D2 receptor( Ki = 12.2 nM ); D3 receptor ( Ki = 12.2 nM ); D4 receptor ( Ki = 59.7 nM ); D1 receptor ( Ki = 1659 nM ); D5 receptor ( Ki = 1691 nM )

Bromocriptine stimulates [35S]-GTPγS binding at the D2 dopamine receptor expressed in CHO cells with pEC50 of 8.15±0.05[1]. Bromocriptine also is a strong inhibitor of brain nitric oxide synthase. Bromocriptine (BKT), an ergot alkaloid, is found to be weakly active against inducible macrophage NOS (IC50>100 μM), but it acts as a strong inhibitor of purified neuronal nitric oxide synthase (NOS) (IC50=10±2 μM) [2]. It has been discovered that at least one human cytochrome P450 enzyme is inhibited by bromocriptine. With an estimated IC50 value for the interaction of 1.69 μM, bromocriptine is a strong inhibitor of CYP3A4[3].

Bromocriptine mesylate (2 mg/kg, i.p.) is given for 7 days in groups of mice participating in the forced swimming test (FST) and tail suspension test (TST). Bromocriptine group exhibits a discernible anti-immobility effect in comparison to the control. The anti-immobility effect of MPE (200 mg/kg, p.o.) is significantly and dose-dependently potentiated when bromocriptine is given 30 minutes after the final dose of the seven-day MPE treatment and the subjects are exposed to FST, in contrast to MPE treatment alone. When compared to the control group, the group receiving bromocriptine treatment exhibits a notable decrease in immobility time. When bromocriptine (100 and 200 mg/kg, p.o.) is administered seven days after MPE pretreatment, the anti-immobility effect of MPE is significantly and dose-dependently enhanced, as compared to MPE treatment alone[4]. When bromocriptine is administered intraceremoniously, the static mechanical allodynia (SMA) score is significantly lower than in sham (saline-injected rats) and the effect lasts for 30 minutes. In the CCI-IoN group, intraperitoneal administration of bromocriptine resulted in a significant, dose-dependent (0.1 mg and 1 mg/kg) decrease in pain scores compared to sham, with a 6-hour duration of effect. The biggest reduction in score is induced by the highest dose (P<0.01). For 20 minutes, bromocriptine has an effect. When compared to a sham group, the CCI-IoN+6-OHDA lesioned group's SMA score significantly decreases upon intraperitoneal administration of bromocriptine. Its impact lasts for half an hour[5].

The assay for [35S]-GTPγS binding is performed. For 30 minutes at 30°C, cell membranes (25 ±75 ug) are incubated in Buffer B, which contains 0.1 mM dithiothreitol (DTT), 1 uM GDP, and medications in a volume of 0.9 mL. This preincubation guarantees that the tested agonists are in an equilibrium state when the final concentration of [35S]-GTPγS (50±150 pM) is added (in 100 uL of Buffer B) to start the reaction. Unless otherwise specified, the assay mixture is incubated for a further 20 minutes. Rapid filtration ends the assays, and bound radioactivity is measured as previously mentioned for the radio-ligand binding assays. Less than 20% of the added GTPγS is bound in total by [35S]-GTPγS[1].

Mice: There are 150 total Swiss mice (20–25 g) of either sex used. One such agonist for the dopamine receptor (D2) is bromocriptine mesylate. Distilled water is used to dilute the medication haloperidol, which is then injected. A single drop of glacial acetic acid is used to dissolve bromocriptine mesylate, which is then diluted with distilled water to the desired volume. Imipramine dissolves in 0.9% regular saline. In groups of mice undergoing the Forced Swimming Test (FST) and Tail Suspension Test (TST), haloperidol (0.1 mg/kg, i.p.) and bromocriptine mesylate (2 mg/kg, i.p.) are given for 7 days. As a standard, positive control groups receive imipramine (10 mg/kg, p.o.) for seven days.
Rats: The rats used are adult male Sprague-Dawleys (N=112, 275–325 g). A couple of weeks following the 6-OHDA injection, the animals undergo a brief (less than three minutes) mask-applied 2% halothane anesthesia before receiving either the vehicle (5 μL of 0.9% saline) or bromocriptine (7 μg/kg dissolved in 5 μL vehicle) intraperitoneally. We used concentrations of SKF81297 (3 mg/kg dissolved in 0.9% saline) and bromocriptine (1 mg/kg) for intraperitoneal injection. A blind experimenter places the rats in the observation field for a 40-minute period test after they have recovered for less than two minutes.

