Bioassay of drug

Question

Application of Langendorff's isolated Heart preparation for Atherosclerosis include following except

Select one!

a. LVP

b. Ventricular L systole

c. Atrial fibrillation

d.Coronary flow

Answer 1

1. A modifiedLangendorffheartpreparationfromtheguinea-pigwasused toanalysecatecholamineresponses. Contractileforce,heartrateandcoronary perfusion pressure were recorded.

2. Fourcomponentsofthevascularresponsecouldbeidentified.

(a) Theinitialphasewasavasoconstrictionmediatedbya-adrenoceptors which preceded any efects on heart rate and force.

(b) A secondary constriction followed, which was due to the increased myocardial compression during positive inotropic and chronotropic responses.

(c) Thethird,morepredominant,efectwasaprolongeddilatationprob- ably associated with the increased metabolic activity of the heart.

(d) A fourth component was a direct vasodilatation mediated by /3-adrenoceptors which was evident when small doses of catecholamines were used but was usually masked by the more pronounced metabolically linkeddilatation.

3. Theactionsofsalbutamolwereexaminedandsinceitcauseddirectvaso- dilatation by stimulation of /8-adrenoceptors without other myocardial efects, theseadrenoceptorswere clasifiedas thefl2-type.

4. I.C.I.50,172was employed to block selectively the myocardial efects due to stimulation of f31-adrenoceptors and leave the vasodilator /32-adrenoceptors unaffected.

5. Adrenaline, noradrenaline and isoprenaline were compared at two dose levels,inthepresenceorabsenceofefectson heartrateandforce.

6. Constrictorordilatorefectswerefoundintheabsenceofothereffectsand were showntodependtosome extenton therateofcoronaryperfusion.