6d59430a-92e7-435e-bbe7-65bc76f3f107.jpeg
Which drug will be at arrow in CAL practical of pharmacology
analyse_media
This is a classic CAL (Computer Assisted Learning) pharmacology practical on the effects of drugs on BP, heart rate, and respiratory rate in a dog - specifically the Atropine Reversal of Acetylcholine (Dale's Vasomotor Reversal) experiment.
What is at the Arrow?
Tracing 1 (top graph):
The arrow points to the downward dip in blood pressure - this represents the injection of Acetylcholine (ACh) at a low/standard dose.
- ACh causes a sharp fall in BP (vasodilation via muscarinic M3 receptors on blood vessels + decreased heart rate via M2 receptors).
- BP quickly recovers due to ACh's rapid breakdown by acetylcholinesterase.
Tracing 2 (bottom graph):
This shows multiple arrows and a later rise in BP - the sequence here is:
- First arrow: ACh (control dip - fall in BP)
- Middle arrows: ACh after atropine - the fall is blocked (atropine blocks muscarinic receptors), unmasking a slight pressor response from nicotinic stimulation
- Last large rise: Adrenaline (Epinephrine) - causes a sustained rise in BP, or this represents large dose ACh after atropine which causes a rise (nicotinic ganglionic stimulation)
Summary Table
| Arrow Position | Drug | Effect on BP |
|---|---|---|
| Tracing 1 - single dip | Acetylcholine (ACh) | Sharp fall (muscarinic) |
| Tracing 2 - first dip | ACh (control) | Fall in BP |
| Tracing 2 - after atropine | ACh post-atropine | Blocked/reversed to rise |
| Tracing 2 - large rise | Large dose ACh / Adrenaline | Rise in BP |
Key Concept: Dale's Vasomotor Reversal
- Low dose ACh → Fall in BP (muscarinic dominant)
- After atropine blocks muscarinic receptors → same ACh now raises BP (nicotinic effect unmasked at ganglia/adrenal medulla)
- This reversal is called Dale's Vasomotor Reversal
The arrow in your tracing (Tracing 1) specifically points to the response of Acetylcholine (ACh) causing a transient fall in BP.
7b6b1549-e0e8-492a-bede-74256d4f3d2b.jpeg
Which drug will be at arrow in CAL practical of pharmacology
analyse_media
This is page 64 of the same CAL practical - Tracings 3 and 4 of the Dale's Vasomotor Reversal / Adrenaline Reversal experiment. Here is the complete drug identification at each arrow:
Tracing 3 - Arrow Identification
| Arrow | Drug | BP Response |
|---|---|---|
| 1st arrow (left) | Adrenaline (Epinephrine) - low dose | Slight rise then return to baseline (α + β effect) |
| 2nd arrow (middle) | Adrenaline - after some intervention | Brief rise |
| Large peak | Large dose Adrenaline OR Adrenaline after alpha-blocker | Tall sharp rise to ~150 mmHg then fall - classic pressor response |
Tracing 3 shows the setup for Adrenaline Reversal - the large BP rise is a standard adrenaline (epinephrine) pressor response before alpha-blocker administration.
Tracing 4 - Arrow Identification
| Arrow | Drug | BP Response |
|---|---|---|
| Large rise (left half) | Adrenaline (control) | Rise to ~160 mmHg then falls - normal pressor response |
| 1st small arrow (middle) | Adrenaline after alpha-blocker (e.g., Phentolamine/Phenoxybenzamine) | Only slight rise or flat - α blocked |
| 2nd small arrow | Adrenaline (repeat) | Same - blunted response (α still blocked) |
| Deep dip (far right) | Adrenaline reversal - now shows pure β2-mediated vasodilation | Sharp FALL in BP - this is Dale's Adrenaline Reversal |
Key Concept: Adrenaline Reversal (Dale's Phenomenon)
- Normal Adrenaline → Rise in BP (α1 vasoconstriction dominates)
- After alpha-blocker (phentolamine) → Same adrenaline now causes a FALL in BP
- This is because alpha receptors are blocked, unmasking the β2-mediated vasodilation
- This reversal is called Adrenaline Reversal or Dale's Vasomotor Reversal
So the arrow pointing to the deep dip in Tracing 4 = Adrenaline given after alpha-blocker - demonstrating pure β2 vasodilatory effect causing BP to fall instead of rise.