Absorption, Distribution and Excretion
Approximately 28% of the oral dose is absorbed; however, due to a significant first-pass effect, only 6% of the oral dose enters the systemic circulation unchanged. Bromocriptine and its metabolites appear in the blood within 10 minutes after oral administration and reach peak plasma concentrations within 1–1.5 hours. Serum prolactin levels may decrease within 2 hours after oral administration, reaching their maximum effect after 8 hours. In patients with acromegaly, a single oral dose of 2.5 mg results in a decrease in growth hormone concentrations within 1–2 hours, with the decreased concentration lasting at least 4–5 hours. The parent drug and its metabolites are almost entirely excreted by the liver, with only 6% excreted by the kidneys. Metabolism/Metabolites Completely metabolized in the liver, primarily through amide bond hydrolysis to produce lysergic acid and peptide fragments, both of which are inactive and non-toxic. Bromocriptine is metabolized by cytochrome P450 3A4 and is primarily excreted in feces via bile secretion.
The known human metabolites of bromocriptine include 5-bromo-N-[2,10-dihydroxy-7-(2-methylpropyl)-5,8-dioxo-4-propyl-2-yl-3-oxa-6,9-diazatricyclo[7.3.0.02,6]dodecano-4-yl]-7-methyl-6,6a,8,9-tetrahydro-4H-indolano[4,3-fg]quinoline-9-carboxamide and 5-bromo-N-[2,11-dihydroxy-7-(2-methylpropyl)-5,8-dioxo-4-propyl-2-yl-3-oxa-6,9-diazatricyclo[7.3.0.02,6]dodecano-4-yl]-7-methyl-6,6a,8,9-tetrahydro-4H-indolano[4,3-fg]quinoline-9-carboxamide. Bromocriptine is completely metabolized in the liver, primarily through amide bond hydrolysis to produce lysergic acid and peptide fragments, both of which are inactive and non-toxic. Bromocriptine is metabolized by cytochrome P450 3A4 and excreted mainly through bile in feces. Excretion pathway: The original drug and its metabolites are almost entirely excreted by the liver, with only 6% excreted by the kidneys. Half-life: 2-8 hours.

Toxicity Summary
The dopamine D2 receptor is a 7-transmembrane G protein-coupled receptor associated with Gi proteins. In lactating cells, activation of the dopamine D2 receptor leads to inhibition of adenylate cyclase, thereby reducing intracellular cAMP concentration and blocking the release of IP3-dependent Ca2+ from intracellular stores. The reduction in intracellular calcium levels may also be achieved through inhibition of calcium influx into voltage-gated calcium channels rather than inhibition of adenylate cyclase. Furthermore, receptor activation blocks phosphorylation of p42/p44 MAPK and reduces phosphorylation of MAPK/ERK kinases. MAPK inhibition appears to be mediated by c-Raf and β-Raf-dependent MAPK/ERK kinase inhibition. Dopamine-stimulated pituitary release of growth hormone is mediated by reduced intracellular calcium ion influx through voltage-gated calcium channels, rather than by inhibition of adenylate cyclase. Stimulation of dopamine D2 receptors in the substantia nigra-striatal pathway can improve muscle coordination in patients with movement disorders. Ergoline alkaloids have been shown to have significant affinity for serotonin receptors 5-HT1 and 5-HT2, dopamine D1 and D2, and α-adrenergic receptors. This can lead to a variety of effects, including vasoconstriction, seizures, and hallucinations. Bromocriptine exerts its effects by directly stimulating dopamine receptors in the striatum. (A2914, A2915, A2916, A2941)

[1]. Agonist action at D2(long) dopamine receptors: ligand binding and functional assays. Br J Pharmacol. 1998 Jul;124(5):978-84.

[2]. Bromocriptine is a strong inhibitor of brain nitric oxide synthase: possible consequences for the origin of its therapeutic effects.FEBS Lett. 1997 Apr 7;406(1-2):33-6.

[3]. Assessment of potential interactions between dopamine receptor agonists and various human cytochrome P450 enzymes using a simple in vitro inhibition screen. Drug Metab Dispos. 1997 Oct;25(10):1211-4.

[4]. Dopamine mediated antidepressant effect of Mucuna pruriens seeds in various experimental models of depression. Ayu. 2014 Jan;35(1):90-7.

[5]. Nigrostriatal dopaminergic depletion increases static orofacial allodynia. J Headache Pain. 2016;17:11.

