2. STEPS
1 โ Animal : Cat.
2 โ Anesthesia : Induction by inhalation of diethylether then
maintenance by I.V. chloralose.
3 โ Dissection : exposure of :
a โ Trachea for endotracheal intubation to allow for
artificial respiration.
b โ Carotid artery for recording arterial blood pressure.
c โ Femoral vein for injection (infusion) of tested drug
(via saline).
4. IMPORTANT STATEMENTS ABOUT ARTERIAL
BLOOD PRESSURE
1- S.B.P. Is controlled by both C.O. and T.P.R.
2 - D.B.P. Is controlled mainly by T.P.R.
5. 3 - Activation of ฮฒ1 โ adrenoceptors
cardiac stimulation increases C.O.
elevates S.B.P. mainly.
4 โ Activation of ฮฒ2 โ adrenoceptors
V.D. Decreases T.P.R
Lowers both S.B.P and D.B.P.
5 - Activation of ฮฑ1 โ adrenoceptors
V.C. increases T.P.R
Elevates both S.B.P. and D.B.P
6. 6 โ Activation of M - cholinoceptors
both cardiac inhibition and V.D.
Decrease both C.O. and T.P.R
lowers both S.B.P and D.B.P
7. 7 โ Activation of Nn - cholinoceptors of both
sympathetic ganglia and adrenal medulla
release of endogenous
catecholamines activation of both ฮฑ
and ฮฒ adrenoceptors increases both
T.P.R. and C.O. Elevates both S.B.P.
and D.B.P.
N.B : Nicotine S.D. activates directly Nn and
indirectly ฮฑ and ฮฒ receptors
8. 8 โ Angiotensin ำำ V.C. Increases
T.P.R. Elevates both S.B.P and
D.B.P.
9 - Vasopressin V.C. Increases
T.P.R. Elevates both S.B.P and
D.B.P.
10 โ Histamine activates both H1 (mainly) and H2
receptors V.D. Decreases
T.P.R. Lower both S.B.P and D.B.P.
9. N.B.
๏ Acetylcholine S.D. acts on muscarinic
receptors only.
๏ Acetylcholine L.D. acts on muscarinic and
nicotinic receptors.
๏ Atropine acts as a competitive blocker of all
muscarinic receptors.
๏ Epinephrine acts on ฮฑ1, ฮฑ2, ฮฒ1, ฮฒ2.
๏ Phentolamine acts as a non-selective ฮฑ-
adrenoceptor blocker.
10. EXPERIMENT
๏ 1- Acetylcholine S.D. produces hypotension.
๏ 2-Injection of atropine, it does not change the blood
pressure.
๏ 3-Re-injection of acetylcholine S.D. after atropine it
does not change the blood pressure.
๏ 4-Injection of acetylcholine L.D. after atropine
produces hypertension. (acetylcholine reversal)
๏ 5- Injection of epinephrine produces hypertension.
๏ 6-Injection of phentolamine produces hypotension.
๏ 7-Re-injection of epinephrine after phentolamine
produces hypotension. (epinephrine reversal)
11. DETERMINATION OF THE
SITE OF ACTION OF AN
UNKNOWN DRUG
AFFECTING BLOOD
PRESSURE
OF ANAESTHETIZED CAT
12. HYPOTENSIVE UNKNOWN
1- Muscarinic receptors only : e.g. Bethanechol
* The hypotensive effect of drugs acting on
muscarinic receptors only could be abolished
completely by atropine.
2 โ Muscarinic & Nicotinic receptors
e.g. Acetylcholine,Carbachol
* The hypotensive effect of these drugs is
reversed by atropine.
13. 3 - ฮฒ2 โ receptors e.g. Isoprenaline
* The hypotensive effect of these drugs is : -
a โ Not anatagonised by atropine.
b โ Abolished by non-selective ฮฒ blockers
e.g. propranolol.
14. 4 โ Histamine (H1 & H2) receptors : -
* The hypotensive effect of histamine is : -
a โ Not anagonised by atropine or
propranolol.
b โ Abolished by combination of
H1 blocker (e.g. Mepyramine)
+ H2 blocker (e.g. Cimetidine).
15. 5 โ Direct effect on vascular smooth muscle
e.g. Hydralazine , Calcium channel
blocke , Nitrites & Nitrates.
* The hypotensive effect of these drugs is
NOT anatagonized by atropine or
Propranolol or combined H1 + H2
blockers
16. HYPERTENSIVE UNKNOWN
1 โ Nicotinic receptors in ganglia and
adrenal medulla e.g. : Nicotine small dose
* the hypertensive effect of these drugs is :-
a โ Blocked by ganglion blockers
(e.g. Mecamylamine)
b โ Reversed by alpha โ blockers
(e.g. Phentolamine)
17. 2 โ ฮฑ & ฮฒ โ adrenoceptors e.g. Epinephrine.
* the hypertensive effect of these drugs is : -
a โ Not abolished by ganglion blockers
(e.g. Mecamylamine).
b โ Reversed by alpha-blockers
(e.g. Phentolamine).
18. 3 โ ฮฑ-adrenoceptors e.g. Norepinephrine (ฮฑ + ฮฒ1) &
Phenylephrine (ฮฑ1 only).
* The hypertensive effect of these drugs is :-
a โ Not blocked by ganglion blockers
(e.g. Mecamylamine).
b - Abolished by alpha-blockers e.g
Phentolamine & Phenoxybenzamine.
19. 4 โ Angiotensin ำำ receptors
* The hypertensive effect of these drugs is :-
a โ Not blocked by ganglion blockers
(e.g. Mecamylamine) or alpha-blockers
(e.g. Phentolamine).
b โ Abolished by Saralasin (Angiotensin ำำ
receptors blockers).
20. 5 โ Vasopressin receptors
* The hypertensive effect of vasopressin is
NOT anatagonized by ganglion blockers
(e.g. Mecamylamine) or ฮฑ blockers
(e.g. phentolamine ) or Saralasin.