Hypothalamus and preoptic area in breeding rodent: a review

Rodent is a diversified group of mammals and characterized by small body, short limb, long tail and incisor teeth. Majority of mammals fall under this category including mice and rats which are commonly used as laboratory animal. Brain of rodent shows compartmentalization and comprises of cerebral cortex, cerebellum, hippocampus, hypothalamus and thalamus. Among different brain regions, hypothalamus and preoptic area (POA) specifically are considered as the complex region responsible for sleep, thermoregulation, nest building, maternal behavior and reproductive physiology. Rodents exhibit plasticity in terms of learning, increase in sex hormones, decline in immunity with aging, circadian rhythm drive temperature and neurotransmitter release during maturity. Ovulatory stage in females which involves development of growth follicle and ova is marked as estrous cycle in non-primates. It is usually differentiated into four phase namely: proestrus, metaestrus, estrus and diestrus. Sex steroid hormones are known to be involved in reproductive physiology. All gonadal hormones mainly estradiol, progesterone and prolactin activity has been observed to increase in estrus female rat. The level of cortisol and oxytocin also fluctuates during estrous cycle. The present article attempts at highlighting reported seasonality and function of hypothalamus and POA within rodents. Graphical Abstract