Pharmacodynamics
Bromocriptine stimulates central dopaminergic receptors, thereby producing a variety of pharmacological effects. Currently, five dopamine receptors from two dopaminergic subfamilies have been identified. The dopamine D1 receptor subfamily includes D1 and D5 subreceptors, which are associated with motor disorders. The dopamine D2 receptor subfamily includes D2, D3, and D4 subreceptors, which are associated with the improvement of motor disorder symptoms. Therefore, specific agonist activity of D2 subfamily receptors (mainly D2 and D3 receptor subtypes) is a major target for dopaminergic anti-Parkinson's disease drugs. It is believed that postsynaptic D2 receptor activation is the main reason for the anti-Parkinson's disease effect of dopamine agonists, while presynaptic D2 receptor activation has a neuroprotective effect. This semi-synthetic ergot derivative exhibits potent agonist activity against dopamine D2 receptors. It also exhibits agonist activity against serotonin (5-HT)1D, dopamine D3, 5-HT1A, 5-HT2A, 5-HT1B, and 5-HT2C receptors (in descending order of binding affinity), antagonist activity against α2A-adrenergic receptors, α2C, α2B, and dopamine D1 receptors, partial agonist activity against 5-HT2B receptors, and inactivation of dopamine D4 and 5-HT7 receptors. Parkinson's disease is caused by the loss of approximately 80% dopaminergic activity in the substantia nigra-striatal pathway of the brain. Because the striatum is involved in regulating and coordinating the intensity of muscle activity (e.g., movement, balance, walking), loss of its activity can lead to dystonia (acute muscle contractions), Parkinson's syndrome (including symptoms such as bradykinesia, tremor, rigidity, and apathy), akathisia (restlessness), tardive dyskinesia (involuntary muscle movements usually associated with prolonged loss of dopaminergic activity), and neuroleptic malignancy, the latter occurring when dopamine is completely blocked in the substantia nigra-striatal pathway. Excessive dopaminergic activity in the mesolimbic pathway can lead to hallucinations and delusions; these side effects of dopamine agonists are common in patients with schizophrenia due to overactivity in this area of their brains. The hallucinogenic side effects of dopamine agonists may also be related to 5-HT2A receptor agonism. The tuberous-infundibular pathway originates in the hypothalamus and terminates in the pituitary gland. In this pathway, dopamine inhibits the secretion of prolactin from the anterior pituitary lactocytes. Increased dopaminergic activity in the tuberous infundibulum pathway can inhibit prolactin secretion; therefore, bromocriptine is an effective drug for treating diseases related to excessive prolactin secretion. Pulmonary fibrosis may be related to the agonistic effect of bromocriptine on 5-HT1B and 5-HT2B receptors.

C33H44BRN5O8S

750.700160000001

749.209

C, 52.80; H, 5.91; Br, 10.64; N, 9.33; O, 17.05; S, 4.27

22260-51-1

Bromocriptine; 25614-03-3

31101

White to off-white solid powder

891.3ºC at 760 mmHg

215-218

492.8ºC

0mmHg at 25°C

3.982

3

6

5

43

1230

6

[H][C@@]12CC3=C(Br)NC4=CC=CC(C1=C[C@@H](C(N[C@@]5(C(C)C)C(N6[C@@H](CC(C)C)C(N7CCC[C@]7([C@]6(O)O5)[H])=O)=O)=O)CN2C)=C43.OS(=O)(C)=O

NOJMTMIRQRDZMT-GSPXQYRGSA-N

InChI=1S/C32H40BrN5O5.CH4O3S/c1-16(2)12-24-29(40)37-11-7-10-25(37)32(42)38(24)30(41)31(43-32,17(3)4)35-28(39)18-13-20-19-8-6-9-22-26(19)21(27(33)34-22)14-23(20)36(5)15-18;1-5(2,3)4/h6,8-9,13,16-18,23-25,34,42H,7,10-12,14-15H2,1-5H3,(H,35,39);1H3,(H,2,3,4)/t18-,23-,24+,25+,31-,32+;/m1./s1

(6aR,9R)-5-bromo-N-[(1S,2S,4R,7S)-2-hydroxy-7-(2-methylpropyl)-5,8-dioxo-4-propan-2-yl-3-oxa-6,9-diazatricyclo[7.3.0.02,6]dodecan-4-yl]-7-methyl-6,6a,8,9-tetrahydro-4H-indolo[4,3-fg]quinoline-9-carboxamide;methanesulfonic acid

CB154; CB-154; CB 154; Bromocriptine Mesylate; 2-Bromoergocryptine Mesylate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ~100~250 mg/mL (133.2~333.0 mM)
H2O: ~1.1 mg/mL (~1.5 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (2.77 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (2.77 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (2.77 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)