Effects of galanin on insulin and glucagon secretion in the rat

Galanin-like immunoreactivity has been visualized in nerve fibers in the islets of Langerhans, suggesting an involvement of galanin in the neural regulation of islet function. In this study, we investigated the effects of galanin on basal and stimulated insulin and glucagon secretion by infusing the peptide at three different dose rates in rats. We also studied the direct effect of galanin on insulin secretion from freshly isolated rat islets. At 320 pmol/kg/min, but not at 20 or 80 pmol/kg/min, galanin lowered basal plasma insulin levels. In contrast, basal plasma glucagon levels were lowered by galanin already at 20 and 80 pmol/kg/min. Furthermore, galanin inhibited both glucose- and arginine-induced insulin release at all three dose levels, whereas arginine-induced glucagon release was not affected by galanin. Glucose-stimulated insulin secretion from isolated rat islets was dose-dependently suppressed by galanin (10^-6-10^-8M). Therefore, it is concluded that galanin in rats inhibits insulin secretion, both in vivo and in vitro, and that at lower dose levels, the peptide also inhibits basal glucagon release.     

Serotonergic interhemispheric asymmetry: Neurochemical and pharmaco-EEG evidence

1. Postmortem neurochemical investigations revealed interhemispheric asymmetry in the mediofrontal region of human brain. Significantly higher right hemisphere serotonin metabolite (5HIAA) content as well as increased maximal imipramine binding (IB) were found in the right hemisphere than in the left side.

2. IB did not show a gender difference in the mediofrontal area. However, women had higher IB in the right orbital frontal cortex than did men.

3. In vivo pharmaco-EEG results tend to support the postmortem neurochemical data. Intravenous chlorimipramine resulted in an asymmetric topographic distribution of the P300 auditory evoked potential, peak amplitudes were shifted to the right hemisphere.     

Sensory axonopathy in hereditary distal spinal muscular atrophy

A girl of 14 year is presented with a distal spinal muscular atrophy (SMA) with autosomal recessive inheritance. The technical findings are in agreement with the diagnosis. Light microscopical examination of sural nerve biopsy, including teased fiber studies and morphometry, showed no abnormalities. Electron microscopical investigation however demonstrated axonal pathology. The question arises if distal SMA is a distal axonopathy mainly of motor nerves, but to some extent also of sensory nerves.