Endogenous Metabolite

Oxytocin is a pleiotropic, peptide hormone with broad implications for general health, adaptation, development, reproduction, and social behavior. Endogenous oxytocin and stimulation of the oxytocin receptor support patterns of growth, resilience, and healing. Oxytocin can function as a stress-coping molecule, an anti-inflammatory, and an antioxidant, with protective effects especially in the face of adversity or trauma. Oxytocin influences the autonomic nervous system and the immune system. These properties of oxytocin may help explain the benefits of positive social experiences and have drawn attention to this molecule as a possible therapeutic in a host of disorders. However, as detailed here, the unique chemical properties of oxytocin, including active disulfide bonds, and its capacity to shift chemical forms and bind to other molecules make this molecule difficult to work with and to measure. The effects of oxytocin also are context-dependent, sexually dimorphic, and altered by experience. In part, this is because many of the actions of oxytocin rely on its capacity to interact with the more ancient peptide molecule, vasopressin, and the vasopressin receptors. In addition, oxytocin receptor(s) are epigenetically tuned by experience, especially in early life. Stimulation of G-protein-coupled receptors triggers subcellular cascades allowing these neuropeptides to have multiple functions. The adaptive properties of oxytocin make this ancient molecule of special importance to human evolution as well as modern medicine and health; these same characteristics also present challenges to the use of oxytocin-like molecules as drugs that are only now being recognized. SIGNIFICANCE STATEMENT: Oxytocin is an ancient molecule with a major role in mammalian behavior and health. Although oxytocin has the capacity to act as a "natural medicine" protecting against stress and illness, the unique characteristics of the oxytocin molecule and its receptors and its relationship to a related hormone, vasopressin, have created challenges for its use as a therapeutic drug [2].

causing a decrease in core body temperature during the LMA task due to cognitive loss. Significantly more hypothermia was caused by subcutaneous injection of oxytocin acetate (0.1 mg/kg–0.3 mg/kg; single dose) than by oxytocin acetate (0.3 mg/kg) with saline or twice as much as 0.3 mg/kg oxytocin acetate 15–60 days after injection. While oxytocin acetate (0.1 mg/kg) created noticeably more batches at the 30-minute time point only, the temperature drop that was produced within minutes was much more than that of the excipient. [1] Oxytocin acetate (0.1 mg/kg) produced noticeably greater anogenital and body sniffing than saline. Additionally, it lengthens social engagement time overall (71.6 s)[1].

Analysis of monoamines[1]
Microdialysis samples were analyzed using High Performance Liquid Chromatography with electrochemical detection as described previously. Defrosted samples were kept on ice before injection (15 µl) into a Targa C18 3 µM column (100 × 1.0 m) using a Perkin Elmer Series 200 autosampler. Dopamine, 5-HT and their major metabolites; 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were detected using a mobile phase (20 mM potassium dihydrogen phosphate, 20 mM sodium acetate, 0.1 mM ethylenediaminetetraacetic acid, 0.15 mM octanesulfonic acid, and 10% methanol, pH 3.9) at 0.4 ml/min (Dionex P680 pump), and measured against standards with a DECADE II SDC Detector I and Clarity software using a potential of + 0.75 V. The percentage change from baseline for every microdialysate molecule was calculated for each individual rat. PFC samples were excluded from one rat due to incorrect probe placement and two others because of flow disruption. In one rat NAc dopamine was below the detection limit; n = 6/7 per group in the PFC, and n = 7/8 in the NAc.

Animal/Disease Models: 50 - six male Lister-hooded rats (150–200 g) [1]
Doses: 0.1 mg/kg-0.3 mg/kg
Route of Administration: subcutaneous injection; 0.1 mg/kg-0.3 mg/kg; Single dose
Experimental Results: produced Dramatically higher hypothermia (0.3 mg/kg) compared to the saline group.

