Ulrike Hanesch

Neuronal architecture of the central complex in Drosophila melanogaster

SummaryOn the basis of 1200 Golgi-impregnated brains the structure of the central complex of Drosophila melanogaster was analyzed at the cellular level. The four substructures of the central complex — the ellipsoid body, the fanshaped body, the noduli, and the protocerebral bridge — are composed of (a) columnar small-field elements linking different substructures or regions in the same substructure and (b) tangential large-field neurons forming strata perpendicular to the columns. At least some small-field neurons belong to isomorphic sets, which follow various regular projection patterns. Assuming that the blebs of a neuron are presynaptic and the spines are postsynaptic, the Golgi preparations indicate that small-field neurons projecting to the ventral bodies (accessory area) are the main output from the central complex and that its main input is through the large-field neurons. These in turn are presumed to receive input in various neuropils of the brain including the ventral bodies. Transmitters can be attributed immunocytochemically to some neuron types. For example, GABA is confined to the R1–R4 neurons of the ellipsoid body, whereas these cells are devoid of choline acetyltransferase-like immunore-activity. It is proposed that the central complex is an elaboration of the interhemispheric commissure serving the fast exchange of data between the two brain hemispheres in the control of behavioral activity.

Innervation of the dura mater encephali of cat and rat: ultrastructure and calcitonin gene-related peptide-like and substance P-like immunoreactivity

Ultrastructural, immunocytochemical, and immunoelectron microscopical examinations are reported that describe the morphology of putative sensory nerve endings in the dura mater encephali of the rat and the cat. Morphometrical measurements and reconstructions showed that in the cat the mean diameter of axons, the bare area of axolemma, and the content of mitochondria and vesicles are highly variable in dural nerve endings. Nerve fibers with a high volume density of mitochondria are thought to be sensory, while nerve fibers containing many small vesicles are considered autonomic. There is, however, a broad overlap of mitochondria-rich and vesicle-rich nerve fibers in the dura, so that discrimination between sensory and autonomic endings by these characteristics frequently fails. Whole-mount preparations treated cytochemically for detection of substance P- and calcitonin gene-related peptide-like immunoreactivity in the rat and the cat showed a network of immunopositive nerve fibers in the vicinity of dural blood vessels. Most of these peptidergic and probably sensory nerve fibers were found terminating in the dural connective tissue far from vessels. Calcitonin gene-related peptide-positive nerve fibers were much more abundant than substance P-positive fibers. Immunoelectron microscopic preparations revealed that calcitonin gene-related peptide- and substance P-like immunoreactivity is found in a small proportion of generally thin unmyelinated nerve fibers. These proportions were very similar in the rat and the cat. Summarizing the recent literature, the morphological characteristics of putative sensory nerve fibers in the dura mater are discussed in relation to their possible functional significance for neurogenic inflammation and nociception.

No-Bridge of Drosophila Melanogaster: Portrait of a Structural Brain Mutant of the Central Complex

The mutant no-bridge (nobKS49) has its name from a structural defect in the protocerebral bridge of the central complex. This rod-shaped neuropil in nobKS49 has a large gap at the sagittal midplane, with some of the missing material accumulated more laterally. Mutant nob flies have a reduced maximal and average walking speed. Leg coordination is disturbed during turning but not while walking straight. Motivation for walking is low and steps are small due to slow forward swinging of the legs. Flies spontaneously may pass into an autistic (and possibly spastic) state in which they can move their legs and even perform cleaning movements but do not walk or fly. They spontaneously recover if left undisturbed. Gynandromorph experiments place the focus of the walking defects into the head. Mutant flies have a reduced tendency to escape when mechanically stimulated. In a brightly lit arena they do not avoid a black square above the horizon and they are negatively phototactic. In tethered flight optomotor responses are normal but the amplitude of spontaneous torque modulations as well as the number of torque spikes are reduced. If a single black bar is slowly rotated around the fly, the normal response pattern is observed. It vanishes, however, at moderately fast angular velocity at which the wild type still is fully responsible. The behavioral defects support the notion that the protocerebral bridge is part of a higher center for the regulation of behavior.