Give this graph all rise and fall details why and from which action
analyse_media
analyse_media
Here is a complete, detailed analysis of all 4 tracings - every rise and fall, the drug responsible, the receptor involved, and the mechanism:
COMPLETE CAL PRACTICAL - DRUG EFFECTS ON BP IN DOG
Experiment: ACh Reversal + Adrenaline Reversal (Dale's Vasomotor Reversal)
📊 TRACING 1 - Control ACh Response
Baseline
- BP: Stable at ~120 mmHg
- Resp: Regular, normal depth
⬇️ FALL - The Single Deep Dip
| Feature | Detail |
|---|---|
| Direction | Sharp fall: 120 → ~75 mmHg |
| Drug | Acetylcholine (ACh) - low dose |
| Receptor | Muscarinic M2 (heart) + M3 (blood vessels) |
| Mechanism | M2: Slows heart rate (negative chronotropy/inotropy) via increased K+ conductance in SA node. M3: Dilates blood vessels via NO release from endothelium → vasodilation → fall in BP |
| Recovery | Quick return to ~120 mmHg (ACh destroyed rapidly by acetylcholinesterase) |
| Respiration | Transient brief apnea/change then returns to normal |
📊 TRACING 2 - ACh After Atropine (Dale's Muscarinic Reversal)
Baseline
- BP: ~120 mmHg (same as Tracing 1)
⬇️ FALL #1 - First dip
| Feature | Detail |
|---|---|
| Direction | Fall: 120 → ~90 mmHg (smaller fall) |
| Drug | ACh (repeat control dose) |
| Mechanism | Same muscarinic action as Tracing 1 |
➡️ PLATEAU - After Atropine given
- Atropine injected IV - blocks ALL muscarinic (M1, M2, M3) receptors competitively
- BP stabilizes at baseline ~120 mmHg
- Heart rate may slightly increase (vagal block → tachycardia)
⬇️➡️⬆️ The Reversal Pattern - Middle arrows
| Feature | Detail |
|---|---|
| Direction | No fall (flat/slight rise) instead of the expected dip |
| Drug | ACh given AFTER atropine |
| Mechanism | Muscarinic receptors blocked by atropine → vasodilation/bradycardia effects gone. Only Nicotinic effects remain: ganglionic stimulation + adrenal medulla release of catecholamines → slight rise in BP |
⬆️ LARGE RISE - Late in Tracing 2
| Feature | Detail |
|---|---|
| Direction | Rise: 120 → ~160 mmHg |
| Drug | Adrenaline (Epinephrine) OR large dose ACh after atropine |
| Receptor | α1 adrenoceptors on blood vessels |
| Mechanism | α1 activation → vasoconstriction → increased peripheral resistance → rise in BP. β1 → increased heart rate/contractility also contributes |
| Followed by | Gradual fall back toward baseline as drug wears off |
📊 TRACING 3 - Adrenaline Control + Alpha Blocker Setup
Baseline
- BP: ~120 mmHg
⬆️ RISE #1 - First arrow (small/moderate rise)
| Feature | Detail |
|---|---|
| Direction | Slight rise: 120 → ~125 mmHg |
| Drug | Adrenaline (low dose) - control |
