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Types, Mechanism of action and more of: 5-Hydroxytryptamine receptors, Opioid receptors, GABA receptors - ePharmacology

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Read about other receptors:

In my other hub I've discussed about:

  1. Cholinergic receptors
  2. Adrenergic receptors
  3. Histamine receptors
  4. Dopamine receptors

Also read about:


Today on ePharmacology we will discuss about the following receptors:

  1. 5 Hydroxytryptamine (Serotonin) receptors
  2. Opioid receptors
  3. GABA receptors

Before starting you should review your knowledge of receptors in general.


types-mechanism-of-action-and-more-of-5-hydroxytryptamine-receptors-opioid-receptors-gaba-receptors-epharmacology
Structure of 5HT-1B receptor

Structure of 5HT-1B receptor

5-Hydroxytryptamine (Serotonin) receptors

5-Hydroxytryptamine (5-HT) / Serotonin receptors are of seven types. The seven Serotonin receptors are further divided into a total of 14 discovered serotonin receptors.

1) 5HT1 receptor

a) 5HT1A

b) 5HT1B

c) 5HT1D

d) 5HT1E

e) 5HT1F

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2) 5HT2 receptors

a) 5HT2A

b) 5HT2B

c) 5HT2C

3) 5HT3 receptors

4) 5HT4 receptors

5) 5HT5 receptors

a) 5HT5A

b) 5HT5B

6) 5HT6 receptors

7) 5HT7 receptors

14 types of 5-HT (Serotonin) receptors and their locations

14 types of 5-HT (Serotonin) receptors and their locations

5-HT 1 and 2 receptor agonists and antagonists

5-HT 1 and 2 receptor agonists and antagonists

5-HT receptorAgonistAntagonist

5-HT1A

F-15,599

BMY 7378

 

Flesinoxan

Cyanopindolol

 

Gepirone

Iodocyanopindolol

 

Haloperidol

Lecozotan

 

Ipsapirone

Mefway

 

Quetiapine

WAY-100,635

 

Trazodone

WAY-100,135

 

Yohimbine

Nefazodone

 

Tandospirone

Nebivolol

 

 

Methiothepin

 

 

NAN-190

 

 

Methysergide

5HT-1B

CP-94,253

Alprenolol

 

Dihydroergotamine

AR-A000002

 

Eltoprazine

Yohimbine

 

Ergotamine

Asenapine

 

Methysergide

SB-216,641

 

RU 24969

Propranolol

 

TFMPP

Pindolol

 

Triptans e.g. Zolmitriptan, Eletriptan, Sumatriptan

Oxprenolol

 

Vortioxetine

Methiothepin

 

CGS-12066A

Metergoline

 

CP-93,129

Isamoltane

 

5-CT

Iodocyanopindolol

 

 

Cyanopindolol

 

 

GR-127,935

5-HT1D

5-CT

BRL-15572

 

Yohimbine

Ziprasidone

 

Triptans

Vortioxetine

 

Methysergide

Ritanserin

 

Ergotamine

Rauwolscine

 

Dihydroergotamine

Methiothepin

 

CP-135,807

Metergoline

 

 

Ketanserin

 

 

GR-127,935

5-HT1E

BRL-54443

 

5-HT1F

Naratriptan

 

 

BRL-54443

 

 

LY-334,370

 

 

Lasmiditan

 

5-HT2A

25I-NBOMe

Atypical antipsychotics Clozapine, Olanzapine, Quetiapine, Risperidone, Ziprasidone

 

TFMPP

Yohimbine

 

Psilocybin

Trazodone

 

Psilocin

Ritanserin

 

PNU-22394

Pizotifen

 

Myristicin

Pimavanserin

 

Mescaline

Nefazodone

 

LSD

Mirtazapine

 

Lisuride

Mianserin

 

Ergonovine

Methysergide

 

DOM

Ketanserin

 

DMT

Iloperidone

 

