RÉSUMÉ
Locus coeruleus [LC] nucleus modulates certain physiological behaviors such as pain, anxiety, awake, sleep, memory and learning. Some studies have shown that the LC nucleus has both adrenergic neurons and alpha 2-adrenoceptors, and also receives oxytocinergic projections from the paraventricular nucleus of the hypothalamus. The effect and mechanism of this neuropeptide is not fully understood. Considering that the chronic usage of oxytocin decreases anxiety, in the present study the effect of acute administration of oxytocin in the locus coeruleus and its interaction with alpha 2 adrenoceptors on anxiety induced vogel's test in male adult rats were investigated. Male adult wistar rats weighing 285 +/- 15 grams were divided into 6 groups: 1] Receiving saline, 2] oxytocin [2ng/2micro l], 3] yohimbine [3.3 micro g/2microl], 4] receiving saline + yohimbine, 5] saline+ oxytocin and 6] yohimbine+oxytocin in locus coeruleus nucleus. Number of received shocks during water drinking was evaluated as an anxiety behavior for 15 minutes in Vogel's test. Oxytocin reduced number of shocks received [Anxiogenic effect]. Blocking of alpha 2 adrenoceptors by yohimbine decreased number of shocks received. Anxiogenic effect of oxytocin increased in presence of yohimbine. It seems that the LC alpha 2-adrenoceptors modulate anxiety and the anxiogenic effect of oxytocin and this effect can be eliminated by the blocking of the alpha 2-adrenoceptors