MONOAMINES IN THE PARABRACHIAL NUCLEUS OF THE CARDIOMYOPATHIC HAMSTER

The development of dystrophic cardiac muscle is related to increases in sympathetic nervous system activity but little is known regarding possible central neural mechanisms that may be involved in cardiomyopathy. The inbred cardiomyopathic hamster is an animal model for studying the development and mechanisms of necrosis in cardiac muscle which resemble non-vascular myocardial diseases of man. Because monoamines are known to play a major role in central regulation of the cardiovascular system, we compared the distribution and density of tyrosine hydroxylase (TH) and 5-hydroxytryptamine (5-HT) immunostaining in the brains of cardiomyopathic hamsters (strain CHF-146), a related strain (CHF-148) of non-cardiomyopathic albino hamsters, and golden Syrian hamsters for possible differences in neurochemical organization. At the time of sacrifice, the cardiomyopathic hamsters exhibit small, calcified lesions on the surface of the ventricular cardiac muscle (early necrotic phase). Brain sections from each group were processed identically and simultaneously. The results show that there were significant differences among strains in the parabrachial nucleus with respect to the two neurochemicals examined. In golden Syrian and albino hamsters, TH and 5-HT immunoreactive axons were lightly-to-moderately stained in the lateral parabrachial nucleus. In the cardiomyopathic hamster, there were significantly more densely stained TH and 5-HT Immunoreactive axons in the lateral parabrachial nucleus, in particular the inner part of the external lateral subnucleus. Because the lateral parabrachial nucleus, including the external lateral subnucleus, is known to be involved in regulation of the cardiovascular system, the differential distribution of TH and 5-HT in the parabrachial nucleus of cardiomyopathic hamsters in comparison to normal hamsters suggests that the parabrachial nucleus could be involved in sympathetic mechanisms related to the development of necrosis in cardiac muscle of the cardiomyopathic hamster.