Localization of SP- and CGRP-immunopositive nerve fibers in the hip joint of patients with painful osteoarthritis and of patients with painless failed total hip arthroplasties

Using immunohistochemical methods we determined the presence of SP‐ and CGRP‐immunopositive nerve fibers in the hip joint of patients with femoral neck fracture (controls, group 1), painful osteoarthritis (group 2), and painless failed total hip arthroplasties (group 3). Immunoreactive nerve fibers were found in the soft tissue of the fossa acetabuli as well as in the subintimal part of the synovial layer in the hip joint capsule of groups 1 and 2. In the capsule of controls the innervation density had a median of 5.7 fibers/cm2 for CGRP‐ir and 3.2 fibers/cm2 for SP‐ir afferents. In the osteoarthritic group, the density significantly increased to a median of 15.6 fibers/cm2 for CGRP‐ir and 8.2 fibers/cm2 for SP‐ir neurons (p = 0.05). Patients with failed hip arthroplasties completely lacked these neuropeptide containing afferents. Innervation density in the fossa acetabuli of osteoarthritc patients showed a median of 14.1 fibers/cm2 for CGRP‐ir and 5.9 fibers/cm2 for SP‐ir afferents. From these data we assume that the hip joint capsule and the soft tissue of the fossa acetabuli are important triggers of nociception. This is supported by the fact, that patients with loosened total hip arthroplasties, where we failed to detect SP‐ and CGRP‐immunoreactive fibers, did not feel pain.

Substance P- and calcitonin gene-related peptide immunoreactivity in primary afferent neurons of the cat's knee joint.

The distribution of substance P and calcitonin gene-related peptide was determined in primary afferent neurons of the medial and posterior articular nerve of the cats knee joint. Perikarya of articular afferents were visualized by retrograde labelling with the fluorescent dye Fast Blue which was applied at the transected end of the peripheral nerves. Substance P was found in about 17% of labelled medial articular afferents and in about 16% of labelled posterior articular afferents, respectively, whereas calcitonin gene-related peptide was present in about 35 and 32% of the medial and posterior articular nerve cells, respectively. Taking into account that these neuropeptides are known to be co-localized, probably not more than one-third of the joint afferents contain substance P and/or calcitonin gene-related peptide. Quantification of cell diameters revealed that substance P was found only in small- or intermediate-sized perikarya (less than 50 microns) indicating that this peptide is predominantly found in unmyelinated neurons. Calcitonin gene-related peptide was present mainly in small- and intermediate- but also in some large-sized neurons (greater than 50 microns) providing evidence that this peptide is found in unmyelinated and to a lesser extent in myelinated neurons. This is consistent with previous studies that show that substance P and calcitonin gene-related peptide are present primarily in unmyelinated and thinly myelinated primary afferents. When the portion of substance P-positive neurons of the medial articular nerve is compared to the number of articular afferents displaying a nociceptive function as determined in earlier electrophysiological studies, it can be calculated that at most 30% of the nociceptive-specific articular afferents contain this neuropeptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and chronic phases of unilateral inflammation in rat's ankle are associated with an increase in the proportion of calcitonin gene-related peptide-immunoreactive dorsal root ganglion cells

Using immunocytochemical methods, the proportion of calcitonin gene‐related peptide immunoreactive perikarya was determined in dorsal root ganglia L4–L6 in four control rats and in ten rats with a unilateral inflammation in the ankle region of the left hindlimb. The inflammation was induced by subdermal injection of Freunds complete adjuvant at the ankle. Swelling and cellular infiltration of the ankle region developed within 2 days, and were stable and restricted to the injected ankle for the duration of the 3‐week study. In control rats ∼24% of 20 419 perikarya showed calcitonin gene‐related peptide (CGRP)‐like immunoreactivity. In rats with unilateral inflammation the proportion of CGRP‐positive neurons was increased on the inflamed side to ∼32% of 11 454 cells at day 2 (P < 0.001 with respect to ganglia in normal rats) and ∼29% of 10 739 perikarya at day 20 post inoculation (P < 0.01). By contrast, no significant changes were found between ganglia in the non‐injected side (∼25% at day 2 and ∼24% at day 20). These results demonstrate that peripheral inflammation is associated with an increase in the proportion of neurons in the dorsal root ganglia that synthetize CGRP. This up‐regulation is already present at an early stage of inflammation but also at later stages, suggesting that the increased synthesis of CGRP is an important neurobiological reaction associated with the acute and chronic phases of inflammation.

