Abnormal cardiac biochemistry in spontaneously diabetic Bio-Breeding/Worcester rat

Diabetes produced by injection of alloxan or streptozotocin results in cardiac dysfunction in rats that is associated with lower cardiac contractile protein ATPase activity. The purpose of this investigation was to examine cardiac myosin biochemistry in the Bio-Breeding Worcester (BB/W) rat, a strain in which diabetes occurs spontaneously and closely resembles insulin-dependent diabetes in humans. Hearts from diabetic BB/W rats were studied at 1, 4, and 7 mo after the onset of diabetes and were compared with age-matched BB/W rats that were bred for resistance to diabetes. Calcium-stimulated myosin ATPase activity was significantly decreased after 4 and 7 mo of diabetes, and actin-activated myosin ATPase was significantly depressed at all time points. Differences between hearts from control and diabetic animals increased with the duration of diabetes. Closely associated with reductions in myosin ATPase activity in the diabetes was a shift in the isomyosin content from the normally predominant V1 to the V3 isoenzyme. Thus diabetes that results from genetic causes leads to depressed myosin enzymatic activity in the rat. Furthermore, since previous studies have shown that BB/W diabetic rats do not develop hypothyroidism, the present results support the view that altered thyroid function does not mediate the abnormalities in cardiac contractile proteins in diabetes.

Behavioral and biochemical effects of knife cuts that preferentially interrupt principal afferent and efferent connections of the striatum in the rat

Knife cuts were made that preferentially interrupted (a) the nigrostriatal pathway; (b) pallidofugal projections to the lower brainstem; (c) caudate-pallidal interconnections; and (d) fibers entering or leaving the striatum ventrally. The effects of these cuts on conditioned (shuttle box) avoidance, passive avoidance, swimming escape, sucrose-rewarded alley running, locomotor activity, and various measures of sensory-motor function were examined. The norepinephrine, dopamine and serotonin content of the striatum, residual forebrain and hypothalamus were determined following the completion of behavioral testing. The pattern of results suggests that striatal functions which are significantly influenced by several afferent and efferent connections are essential for the acquisition and, perhaps, execution of complex behavior in appetitive as well as aversive test paradigms. A special role for the dopaminergic afferents to the striatum was not established in these tests.