| Receptor | α1 (vasoconstriction) dominant at low dose + β1 (cardiac stimulation) |
| Mechanism | α1 → vasoconstriction → raised BP. β2 also present but α1 dominates |
⬆️ RISE #2 - Large Peak (the tallest rise)
| Feature | Detail |
|---|---|
| Direction | Large rise: 120 → ~150 mmHg (tallest peak on tracing) |
| Drug | Adrenaline (standard dose) - control response |
| Receptor | α1 (dominant) + β1 |
| Mechanism | α1 mediated vasoconstriction increases total peripheral resistance → BP rises sharply. β1 increases cardiac output. Both together → prominent pressor response |
| Followed by | Gradual fall back to baseline ~120 mmHg |
➡️ After the peak falls back
- Alpha-blocker (e.g., Phentolamine or Phenoxybenzamine) is now administered
- BP stabilizes at baseline
- Alpha receptors are now blocked
📊 TRACING 4 - Adrenaline Reversal (Dale's Phenomenon)
Baseline
- BP: ~120 mmHg
⬆️ RISE - First large rise (left side)
| Feature | Detail |
|---|---|
| Direction | Large rise: 120 → ~160 mmHg |
| Drug | Adrenaline (one more control dose OR same as Tracing 3 continued) |
| Receptor | α1 + β1 |
| Mechanism | α1 vasoconstriction → large pressor response (same as Tracing 3) |
| Followed by | Falls back to ~120 mmHg |
⬆️ Small arrows (middle) - Post alpha-blocker Adrenaline
| Feature | Detail |
|---|---|
| Direction | Minimal/flat - no significant rise |
| Drug | Adrenaline given after alpha-blocker |
| Receptor | α1 receptors NOW BLOCKED by phentolamine |
| Mechanism | α1 vasoconstriction cannot occur. Only β2 (vasodilation) and β1 (cardiac) remain. The slight trace visible is purely β1 cardiac effect |
⬇️ DEEP FALL - The KEY event (far right - the very deep dip)
| Feature | Detail |
|---|---|
| Direction | Sharp fall: 120 → ~60 mmHg (deepest trough in entire experiment) |
| Drug | Adrenaline given after alpha-blocker (REVERSAL) |
| Receptor | β2 adrenoceptors on blood vessels (unmasked) |
| Mechanism | With α1 blocked → adrenaline can only act on β2 receptors in blood vessels → β2 causes vasodilation → decreased peripheral resistance → FALL in BP |
| This is | DALE'S ADRENALINE REVERSAL |
🔑 Summary: The Two Key Reversals
| Experiment | Drug | Normal Effect | After Blocker | Blocker Used |
|---|---|---|---|---|
| Tracings 1 & 2 | ACh | Fall in BP (muscarinic) | Rise in BP (nicotinic unmasked) | Atropine |
| Tracings 3 & 4 | Adrenaline | Rise in BP (α1 dominant) | Fall in BP (β2 unmasked) | Phentolamine/Phenoxybenzamine |
Dale's Vasomotor Reversal = when the normal pressor/depressor response to a drug is completely reversed after giving the appropriate blocker - demonstrating that the drug acts on two opposing receptor systems.
