Choledocholithiasis in acute gallstone pancreatitis. Incidence and clinical significance

A prospective study of choledocholithiasis was performed using 110 patients with presumptive diagnoses of acute gallstone pancreatitis. The incidence of migrating and persistent bile duct stones was determined using stool screening and intraoperative cholangiography, and the clinical significance of continued stone obstruction of the papilla was investigated using ultrasound assessment of migration time and a second evaluation of prognostic signs. Pancreatic inflammation was confirmed at surgery in 51 patients, of whom only 27 had stones in the stools (n = 22) or the bile duct (n = 5), suggesting that choledocholithiasis may not be the sole triggering factor of acute gallstone pancreatitis. Neither delayed migration nor persistent stone obstruction of the papilla promoted pancreatic inflammation.

Release of [3H]dopamine from rat prefrontal cortex: modulation through presynaptic cholinergic heteroreceptors

The release of tritiated dopamine ([3H]DA) from slices of the rat prefrontal cortex was studied using a superfusion technique. Release appeared to be voltage-dependent and also dependent on external Ca2+, suggesting the presence of a specific neurotransmitter release mechanism. gamma-Aminobutyric acid (GABA), aspartate, glutamate and serotonin had no effect on either basal DA release or K(+)-stimulated release. Carbachol, a cholinergic agonist, inhibited K(+)-stimulated DA release. The results demonstrate that cholinergic heteroreceptors on dopaminergic terminals of the prefrontal cortex modulate DA release.

Study of the mechanism of release of [3H]GABA from a teleost retina in vitro

gamma-Aminobutyric acid (GABA) is thought to be a neurotransmitter in the vetebrate retina. We studied the voltage and Ca2+ dependency of the process of release of [3H]GABA from the retina of the teleost Eugerres plumieri, using a microsuperfusion technique. Two depolarizing agents, veratridine and high potassium, produced a concentration-dependent release of [3H]GABA. The veratridine effect was inhibited in Na+-free solution, but was not affected by 1 microM tetrodotoxin. A substantial inhibition (about 75%) of the veratridine- and potassium-stimulated release of [3H]GABA occurred in Ca2+-free medium. Inhibitors of the Ca2+ channel, such as Mg2+ (20 mM), La3+ (0.1 mM), and methoxy-verapamil (4 microM-0.4 mM), inhibited the veratridine- and K+-stimulated release. However, Co2+ and Cd2+ caused a potentiation and no change of the K+- and veratridine-stimulated release, respectively. This release process is apparently specific, since both depolarizing agents were unable to release [3H]methionine, a nontransmitter amino acid, under the same experimental conditions. Autoradiographic studies with [3H]GABA, using the same incubation conditions as for the release experiments, showed a high density of silver grains over the horizontal cells with almost no accumulation by amacrine cells and Müller cells. beta-Alanine and nipecotic acid were used as two relative specific inhibitors of the glial and neuronal GABA uptake mechanisms, respectively. Only a small heteroexchange with [3H]GABA was found with beta-alanine, and no inhibition of the subsequent veratridine-stimulated release. On the other hand, nipecotic acid produced a strong heteroexchange with [3H]GABA and lacked the capacity to induce the veratridine-stimulated release of [3H]GABA. These results suggest a voltage- and Ca2+-dependent neuronal release of [3H]GABA from retina.