Functional consequences following infection of the olfactory system by intranasal infusion of the olfactory bulb line variant (OBLV) of mouse hepatitis strain JHM

7The present study assessed the functional consequences of viral infection with a neurotropic coronavirus, designated MHV OBLV, that specifically targ ets central olfactory structures. Using standard operant techniques and a ' go, no-go' successive discrimination paradigm, six BALB/c mice were trained to discriminate between the presentation of an air or odor stimulus (three mice for each of the odorants propanol and propyl acetate). Two additional BALB/c mice were trained to discriminate between the presentation of air a nd the presentation of either vanillin or propionic acid. Following criteri on performance, each mouse received an additional 2000 trials of overtraini ng. At completion of overtraining one mouse from the propanol and propyl ac etate groups were allocated as untreated. The remaining six mice were inocu lated with 300 mul of the OBLV stock per nostril for a total of 1.5 x 10(6) p.f.u. in 600 mul, Following a 1 month rest, untreated and inoculated anim als were again tested on their respective air versus odor discrimination ta sk. Untreated animals immediately performed at criterion levels. in contras t, inoculated animals varied in their capacity to discriminate between air and odorant. Five of the six inoculated mice showed massive disruption of t he olfactory bulb, including death of mitral cells; the other was more mode stly affected. In addition, the density of innervation of the olfactory muc osa by substance P-containing trigeminal fibers is also affected by inocula tion. Those mice that remained anosmic to the training odorants had the mos t severe reduction in mitral cell number and substance P fiber density amon g the inoculated animals.