1. Effect of autonomic drugs on rabbit’s isolated intestine
Dr Muhammad Raza

2. Action of autonomic drugs on the isolated Rabbit’s intestine
The smooth muscle of small intestine receives both parasympathetic and sysmpathetic innervation.
PARASYMPATHETIC preganglionic fibres relay in neurons located in the wall of the intestine in myenteric plexus and submucus plexus, and from there the post ganglionic fibres travel to the smooth muscle of intestine.
SYMPATHETIC preganglionic fibres relay in collateral ganglia OUT SIDE THE WALL OF INTESTINE. From these ganglia, postganglionic fibres arise and run with the blood vessels to supply the small intestine.
Parasympathetic nerves reach the intestine as preganglionic fibres and isolated intestine contains ONLY PARASYMPATHETIC GANGLIA.
PARASYMPATHETIC Stimulation  intestinal motility whereas sympathetic stimulation  it.

3. TYPES OF RECEPTORS IN THE ISOLATED RABBIT’S INTESTINE
Nicotinic cholinoceptors (N) in parasympathetic ganglia
Muscarinic cholinoceptors (M) in smooth muscle
Adrenoceptors (, )
Other receptors for histamine, serotonin, vasopressin

4. INNERVATION AND RECEPTORS IN THE ISOLATED INTESTINE

5. Classification Adrenaline (α, β) Phenylephrine, α adrenergic
Receptors
Agonist
Blocker
Nicotinic
Nicotine SD
Lobeline SD
Ganglion Blockers
Depolarizing, Nicotine Large Dose (initial stimulation followed by block of ganglion)
Competitive, Chlorisondamine (Ganglion block without stimulation) or mecamylamine
Muscarinic
ACh
Anti muscarinics i.e Atropine H1
Histamine
Mepyramine, Cyproheptadine
5-HT2
Serotonin
Methysergide, Cyproheptadine H2
Cimetidine
Angiotensin II
Angiotensin
Saralasin
Vasopressin
Papaverine (direct acting spasmolytic)
Adrenergic
Adrenaline (α, β)
Phentolamine, α adrenergic blocker +
Propranolol, β adrenergic blocker
Phenylephrine,
α adrenergic
Phentolamine, α adrenergic blocker
Isoprenaline,
β adrenergic

6. APPARATUS FOR RECORDING CONTRACTIONS OF ISOLATED RABBIT’S INTESTINE

7. Parts of apparatus (PowerLab)

10. CONCEPTS
NIC (SD)  stimulation of NN receptors of Parasympathetic ganglia located in the wall of intestine,  cause release of ACh from postganglionic parasympth nerve endings resulting in intestinal stimulation via muscarinic receptors.
NIC (LD) –Initial stimulation followed by block (DEPOLARIZING GANGLION BLOCK) of the Para-symp ganglia in the wall of the intestine. Chlorisondamine is a Competitive Ganglion blocker without stimulation.
NIC (SD) after NIC (LD) no response indicating BLOCKADE of Parasymp ganglia
ACh ---  Activation of muscarinic receptors
Atropine – Blocks muscarinic receptors by competing ệ ACh.
ACh after Atropine  no change indicating complete blockade of Muscarinic receptors.
Adrenaline – Activation of Adrenoceptors (, ) ---   of intestinal tone and motility.
Propranolol – Blockade of  receptors
Phentolamine --  Blockade of  receptors
ADR after Phentolamine+Propranolol ---  No effects ---  Adrenoceptors (, ) are blocked

11. Effect of unknown stimulant

12. Effect of unknown stimulant

13. Effect of unknown stimulant

14. Effect of unknown stimulant

15. Effect of unknown stimulant

17. CONCEPTS
Adrenaline  Activation of Adrenoceptors (, )   of intestinal tone and  motility.
Propranolol  Blockade of  receptors
Phentolamine  Blockade of  receptors
ADR after Phentolamine+Propranolol  No effects  Adrenoceptors (, ) are blocked