THE CHARACTERIZATION OF HISTIDINE DECARBOXYLASE AND ITS DISTRIBUTION IN NERVES, GANGLIA AND IN SINGLE NEURONAL CELL BODIES FROM THE CNS OF APLYSIA CALIFORNICA

Histamine (HA) is present in substantial quantities in all ganglia of Aplysia californica. Within the cerebral ganglia this amine is known to be concentrated in at least two identified neurons designated C-2 neurons. In this study a combination of chemical and enzymatic analyses was employed to provide evidence for the existence of a biochemical pathway for HA synthesis in ganglia and individual neurons of this marine mollusk. Examination of extracts of individual neurons dissected from ganglia organ-cultured in the presence of [³H]histidine showed that every neuron accumulated labelled histidine, but only the HA-containing C-2 neurons synthesized and stored labelled HA suggesting that the formation of HA in Aplysia could be catalyzed by the enzyme histidine decarboxylase (HDC). HDC activity was studied with a new microradiometric assay. Many of the properties of the molluscan HDC studied were found to correspond to the vertebrate enzyme. Enzyme activity was inhibited by α-hydrazino-histidine but unaffected by concentrations of α-methyldopa or by 5-(3,4-dihydroxycinnamoyl) salicylic acid which produced nearly complete inhibition of aromatic amino acid decarboxylase activity. HDC was measurable in nervous but not other Aplysia tissues assayed. All 5 major ganglia contained HDC activity which spanned a 15-fold range between the least and most active ganglia. Only 4 of the 13 nerve trunks assayed yielded measurable enzymic activity; these active nerves were associated with the cerebral ganglia which has the highest HDC activity of all measured ganglia. Of the numerous individual neurons assayed for HDC, only the C-2 cells showed measurable enzyme activity, about 25 pmol/cell/h or 70 μmol/g protein/h. Since the activity of HDC in the HA-containing neurons was at least three orders of magnitude larger than all other neurons assayed in the cerebral and other ganglia, these data appear to provide a direct metabolic basis for the selective presence of HA in these cells, and they indicate that the cellular presence of HDC provides a useful biochemical marker for the location of HA-rich neurons in Aplysia.     

METABOLISM OF PUTATIVE TRANSMITTERS IN INDIVIDUAL NEURONS OF APLYSIA CALIFORNICA

The activities of acetylcholinesterase (acetylcholine acetyl-hydrolase; EC 3.1.1.7) and catechol-O-methyl transferase (S-adenosylmethionine: catechol-O-methyl transferase; EC 2.1.1 .a) were measured in the various ganglia of the nervous system of Aplysia californica and in some of the individually identifiable neurons in these ganglia. All of the neurons studied had measurable levels of activity for both enzymes. Since different individual neurons exhibited approximately the same level of activity we concluded that neither of these enzymes could be used to classify neurons as ‘cholinergic’ vs. ‘aminergic’ or ‘cholinoceptive’ vs. ‘aminoceptive'. The ubiquitous distribution of either or both of these enzymes in different single neurons may be related to glial contamination.     

Modulation of glial glycogen metabolism by 5-hydroxytryptamine in leech segmental ganglia

Leech segmental ganglia (16 out of 23 per animal) were divided into experimental and control groups (4 ganglia per group). The amounts of glycogen in the ganglia were assayed by a specific extraction procedure and fluorimetry, or by liquid scintillation counting following labelling of the glycogen by [³H]glucose. Within any individual animal the amounts of glycogen in the ganglia were relatively constant (max. variation 16%). 5-HT (10⁻⁶–10⁻⁴ M) reduced in a dose-dependent manner the endogenous glycogen (max. 20% reduction), and the [³H]glycogen (max. 60% reduction). The glycogenolytic effect was studied by light-microscope autoradiography in serial sections of segmental ganglia previously exposed to [³H]glucose. The 5-HT-mediated glycogenolysis was localized principally in the glial cells surrounding the neuron perikarya. 5-HT, in addition to its conventional transmitter role, may regulate the supply of energy substrate from glial cells to neurons within domains defined by the projections of the neurons from which it is released.     

