scholarly journals The physiology of wandering behaviour in Manduca sexta. IV. Hormonal induction of wandering behaviour from the isolated nervous system

1986 ◽  
Vol 121 (1) ◽  
pp. 133-151 ◽  
Author(s):  
O. S. Dominick ◽  
J. W. Truman
Keyword(s):  
Nervous System ◽  
Manduca Sexta ◽  
Extracellular Recording ◽  
Behavioural Effects ◽  
Average Latency ◽  
Motor Nerves ◽  
Spontaneous Bursts ◽  
Necessary And Sufficient ◽  
Manduca Sexta Larvae ◽  
The Brain

Prior to exposure to ecdysteroids, the isolated central nervous system (CNS) of the fifth instar Manduca sexta larvae exhibited infrequent motor bursts over a 24-h period of extracellular recording from segmental motor nerves. In contrast, the CNS isolated from wandering larvae was characterized by persistent, frequent spontaneous motor bursts throughout the 24-h incubation. The motor bursts generated by the isolated CNS of wandering larvae were similar to those observed in deafferented segments of partially dissected wandering larvae during locomotion. In both cases bursts in the deafferented ganglia were synchronous and had a lower frequency than in intact animals. Removal of the brain from a CNS isolated prior to ecdysteroid exposure resulted in the appearance of spontaneous bursts, which were abolished by removing the suboesophageal ganglion (SEG). By contrast, when the brain was removed from the isolated CNS of wandering larvae, spontaneous bursts ceased. These results parallel the behavioural effects of the same lesions in intact larvae of the respective stages. The CNS isolated from larvae prior to ecdysteroid exposure initiated sustained frequent bursting after an average latency of 15 h following incubation in haemolymph taken from larvae during the interval of ecdysteroid secretion. Incubations of the CNS with 1 microgram ml-1 20-hydroxyecdysone (20-HE) resulted in the onset of the same pattern of sustained motor activity. In a CNS isolated prior to ecdysone release, it was necessary and sufficient to expose the brain to 20-HE in order to induce the state of persistent motor bursts characteristic of wandering. We conclude that the spontaneous persistent motor bursts observed in the isolated CNS of wandering larvae are directly related to the sustained locomotion seen during the wandering behaviour. 20-HE acts directly on the CNS, specifically the brain, to induce this state of neural activity.

The Larval Eclosion Hormone Neurones in Manduca Sexta: Identification of the Brain-Proctodeal Neurosecretory System

1989 ◽  
Vol 147 (1) ◽  
pp. 457-470 ◽  
Author(s):  
JAMES W. TRUMAN ◽  
PHILIP F. COPENHAVER
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Manduca Sexta ◽  
Nerve Cord ◽  
Release Site ◽  
Neurosecretory System ◽  
Nerve Activity ◽  
Eclosion Hormone ◽  
The Central Nervous System ◽  
The Brain

Larval and pupal ecdyses of the moth Manduca sexta are triggered by eclosion hormone (EH) released from the ventral nervous system. The major store of EH activity in the latter resides in the proctodeal nerves that extend along the larval hindgut. At pupal ecdysis, the proctodeal nerves show a 90% depletion of stored activity, suggesting that they are the major release site for the circulating EH that causes ecdysis. Surgical experiments involving the transection of the nerve cord or removal of parts of the brain showed that the proctodeal nerve activity originates from the brain. Retrograde and anterograde cobalt fills and immunocytochemistry using antibodies against EH revealed two pairs of neurons that reside in the ventromedial region of the brain and whose axons travel ipsilaterally along the length of the central nervous system (CNS) and project into the proctodeal nerve, where they show varicose release sites. These neurons constitute a novel neuroendocrine pathway in insects which appears to be dedicated solely to the release of EH.

Patterned activation of unpaired median neurons during fictive crawling in manduca sexta larvae

1999 ◽  
Vol 202 (2) ◽  
pp. 103-113 ◽  
Author(s):  
R.M. Johnston ◽  
C. Consoulas ◽  
H. Pflüger ◽  
R.B. Levine
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Manduca Sexta ◽  
Motor Pattern ◽  
Intracellular Recordings ◽  
Subesophageal Ganglion ◽  
Synaptic Inputs ◽  
Functional Consequences ◽  
Manduca Sexta Larvae ◽  
Synaptic Drive

The unpaired median neurons are common to the segmental ganglia of many insects. Although some of the functional consequences of their activation, among them the release of octopamine to modulate muscle contraction, have been described, less is understood about how and when these neurons are recruited during movement. The present study demonstrates that peripherally projecting unpaired median neurons in the abdominal and thoracic ganglia of the larval tobacco hornworm Manduca sexta are recruited rhythmically during the fictive crawling motor activity that is produced by the isolated central nervous system in response to pilocarpine. Regardless of the muscles to which they project, the efferent unpaired median neurons in all segmental ganglia are depolarized together during the phase of the crawling cycle when the thoracic leg levator motoneurons are active. During fictive crawling, therefore, the unpaired median neurons are not necessarily active in synchrony with the muscles to which they project. The rhythmical synaptic drive of the efferent unpaired median neurons is derived, at least in part, from a source within the subesophageal ganglion, even when the motor pattern is evoked by exposing only the more posterior ganglia to pilocarpine. In pairwise intracellular recordings from unpaired median neurons in different ganglia, prominent excitatory postsynaptic potentials, which occur with an anterior-to-posterior delay in both neurons, are seen to underlie the rhythmic depolarizations. One model consistent with these findings is that one or more neurons within the subesophageal ganglion, which project posteriorly to the segmental ganglia and ordinarily provide unpatterned synaptic inputs to all efferent unpaired median neurons, become rhythmically active during fictive crawling in response to ascending information from the segmental pattern-generating network.

