Temporal bone surgery causes reduced nitric oxide synthase activity in the ipsilateral guinea pig hippocampus.

There is a lack of data on the neurochemical basis for the interaction between the vestibular system and the hippocampus. The aim of the present study was to determine levels of nitric oxide synthase (NOS) activity in the ipsilateral and contralateral hippocampi at 10 h following unilateral deafferentation of the peripheral vestibular nerve (UVD) in guinea pig, using a radio-enzymatic technique. The levels of NOS activity were similar in the contralateral hippocampus following either a sham temporal bone operation or the UVD. However, NOS activity was significantly lower in the ipsilateral hippocampus following both the UVD and the sham temporal bone surgery (P<0.05 for both comparisons). These results suggest that even sham temporal bone surgery results in a reduction in NOS activity in the ipsilateral hippocampus.