Expt 9 Effect of drugs on rabbit eye

For educational purpose

1. AIM: Effect of various drugs on Rabbit’s eye Presented by: Prof. Mirza Anwar Baig Dept of Pharmcaology AIKTC, School of Pharmacy, New Panvel

2. REQUIREMENTS : Animal – Rabbit in rabbit holder. Drugs- Acetylcholine, Physostigmin , Atropine, Adrenaline

3. THEORY: Mydriatics are the drugs that dilate the pupils Miotics constrict the pupiles . Atropine , a common mydriatic used in clinics, cannot be used as a mydriatic in rabbit, as it is rapidly hydrolysed by Atropinase enzymes . Ephedrine is used as mydriatic and pilocarpine is used as miotics in rabbits. Iris of eye contains two types of muscles: Sphincter muscle- which contains cholinergic muscarinic receptors Radial muscles - which contain adrenergic α-receptors

4. THEORY: Physostigmine is reversible cholinesterase inhibitor drug which inhibit breakdown of acetylcholine (Potentiate activity of Ach). Ephedrine binds to α-receptors in radial muscles of the Iris due to which sphincter muscle dilate and pupil size increased causing Mydriasis .

5. THEORY: Pilocarpine is a cholinomimetic alkaloid that constrict circular muscles of iris and causes miosis . Atropine is a competitive antagonist of acetylcholine at muscarinic receptors . (causes paralysis of sphincter muscle and resultant increases in the size of pupil).

6. PROCEDURE: Keep the rabbit in rabbit holder. The right eye of rabbit is used as a control and 3 drops of saline solution are put in same eye. The left eye of the same rabbit is used to see the effect of drug. A separate rabbit is used for individual drug. The two drops of drug is put in the left eye of the rabbit and the effect of drug is checked by giving touch stimulus and light stimulus. The effect of given drug is verified by these touch reflexes and light reflexes.

7. Sr. No. Drug solution Pupil size Light reflex Touch reflex 1. Saline 2. Ephedrine 3. Carbachol 4. Physostigmine 5. Atropine 6. Lignacaine OBSERVATION TABLE:

8. RESULT: Saline: There is no change in pupil size by instilling of saline. The touch and light reflexes present. Carbachol : Carbacol causes decrease in pupil size and decease in diameter of Iris. Thus, it causes miosis , and touch and light reflexes are present. Physostigmine : Also depends as it also decreases the pupil size and causes miosis . The touch and light reflexes are present.

9. Ephedrine: Cause the increase in pupil size and increase in diameter of Iris. Thus cause the mydriasis . The touch and light reflexes are present. Atropine: It also increases the pupil size and increase in diameter of Iris cause mydriasis . The touch reflex is present but light reflex is absent. Lignocaine : There is no change on pupil size by Lignocaine.The touch reflex is absent but light reflex is present. Thus Carbacol and Physostigmine cause miosis , Ephedrine and Atropine cause mydriasis .

10. References: Ghosh MN. Fundamentals of Experimental Pharmacology. Hilton & Company, Kolkata. Kulkarni SK. Handbook of experimental pharmacology. VallabhPrakashan

11. Thank You