Awatif B. Al-Backer

Purpose of Pharmacological Experiments 1. Qualitative: For determination of the activity or the mechanism of action of the drug, if it has analgesic, hypoglycemic, hypotensive effect and so on. 2. Quantitative: To assay the activity of the drug ( toxic level, ED50) & therapeutic level.

Awatif B. Al-Backer Types of pharmacological experiments In vitro Isolated tissue In vivo Whole animal or intact animal

Awatif B. Al-Backer In vivo experiments Advantages 1. 1.Determine the exact & direct biological & chemical effects. Disadvantages 1. 1.Difficult to study the MOA Difficult to determine the potency of the drug There is interference by compensatory mechanisms of body.

Awatif B. Al-Backer In vitro experiments The physiological condition must be adjusted Advantages 1.Allow to study the MOA of the drug 2.Determine the potency of the or dose response curve. 3.There is interference by compensatory mechanisms of body Disadvantages Difficult to determine the exact & direct biological & chemical effects. Difficult to determine the exact & direct biological & chemical effects.

Awatif B. Al-Backer In vitro experiments * Involve the use of isolated organ, muscle, or tissue & the conditions of the experiment should be adjusted. Physiological conditions: 1.Electrolytes 2.Nutrients 3.Physiological pH 4.Temperature 5.Aeration

Awatif B. Al-Backer Electrolytes Physiological solution: Ex. Tyrode’s & Kreb’s solutions Ingredients: 1.Nacl → adjust the isotonicity 2.Ca+2, K+, Mg+2 as chloride salts → for muscle contraction 3.Sodium bicarbonate → adjust the pH 4.NaH2PO4 → compensate any change in the pH 5.Glucose → nutrient * All these ingredients are dissolved in water, and their concentration depend on the organ bathed.

AerationExamples:  Pure oxygen → heart tissues  Air → for intestine  Carbogen (95% O2, 5% CO2) → uterus Awatif B. Al-Backer

Temperature  Temperature should be kept constant during the experiment.  Physiological temp. (37°C) is needed for mammalian tissues e.g. rabbit intestine.  The temp. should be reduced in some experiments to decrease spontaneous contraction e.g. isolated guinea-pig ileum (32°C).  Amphibian tissues can survive in room temp. e.g. isolated frog rectus abdominus (25°C). * There is direct relation between contraction & temperature. Awatif B. Al-Backer

Types of normal myogenic contraction in the tissue Ileum Intestine

Effect of different drugs on smooth muscle intestine tissue Awatif B. Al-Backer StimulatoryInhibitory

Awatif B. Al-Backer Stimulatory ↑ amplitude ↑ tone ↑ tone & amplitude

Awatif B. Al-Backer Inhibitory ↓ tone ↓ tone & amplitude ↓ amplitude

Awatif B. Al-Backer Autonomic nervous system innervations in the intestine SympatheticParasympatheticTransmitter: Adrenaline & noradrenaline (NA) Acetylcholine (Ach) Receptors(intestine) α1, β2 (Adrenergic-R) Nicotinic (Nn) & muscarinic (M3) (Cholinergic R) Action(intestine) inhibitory (↓cont.)excitatory (↑cont.)

Awatif B. Al-Backer Dose cycle (DC) DC= NT+CT+WT Where: NT (normal time)= time recovering without drug CT (contact time)= time of drug contact with tissue WT (washing time)= time required for washing out of the drug from the tissue * DC= 60 sec+ 30 sec+ 90 sec = 3 min

Awatif B. Al-Backer The effect of different doses of acetylcholine on smooth muscle of intestine N 0.05ml 0.1ml 0.2ml 0.3ml 0.4ml Ach Ach Ach Ach Ach