Peripheral modulation of rat knee joint afferent mechanosensitivity by nociceptin/orphanin FQ.

The peripheral effects of nociceptin were examined in normal and acutely inflamed rat knee joints by analyzing single unit recordings from articular primary afferents in response to normal and extreme rotation of the knee. Bolus close intraarterial injection of nociceptin (0.01, 1 and 100 microM) caused a sensitization of normal and inflamed knee joint afferents in response to movements in the normal working range of the joint. When the joint was hyper-rotated, nociceptin had no significant effect on afferent discharge rate in normal knees, however, in inflamed joints the top dose of the neuropeptide caused a decrease in articular mechanosensitivity. These findings suggest that nociceptin seems to be involved in the control of peripheral nociceptive mechanisms, although the behaviour of the peptide is dependent upon the inflammatory status of the tissue.

Gabapentin reduces the mechanosensitivity of fine afferent nerve fibres in normal and inflamed rat knee joints

&NA; The antiepileptic drug gabapentin has been shown to have an antihyperalgesic effect following central administration. This electrophysiological investigation examined whether peripherally administered gabapentin could modulate the mechanosensitivity of primary afferents innervating normal and kaolin/carrageenan inflamed rat knee joints. Close intraarterial injection of gabapentin (0.01, 1 and 100 mg/kg) dose‐dependently reduced afferent firing rate in both normal and acutely inflamed rat knees in response to normal and hyper‐rotation of the joint. Thus, in addition to its central mode of action, peripheral administration of gabapentin reduces nociception locally and this may prove to be beneficial in the treatment of various pain syndromes including inflammatory arthritis.

Release of endogenous histamine in the hypothalamus of anaesthetized cats and conscious, freely moving rabbits

SummaryThe hypothalamus of anaesthetized cats and conscious, freely moving rabbits was superfused with CSF through double-walled, push-pull cannulae and the release of endogenous histamine was determined in the superfusates by a radioenzymatic assay.In the posterior hypothalamic area of the anaesthetized cat, the rate of release of endogenous histamine varied rhythmically; phases of high rate of release appeared at 60 min cycles. The release of histamine was increased by electrical stimulation of the superfused area, as well as by hypothalamic superfusion with potassium-rich CSF.In the conscious rabbit, the anterior hypothalamic area and the posterior hypothalamic nucleus were superfused simultaneously. In both regions, the resting release of histamine varied rhythmically at approximately 70 min cycles. Phases of high or low-rate of release in the anterior hypothalamic area coincided with the corresponding phases in the posterior hypothalamic nucleus.The rhythmic release of endogenous histamine in the hypothalamus, as well as the ability of depolarizing stimuli to enhance the release of the amine support the idea that histamine acts as a neurotransmitter in the central nervous system.

The effect of a unilateral inflammation at the rat´s ankle joint on the expression of preprotachykinin-A mRNA and preprosomatostatin mRNA in dorsal root ganglion cells - a study using non-radioactive in situ hybridization.

In rats with an acute (2 days) and chronic (20 days) unilateral ankle joint inflammation (induced by Freunds complete adjuvant), the proportion of dorsal root ganglion cells containing preprotachykinin-A mRNA or preprosomatostatin mRNA was determined using non-radioactive in situ hybridization. At the acute stage of inflammation, the proportion of neurons containing preprotachykinin-A mRNA was similar to that in control rats. At the chronic stage, the proportion of neurons expressing preprotachykinin-A mRNA was significantly higher on the inflamed side than on the contralateral side. The proportion of dorsal root ganglion cells containing preprosomatostatin mRNA did not change. These data suggest that inflammation influences the synthesis of substance P but not of somatostatin in afferent neurons.