changes in the pig oviduct mediated by the presence of gametes in genital tracts collected at slaughterhouses or in animals undergoing surgical intervention, but there is still a lack of information concerning the complete transcriptomic profile of this organ in fertile sows in conditions close to physiological. The hormonal induction of ovulation, used in some 
experimental designs, alters the physiological pathways leading to gamete encounter and a number of immature oocytes can be found in the oviductal ampulla after such treatments. Direct insemination of spermatozoa into the pig oviduct produces polyspermy and surgical interventions can induce inflammatory responses, thus altering the transcriptome of a specific tissue, leading to erroneous or contradictory outcomes when experimental designs involving some of these processes are used. Although specific targeted genes have been analysed by real time quantitative polymerase chain reaction , and microarray technology has been PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/1970500 used recently in one experiment involving surgical insemination of sex-sorted spermatozoa directly into the oviduct, no data are available concerning the effect of gametes or zygotes during the very early stages of fertilization on the porcine oviductal transcriptome in conditions resembling physiological situation. The question therefore arose as to whether the meeting of male and female gametes in the oviduct could influence the transcriptome. The objective of this study was to investigate differences in oviductal PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19703900 transcriptome between inseminated and non-inseminated pigs during spontaneous oestrus in a specific area of the oviduct. We decided to analyse this specific part of the oviduct where spermatozoa released from sperm reservoir arrive close to the time of ovulation because it is where fertilization and zygote formation occurs. We used an in vivo model approaching the study from a physiological point of view in which no hormonal treatment and no artificial sperm selection were imposed. It is therefore emphasised that no surgical introduction of spermatozoa and no insemination at a site other than the physiological one were used. The principal tool used to achieve our objective was the Porcine Gene Expression Microarray. 2 / 18 Insemination Influences Oviductal Transcriptome in Pigs Materials and Methods Animals This study was carried out in strict accordance with the recommendations in the Guiding Principles for the Care and Use of Animals. The protocol was approved by the Ethical Committee for Experimentation with Animals of the University of Murcia, Spain. Surgery was performed under analgesic and anaesthetic protocols, and all efforts were made to minimize suffering. Ten cyclic commercial hybrid sows Landrace x Large White were kept under standard conditions of housing and feeding. All were in lactation at the same time and no hormonal induction or surgery was performed in the animals of this study. Oestrous detection, artificial insemination and tissue collection The animals were weaned on day -4. Five animals were artificially inseminated 10 hours after showing signs of standing oestrus, whereas the remaining 5 were not inseminated. Previous ultrasonographic scanning was performed to Fig 1. LY341495 site Representative diagram of the experimental protocol for the recovery of the oviductal tissue samples and image of the left ovary of sow number 5, showing the recently ovulated follicles as corpora haemorrhagica. Animal dataset. Comparative histograms of physiologi