The presence of CB1 in KP afferents of GnRH neurons was studied in CD1 and KP-CRE mice (Fig. 4) by immunohistochemical labeling of preoptic sections for CB1, GnRH, and KP (Fig. 5A–C) or alternatively YFP (Fig. 5D–F), expressed after transmission of its gene by viral-infection of KP-CRE neurons. This evidence concerns the gene CNR1 and viral infectious disease.