Increase in the stimulation-induced overflow of glutamate by fluoroacetate, a selective inhibitor of the glial tricarboxylic cycle.

Fluoroacetate is known to be taken up selectively by glia, where after forming fluorocitrate, it inhibits the tricarboxylic acid cycle. Since uptake into glia has a major role in the inactivation of synaptically released glutamate, the effect of fluoroacetate on the overflow of glutamate evoked by electrical field stimulation in slices of rat hippocampus was investigated. In agreement with previous reports, 1 mM fluoroacetate reduced the release and content of glutamine, but increased only slightly the overflow of glutamate induced by stimulation.

Effect of epinephrine on carbohydrate metabolism in exercising dogs.

Well-trained dogs with indwelling arterial and venous catheters ran on a treadmill (15%, 133 m/minute). A mixture of 3-3H: glucose and 14C-glucose (U) or 14C-lactate was infused at a constant rate. Hepatic glucose output (Ra), metabolic clearance rate of glucose (MCR), the percent participation of plasma glucose (G) in lactate production (%L comes from G), peripheral glycogenolysis (GLY) and lactate turnover (RaL) were calculated.

Effect of propranolol in dinitrophenol poisoning.

The effect of the beta-blocker propranolol (PR) in sublethal poisoning with 2, 4,-dinitrophenol (DNP) was studied on carbohydrate kinetics in dogs. Parameters of glucose and lactate turnovers were measured by using a mixture of 3-3H-glucose and 14C-lactate according to the primed constant rate infusion technics. Participation of plasma glucose in lactate production (% L----G) and the rate of peripheral glycogenolysis (GLY) was estimated in experiments using a mixture of 3-3H-glucose and 14C-glucose (U).

Effect of beta-adrenergic blockade on lactate turnover in exercising dogs.

Dogs with indwelling catheters in the jugular vein and in the carotid artery ran on the treadmill (slope: 15%, speed: 133 m/min). Lactate turnover and glucose turnover were measured using [U-14C]lactate and [3-3H]glucose as tracers, according to the primed constant-rate infusion method. In addition, the participation of plasma glucose in lactate production (Ra-L) was measured with [U-14C]glucose.

Effects of glucose infusion on hepatic and muscle glycogenolysis in exercising dogs.

Hepatic glucose production (Ra) and the rate of utilization of nonglucose sources (essentially muscle glycogen) were measured in dogs running on a treadmill (15%, 133 m/min) with indwelling catheters in the jugular vein and carotid artery. A mixture of [3-3H]glucose and [U-14C]glucose was used as tracer according to the principles of the primed constant-rate infusion techniques. Glucose was infused intravenously at a rate (12 mg.