Tracing 3 me phele to fall ho rha h
analyse_media
Aapka bilkul sahi hai! Tracing 3 mein pehle FALL hota hai, phir rise. Ab poori corrected analysis:
✅ TRACING 3 - Corrected Complete Sequence
Yeh experiment hai: Adrenaline Reversal - Adrenaline pehle, phir Alpha-blocker dene ke baad Adrenaline
STEP 1 - Baseline
- BP: ~120 mmHg, stable
- Normal baseline
⬇️ STEP 2 - PEHLA FALL (1st Arrow)
| Direction | Fall: 120 → ~105-110 mmHg |
| Drug | Acetylcholine (ACh) - ya phir yeh Adrenaline ka biphasic response ka initial dip |
| Receptor | Muscarinic M3 (vessels) + M2 (heart) |
| Mechanism | ACh → NO release from endothelium → vasodilation → BP falls. Ya Adrenaline ke low-dose beta2 effect se bhi initial dip ho sakta hai |
| Recovery | BP wapas ~120 mmHg pe aata hai |
Context se: Yeh most likely Adrenaline ka biphasic response hai - adrenaline low dose mein initially β2 dominant hota hai → vasodilation → fall → phir α1 kick in karta hai → rise
⬆️ STEP 3 - BADA RISE (2nd Arrow)
| Direction | Sharp rise: 120 → ~155-160 mmHg (tallest peak) |
| Drug | Adrenaline (standard/control dose) |
| Receptor | α1 adrenoceptors (blood vessels) + β1 (heart) |
| Mechanism | α1 activation → vasoconstriction → ↑ peripheral resistance → BP rises sharply. β1 → ↑ HR and cardiac output → further ↑ BP |
⬇️ STEP 4 - POST-PEAK FALL (Undershoot)
| Direction | Falls sharply: 160 → ~105-110 mmHg (overshoot below baseline) |
| Drug | Same adrenaline wearing off |
| Mechanism | Adrenaline ka effect khatam hota hai + baroreceptor reflex → compensatory bradycardia → BP baseline se bhi neeche chala jaata hai (undershoot) |
⬆️ STEP 5 - Return to Baseline
| Direction | Rise back: 105 → ~120 mmHg |
| Mechanism | Normal cardiovascular homeostasis restores BP |
📌 Adrenaline Biphasic Response - KEY CONCEPT
Adrenaline ek drug se DONO effects deta hai:
LOW DOSE:
β2 > α1 → Vasodilation → BP FALLS (pehla dip)
HIGHER DOSE:
α1 > β2 → Vasoconstriction → BP RISES (bada peak)
Isee "BIPHASIC RESPONSE of Adrenaline" kehte hain
Summary Table - Tracing 3
| Event | BP Change | Drug | Receptor | Mechanism |
|---|---|---|---|---|
| Baseline | ~120 mmHg | - | - | - |
| 1st Arrow | ⬇️ Fall to ~105 | Adrenaline (low) | β2 dominant | Vasodilation → ↓ BP |
| 2nd Arrow | ⬆️ Rise to ~160 | Adrenaline (standard) | α1 + β1 dominant | Vasoconstriction + ↑ CO |
| Post-peak | ⬇️ Fall to ~105 | Drug wearing off | Baroreceptor reflex | Undershoot |
| Recovery | ⬆️ Back to ~120 | Homeostasis | - | Normal recovery |
78065f4e-375e-4bc5-8ebe-52cb783fb80a.jpeg
Explain these also
analyse_media
Here is the complete explanation of Tracings 5, 6, and 7:
TRACINGS 5, 6, and 7 - Complete Analysis
📊 TRACING 5 - Effect of a Sympathomimetic Drug (Noradrenaline / Vasopressor)
Baseline
- BP: ~120 mmHg, stable
- Resp: Regular
⬇️ STEP 1 - Sharp Deep Fall
| Direction | Fall: 120 → ~60-65 mmHg (very deep) |
| Drug | Acetylcholine (ACh) large dose OR Histamine |
| Receptor | Muscarinic M2 + M3 (ACh) / H1 receptors (Histamine) |
| Mechanism | Massive vasodilation + bradycardia → BP falls steeply. Adrenaline block ke baad yeh "reversal dip" bhi ho sakta hai |
| Resp change | Apnea or slowing of breathing briefly |
| Recovery | BP slowly comes back to ~120 mmHg |
➡️ Return to Baseline
- BP recovers back to ~120 mmHg
- This is the longest sustained fall in the series - characteristic of a powerful vasodilator
📊 TRACING 6 - Effect of Noradrenaline (Norepinephrine)
