Detection of specific chemicals from the environment by the olfactory system can elicit distinct responses in animal behavior and physiology,suggesting the existence of unique olfactory receptors(OR)that can detect these chemicals and hard-wired neural circuits that impinge on brain functional centers to drive corresponding innate responses.In order to identify subsets of ORs involved in sensing chemical cues that induce innate reproductive response,we have devised a novel approach that combines retrograde trans-synaptic tracing with RNA sequencing(RNA-seq)from single glomerulus cDNA libraries.We developed novel conditional pseudorabies virus(PRV)tracers and mapped neural circuits upstream of gonadotropin-releasing hormone neurons(GnRH),master regulators of reproductive hormones.Laser Capture Microdissection(LCM)was then used to precisely isolate single PRV-infected glomeruli and RNA-seq performed to identify expressed ORs.Out of a total of 55 identified receptors,18 ORs and 1 Trace amine-associated receptor(TAAR)were found in more than 1 animal,suggesting that there are indeed specific ORs that signal to brain reproductive center through stereotyped neural circuits.These 19 candidate receptors recognize gender-specific cues and predator odors,implying both positive and negative regulations of olfactory inputs on reproductive behavior and physiology.