Bufotenin

Hydroxyzine

 

BZP

Haloperidol

 

5-MeO-DMT

Etoperidone

 

2C-B

Eplivanserin

 

 

Cyproheptadine

 

 

Clomipramine

 

 

Amitriptyline

 

 

Asenapine

 

 

Aripiprazole

5-HT2B

BW-723C86

Agomelatine

 

Ro60-0175

Yohimbine

 

PNU-22394

Tegaserod

 

Norfenfluramine

RS-127,445

 

MDMA

Ritanserin

 

Fenfluramine

Methysergide

 

 

Ketanserin

 

 

BZP

 

 

Asenapine

5-HT2C

A-372,159

Agomelatine

 

YM-348

Ziprasidone

 

Trazodone

Trazodone

 

TFMPP

Tramadol

 

Ro60-0175

Ritanserin

 

PNU-22394

Risperidone

 

Lorcaserin

Quetiapine

 

Ergonovine

Paroxetine

 

Aripiprazole

Olanzapine

 

AL-38022A

Nefazodone

 

 

Mirtazapine

 

 

Mianserin

 

 

Methysergide

 

 

Lisuride

 

 

Ketanserin

 

 

Iloperidone

 

 

Haloperidol

 

 

Fluoxetine

 

 

Etoperidone

 

 

Eltoprazine

 

 

Dimebolin

 

 

Cyproheptadine

 

 

Clozapine

 

 

Clomipramine

 

 

Asenapine

 

 

Amitriptyline

5-HT 3, 4, 5, 6 and 7 receptor agonists and antagonists

5-HT 3, 4, 5, 6 and 7 receptor agonists and antagonists

5-HT ReceptorAgonistAntagonist

5-HT3

2-Methyl-5-HT

Alosetron

 

RS-56812

Vortioxetine

 

Quipazine

Quetiapine

 

BZP

Olanzapine

 

 

Mirtazapine

 

 

Mianserin

 

 

Metoclopramide

 

 

Memantine

 

 

Clozapine

 

 

Several antiemetics: Dolasetron, Ondansetron, Granisetron, Tropisetron

5-HT4

5-MT

L-Lysine

 

Zacopride

Piboserod

 

Tegaserod

 

 

Renzapride

 

 

RS-67333

 

 

Prucalopride

 

 

Mosapride

 

 

Metoclopramide

 

 

Dazopride

 

 

Cisapride

 

 

Cinitapride

 

 

BIMU-8

 

5-HT5A

5-CT

Asenapine

 

Valerenic Acid

SB-699,551-A

 

Ergotamine

SB-699,551

 

 

Ritanserin

 

 

Methiothepin

 

 

Dimebolin

5-HT5B

 

 

5-HT6

EMD-386,088

Amitriptyline

 

EMDT

SB-399,885

 

 

SB-357,134

 

 

SB-271,046

 

 

SB-258,585

 

 

Ro04-6790

 

 

Olanzapine

 

 

MS-245

 

 

Iloperidone

 

 

Haloperidol

 

 

EGIS-12233

 

 

Dimebolin

 

 

Clozapine

 

 

Clomipramine

 

 

Asenapine

 

 

Aripiprazole

5-HT7

5-CT

Amitriptyline

 

RA-7

Vortioxetine

 

E-55888

SB-269,970

 

AS-19

Risperidone

 

Aripiprazole

Ritanserin

 

8-OH-DPAT

Olanzapine

 

 

Mirtazapine

 

 

Ketanserin

 

 

Imipramine

 

 

Iloperidone

 

 

Haloperidol

 

 

EGIS-12233

 

 

Clozapine

 

 

Clomipramine

 

 

Asenapine

Type 1, 2, 4, 5, 6, and 7 are G-coupled receptors and type 3 is a Ligand-gated Na+ and K+ cation channel. These receptors are present in the CNS and vascular smooth muscle.

