EPILEPSY.pptx neuropharmacology pharmacology

pharmacy

1. 1 VISHNUPRIYA.B EZTHUTHACHAN COLLEGE OF PHARMACEUTICAL SCIENCES, MARAYAMUTTOM, NEYYATTINKARA ,THIRUVANANTHAPURAM First Semester M. Pharm Department of Pharmacology TOPIC: PHARMACOLOGICAL SCREENING OF ANTIEPILEPTIC AGENTS Submitted to M rs. ASHEETA. A Associate Professor Department of Pharmacology Mrs. ANCY P. M Assistant Professor Department of Pharmacology

2. INTRODUCTION N eurological disorder in which brain activity becomes abnormal Seizures : imbalance between excitatory and inhibitory transmission Two types: Generalized seizures Partial seizures Agent used called antiepileptic drugs Act by modulating GABA or glutamate transmission 2

3. PHARMACOLOGICAL SCREENING OF ANTIEPILEPTIC AGENTS In vitro models GABA uptake and release in rat hippocampal slices 3 H strychnine sensitive glycine receptor Electrical recording model of Hippocampal Slice culture Electrical recording from isolated Brain cells Isolated neonatal rat spinal cord 3

4. 6. GABA B receptor binding assay 7. GABA A receptor binding assay 8 . 3 H- GABA uptake in rat cerebral cortex synaptosomes 9 . 3 H Muscimol binding assay 10 . 3 H SR 95531 binding assay 11 . 35 S TBPS binding assay 12 . 3 H CPP binding assay 13 . 3 H TCP binding assay 14 . 3 H Glycine binding in rat cerebral cortex 4

5. 1. GABA uptake and release in rat hippocampal slices R at hippocampal slices are cut D ispersed in ice-cold buffer I ncubated at 37 °C for 15 min 0.05 µM [ 3 H]-GABA is added and incubated again Samples are then washed twice with 0.9 %saline M easured for radioactivity Procedure 5

6. 2. [ 3 H] Strychnine sensitive glycine receptor Procedure Male Wistar rats (200 g) are sacrificed Tissues are homogenized H omogenate is centrifuged for 10 min at 30, 000 g at 0–4 °C R ehomogenized in the same buffer and recentrifuged F inal pellet is resuspended in 200 vol/g in buffer 6

7. A ssays consist of 1 ml tissue homogenate, 50 µl test solution and 25 µl [ 3 H]strychnine to a final concentration S amples are mixed and incubated for 20 min Free and bound radioactivity is measured Nonspecific binding is determined 7

8. 3. Electrical recordings from hippocampal slices in vitro Procedure Male guinea pigs (300–400g) are decapitated B rain removed and the hippocamp is dissected out S lices are submerged in 28 °C warm saline After 2 hr, slices are transferred in to a chamber 8

9. C hamber is mounted on an inverted microscope Intracellular recordings are taken by a micropipettes T ips of the micropipettes are placed within the stratum pyramidale R esting membrane potential and paroxysmal depolarizations are recorded 9

10. II. In vivo models Chemical stimulation models Pentylenetetrazole (PTZ) model Strychnine model Picrotoxin model Isoniazid model Lithium pilocarpine model Bicuculline model 7. Kainic Acid (KA) model 8. Penicillin model 9. 4- aminopyridine model 10. n- methyl d-aspartate model 11. Aluminium , Cobalt, Zinc model 12. Cortically implanted metals model 13. Administration of Tetanic Toxin model 14. Epilepsy induced by focal lesions 15. Post-hypoxic myoclonus in rats 10

11. Genetic models Photosensitive baboons Audiogenic seizures mice Totterer mice or seizure prone mouse strains Genetically epilepsy- prone rats Electrical stimulation models Maximal Electroshock Seizures (MES) test Kindling animal model Threshold for Maximal Electroconvulsions 11

12. Electroshock in mice 2 Groups of 6–10 male NMRI mice (18–30 g) are used The test is started 30 min after i.p. injection or 60 min after orally Animals are placed on electroconvulsiometer D eliver the stimuli through electrodes Observe the animals 12

13. 2. Pentylenetetrazole (PTZ) /Metrazol induced convulsions 2 groups mice of either sex (18-22g) are used Inject PTZ (60mg/kg) to both test and control groups sc / ip Then inject test (4mg) and vehicle intravenously Each animal is placed into an individual plastic cage for observation lasting 1 hr Seizures and tonic- clonic convulsions are recorded. 13

14. 3. Strychnine-induced convulsions Groups of 6 mice of either sex (18 and 22 g )are used Treated test drug orally (e.g. diazepam 5 mg/kg) After 1 hr , the mice are injected with 2 mg/kg strychnine nitrate i.p. Observe both groups of animals The time until occurrence of tonic extensor convulsions and death is noted 14

15. 4. Picrotoxin-induced convulsions Groups of 6 mice of either sex( 20 -22g) are treated either orally or i.p. (10 mg/kg diazepam) After 30 min i.p or 60 min orally, administered 3.5mg/kg s.c. picrotoxin Observe the symptoms during the next 30 min Times of onset of seizures and time to death are recorded 15

16. 5. 4-aminopyridine-induced seizures in mice Male Swiss mice (25–30g) are taken A cclimatize with free access to food and water for a 24-h period before testing Test drugs are administered ip After 15 min inject 4-aminopyridine (13.3 mg/kg) sc Controls treated with 4-aminopyridine only Observe the animals in both groups 16

17. H.Gerhard Vogel. Drug Discovery and Evaluation.2nd edition;422-24, 459-93 SK Gupta.Drug Screening Methods.3rd edition;412-435 Dr.Nishant S Jain.Pharmacological Screening Methods.5th edition;186-194   REFERENCES: 17