Baseline
- BP: ~120 mmHg
⬆️ STEP 1 - Large Sustained Rise
| Direction | Gradual then sustained rise: 120 → ~160-165 mmHg |
| Drug | Noradrenaline (Norepinephrine) |
| Receptor | α1 adrenoceptors (very strong) + mild β1 |
| Mechanism | Noradrenaline is a pure alpha agonist (unlike adrenaline which has both α and β). α1 → powerful vasoconstriction → marked ↑ peripheral resistance → sustained rise in BP |
| Note | No β2 vasodilation because noradrenaline has no significant β2 activity |
⬇️ STEP 2 - Gradual Fall Back (Plateau then Decline)
| Direction | Sustained fall: 165 → ~120 mmHg (gradual decline) |
| Mechanism | Drug effect waning as it is metabolized (by COMT and MAO). Baroreceptor reflex also causes reflex bradycardia which helps bring BP down |
| Special feature | This fall is slow and gradual (unlike adrenaline which falls fast) - signature of Noradrenaline's sustained alpha effect |
KEY DIFFERENCE - Noradrenaline vs Adrenaline:
| Feature | Adrenaline | Noradrenaline |
|---|---|---|
| α1 | ++ | +++ (very strong) |
| β1 | ++ | + (mild) |
| β2 | ++ | Nil/negligible |
| BP effect | Rise → fall (biphasic) | Sustained rise only |
| Heart rate | Increases (β1) | Decreases (reflex bradycardia) |
| After alpha-blocker | BP FALLS (reversal) | BP still rises slightly or neutral |
📊 TRACING 7 - Noradrenaline Reversal / Effect with Pretreatment
Baseline
- BP: ~120 mmHg
- Resp: Regular with some variation
⬆️ STEP 1 - First Large Rise (1st Arrow)
| Direction | Rise: 120 → ~165-170 mmHg |
| Drug | Noradrenaline (control dose) |
| Receptor | α1 dominant |
| Mechanism | Same as Tracing 6 - strong vasoconstriction → large pressor response |
⬇️ STEP 2 - Fall Back + Undershoot
| Direction | Falls: 170 → ~120 then dips to ~110 mmHg |
| Mechanism | Drug metabolism + baroreceptor reflex bradycardia → BP overshoots below baseline |
➡️ Brief Plateau
- BP stabilizes at ~120 mmHg
- Alpha-blocker (Phentolamine) given at this point
⬆️ STEP 3 - Second Rise (2nd Arrow) - Post Alpha-blocker
| Direction | Rise again: 120 → ~170-175 mmHg (similar height) |
| Drug | Noradrenaline given AFTER alpha-blocker |
| Result | BP still RISES (does NOT reverse to fall) |
| Mechanism | Noradrenaline has no β2 activity - so even after α1 is blocked, there is NO vasodilation component to unmask. Slight residual α2 or other effects still cause some rise |
⬇️ STEP 4 - Gradual fall back
| Direction | Gradual fall: ~170 → ~120 mmHg |
| Mechanism | Drug wears off |
🔑 KEY CONCEPT - Why Noradrenaline Does NOT Reverse:
ADRENALINE:
α1 (vasoconstriction) + β2 (vasodilation)
→ After alpha-blocker: β2 unmasked → BP FALLS (REVERSAL ✓)
NORADRENALINE:
α1 (vasoconstriction) + NO β2
→ After alpha-blocker: Nothing to unmask → BP does NOT fall
→ NO REVERSAL ✗
This is why Noradrenaline Reversal does NOT occur - it has no β2 receptor activity to produce vasodilation when α1 is blocked.
Summary Table - All 3 Tracings
| Tracing | Drug | BP Change | Key Receptor | Special Feature |
|---|---|---|---|---|
| 5 | ACh / Histamine (large dose) | ⬇️ Deep sustained fall | M2, M3 / H1 | Powerful vasodilation |
| 6 | Noradrenaline | ⬆️ Gradual sustained rise → slow fall | α1 dominant | Reflex bradycardia, no β2 |
| 7 | Noradrenaline × 2 (2nd after alpha-blocker) | ⬆️ Rise → ⬆️ Rise again (NO reversal) | α1 only | No adrenaline reversal - proves β2 absence |
This is a shared conversation. Sign in to Orris to start your own chat.