Oxytocin neuron activation by acute infusion of Montanoa genus plants in the Wistar rats

In traditional Mexican medicine, plants from the Montanoa genus, family Asteraceae (Montanoa tomentosa, Montanoa grandiflora, and Montanoa frutescens) have been used to induce labor owing to their uterotonic properties like those produced by oxytocin (OXT). However, whether infusions of these plants can activate hypothalamic OXT-producing neurons is unknown. To test this possibility, five independent groups of Wistar rats (n=4) were included: intact, vehicle, and three groups that received 50 mg/kg p.o. of M. tomentosa, M. grandiflora, and M. frutescens infusions, respectively. Ninety min after treatment, the brains were obtained and processed using double-labeled immunohistochemistry for Fos protein and oxytocin (Fos/OXT-ir). Rats that received Montanoa infusions had significantly greater number of Fos/OXT-ir cells in the paraventricular (PVN) and supraoptic (SON) nuclei, with respect to intact and vehicle groups. These findings demonstrate that Montanoa infusions activated OXT neurons, an effect that may be related to the reported pharmacological properties.