Female oxytocin-deficient mice
display enhanced anxiety-related behavior

Mantella RC, Vollmer RR, Li X, Amico JA.
Departments of Pharmaceutical Sciences
(R.C.M., R.R.V., X.L., J.A.A.)
and Medicine (J.A.A.), University of Pittsburgh,
Pittsburgh, Pennsylvania 15261.
Endocrinology 2003 Jun;144(6):2291-6


Previous studies have suggested that oxytocin (OT) may be anxiolytic in female laboratory rats and mice. The elevated plus-maze was used to compare anxiety-related behaviors of OT-deficient (OT-/-) and wild-type (OT+/+) mice. Female OT-/- mice displayed increased anxiety-related behavior compared with OT+/+ mice. The percentage of entries (P < 0.0002) and time spent (P < 0.003) in the open arms was less in female OT-/- than OT+/+ mice. Administration of synthetic OT, 2 ng by intracerebroventricular (icv) injection to female OT-/- mice, increased the percentage of entries (P < 0.003) and time spent (P < 0.004) in the open arms compared with artificial cerebrospinal fluid female OT-/- mice. Administration of an OT receptor antagonist (Atosiban, d[Dtyr(Et)(2), Thr(4)]ornithine vasotocin) 100 ng icv, to female OT+/+ mice increased anxiety-related behavior by decreasing the percentage of entries (P < 0.01) and time spent (P < 0.04) in the open arms compared with artificial cerebrospinal fluid-treated controls. Central infusion of an OT receptor antagonist, 100 ng icv, before administration of synthetic OT, 2 ng icv, in female OT-/- mice blocked the anxiolytic affect of OT. In contrast, male OT-/- mice displayed decreased anxiety-related behavior compared with male OT+/+ mice. The percentage of entries (P < 0.007) and time spent (P < 0.004) in the open arms was greater in male OT-/- vs. OT+/+ mice. Our findings indicate that OT pathways play a role in modulating anxiety in female mice of the C57BL/6 background, and the effect is mediated by the OT receptor.
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