Thyroid hormone regulation of cardiac glycogen metabolism

The administration of thyroxin to rats (500 [mu]g daily for 2-3 weeks, 500 [mu]g daily for 1 week, or 50 [mu]g daily for 2 weeks) or triiodothyronine (100 [mu]g daily for 3-5 days) increased cardiac phosphorylase a levels. Total cardiac phosphorylase activity was unchanged. Pretreatment with reserpine prevented and the [beta]-adrenergic blocking agents reduced this thyroxin-induced increase in phosphorylase a. Thyroxin or triiodothyronine treatment potentiated the response of cardiac phosphorylase to exogeneously administered catecholamines. This enhancement of the catecholamine-induced increase in phosphorylase a could be clearly demonstrated after the animals were pretreated with reserpine. Dose-response relationships for these agents are illustrated. Glycogen analyses on the same hearts indicated a parallelism between the increase in phosphorylase a and the reduction in glycogen content. While hearts of thyroidectomized animals showed a decrease in phosphorylase a levels and an increase in glycogen relative to controls, the response after catecholamines was unchanged. These data suggest that thyroxin may enhance these catecholamine responses by modulation of the myocardial metabolic adrenergic receptor.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32022/1/0000064.pd

Patterns of dog gastrointestinal contractile activity monitored in vivo with extraluminal force transducers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44363/1/10620_2005_Article_BF02233437.pd

Pargyline-induced increases in sensitivity to the effects of drugs on operant behavior in pigeons

Pigeons responded under a multiple fixedinterval 5-min, 30-response fixed-ratio schedule of food reinforcement. Acute pargyline doses between 10.0 and 50.0 mg/kg (i.m.), given immediately prior to the session, decreased responding. Daily administration of 50 mg/kg pargyline (24 mg/kg, every 12 h) initially decreased responding. Tolerance developed so that after 4 days of daily pargyline, responding had returned to control values. Chronic pargyline resulted in an enhanced sensitivity to the effects of d -amphetamine, ephedrine, tyramine, and morphine on schedule-controlled responding. Both d -amphetamine and pentobarbital increased fixed-interval responding at relatively low doses, while higher doses decreased responding. Daily pargyline resulted in an increased sensitivity to both the increases and decreases in response rates produced by d -amphetamine. In contrast, sensitivity to pentobarbital was not changed after daily pargyline. Ephedrine, tyramine, and morphine only decreased fixed-interval responding. Chronic pargyline resulted in an increased sensitivity to the response-rate decreasing effects of ephedrine, tyramine, and morphine. In addition to the increased sensitivity of fixed-interval responding to the effects of tyramine, the dose-effect curve for fixed-ratio responding was also a shifted to the left. Daily pargyline did not result in changes in sensitivity of fixedratio responding to the effects of the other drugs tested.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46399/1/213_2004_Article_BF00426607.pd