1 PHL. 313 Dr. Khairy Zoheir

Lab.1 INTRODUCTION TO NS PHARMACOLOGY and DOSE- RESPONSE CURVE

Nervous System 3 Central Nervous System Brain stem Cerebrum Spinal cord Peripheral Nervous System Afferent Efferent Sensory division Autonomic Somatic

Afferent and efferent neurons Afferent is known as sensory or receptor neurons which carry nerve impulses from receptors or sense organs toward the central nervous system.sensoryneuronsnerve impulsesreceptorscentral nervous system Efferent is known as motor or effector neurons which carry nerve impulses away from the central nervous system to effectors such as muscles or glandsmotorneuronsnerve impulsescentral nervous system musclesglands 4

5 The Peripheral Nervous System Somatic nervous system (voluntary) Skeletal muscle Autonomic nervous system (involuntary) Heart, blood vessels, glands, other visceral organs, smooth muscle Efferent nervous system

6 Anatomic classification 1- sympathetic (fight and flight) To maintain homeostasishomeostasis

2- Parasympathetic (rest and digest) Its actions can be summarized as "rest and digest", as opposed to the "fight-or-flight" effects of the sympathetic nervous system.. 7

8 Neurotransmitter: A chemical that transmits signals from one neuron to another or from a neuron to an effector cell. Electrical Stimulation (impulse) Chemical (neurotransmitter) Chemical (intracellular messengers) Electrical (membrane ion channels) Physiological functions

Neurotransmitter-based classification 1- Cholinergic, 2- Adrenergic, and 3- Dopaminergic 9

1- Cholinergic transmitter It means related to the neurotransmitter Acetylcholine. The parasympathetic nervous system is entirely cholinergic. Neuromuscular junctions, preganglionic neurons of the sympathetic nervous system, and the sweat glands 10

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12 Definition of Agonist and Antagonist Agonist: A structural analog that is capable of stimulating a biological response. Antagonist: A receptor-specific blocker (e.g., enzyme inhibitor) or a physiologic agent (e.g., hormone), that prevents the action of another molecule.

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14 Mode of Action Direct-acting: Molecule that physically binds to the target for its effect. Example: ACh activates cholinergic receptors. Indirect-acting: Molecule that exerts effect on the target by interacting with another molecule. Example:neostigmine blocks AchE, causing Ach accumulation.

Acetylcholine (ACh) Cholinergic neurotransmitter. Parasympathomimetic. Muscarinic action.(M3)  Sites of release:  Preganglionic synapses of both sympathetic and parasympathetic ganglia.  Parasympathetic postganglionic neuroeffector junctions.  All somatic motor end-plates on skeletal muscles.

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Muscarinic Autonomic Effects of Ach Affect on gatsrtointestinal tract (GIT) as follow 1- Motility (Increase contraction) 2- Secretion (increase) 3- Sphincters (relaxation) 17

Muscarinic Actions The “Muscarinic Actions” -- Similar to those of parasympathetic stimulation (M1): CNS, PNS, gastric parietal cells (M2): conducting tissue (M3): exocrine glands; smooth muscle 18

Action of acetylcholine on smooth muscle. Contraction of smooth muscle by acetylcholine is mediated by activation of muscarinic receptors M2 and M3 subtypes. Acetylcholine (ACh) has virtually no systemic therapeutic applications because its actions are diffuse, and its hydrolysis, catalyzed by both acetylcholinesterase (AChE) and plasma butyrylcholinesterase, is rapid. 19

Dose-Response Curve

21 Apparatus Valve (Wash) valve H2OH2O physiogragh Tyroide Solution Intestine part 25 ml Oxygen supply NaCl: Isotenicity CaCl2: Contraction of muscle Glucose: Energy NaHCO 3 : PH MgCL 2 : relaxation

Why Tryroid Solution: 1- To maintain the muscle alive throughout the experiment. 2- To maintain the same environmental condition for the cells inside the animal (In vivo) as outside the animal (In vitro).

Why small intestine? 1- Easy handling in the lab. 2- Good model to study the effects of cholinergic drugs. 3- Longitudinal muscle of guinea pig intestine contains muscarinic receptors of which M2 and M3 subtypes. 23

Definition of dose- response curve: It is a relationship between dose & response which describes the change in effect on an organ caused by differing levels of exposure (or doses) to a stressor (usually a chemical) after a certain exposure time.

25 Dose – Response Curve It is a relationship between Dose and (Response %) From this curve we can see : Potency (a measure of the activity of a drug in a biological system) Efficacy (the capacity to produce an effect) Therapeutic index (dose of a drug for 50% of the population divided by the minimum effective dose for 50% of the population ED 50 :dose in pharmacology is the amount of drug that produces a therapeutic response in 50% of the people taking it

Procedure 1- Cut 1 Cm from Guine pig small intestine and hang it in the organ bath which has tyroid solution. 2- Use MP36 to measure the contraction of the intestine inside the organ bath. 3- Add 0.1 ml Acetylcholine (Ach) (0.1 %) to the intestine which in the organ bath and record the response then stop the MP36 and make washing for the tyroid in the organ bath. 4- Add 0.2 ml of Ach and record the response and then wash. 3- Add 0.4, 0.8, 1.6,>>>>. Till get maximum response for the contraction of the intestine as showing in next slide. 4- Tabulate the relationship between the dose and response (cm) and % of response. 5- Make histogram between the dose and % response to get ED50 as shown.

27 Dose – Response Curve D + R DR complex Response cm 0.1ml 0.2ml 0.4ml 0.8ml 1.6ml wash

28 Dose – Response Curve Response % (x/ max )*100 Response (cm) Dose (ml)

29 ED 50 = xxx ml