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Dose–response and antagonist studies with oxytocin on core body temperature and locomotor activity[1]
To establish a suitable dose of oxytocin, which would not suppress locomotor activity (LMA) or produce hypothermia during microdialysis studies, rats (n = 12) were tested using a within-subjects design on four occasions at weekly intervals following injection of vehicle and each dose of oxytocin (0.03, 0.1, or 0.3 mg/kg s.c.) in a pseudo-random order to serve as their own control. This range was selected from previous reports showing that oxytocin doses above 0.3 mg/kg s.c. or i.p. suppress spontaneous locomotion in other rat strains so we included lower doses to identify those devoid of this unwanted effect. To establish the relative contribution of oxytocin and vasopressin V1a receptors to hypothermia produced by the highest dose, a further 12 rats received vehicle or oxytocin (0.3 mg/kg s.c.) in the presence and absence of the non-peptide selective V1a receptor antagonist SR49059 (1 mg/kg i.p.) or the selective oxytocin antagonist L-368,899 (2 mg/kg i.p.), on six occasions at weekly intervals (within-subjects design). Although original peptide antagonists for these receptors showed poor stability and selectivity the development of non-peptide antagonists greatly improved pharmacokinetic properties. The current non-peptide antagonists (SR49059 and L-368,889) were selected because they possess the best overall profile of commercially available oxytocin and V1a antagonists; having high affinity, relative selectivity, good BBB penetration, and plasma half-life and are devoid of partial agonist activity. Doses of these brain penetrant antagonists were selected from previous studies showing < 15 min onset and 2–4 h duration in rodents. SR49059 prevented oxytocin-induced pro-social behavior and hypothermia, whereas L-368,899 (which has brain penetration demonstrated by PET studies), prevented anxiolytic effects of oxytocin in the open field, reduced conditioned disgust behavior during social interaction and attenuated sexual motivation in male rats]. The cross-over repeat within-subject design for dose–response and antagonist studies greatly reduced the number of rats required and the inter-individual variation of measurements made in line with the 3 R’s principle.

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Doses and routes of administration:
Compounds were dissolved in 0.154 M saline (vehicle also containing 5% dimethyl sulfoxide for the antagonists) and administered at volume of 1 ml/kg subcutaneous (s.c.) (oxytocin)

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Effect of oxytocin on PCP-induced hyperactivity, social interaction, and PFC and NAc dopamine and 5-HT efflux[1]
Oxytocin at 0.03 and 0.1 mg/kg were selected for further investigation, as these doses did not produce confounding effects on ambulation and body temperature in dose–response studies described above. A separate group of rats (n = 32, Figure S1) was used to examine the effect of these two doses on PCP-induced hyperactivity, and on the basis of these findings 0.1 mg/kg oxytocin was administered 7 days later, prior to assessment of social interaction and USVs. The following week rats underwent stereotaxic surgery to implant microdialysis probes into the PFC and NAc and after 7 days recovery the effects of oxytocin on dopamine efflux from these brain regions was assessed. One week was left between each of the three protocols (Figure S1) to ensure complete drug wash-out and minimize any carry over effects from the previous procedure.

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Locomotor activity[1]
LMA was assessed on a single occasion as described above. Animals received oxytocin or vehicle after 30 min arena habituation, and vehicle or PCP (5.6 mg/kg i.p.; an established dose to examine “antipsychotic-like” activity) 30 min later, resulting in four treatment combinations: vehicle + vehicle, PCP + vehicle, PCP + 0.03 mg/kg oxytocin, PCP + 0.1 mg/kg (n = 8/group; between-subjects design).

[1]. Shivali Kohli, et al. Oxytocin attenuates phencyclidine hyperactivity and increases social interaction and nucleus accumben dopamine release in rats. Neuropsychopharmacology. 2019 Jan;44(2):295-305.
[2]. C Sue Carter, et al. Is Oxytocin "Nature's Medicine"? Pharmacol Rev. 2020 Oct;72(4):829-861.

