Corpora Pedunculata Research Articles

Histochemical localization of catecholamines in the brain of normal and drug-treated cockroaches

The localization of catecholamines has been studied in the brain of the cockroach Periplaneta americana by means of a fluorescence histochemical method. The yellow-green fluorescence reaction specific for catecholamines has been found in several cell groups (which have been defined with letters from A-M) and in the neuropile, where it follows a characteristic pattern. As regards the corpora pedunculata, no specific fluorescence has been found in the calyx cells, in the calyces, or in the stem; but the α- and β-lobes have been found to be markedly fluorescent, with transverse striations of stronger fluorescence. Treatment with reserpine, when prolonged for several days, was followed by complete disappearance of the specific fluorescence of the neuropile and of the cells, with the exception of groups A and B. Treatment with nialamide and DOPA was followed by a moderate increase in fluorescence.

Cholinergische Synapsen im Oberschlundganglion der Waldameise (Formica lugubris Zett.)

The corpora pedunculata of the wood ant (Formica lugubris Zett.) consist of two sharply defined layers: The perikaryon layer and the subjacent neuropil. Synaptic endings are found exclusively in the neuropil. The synapses consist of a central, presynaptic end knob of 1.2–2.5 μ diameter and a relatively large number of surrounding postsynaptic processes of 0.3–1.1μ diameter. These junctions are analogous to axodendritic synapses of the vertebrates. The presynaptic process contains mitochondria and a multitude of light vesicles (300–600 A diameter). Larger vesicles 700–1000 A with a dark center are seen more rarely. The synaptic cleft has a diameter of approximately 130 A and varies somewhat with different fixation methods. With glutaraldehyde-osmium fixation, this relatively wide gap is maintained only in circumscribed areas of the junction, while in adjacent areas it tends to contract and an “external compound membrane” is formed. The postsynaptic region is characterized by the presence of a subsynaptic network which is revealed only by suitable fixation methods. This and the persistent synaptic cleft are the main structural differentiations found in junctional areas thus far.

Multimodal Interneurones of Locust Optic Lobe

THE auditory interneurones which ascend the ventral cord of the migratory locust have been traced forward only as far as the neck connectives1,2. Fibres which give a similar response can occasionally be found in the lateral parts of the protocerebrum or in the optic lobes by probing with indium-filled platinum-plated microelectrodes. They have not been found, although sought, in the corpora pedunculata. However, by probing in the optic lobe, higher-order neurones which give a different set of responses to auditory stimuli are commonly encountered. These also respond to vibration or touch stimuli of all kinds, to a wide range of visual stimuli via either compound eye, but only to high-intensity stimulation of the ocelli. The most easily found example is in the outer layers of the medulla in the optic lobe. Typically they consist of units which are presumably large because they give large spikes, with a background spike discharge ranging from 1 impulse per 10 sec to 10 per sec. Sensitivities to all modalities are low, compared with other units which respond typically to only one of the modalities. No evidence of association between inputs has been found, although sought. When the stimulus is repeated regularly at intervals of up to 10 sec, the response almost always declines in number of impulses, occasionally down to no response with irregular return of the response to some of the stimuli. The upper limit of repetition frequency varies greatly between units, or between what appear to be the corresponding units in different animals. Also, the rate of decline of the response varies greatly as between units for a standard frequency of stimulus repetition. Responses to different modalities adapt at different rates. Adaptation to a stimulus of one modality does not usually influence the response to a different modality of stimulus newly introduced, demonstrating an independence of inputs, and separate adaptation to each.

The anatomy of the nervous system in the genus Gerris (Hemiptera-Heteroptera)

The most successful methods used in this study were Palmgren’s silver-on-the-slide technique, the rapid silver nitrate method of Golgi, and a method that has seldom been applied to insect material, the Golgi-Cox mercuric chloride method. A way of preparing sections of adult hardened insects by infiltrating with wax prior to softening with chlorinated acetic acid and nitric acid was also employed. The nervous system of Gerris shows a high degree of condensation in that all the segmental neuromeres are fused. This characteristic of the nervous system may be associated with the disposition of the one hundred and twenty-two pairs of muscles. The nerves of the head are specialized in association with the complex mouthparts. There are distinct stylet and labral ganglia, and peripheral interconnexions between some of the nerves. The posterior labral nerve was traced to the principal salivary gland. The reticulum described by Baptist (1941) as of a nervous nature was shown to consist of fine muscle fibres: the much finer nerve fibres were also stained in silver preparations. The many separate nerves of the prothorax reflect the unspecialized nature of this segment as compared with the meso- and metathorax in which most of the fibres are gathered into a few nerve trunks. The coalesced neuromeres of the abdominal region give rise to a pair of posterior nerve trunks connected with small ganglia or lateral bodies lying near the spiracles. These ganglia appear similar to the structures described by Landois & Thelen (1867), as controlling spiracular movements in Cossus . Rough estimates of the number of cells in different parts of the nervous system were correlated with the percentage success of staining methods, and specialization of the neuromeres. The form and arrangement of neurones within the optic and protocerebral centres of Gerris conforms for the most part to the patterns worked out in other insects, though there do not seem to be as many different types of internuncial neurone in the optic lobes of Gerris as exist in Apis or Calliphora (Cajal & Sanchez 1915). The corpora pedunculata are connected through a dorsal glomerulus with the deutocerebrum, the glomerulus having the form of a loose meshwork of fine fibres rather than of a distinct calyx. The deutocerebrum is indistinctly divided into anterior and posterior glomeruli, as described in Apis by Sanchez (1936). The form and size of the elements composing the somewhat enigmatic posterior glomerulus in Gerris supports the view that this is a motor centre. The close association between the maxillary and mandibular nerves is to some extent reflected in the internal organization of these neuromeres. Separate ventral areas could be distinguished, but ganglionic boundaries were indistinct. The large labral centre shows many of the features of a trunk ganglion. The pattern of neurones in the thoracic and abdominal centres could be compared in detail with the pattern described by Zawarzin (1924) in the larva of Aeschna . There are three unusually large internuncials with processes in this region, and cell bodies in the protocerebrum and suboesophageal centres. It is suggested that they form part of a dual physiological system controlling the motor centres of the thorax (Roeder 1953). The mesothoracic centre was made a special object of study as representative of the thoracic neuromeres. The fibre tracts are clearly marked and can be seen to correspond to functional regions within the centre. The alary nervous system of the mesothorax was investigated in some detail in both winged and wingless forms of Gerris . In the flying forms dorsal and ventral tracts can be distinguished, associated with motor and sensory regions of the mesothoracic neuropile respectively. In forms without wing muscles or fully developed wings the dorsal tract is absent or vestigial and the ventral tract is clearly reduced. The abdominal neuromeres are very closely compacted so that they tend to lose their identity. The ventral longitudinal tracts are unusually well developed and this may be correlated with the importance of the sensory areas.