The dromedary camel displays annual variation in hypothalamic kisspeptin and Arg-Phe-amide-related peptide-3 according to sex, season, and breeding activity

Distribution of GnRH and Kisspeptin Immunoreactivity in the Female Llama Hypothalamus

Llamas are induced non-reflex ovulators, which ovulate in response to the hormonal stimulus of the male protein beta-nerve growth factor (β-NGF) that is present in the seminal plasma; this response is dependent on the preovulatory gonadotrophin-releasing hormone (GnRH) release from the hypothalamus. GnRH neurones are vital for reproduction, as these provide the input that controls the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. However, in spontaneous ovulators, the activity of GnRH cells is regulated by kisspeptin neurones that relay the oestrogen signal arising from the periphery. Here, we investigated the organisation of GnRH and kisspeptin systems in the hypothalamus of receptive adult female llamas. We found that GnRH cells exhibiting different shapes were distributed throughout the ventral forebrain and some of these were located in proximity to blood vessels; sections of the mediobasal hypothalamus (MBH) displayed the highest number of cells. GnRH fibres were observed in both the organum vasculosum laminae terminalis (OVLT) and median eminence (ME). We also detected abundant kisspeptin fibres in the MBH and ME; kisspeptin cells were found in the arcuate nucleus (ARC), but not in rostral areas of the hypothalamus. Quantitative analysis of GnRH and kisspeptin fibres in the ME revealed a higher innervation density of kisspeptin than of GnRH fibres. The physiological significance of the anatomical findings reported here for the ovulatory mechanism in llamas is still to be determined.

Seasonal morphology and immunoreactivity of cytokeratin and atrial natriuretic peptide in dromedary camel poll glands

Poll glands are characteristic feature of dromedary camels; although they yield a yellowish offensive secretion, especially during rutting (breeding) season, their function is not yet exactly specified. The present study shows the seasonal morphology and immunoreactivity of cytokeratin (CK) and atrial natriuretic peptide (ANP) in the camel poll gland; the result could clearly specify the role of the gland in camel reproduction. Poll glands are compound tubulo-alveolar in structure. During rutting season, the secretory units showed wide lumina and simple squamous epithelium surrounded by myoepithelial cells; the lumina became narrower and the epithelium changed to simple cuboidal during non-rutting season. Many glandular lobules showed abundant interlobular connective tissue with fewer and smaller secretory units during non-rutting season compared to rutting season. Positive CK and ANP immunoreactivity was detected in the cytoplasm of epithelial cells of secretory units and ducts together with the myoepithelial cells and blood vessels. Although CK immunoreactivity was more intense during rutting season in comparison to non-rutting season, there was no seasonal variation in ANP immunoreactivity. During both seasons, while the glandular capsule, connective tissue septa, interstitium showed negative CK immunoreactions, they reacted moderately to ANP. In conclusion, the poll gland undergoes annual structural and functional changes which are suggested to correlate with the male seasonal sexual behaviour. Further, the biological role of CK and ANP proteins together with their immunohistochemical expression in the camel poll gland suggests a stimulatory effect in the glandular secretory cells, and hence, they might modify camel sexual activity.

The kisspeptin system in domestic animals: what we know and what we still need to understand of its role in reproduction

The discovery of the kisspeptin (Kp) system stirred a burst of research in the field of reproductive neuroendocrinology. In the last 15 yr, the organization and activity of the system, including its neuroanatomical structure, its major physiological functions, and its main pharmacological properties, were outlined. To this endeavor, the use of genetic tools to delete and to restore Kp system functionality in a specific tissue was essential. At present, there is no question as to the key role of the Kp system in mammalian reproduction. However, easily applicable genetic manipulations are unavailable for domestic animals. Hence, many essential details on the physiological mechanisms underlying its action on domestic animals require further investigation. The potentially different effects of the various Kp isoforms, the precise anatomical localization of the Kp receptor, and the respective role played by the 2 main populations of Kp cells in different species are only few of the questions that remain unanswered and that will be illustrated in this review. Furthermore, the application of synthetic pharmacologic tools to manipulate the Kp system is still in its infancy but has produced some interesting results, suggesting the possibility of developing new methods to manage reproduction in domestic animals. In spite of a decade and a half of intense research effort, much work is still required to achieve a comprehensive understanding of the influence of the Kp system on reproduction. Furthermore, Kp system ramifications in other physiological functions are emerging and open new research perspectives.

Dromedary camel: A model of heat resistant livestock animal

Camels are highly adapted to harsh environments. The dromedary camel is adapted to a wide range of arid and semi-arid conditions. The aim of the present paper is to review some of the key adaptation characteristics of the dromedary and how they affect reproductive patterns. Special attention is given to the reproductive seasonality and interaction between lactation and reproduction. Adaptive mechanisms are described including some of the recent molecular aspects with respect to heat shock protein expression in camels.