The pituitary neuropeptide oxytocin promotes social behavior, and is a potential adjunct therapy for social deficits in schizophrenia and autism. Oxytocin may mediate pro-social effects by modulating monoamine release in limbic and cortical areas, which was investigated herein using in vivo microdialysis, after establishing a dose that did not produce accompanying sedative or thermoregulatory effects that could concomitantly influence behavior. The effects of oxytocin (0.03-0.3 mg/kg subcutaneous) on locomotor activity, core body temperature, and social behavior (social interaction and ultrasonic vocalizations) were examined in adult male Lister-hooded rats, using selective antagonists to determine the role of oxytocin and vasopressin V1a receptors. Dopamine and serotonin efflux in the prefrontal cortex and nucleus accumbens of conscious rats were assessed using microdialysis. 0.3 mg/kg oxytocin modestly reduced activity and caused hypothermia but only the latter was attenuated by the V1a receptor antagonist, SR49059 (1 mg/kg intraperitoneal). Oxytocin at 0.1 mg/kg, which did not alter activity and had little effect on temperature, significantly attenuated phencyclidine-induced hyperactivity and increased social interaction between unfamiliar rats without altering the number or pattern of ultrasonic vocalizations. In the same rats, oxytocin (0.1 mg/kg) selectively elevated dopamine overflow in the nucleus accumbens, but not prefrontal cortex, without influencing serotonin efflux. Systemic oxytocin administration attenuated phencyclidine-induced hyperactivity and increased pro-social behavior without decreasing core body temperature and selectively enhanced nucleus accumbens dopamine release, consistent with activation of mesocorticolimbic circuits regulating associative/reward behavior being involved. This highlights the therapeutic potential of oxytocin to treat social behavioral deficits seen in psychiatric disorders such as schizophrenia.[1]

C43H66N12O12S2.C2H4O2

1067.2393

1066.4576

C, 50.64; H, 6.61; N, 15.75; O, 20.99; S, 6.01

6233-83-6

6233-83-6 (acetate);50-56-6;

12004215

Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2 (Disulfide bridge:Cys1-Cys6)

CYIQNCPLG-NH2 (Disulfide bridge:Cys1-Cys6)

White to off-white solid powder

Endogenous Metabolite

487Ų

CC(O)=O.O=C([C@H](CSSC[C@@H](C(N[C@H](C1=O)CC2=CC=C(O)C=C2)=O)N)NC([C@@H](NC([C@@H](NC(C(N1)[C@@H](C)CC)=O)CCC(N)=O)=O)CC(N)=O)=O)N(CCC3)[C@@H]3C(N[C@@H](CC(C)C)C(NCC(N)=O)=O)=O

DSZOEVVLZMNAEH-BXUJZNQYSA-N

InChI=1S/C43H66N12O12S2.C2H4O2/c1-5-22(4)35-42(66)49-26(12-13-32(45)57)38(62)51-29(17-33(46)58)39(63)53-30(20-69-68-19-25(44)36(60)50-28(40(64)54-35)16-23-8-10-24(56)11-9-23)43(67)55-14-6-7-31(55)41(65)52-27(15-21(2)3)37(61)48-18-34(47)59;1-2(3)4/h8-11,21-22,25-31,35,56H,5-7,12-20,44H2,1-4H3,(H2,45,57)(H2,46,58)(H2,47,59)(H,48,61)(H,49,66)(H,50,60)(H,51,62)(H,52,65)(H,53,63)(H,54,64);1H3,(H,3,4)/t22-,25-,26-,27-,28-,29-,30-,31-,35-;/m0./s1

(S)-N-((S)-1-((2-amino-2-oxoethyl)amino)-4-methyl-1-oxopentan-2-yl)-1-((4R,7S,10S,13S,16S,19R)-19-amino-7-(2-amino-2-oxoethyl)-10-(3-amino-3-oxopropyl)-13-((S)-sec-butyl)-16-(4-hydroxybenzyl)-6,9,12,15,18-pentaoxo-1,2-dithia-5,8,11,14,17-pentaazacycloicosane-4-carbonyl)pyrrolidine-2-carboxamide acetate

Orasthin; Oxystin; Ossitocina; Pitocin; Oxoject; Piton S; Ossitocina; Oxetakain; Oxitocina; Partocon; Oxt; Oxytocin.

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, avoid exposure to moisture.

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

DMSO : ~125 mg/mL (~117.12 mM)
H2O : ~50 mg/mL (~46.85 mM)

Solubility in Formulation 1: 25 mg/mL (23.42 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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