CHOLINE ACETYLTRANSFERASE, ACETYLCHOLINESTERASE AND AROMATIC l-AMINO ACID DECARBOXYLASE IN SINGLE IDENTIFIED NERVE CELL BODIES FROM SNAIL HELIX ASPERSA

—The distribution of choline acetyltransferase, aromatic l -amino acid decarboxylase and acetylcholinesterase in the nervous system of Helix aspersa has been studied using homogenates of whole ganglia, microdissection from freeze-dried sections and dissection of single neurons from fresh tissue. Choline acetyltransferase was found in both the cell body and neuropil layers of all the Helix ganglia. The enzyme was not specifically localized to any ganglion or region of ganglion. Between 10 and 30 per cent of the isolated single cell bodies contained the enzyme. The enzymic activity corresponded to 50–200 mmol ACh/1 cell bodies/h. Choline acetyltransferase is probably a specific marker for cholinergic cells in this species. Aromatic l -amino acid decarboxylase was more selectivity localized and its distribution corresponded well with that of monoamine containing cells as visualized by the fluorescence histochemical technique. A large proportion of cell bodies were localized in the boundary between the visceral and right parietal ganglia and in the pedal ganglion. The other ganglia contained few such cells. The activity of aromatic l -amino acid decarboxylase corresponded 10–50 mmol dopamine/1 cell bodies/h. A method was developed to measure the enzyme activity towards 5-hydroxytryptophan and DOPA in single cells simultaneously. The ratio between the activity towards both substrates did not vary significantly for the different cells. The enzyme is probably a specific marker for monoamine cells, but cannot be used to differentiate between the different monoamine cells. Acetylcholinesterase was uniformly distributed in the ganglia and was probably present in all nerve cells.     

Neuronal localization of dopamine and 5-Hydroxytryptamine in some mollusca

Summary The localization of biogenic monoamines in ganglionic tissues from Anodonta piscinalis, Helix pomatia, and Buccinum undatum has been studied by means of the histochemical fluorescence method of Falck and Hillarp.In cerebral, visceral, and pedal ganglia (besides nonfluorescent nerve cells) neurons emitting a green or yellow fluorescence were found. No other cell systems exhibiting a specific fluorescence were observed. An abundance of monoaminergic terminals were found in the central parts of these ganglia. Spectrophotofluorimetric determinations showed that there are large quantities of dopamine and 5-hydroxytryptamine in the tissues investigated. The amounts of dopamine and 5-hydroxytryptamine agree well with the distribution of green and yellow fluorescence, respectively, in the ganglia.There are many similarities between the vertebrate and the molluscan monoaminergic neurons. The morphology of the neurons is the same, the intraneuronal distribution of the monoamines is identical, depletion experiments with reserpine and denervation experiments give the same results, and the synaptic arrangement of monoaminergic fibres on non-adrenergic neurons has the same appearance. Apparently, however, dopamine and 5-hydroxytryptamine are the only monoamines acting as neuronal transmitters in the species investigated.The research reported in this document has been sponsored by the Air Force Office of Scientific Research under Grant AF EOAR 64-5 through the European Office of Aerospace Research (OAR), United States Air Force and by the Swedish Natural Science Research Council.     

5-Hydroxytryptamine Measurements in Molluscan Ganglia and Neurons Using a Modified Radioenzymatic Assay

A radioenzymatic procedure for the determination of sub-picomole amounts of 5-hydroxytryptamine (5-HT) is described. It is a modification of the method originally described by Saavedra et al. (1973), in which 5-HT was measured as the radiolabelled product [3H]5-methoxy-N- acetyltryptamine , after incubation with [3H]S-adenosylmethionine, acetyl-CoA, and the enzymes hydroxyindole-O-methyltransferase (EC 2.1.1.4) and N-acetyltransferase (EC 2.3.1.5). Ganglia from various gastropod molluscs (Aplysia californica, Tritonia diomedia , Lymnaea stagnalis, and Helisoma trivolvis ), as well as individual neuronal somata isolated from these ganglia, were assayed for 5-HT. Among the homologous giant cerebral cells in these animals, the 5-HT concentrations were similar. Statistical analysis of the 5-HT values in paired 5-HT-containing neurons demonstrated that the variability was considerably greater in samples obtained from different animals than in those obtained from the same animal. This suggests that experiments aimed at manipulating amine levels in individual neurons may benefit by using a paired-cell paradigm. The effects of incubating Aplysia ganglia with 5-HT or with the 5-HT precursors tryptophan and 5-hydroxytryptophan (5-HTP) were studied. High concentrations of 5-HTP and 5-HT (100 microM) increased the levels of 5-HT in ganglia, but only incubation in high concentrations of 5-HTP resulted in an increase of 5-HT in the isolated somata of 5-HT-containing neurons C1 and P5.     

