MONOAMINES IN THE PARABRACHIAL NUCLEUS OF THE CARDIOMYOPATHIC HAMSTER

The development of dystrophic cardiac muscle is related to increases i n sympathetic nervous system activity but little is known regarding po ssible central neural mechanisms that may be involved in cardiomyopath y. The inbred cardiomyopathic hamster is an animal model for studying the development and mechanisms of necrosis in cardiac muscle which res emble 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 hydroxyl ase (TH) and 5-hydroxytryptamine (5-HT) immunostaining in the brains o f cardiomyopathic hamsters (strain CHF-146), a related strain (CHF-148 ) of non-cardiomyopathic albino hamsters, and golden Syrian hamsters f or possible differences in neurochemical organization. At the time of sacrifice, the cardiomyopathic hamsters exhibit small, calcified lesio ns on the surface of the ventricular cardiac muscle (early necrotic ph ase). Brain sections from each group were processed identically and si multaneously. The results show that there were significant differences among strains in the parabrachial nucleus with respect to the two neu rochemicals examined. In golden Syrian and albino hamsters, TH and 5-H T immunoreactive axons were lightly-to-moderately stained in the later al parabrachial nucleus. In the cardiomyopathic hamster, there were si gnificantly more densely stained TH and 5-HT Immunoreactive axons in t he lateral parabrachial nucleus, in particular the inner part of the e xternal 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 hamster s in comparison to normal hamsters suggests that the parabrachial nucl eus could be involved in sympathetic mechanisms related to the develop ment of necrosis in cardiac muscle of the cardiomyopathic hamster.