Fig. 10. Major structures in the neural pathway from olfactory bulbs to spinal cord (adapted from Shipley et al., 1995), and estimates of their importance in the regulation of NCE. The roles of structures depicted as ovals remain to be explored. The roles of each of the rectangular structures have been explored in at least one experiment, and the rectanglesare shaded in approximate proportion to their importance in the process of NCE. Lesions in MeA eliminate NCE (Kondo et al., 1997), lesions in BST impair NCE (Experiment 4), and lesions in MPOA have no reliable effect (Experiments 1–3). Preliminary reports on medullary structures suggest moderate facilitation by lesions innROb (Kondo et al., 1996), but no reliable effect fromnPGi lesions (Liu et al., 1995). Solid lines indicate known direct projections, usually reciprocal, between structures. Dashed lines indicate hypothetical extra-MPOA projections, not necessarily direct ones, based primarily on the apparent redundancy of the MPOA to the process of NCE. No attempt has been made to distinguish excitatory from inhibitory influences, although some of those from the medulla toLSC are almost surely inhibitory. AOB, Accessory olfactory bulb; BST, bed nucleus of stria terminalis; LSC, lumbosacral spinal cord;MOB, main olfactory bulb; MeA, medial amygdala; MPOA, medial preoptic area;nPGi, nucleus paragigantocellularis;nROb, nucleus raphé obscurus.