CENTRAL CONNECTIONS OF THE OVINE OLFACTORY-BULB FORMATION IDENTIFIED USING WHEAT-GERM AGGLUTININ-CONJUGATED HORSERADISH-PEROXIDASE

Pheromonal stimuli elicit rapid behavioral and reproductive endocrine changes in the ewe, The neural pathways responsible for these effects in sheep are unknown, in part, because the olfactory bulb projections have not been examined in this species, Using the anterograde and retr ograde neuronal tracer, wheat germ agglutinin-conjugated horseradish p eroxidase (WGA-HRP), we describe the afferent and efferent olfactory b ulb connections of the Suffolk ewe. Injections of WGA-HRP limited to t he main olfactory bulb resulted in retrograde labeling of cells in num erous telencephalic, diencephalic, and metencephalic regions, Terminal labeling was limited to layer la of ipsilateral cortical structures e xtending rostrally from the anterior olfactory nucleus (AON), piriform cortex, anterior-, and posterolateral-cortical amygdaloid nuclei to l ateral entorhinal cortex caudally, Injections involving the accessory olfactory bulb and AON produced additional labeling of cells within th e bed nucleus of the stria terminalis (BNST), medial nucleus of the am ygdala, and a few cells in the posteromedial cortical nucleus of the a mygdala, Terminal labeling included a small dorsomedial quadrant of BN ST and also extended to the far lateral portions of the supraoptic nuc leus, A clearly defined accessory olfactory tract and nucleus was not evident, perhaps due to limitations in the sensitivity of the method. With this possible exception, the afferent and efferent olfactory conn ections in the sheep appear similar to those reported for other specie s. (C) 1998 Elsevier Science Inc.