INCREASED TYROSINE-HYDROXYLASE IMMUNOREACTIVITY IN THE LOCUS-COERULEUS OF CATS WITH INTERSTITIAL CYSTITIS

Purpose: Environmental stressors seem to play a role in exacerbation o f symptoms of interstitial cystitis (IC), both in cats and in human be ings. These observations suggest a role for the sympathetic nervous sy stem in the pathophysiology of IC. To begin to assess the underlying r ole in IC of the pontine nucleus locus coeruleus (LC), the most import ant source of norepinephrine in the central nervous system, we compare d the intensity of tyrosine hydroxylase immunoreactivity (THIR) in sec tions of LC obtained from cats with IC and from healthy cats. Cats wit h IC were studied during quiescent periods in an attempt to avoid the risk of flare-induced activation of the LC. Materials and Methods: Six cats diagnosed with IC and six healthy cats were studied. Cats with I C were monitored to ensure that no behavioral or urinary signs attribu table to IC had been observed for at least two weeks prior to the stud y. Cats were euthanized and perfused with 4% paraformaldehyde, after w hich brainstem tissues were collected. Coronal sections (10 mu m.) of LC were prepared and examined for THIR. Results: THIR in total LC, par abrachial nucleus and LC complex was significantly greater (p <0.05) i n samples from cats with IC than from healthy cats. Conclusions: The i ncreased THIR in the LC of cats with IC provides additional evidence f or increased sympathetic nervous system activity in patients with IC, even during periods of absence of clinical signs.