Influence of the pteropod mollusk pedal ganglia locomoter system on anatomically isolated neurons

It was established during experiments on pedal ganglia generating locomotor rhythm isolated fromClione limacina, a pteropod mollusk, that this rhythm was irregular in 30% of preparations; i.e., the locomotor generator worked in bursts which alternated with periods of regular activity. Locomotor bursts were produced by excitation in command neurons located within the pedal ganglia. Single neurons were extracted from the ganglia in these preparations generating locomotor bursts by means of an intracellular microelectrode; their somata were then placed in their original sites amongst the ganglia cells. A total of 35 neurons were isolated showing changed activity during bursts. Nine of these cells renewed their erratic activity (linked to locomotor bursts) following reinsertion into the ganglion. Neurons which had initially shown an excitatory pattern during bursts continued to be excited; the same was true for inhibitory types. These observations indicate that the command neurons governing generator operation can act on target cells when morphological contact with them has been suppressed.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow; M. V. Lomonosov State University. Moscow. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 756–763, November–December, 1986.     

A distinctly regulated protein repair L-isoaspartylmethyltransferase from Arabidopsis thaliana

Protein-L-isoaspartate (D-aspartate) O-methyltransferases (EC 2.1.1.77) that catalyze the transfer of methyl groups from S-adenosylmethionine to abnormal L-isoaspartyl and D-aspartyl residues in a variety of peptides and proteins are widely distributed in procaryotes and eucaryotes. These enzymes participate in the repair of spontaneous protein damage by facilitating the conversion of L-isoaspartyl and D-aspartyl residues to normal L-aspartyl residues. In this work, we have identified an L-isoaspartyl methyltransferase activity in Arabidopsis thaliana, a dicotyledonous plant of the mustard family. The highest levels of activity were detected in seeds. Using degenerate oligonucleotides corresponding to two highly conserved amino acid regions shared among the Escherichia coli, wheat, and human enzymes, we isolated and sequenced a full-length genomic clone encoding the A. thaliana methyltransferase. Several methyltransferase cDNAs were also characterized, including ones that would encode full-length polypeptides of 230 amino acid residues. Messenger RNAs for the A. thaliana enzyme were found in a variety of tissues that did not contain significant amounts of active enzyme suggesting the possibility of translational or posttranslational controls on methyltransferase levels. We have identified a putative abscisic acid-response element (ABRE) in the 5-untranslated region of the A. thaliana L-isoaspartyl methyltransferase gene and have shown that the expression of the mRNA is responsive to exogenous abscisic acid (ABA), but not to the environmental stresses of salt or drought. The expression of the A. thaliana enzyme appears to be regulated in a distinct fashion from that seen in wheat or in animal tissues.     

Enzyme levels in cultured astrocytes,oligodendrocytes and Schwann cells,and neurons from the cerebral cortex and superior cervical ganglia of the rat

