Oxytocin Antibody

Excellent signal in mouse hypothalamus when used at 1:2000. Brains were first perfused with PBS and then with 4% PFA followed by overnight drop-fixation in 4% PFA. 30um-thick slices were cut on a sliding blade microtome and then immunostained as floating sections. Slices were incubated in the primary anti-oxytocin antibody overnight rocking at 4oC. Primary antibodies were visualized with anti-rabbit secondaries, incubation for 1h at RT the following day.

This antibody worked very well at 1:2,000 in PFA-fixed, cryosectioned mouse brain tissue. OXT-positive cells in the PVN were very clearly labeled with minimal background.

As stated on the antibody product page, this antibody exhibits reactivity to forms of oxytocin across a wide range of species, including species that express Ile8-oxytocin (mesotocin), the oxytocin form found in most marsupials, birds, reptiles and amphibians. Published work in birds (Cantwell and Cassone; PubMed ID: 1699890; cited on the antibody product page) demonstrates that preadsorption with mesotocin does in fact eliminate immunolabeling in birds. However, those authors did not conduct preadsorptions with the closely related neuropeptide vasotocin, which differs from mesotocin by only one amino acid. Vasotocin is the nonmammalian homologue of vasopressin and is the ancestral peptide for all vertebrate peptides of the oxytocin-vasopressin family. Importantly, vasotocin and mesotocin are expressed in separate subpopulations of neurons in the hypothalamus (e.g., separate subpopulations in the paraventricular nucleus), as are vasopressin and oxytocin, but the oxytocin antibody 20068 labels both, as we have discovered in pilot experiments using a selective vasotocin antibody alongside the oxytocin 20068. The oxytocin antibody also labels extrahypothalamic neurons in the bed nucleus of the stria terminalis that are known to express only vasotocin, not mesotocin (see Goodson et al., 2012, PNAS, 109 supp. 1, 10685-10692). Thus, although the oxytocin antibody 20068 does recognize nonmammalian forms of oxytocin, it is not useful for experiments in nonmammalian species due to its cross-reactivity to vasotocin, a peptide found in all nonmammalian vertebrates.