Specific agonists for 5HT1 receptors are sumatriptan and buspirone. Spiperone, methiothepin and quipazine are the 5HT1 receptor antagonists.

Methysergide, ketanserin and cyproheptadine are the examples of 5HT2 receptor antagonists.

Specific agonist for 5HT3 receptor is 2-methyl-5-HT. Ondansetron and tropisetron are the 5HT3 receptor antagonists.

Metoclopramide is the specific agonist for 5HT4 receptor.

types-mechanism-of-action-and-more-of-5-hydroxytryptamine-receptors-opioid-receptors-gaba-receptors-epharmacology

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Opioid receptors

Morphine and related drugs produce their responses by acting on their specific receptors which are called opioid receptors. There are 3 well defined or classical subtypes of opioid receptor:

  • μ (Mu) opioid receptor
  • κ (Kappa) opioid receptor
  • δ (Delta) opioid receptor

More recently, cDNA encoding an orphan receptor was identified which has a high degree of homology to the classical opioid receptors. On structural grounds this receptor is an opioid receptor and has been named ORL1 (opioid receptor-like). Later an endogenous ligand was discovered for this receptor which is called Nociceptin. So ORL1 is now an adopted receptor.

Subtypes of opioid receptors and their locations

Subtypes of opioid receptors and their locations

Opioid receptors are G-protein coupled receptors. All of the opioid receptors possess the same general structure of an extracellular N-terminal region, seven transmem­brane domains and intracellular C-terminal tail structure.

Different agonists act on different subtypes of receptor. For example, morphine predominantly acts on μ and κ opioid receptors. Enkephalins mainly bind with δ opioid receptors but have weak affinity to μ opioid receptors. Dynorphin preferentially binds with κ opioid receptors.

Selective and non-selective antagonists for opioid receptors:

Opioid ReceptorSelective AntagonistNon-selective (for all opioid receptors) antagonists

Mu (μ) receptor

Cyprodime

Naloxone

Delta (δ) receptor

Naltrindole

Naltrexone

Kappa (κ) receptor

Norbinaltorphimine

Nalorphine

Nociceptin receptor

J-113,397

Levallorphan

 

 

AT-076

types-mechanism-of-action-and-more-of-5-hydroxytryptamine-receptors-opioid-receptors-gaba-receptors-epharmacology

GABA receptors

GABA receptors are of two types:

  • GABAA
  • GABAB

Both types of recep­tors are present in the CNS. However, the concentration of GABA A receptors is more than that of GABAB receptors. GABAA receptors are widely distributed in the granular cell layers of the cerebellum and are directly associated with a Cl- channel (pore size ~5 Å). The concentration of GABAB receptor in the interpeduncular nucleus is far greater than the concentration of GABAA receptors and it appears to be linked to calcium and potassium channels via GTP-binding proteins.

GABA receptors appear to exist as pentamers of three distinct subunits in the arrangement αmβnγ. The β subunit appears to have the recognition capacity for GABA and related agonists. GABAA receptor agonists are GABA, muscimol, and isoguvacine. GABAB receptor agonists are GABA and baclofen. GABAA receptor antagonists are bicuculline and picrotoxin. GABAB receptor antagonist is phaclofen.

Recently a third type of GABA receptor, named GABAC is reported to be distrib­uted in the mammalian CNS which has central chloride pore and is insensitive to both bicuculline and baclofen. GABAC receptors are composed of p-subunits. cis-4-aminocrotonic acid (CACA) is the selective agonist for GABAC receptor. Although the term GABAС receptor is frequently used, GABAС may be viewed as a variant within the GABAA receptor family

GABA receptor agonists and antagonists

GABA receptorAgonistsAntagonists

GABA-A

GABA

Bicuculline

 

Isoguvacine

Picrotoxin

 

Muscimol

 

GABA-B

GABA

Phaclofen

 

Baclofen

 

GABA-C

cis-4-aminocrotonic acid (CACA)

 

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© 2015 Oyon B

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