Data are presented for 16 enzymes from 8 metabolic systems in cell cultures consisting of approximately 95% astrocytes and 5% oligodendrocytes. Nine of these enzymes were also measured in cultures of oligodendrocytes, Schwann cells, and neurons prepared from both cerebral cortex and superior cervical ganglia. Activities, in mature astrocyte cultures, expressed as percentage of their activity in brain, ranged from 9% for glycerol-3-phosphate dehydrogenase to over 300% for glucose-6-phosphate dehydrogenase. Creatine phosphokinase activity in astrocytes was about the same as in brain, half as high in oligodendrocytes, but 7% or less of the brain level in Schwann cells and superior cervical ganglion neurons and only 16% of brain in cortical neurons. Three enzymes which generate NADPH, the dehydrogenases for glucose-6-phosphate and 6-phosphogluconate, and the NADP-requiring isocitrate dehydrogenase, were present in astrocytes at levels at least twice that of brain. Oligodendrocytes had enzyme levels only 30% to 70% of those of astrocytes. Schwann cells had much higher lactate dehydrogenase and 6-phosphogluconate dehydrogenase activities than oligodendrocytes, but showed a remarkable similarity in enzyme pattern to those of cortical and superior cervical ganglion neurons.Special issue dedicated to Dr. Lewis Sokoloff.     

Projections of nitric oxide synthesizing neurons in the guinea-pig colon

The neuronal form of the enzyme nitric oxide synthase, which is an obligatory constituent of neurons that utilise nitric oxide as a transmitter, was revealed histochemically in this study by its ability to transfer a proton from reduced nicotinamide adenine dinucleotide phosphate to nitro-blue tetrazolium. In the guinea-pig colon, nitric oxide synthase was located in numerous irregularly-shaped myenteric neurons with single axons. In the submucosa, a small number of neurons had strong enzyme activity, whereas many were weakly stained. Nerve fibres were found in the longitudinal muscle, circular muscle, muscularis mucosae and ganglia of the two plexuses. No nerve fibres were found in the lamina propria of the mucosa. The same distribution of nerve cells and fibres was revealed using immunohistochemistry for nitric oxide synthase. Lesion studies showed that the axons of myenteric neurons all projected anally. Myenteric cells were the source of nerve fibres in the circular muscle and in more anally located myenteric ganglia. The sparse innervation of submucous ganglia was intrinsic to the submucous plexus. It is suggested that nitric oxide synthase is one of the transmitters of inhibitory neurons to the muscle and is also utilized by descending interneurons of the myenteric plexus.     

Pyridoxal phosphatase: cytochemical localization in GERL and other organelles of rat neurons.

A phosphatase, hydrolyzing pyridoxal-5-phosphate (P5P), a physiologically active component of the vitamin B6 complex and an essential co-enzyme in the synthesis of neurotransmitters, has been localized cytochemically in the perikarya of neurons in the peripheral, autonomic and central nervous systems of the rat. Neurons in dorsal root ganglia, sympathetic ganglia and ventral horn of spinal cord were studied by light and electron microscopy, while Purkinje cells, neurons in the dentate nucleus of the cerebellum, thalamus, and hypothalamus were studied by light microscopy only. Optimal conditions for demonstrating this activity in aldehyde-fixed tissue were determined with dorsal root ganglia. At the optimal pH of 5.0, neurons in these ganglia and in all other neurons studied show pyridoxal-5-phosphatase (P5Pase) activity in GERL. Small neurons in dorsal root ganglia also display enzyme activity in the endoplasmic reticulum (ER); activities in GERL and ER are also appreciably high at neutral pH. Small and large neurons in these ganglia, and neurons of sympathetic ganglia, show variable P5Pase activity in the Golgi apparatus. These localizations differ from the usual sites of both acid phosphatase and alkaline phosphatase activities. The P5Pase activity, demonstrated cytochemically, is a new acid hydrolase activity in GERL.     

NO-Dependent Regulation by Glutamate of Activity of the Serotoninergic System of the Edible Snail Helix lucorum

This work is a continuation of the study on transmitter regulation of the serotoninergic system activity in the brain of the edible snail Helix lucorum, in which serotonin and NO donors have been shown to excite serotoninergic neurons from various snail ganglia (more than 60 of them were studied) and synchronize their activity by activation of the synchronous synaptic inputs. In the current work, it has been shown that glutamate, on the contrary, has an inhibitory and desynchronizing action on the same serotonin-containing neurons by suppressing their own activity and switching off the synchronous synaptic inputs. In the same neurons, another glutamate receptor agonist, NMDA, has a pronounced excitatory effect and activates the synchronous synaptic inputs. The glutamate effects are NO-dependent: the NO donor sodium nitroprusside decreases, switches off entirely, or transforms the glutamate inhibitory effect into the excitatory one. A possible mechanism of interaction of serotonin, glutamate, and NO in regulation of the snail serotoninergic system activity is discussed.     

