EN
Housing females in groups prolongs the dioestrous phases in cycling laboratory mice Mus rnusculus Linnaeus, 1758. Olfactory signals play an important role in interaction between females, and the vomeronasal system is involved in mediation of hormonal responses to pheromones. Present results show that removal of the vomeronasal system (VNX), or bulbectomy (OBX), leads to in decreased numbers of oestrous mice in comparison to non-operated (NON) or sham-operated (SHAM-OBX) singly reared females. Oestrous cyclicity was also affected by social factors. Cohabitation of NON, VNX, OBX or SHAM-OBX females with adult females results in decreased oestrous frequency in comparison to females reared alone. Moreover, VNX females exposed to male bedding inhibited oestrus in comparison to nonexposed VNX animals. The results provide evidence that different external stimuli evoke hormonal responses which are manifested in inhibition of oestrous cycle in female mice.