Pii: S0304-3940(01)01623-8

Here we examine hypothesis that short-term peripheral ZnSO4-induced anosmia can produce effects on c-fos expression within spinal cord and caudal medulla in male Wistar rats (n ˆ 4). Fos-like-immunoreactive cells revealed by avidinbiotin-peroxidase method show a signi®cant bilateral increase in the nucleus proprius (layers 3 and 4) and medial part of layers 5 and 6. In substantia gelatinosa (layer 2i) and area 10 Fos-positive neurons were intermixed together with nicotinamide adenine dineucleotide phosphate-diaphorase (NADPH-d)-reactive cells. Short-term anosmia enhanced c-fos expression in ventral horn (layers 7 and 8), ventrolateral segment and dorsal part of the spinal trigeminal nuclei. In anosmic rats varicose ®bres and numerous NADPH-d-stained neurons were present in the gelatinous layer of the spinal trigeminal nucleus caudalis, and a separate population of Fos-positive cells was detected within this layer. Nucleus tractus solitaris also contained a few NADPH-d-reactive, medium sized neurons intermixed with Fos-immunoreactive cells. q 2001 Elsevier Science Ireland Ltd. All rights reserved.