Superoxide anion is elevated in sympathetic neurons in DOCA-salt hypertension via activation of NADPH oxidase

Superoxide anion (O2-*) production is elevated in sympathetic ganglion neurons and in the vasculature of hypertensive animals; however, it is not known what enzymatic pathway(s) are responsible for O2-* production. To determine the pathway(s) of O2-* production in sympathetic neurons, we examined the presence of mRNA of NADPH oxidase subunits in sympathetic ganglionic neurons and differentiated PC-12 cells. The mRNAs for NADPH oxidase subunits p47phox, p22phox, gp91phox, and NOX1 were present in sympathetic neurons and PC-12 cells, whereas the NOX4 homologue was present in sympathetic neurons but not PC-12 cells. Freshly dissociated celiac ganglion neurons from normal rats and PC-12 cells produced O2-* when treated with the PKC activator PMA; O2-* production increased by 317% and 254%, respectively. The PMA-evoked increases were reduced by pretreatment with the NADPH oxidase inhibitor apocynin. These findings indicate that NADPH oxidase is the primary source of O2-* in sympathetic ganglion neurons. When celiac ganglia from hypertensive rats were incubated with apocynin, O2-* levels were reduced to the same levels as normotensive animals, indicating that NADPH oxidase activity accounted for the elevated O2-* levels in hypertensive animals. To test this latter finding, we compared NADPH oxidase activity in extracts of prevertebral sympathetic ganglia of DOCA-salt hypertensive rats and sham-operated rats. NADPH oxidase activities were 49.9% and 78.6% higher in sympathetic ganglia of DOCA rats compared with normotensive controls when using beta-NADH and beta-NADPH as substrates, respectively. Thus elevated O2-* levels in hypertension may be a result of the increased activity of NADPH oxidase in postganglionic sympathetic neurons.     

CHANGES OF ENZYME PATTERN IN THE SYMPATHETIC NERVOUS SYSTEM OF ADULT MICE AFTER SUBMAXILLARY GLAND REMOVAL; RESPONSE TO EXOGENOUS NERVE GROWTH FACTOR

—Removal of the submaxillary glands, the apparent site of NGF synthesis in adult mice, caused a decrease in the activity of all the enzymes involved in the biosynthesis of noradrenaline in the peripheral sympathetic nervous system. Thus, tyrosine hydroxylase (phenylalanine 4-monooxygenase, EC 1.14.16.1) DOPA decarboxylase (EC 4.1.1.28.) and dopamine β-hydroxylase (EC 1.14.17.1.) showed reduced activity 10 days after removal of the submaxillary glands in both superior cervical and stellate ganglia. This decrease in enzyme activity persisted up to 100 days after surgery. The fourth enzyme studied, choline acetyl-transferase (EC 2.3.1.6.) which is exclusively localized within the presynaptic cholinergic terminals of the ganglia was not affected by sialectomy. A dose of 50 μg NGF/animal/day given over 4 days was only able to restore the enzyme activity to control levels in the superior cervical ganglia of sialectomized mice whereas in stellate ganglia the enzyme activities rose above control levels to a similar extent in sialectomized and non-sialectomized animals. These results provide biochemical evidence that NGF may play a role not only during the growth and normal development of the peripheral sympathetic nervous system but also in the maintenance of its functional integrity in the adult animal.     

A histochemical study of the distribution of choline acetyltransferase and acetylcholinesterase activity in sensory ganglia and nerve roots of the bullfrog

