Sepsis is known to affect neuroendocrine circuits: injections of lipopolysaccaride are potent stimulators of oxytocin secretion from the posterior lobe, acute sepsis leads to uterus contractions and spontaneous abort. Here, we report changes in expression and distribution of hypothalamic oxytocin in rats that had been subjected to caecal ligation and puncture which led to acute sepsis. Septic animals showed loss of oxytocin immunostaining in perikarya of the supraoptic and paraventricular nuclei and an increase of oxytocin positive fibres, suggesting a shift of oxytocin pools into the axonal compartment. Immunostaining of the posterior lobe revealed reduction of oxytocin in septic rats. Magnocellular neurons in supraoptic- and to a lesser extent in paraventricular nuclei showed nuclear immunoreactivity for the protooncogene c-Fos, indicating stimulation of transcriptional activity upon sepsis. Contrary to magnocellular oxytocin immunoreactivity, we observed increased oxytocin immunoreactivity in cell bodies and processes of periventricular nucleus and in perivascular neurons. Oxytocin neurons in other regions of the hypothalamus and the preoptic region did not appear to be affected by acute sepsis. Our findings suggest a differential activation of neurohypophyseal and cerebrospinal fluid contacting oxytocin systems while centrally projecting oxytocin neurons may not be affected. Systemic oxytocin levels may serve as additional diagnostic marker for sepsis. (C) 2013 Elsevier B.V. All rights reserved.