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H Schuppe

Publications and source records attributed to H Schuppe.

6 recordsLinked to original sources
PubMed2001

NADPH-diaphorase histochemistry in the terminal abdominal ganglion of the crayfish.

Nitric oxide (NO) has an important modulatory role on the processing of sensory signals in vertebrates and invertebrates. In this investigation we studied the potential sources of NO in the terminal abdominal ganglion of the crayfish, Pacifastacus leniusculus, using NADPH-diaphorase (NADPHd) histochemistry, with NADPHd acting as a marker for NO synthase (NOS). In the terminal ganglion a mean of 27 strongly labelled NADPHd-positive cell bodies were found, and of these 80% [of stained cell bodies] [corrected] occurred in three regions located in antero-lateral, central and posterior parts of the ganglion. Ventral and antero-ventral commissures as well as specific dorsal and ventral areas of the dendritic neuropil showed positive staining. Intense labelling was seen in the ventro-medial tract, and in the connective between the terminal ganglion and the 5th abdominal ganglion. In addition, some motor neurones and neurones with branches in the sensory commissures were NADPHd positive. Our finding that NADPHd-positive cells occur in consistent patterns in the terminal abdominal ganglion implies that NO may have a role in mechanosensory processing in the crayfish.

Animals↗
PubMed2001

Distribution of NADPH-diaphorase-positive ascending interneurones in the crayfish terminal abdominal ganglion.

Previous neuropharmacological studies have described the presence of a nitric oxide-cGMP signalling pathway in the crayfish abdominal nervous system. In this study we have analysed the distribution of putative nitric oxide synthase (NOS)-containing ascending interneurones in the crayfish terminal abdominal ganglion using NADPH-diaphorase (NADPHd) histochemistry. Ascending intersegmental interneurones were stained intracellularly using the fluorescent dye Lucifer yellow and the ganglia containing the stained interneurones subsequently processed for NADPHd activity. Fluorescence persisted throughout histochemical processing. These double-labelling experiments showed that 12 of 18 identified ascending interneurones were NADPHd positive. Thus many ascending interneurones that process mechanosensory signals in the terminal ganglion may contain NOS, and are themselves likely sources of NO which is known to modulate their synaptic inputs. Three clear relationships emerged from our analysis between the effects of NO on the synaptic inputs of interneurones, their output properties and their staining for NADPH-diaphorase. First were class 1 interneurones with no local outputs in the terminal ganglion, the NE type interneurones, which had sensory inputs that were enhanced by NO and were NADPHd positive. Second were class 1 interneurones with local and intersegmental output effects that had sensory inputs that were also enhanced by NO but were NADPHd negative. Third were class 2 interneurones with local and intersegmental outputs that had synaptic inputs that were depressed by the action of NO but were NADPHd positive. These results suggest that NO could selectively enhance specific synaptic connections and sensory processing pathways in local circuits.

Abdomen↗
PubMed1998

Arousal shifts in quiescent locusts

Locusts are usually quiescent at night, but this state can be interrupted by spontaneous periods of motor activity, or arousals, that can also be induced by exposure to light stimuli. To investigate whether repeated arousing stimulation has any lasting effect on behaviour, locusts were confronted at night with a series of 1 s light stimuli. Groups of three stimuli at intervals of 60 s were repeated 11 times at 10 min intervals during the first experimental night, and three stimuli at intervals of 90 s were repeated at 15 min intervals during the next night. Arousals and the effects of stimulation were monitored as changes in the spike activity of muscles in the basal part (the scapus) of the right antenna. In the early part of the night preceding the presentation of the light stimuli, neither 60 s nor 90 s periods were present as significant peaks in spontaneous changes in spike activity. The initial stimulus of a series evoked an arousal response that habituated on repetition of the stimulus. The end of the series of stimuli was followed by changes in spike activity that tended to have the same periodicity as the preceding stimuli. Furthermore, a single light stimulus at the end of the night evoked changes in spike activity that again tended to have the same periodicity as the preceding entraining stimuli. Repeated stimulation may therefore establish a memory trace for the period of stimulation that can be recalled either spontaneously or by the application of an appropriate external stimulus.

Journal Article↗
PubMed1995

[Rhythmic brain activity in sleeping bees].

In honeybees, which are in a sleep-like state of rest the neuronal activity can be recorded in brain regions where memory traces are stored including the mushroom bodies. During nocturnal resting periods short episodes occurred during which the overall spike activity was markedly increased. In addition, ongoing rhythmic variations of spike rate could be recorded. The variations covered 2 frequency bands within the range of 0.4 Hz to 1.2 Hz. Periodical variations of spike rate were present when no visible antennal movements occurred and also when accompanied by spontaneous antennal twitches or during swaying movement of the antennae. Swaying movements took place at the end of short antennal movement episodes with a frequency that corresponded to the periodical variations in spike rate. Thus, there may be a relation between episodes of antennal movements and rhythmic spike activity recorded in the mushroom bodies during episodes of antennal immobility.

Animals↗
PubMed1986

Modulation of LH-secretion in ovariectomized ewes by constant infusions of oestradiol and 4-hydroxyoestradiol: effects of varying infusion times and of high oestrogen doses.

Ovariectomized ewes were infused for different times (2-24 h) during the breeding season (September to February) with oestradiol (E2, 2 micrograms/h) or the catecholoestrogen 4-hydroxyoestradiol (4-OHE2, 10 micrograms/h). At these infusion rates comparable plasma levels of E2 and 4-OHE2 were obtained when steady state was reached after 3 h (E2: 20 +/- 4 pg/ml; 4-OHE2: 22 +/- 3 pg/ml). When E2 was infused for at least 6 h, all animals had significant LH-surges, starting 14-16 h after the beginning of oestrogen treatment, even when E2 was infused for up to 24 h. 4-OHE2, however, had only to be infused for 4 h to induce significant LH-surges in all animals tested. When E2 was infused for 12 h at a rate of 100 micrograms/h, the LH-surges in these ewes were significantly lower than the LH-surges in the same animals treated for 12 h with E2 at a rate of 2 micrograms/h. These data indicate: Once E2 has been administered at a specific infusion rate for a critical time period of 6 h, LH-surges occur, no matter whether the E2-infusion is continued or stopped. For the catecholoestrogen 4-OHE2 this critical time period amounts only to 4 h, if comparable plasma levels of either oestrogen are achieved. This might hint at a prolonged intracellular action of 4-OHE2 as compared to E2. At extremely high infusion rates of E2 (100 micrograms/h for 12 h) the positive oestrogen effect is significantly impaired, a finding supporting the concept of a bell-shaped dose-response relationship between oestrogens and their positive effect on LH-secretion.

Animals↗