Synopsis Histochemical techniques were employed for the localization of choline acetyltransferase (ChAc; EC 2.3.1.6.), acetylcholinesterase (AChE; EC 3.1.1.7) and cholinesterase (ChE; EC 3.1.1.8) activities in dorsal and ventral roots and dorsal root ganglia of the bullfrog. AChE activity was present in most of the neuronal elements of dorsal root ganglia, in some nerve fibres in the dorsal roots, and in all nerve fibres in ventral roots. ChE activity in dorsal root ganglia and in the dorsal roots was confined to non-neuronal elements. No ChE activity was demonstrable in the ventral roots. ChAc activity was localized in many neurons of the dorsal root ganglia and in some nerve fibres of the dorsal roots; however, none of the ventral root fibres were visibly reactive. Some supportive cells of the dorsal roots and ganglia contained small amounts of ChAc activity. Except for the ventral roots, the histochemical distribution of AChE and ChAc activity was similar. The results of solubility studies indicated that under the histochemical conditions, approximately 50% of the ChAc remained bound to the dorsal roots and ganglia, whereas more than 90% of the ChAc in the ventral roots was soluble. This would account for the lack of reactivity in ventral root fibres. Differences in ChAc solubility are discussed in relation to the interpretation of histochemical data and in relation to the concept of multiple forms of ChAc. The results of this study indicate that at least one-third of the neurons of the dorsal root ganglia contain significant levels of the enzymes involved in both the synthesis and hydrolysis of acetylcholine.     

Pedal serotonergic neurons modulate the synaptic input of withdrawal interneurons ofHelix

A group of serotonergic cells, located in the pedal ganglia ofHelix lucorum, modulates synaptic responses of neurons involved in withdrawal behavior. Extracellular or intracellular stimulation of these serotonergic cells leads to facilitation of spike responses to noxious stimuli in the putative command neurons for withdrawal behavior. Noxious tactile stimuli elicit an increase in background spiking frequency in the modulatory neurons and a corresponding increase in stimulus-evoked spike responses in withdrawal interneurons. The serotonergic neurons have processes in the neuropil of the parieto-visceral ganglia complex, consistent with their putative role in modulating the activity of giant parietal interneurons, which send processes to the same neuropil and to the pedal ganglia. The serotonergic cells respond to noxious tactile and chemical stimuli. Although the group as a whole respond to noxious stimuli applied to any part of the body, most cells respond more to ipsilateral than contralateral stimulation, and exhibit differences in receptive areas. Intracellular investigation revealed electrical coupling between serotonergic neurons which could underlie the recruitment of members of the group not responding to a given noxious stimulus.     

PBAN/pyrokinin peptides in the central nervous system of the fire ant, <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

The pyrokinin/pheromone-biosynthesis-activating neuropeptide (PBAN) family of peptides found in insects is characterized by a 5-amino-acid C-terminal sequence, FXPRLamide. The pentapeptide is the active core required for diverse physiological functions, including the stimulation of pheromone biosynthesis in female moths, muscle contraction, induction of embryonic diapause, melanization, acceleration of puparium formation, and termination of pupal diapause. We have used immunocytochemical techniques to demonstrate the presence of pyrokinin/PBAN-like peptides in the central nervous system of the fire ant, Solenopsis invicta. Polyclonal antisera against the C-terminal end of PBAN have revealed the location of the peptide-producing cell bodies and axons in the central nervous system. Immunoreactive material is detectable in at least three groups of neurons in the subesophageal ganglion and corpora cardiaca of all adult sexual forms. The ventral nerve cord of adults consists of two segmented thoracic ganglia and four segmented abdominal ganglia. Two immunoreactive pairs of neurons are present in the thoracic ganglia, and three neuron pairs in each of the first three abdominal ganglia. The terminal abdominal ganglion has no immunoreactive neurons. PBAN immunoreactive material found in abdominal neurons appears to be projected to perisympathetic organs connected to the abdominal ganglia. These results indicate that the fire ant nervous system contains pyrokinin/PBAN-like peptides, and that these peptides are released into the hemolymph. In support of our immunocytochemical results, significant pheromonotropic activity is found in fire ant brain-subesophageal ganglion extracts from all adult fire ant forms (queens, female and male alates, and workers) when extracts are injected into decapitated females of Helicoverpa zea. This is the first demonstration of the presence of pyrokinin/PBAN-like peptides and pheromonotropic activity in an ant species. This research was supported in part by a US-Israel Binational Science Foundation Grant (no. 2003367).     

