Lutz Lachenmayer

Evidence for the existence of serotonin-, dopamine-, and noradrenaline-containing neurons in the gut of Lampetra fluviatilis

SummaryMonoamine-containing neurons in the gut of Lampetra fluviatilis are characterized by histochemical, electron microscopical and biochemical methods. Strongly yellow fluorescent, probably serotonin-containing intrinsic neurons are found along the entire length of the intestine. Their processes aggregate to form large bundles of mainly non-terminal axons, constituting a subepithelial fibre plexus. This subepithelial, ganglion cell comprising plexus is connected to a wide-meshed subserosal plexus which has ganglion cells of different size and few varicose, single axons. Intermingled with both plexus there occur — in the anterior and middle but not in the preanal portion of the lamprey intestine — scattered green fluorescent intrinsic perikarya, emanating faintly green fluorescent, poorly varicosed axons.The formaldehyde-induced neuronal fluorophores conform to serotonin (yellow fluorescent compound), noradrenaline, and dopamine (green fluorescent substance), as revealed in microspectrofluorimetric recordings. The electron microscopical analysis of the yellow fluorescent intrinsic neurons in the terminal hindgut shows nerve cell pericarya and axons equipped with a typical population of occasional small granular and many large granular vesicles (750–1600 Å). The number and opacity of cores of the small and the osmiophilia of the cores of the large granular vesicles are significantly increased following short-term treatment with 5,6-dihydroxytryptamine. Long-term treatment with 5,6- or 5,7-dihydroxytryptamine provokes severe signs of ultrastructure impairment and eventual degeneration in the supposed serotonin-containing axons, besides indications of piling-up of organelles in the non-terminal axons due to arrest of axonal transport.Chromatography of acid extracts from the lamprey intestine, gills and kidney reveals the presence of serotonin (besides another unidentified indoleamine) and dopamine and noradrenaline in the gut, but only dopamine in the brain. The detection of serotonin, noradrenaline and dopamine in the lamprey gut is confirmed by chemical determinations.The occurrence of intrinsic serotonin-, noradrenaline- and dopamine-containing neurons in the gut of Lampetra fluviatilis deviates from the established pattern of innervation of the vertebrate intestine and is considered to be a remnant of an autonomic innervation principle common in invertebrates.

De- and regeneration of the bulbospinal serotonin neurons in the rat following 5,6-or 5,7-Dihydroxytryptamine treatment

SummaryIn an attempt to determine the conditions which permit central 5-HT neurons to respond to a chemical injury of their axons by sprouting and regeneration, the pattern and time-course of recovery of 5-HT concentrations and regrowth of bulbospinal 5-HT axons were evaluated in rats subjected to intraventricular treatment with either 75 μg 5,6- or 150 μg 5,7-DHT. While 5,6-DHT treatment is followed by a significant recovery of 5-HT concentrations in the telodiencephalon, brainstem and upper part of the spinal cord within 3 months, there is no significant restoration of the severely depleted 5-HT levels in the telodiencephalon and spinal cord, and only limited recovery in 5-HT content of the brainstem preparation after 5,7-DHT.These differences conform to the observation of widespread and effective regrowth and regeneration of the bulbospinal 5-HT neurons in the 5,6-DHT treated lower brainstem and upper spinal cord but restricted and localized sprouting efforts in the 5,7-DHT treated lower medulla oblongata. This could be explained by a cell body near lesion of the non-terminal indoleamine axons by 5,7-DHT which results in a late retrograde, irreversible degeneration of most of the indoleamine pericarya from group B1 and many of group B3.It is concluded that the preservation of a critical length of the main axon and part of its collaterals is necessary for the neurons survival, and that the individual pattern of the neuropil architecture of brain centres which are invaded by the axonal sprouts may significantly influence their growth characteristics and thus either favour or impede their chance to reestablish connections with their original effector. Aberrant, localized, intense sprouting of drug-damaged axons may in itself reflect the need of the neuron—deprived of most of its axonal tree—to reestablish its original total axonal length by multiple branching.

Indoleamine-containing nerve terminals in the rat median eminence

SummaryElectron microscopical evidence for the existence of an important serotonergic input to the rat median eminence is presented. This evidence is based on the demonstration of degenerating nerve terminals in the external layer of the rat median eminence following the application of 5,6-dihydroxytryptamine or 5,7-dihydroxytryptamine, drugs known to exert more or less selective toxic effects on central serotonin neurons.The finding of a serotonergic innervation of the median eminence in mammals has important implications for 5-hydroxytryptamine as a modulator of synthesis and/or release of hypothalamic, hypophysiotropic hormones.

Adrenergic innervation of the umbilical vessels

SummaryThe intra- and extrafetal portions of the umbilical vessels in the guinea-pig and the umbilical cord of man, mouse and rabbit have been investigated by means of the Falck-Hillarp method for the fluorescence microscopical demonstration of catecholamines.The umbilical cord was found to be devoid of nerves in all species investigated. Adrenergic nerves are present only in the immediate vicinity of the umbilicus.The intrafetal portions of the umbilical artery and umbilical vein receive adrenergic nerves, the distribution pattern of which is different for each vessel. In the guinea-pig the ductus venosus is an intrahepatic branch of the vena umbilicalis. No adrenergically innervated sphincter has been detected in the initial segment of the ductus venosus. Regional variations in the pattern of innervation of the intrafetal portion of the umbilical vein are paralleled by regional differences in the construction pattern of the vessels wall. Regional differences in the noradrenaline concentration (measured by fluorometry) which correspond to the fluorescence microscopical findings have been detected in umbilical vessels: low noradrenaline content of the umbilical cord, high concentrations in the intrafetal sections of the umbilical vessels. The noradrenaline concentration of the guinea-pig umbilical artery is three times that of the umbilical vein.

The Susceptibility of the Central Nervous System to Open Heart Surgery

The occurrence of transient or persistent neurological deficits in the perioperative course of open-heart surgery is one of the potentially most serious complications limiting a favorable outcome for cardiac patients. While permanent brain damage is only rarely encountered in this setting, several studies indicate that intermittent neurological abnormalities in the postoperative period are a much more common feature unique to cardio-surgical procedures [1, 2, 3]. Such syndromes of impaired cerebral function until now could not be correlated with a particular type of cardiac surgery, the obvious presence of metabolic disturbances, or the type of anesthesia used [4]. The absence of such an ostensible relationship is further evidenced by the fact that we do not observe similar neurological abnormalities after other surgical procedures [5].