3.5.3 Pharmacology I
Lab 4 Effects of Pilocarpine on Rabbit's or Guineapig's Eye
Developed by Prova Biswas
To observe the changes in pupillary diameter, lighting reflex and conjunctival reflex of Rabbit's eye after the installation of Pilocarpine nitrate solution.
Pilocarpine, a parasympathomimetic drug, is a tertiary amine and alkaloid in nature. Pilocarpine has a high affinity for muscarinic receptors. It binds with cholinergic muscarinic receptors and produced the similar action as the acetylcholine does produce. But, it is less potent than Acetylcholine.
Action of Pilocarpine on eyes:
There are five classes of muscarinic receptors, distributed in human eye. Both M1 and M2 receptors are present in human eye (in ciliary muscle, iris and ciliary epithelium). M3 receptors are present in the sphincter pupillae of iris and ciliary body in human eye. Lower level of M4 receptors are also distributed in these tissues. M5 is found in the
iris sphincter [Daniel W. G. et. al., 1997].
It is reported that the M3 receptors, present in the ciliary muscle of human eye is responsible for the miotic action of parasympathomimetics and the constriction pupillae of iris is important for the adjustment of pupil in the response to the changes of light intensity and to regulate the intraocular pressure [Rang M. P. et al., 2007].
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