RNA POLYMERASE ACTIVITY IN THE SUPERIOR CERVICAL GANGLION OF THE NEONATAL RAT: THE EFFECT OF NERVE GROWTH FACTOR

The activity of RNA polymerase in the superior cervical ganglia of the neonatal rat has been studied. The characteristics of the activity with respect to enzyme concentration, temperature, time, and ion concentrations are presented. Ionic conditions of the assay favoring polymerase I and polymerase II were each studied in the presence of specific inhibitors of DNA-dependent RNA synthesis. The K_m for GTP under either polymerase I or polymerase II conditions was found to be 10^?5M, and the relative amounts of poly(A)-containing RNA synthesized under both conditions was 4-5%. A decrease in the activity of RNA polymerase with age has been observed. The time course of increased activity following treatment of the animals in vivo or treatment of the isolated ganglia in organ culture with nerve growth factor is presented. The increase in activity observed after the administration of nerve growth factor is discussed in terms of possible mechanisms of action of nerve growth factor in this tissue.     

Flight motor patterns recorded in surgically isolated sections of the ventral nerve cord ofLocusta migratoria

Summary In the locust,Locusta migratoria, the pairs of connectives between the three thoracic ganglia and in the neck were transected in all possible combinations. Each of these preparations was tested for the production of rhythmic flight motor activity, with sensory input from the wing receptors intact and after deafferentation. The motor activity elicited in these preparations was characterized by intracellular recordings from motoneurons and electromyographic analyses.The motor patterns observed in locusts with either the neck or the pro-mesothoracic connectives severed (Figs. 2, 3, and 4) were very similar to the flight motor pattern produced by animals with intact connectives. The activity recorded in mesothoracic flight motoneurons of locusts with either only the meso-metathoracic connectives cut or both the meso-metathoracic and the neck connectives transected were similar to each other. Rhythmic motor activity could be observed in these preparations only as long as sensory feedback from the wing receptors was intact. These patterns were significantly different from the intact motor pattern (Figs. 5, 6, and 7). Similar results were obtained when the mesothoracic ganglion was isolated from the other two thoracic ganglia, although the oscillations produced under these conditions were weak (Fig. 8 upper). In the isolated metathorax no rhythmic flight motor activity could be recorded (Fig. 8 lower), even when wing afferents were intact.Considering the differences between the motor patterns observed in the various preparations these results suggest that the ganglia of the locust ventral nerve cord do not contain segmental, homologous flight oscillators which are coupled to produce the intact flight rhythm. Instead they support the idea that the functional flight oscillator network is distributed throughout the thoracic ganglia (Robertson and Pearson 1984). The results also provide further evidence that sensory feedback from the wing sense organs is necessary for establishing the correct motor pattern in the intact animal (Wendler 1974, 1983; Pearson 1985; Wolf and Pearson 1987 a).Abbreviations CPG central pattern generator - EMG electromyogram     

Influence of interganglionic interactions on steroid-mediated dendritic reorganization and death of proleg motor neurons during metamorphosis in Manduca sexta

In Manduca sexta, the larval abdominal prolegs and their muscles degenerate at pupation. The proleg motor neurons undergo a period of dendritic regression, after which a specific subset of them dies. The surviving motor neurons undergo dendritic outgrowth during pupal-adult development, and most die after adult emergence. All of these events are regulated hormonally by ecdysteroids and juvenile hormone, but interactions of the motor neurons with other cells may potentially contribute as well. To investigate the possible influence of interganglionic neural interactions, we chronically isolated individual abdominal ganglia by severing the adjacent rostral and caudal connectives in the larval stage. Subsequent metamorphic changes in proleg motor neurons were examined in the isolated ganglia and ganglia adjacent to the isolated ganglia. Two abnormalities were observed: (1) some imprecision in the timing of motor neuron death, both at pupation and after adult emergence, and (2) the growth of ectopic neurites outside the neuropil boundaries during pupal-adult development (in ganglia with or without neuromas caused by connective transections). Other aspects of proleg motor neuron metamorphosis, including the segment-specific death of motor neurons at pupation, were the same as that in intact and sham-operated insects. Thus, interganglionic interactions appear to play a relatively minor role in the steroid-mediated metamorphic transformation of proleg motor neurons. © 1994 John Wiley & Sons, Inc.