first pain response (paw licking/jumping) Press the footpad to stop heating and immediately remove the animal
Dr Kaustubh Bhardwaj 22 20-09-2025 Record the latency time (reaction time) using the timer Allow the animal to recover in a safe environment Repeat for control and drug-treated groups Analyze and compare the latency times for results
Dr Kaustubh Bhardwaj 23 Precautions 20-09-2025 • Clean the paw and hot plate for uniform temperature distribution • Ensure the lid is enclosed for accurate and fast temperature • Wait until the hot plate reaches the set temperature before use • Handle animals gently to avoid stress and altered responses • Always follow the cut-off time (15–20 sec in mice, 20–30 sec in rats) to prevent tissue injury
Dr Kaustubh Bhardwaj 24 Observation Table (Control Group) 20-09-2025 S.No Animal Weight (gms) Basal Reaction Time (sec) Reaction time (sec) 20 mins 60 mins 90 mins 1. 165 4.8 4.4 4.1 4.8 2. 182 5.4 5.2 5.2 4.4 3. 167 5.2 5.0 5.4 4.8 4. 175 5.6 4.8 4.6 4.4 5. 185 3.8 4.0 4.4 4.2 6. 174 4.6 4.5 4.8 4.6
Dr Kaustubh Bhardwaj 25 Observation Table (Treated Group) 20-09-2025 S.No Animal Weight (gms) Basal Reaction Time (sec) Reaction time after treatment (sec) 20 mins 60 mins 90 mins 1. 172 3.4 6.3 4.0 3.6 2. 190 4.2 7.2 4.5 4.5 3. 165 5.1 7.6 5.6 5.2 4. 176 4.4 5.2 4.7 4.6 5. 190 5.4 6.1 5.8 5.6 6. 170 4.5 5.5 5.0 4.7
Dr Kaustubh Bhardwaj 26 Data Analysis 20-09-2025 • Paired t-test → Same rats before vs after drug. • Unpaired t-test → Control vs drug (2 groups). • One-way ANOVA → 3+ independent groups (different doses). • Repeated measures ANOVA → Same rats at multiple time points. • Non-parametric equivalents → Wilcoxon (paired), Mann–Whitney (unpaired), Kruskal–Wallis (one-way ANOVA), Friedman (repeated measures).
27 Alternate Models of Eddy's Hot Plate Analgesiometer 1. Hot and Cold Plate Analgesiometer 2. Thermal Place Preference Analgesiometer 20-09-2025 Dr Kaustubh Bhardwaj
Specific learning objectives achieved By the end of this teaching-learning session, co-learners are now able to: • Understand the principle of Eddy’s Hot Plate experiment • Describe the procedure to evaluate analgesic activity in rodents • Identify apparatus, cut-off times, and precautions • Analyze drug-induced analgesia using reaction time 20-09-2025 Dr Kaustubh Bhardwaj 3
29 Summary • Eddy's Hot Plate Analgesiometer is a reliable model for screening analgesics. • Rodents show aversion to thermal stimulus by chaotic defensive movements. • Supraspinal response can be tested by this method to analyse central analgesic effect in opioids. • Antidepressants, anticonvulsants, cannabinoids, nmda antagonists with prominent central analgesic effect can also be screened. 20-09-2025 Dr Kaustubh Bhardwaj
30 References 20-09-2025 Dr Kaustubh Bhardwaj • Kunnoor N, R V, A B, K L. Hot plate method: A painful stimulus to induce anxiety in Wistar rats. Natl J Physiol Pharm Pharmacol. 2023;(0):1. • Bikas Medhi, Ajay Prakash, Practical Manual of Experimental and Clinical Pharmacology, 2nd edition, Jaypee, New Delhi; 2017. p 212-14. • Hot Plate Analgesia Meter. Orchid. Available from: https://orchidscientific.com/product/hot-plate-analgesia-meter/index.php • Sarkar S, Srivastava V, Mohanty M. Postgraduate pharmacology. 2nd ed. Hyderabad: Paras Medical Publisher; 2024. p.332.
31 20-09-2025 Dr Kaustubh Bhardwaj • Inder D, Rehan HS, Bajaj VK, Kumar P, Gupta N, Singh J. Analgesic activity and safety of ash of silver used in Indian system of medicine in mice: a reverse pharmacological study. Indian J Pharmacol. 2012 Jan;44(1):46-50. • Bhagyashree A, Manikkoth S, Sequeira M, Nayak R, Rao SN. Central dopaminergic system plays a role in the analgesic action of paracetamol: Preclinical evidence. Indian J Pharmacol. 2017;49(1):21–5.
32 AUDIENCE QUESTION 20-09-2025 Dr Kaustubh Bhardwaj
Dr Kaustubh Bhardwaj 33 Questions Q1. Define the principle of Eddy’s hot plate method. Q2. What are the cut-off times for mice and rats? Q3. Which drug was used in this experiment and by which route? Q4. Why is it important to set a cut-off time? Q5. How are results statistically analyzed? 20-09-2025
Dr Kaustubh Bhardwaj 34 Thank You 20-09-2025