The novel guanylyl cyclase MsGC-I is strongly expressed in higher-order neuropils in the brain of Manduca sexta

2001 ◽  
Vol 204 (2) ◽  
pp. 305-314 ◽  
Author(s):  
A. Nighorn ◽  
P.J. Simpson ◽  
D.B. Morton
Keyword(s):  
Nervous System ◽  
Manduca Sexta ◽  
Guanylyl Cyclase ◽  
Higher Order ◽  
Adult Brain ◽  
Central Complex ◽  
Amino Acid Residues ◽  
Order Processing ◽  
Guanylyl Cyclases ◽  
The Brain

Guanylyl cyclases are usually characterized as being either soluble (sGCs) or receptor (rGCs). We have recently cloned a novel guanylyl cyclase, MsGC-I, from the developing nervous system of the hawkmoth Manduca sexta that cannot be classified as either an sGC or an rGC. MsGC-I shows highest sequence identity with receptor guanylyl cyclases throughout its catalytic and dimerization domains, but does not contain the ligand-binding, transmembrane or kinase-like domains characteristic of receptor guanylyl cyclases. In addition, MsGC-I contains a C-terminal extension of 149 amino acid residues. In this paper, we report the expression of MsGC-I in the adult. Northern blots show that it is expressed preferentially in the nervous system, with high levels in the pharate adult brain and antennae. In the antennae, immunohistochemical analyses show that it is expressed in the cell bodies and dendrites, but not axons, of olfactory receptor neurons. In the brain, it is expressed in a variety of sensory neuropils including the antennal and optic lobes. It is also expressed in structures involved in higher-order processing including the mushroom bodies and central complex. This complicated expression pattern suggests that this novel guanylyl cyclase plays an important role in mediating cyclic GMP levels in the nervous system of Manduca sexta.

Physiology of Insect Rhythms

1974 ◽  
Vol 60 (2) ◽  
pp. 371-382 ◽  
Author(s):  
JAMES W. TRUMAN ◽  
LYNN M. RIDDIFORD
Keyword(s):  
Developmental Stage ◽  
Manduca Sexta ◽  
Prothoracic Gland ◽  
Dorsal Midline ◽  
Prothoracic Glands ◽  
The Times ◽  
Manduca Sexta Larvae ◽  
The Brain ◽  
Pink Pigment ◽  
Stimulation Of

1. Late in the fifth instar, Manduca sexta larvae cease feeding and become ‘wandering larvae’ which are morphologically characterized by an ‘exposed heart’ and the appearance of a pink pigment along the dorsal midline. Two days later ocellar retraction signals the beginning of the prepupal period and 3 days thereafter the pupal ecdysis occurs. 2. The timing of the endocrine events which are responsible for these changes was determined by ligaturing animals of the appropriate developmental stage at various times of day. The times of prothoracicotropic hormone (PTTH) release by the brain were determined by neck ligations. Estimates of the times of prothoracic gland activity were obtained through the isolation of abdomens. 3. It was found that the fifth stage larva releases PTTH on two occasions. The first release lasts approximately 3.5 h and triggers the transformation to the wandering stage. The second release occurs two days later, lasts at least 7 h, and provokes the onset of the pupal moult. 4. The prothoracic glands are involved in triggering the same two changes. In the first instance the glands apparently require the continuing influence of the brain and consequently secrete for about 3.5 h. During the stimulation of the pupal moult the prothoracic glands become ‘turned-on’ and continue to secrete for at least 10 h after the time when the brain is no longer required. In this latter instance the total time of prothoracic gland activity may be as long as 17 h.

The diameters of the fibres of the peripheral nerves of Octopus

1965 ◽  
Vol 162 (986) ◽  
pp. 47-79 ◽  
Keyword(s):  
Nervous System ◽  
Peripheral Nerves ◽  
Distinct Group ◽  
Nerve Fibres ◽  
Stellate Ganglia ◽  
Vasomotor Nerves ◽  
Motor Nerves ◽  
The Brain ◽  
Great Resolution ◽  
Medium Diameter

The diameters and numbers of fibres have been measured throughout the peripheral nervous system. The nerves of the muscles that act upon the outside world contain few fibres, having very large and medium-sized fibres but no very small ones. Thus the muscles of the head receive 6000 fibres, the largest of 30 μ m diameter. The eye muscles receive 3300 fibres, reaching 24 μ m. The stellar nerve fibres are more numerous (150 000), but smaller (< 20 μ m). The preganglionic fibres joining the c. n. s. to the stellate ganglia are fewer than the postganglionic ones (4000, < 16 μ m). In some of the somatic motor nerves the longest bundles contain the largest fibres. However these are accompanied by a distinct group of smaller fibres, whose significance is uncertain. It is not clear that there is a distinct proprioceptor group. The fibres to the chromatophores are numerous (30000) and of medium diameter (< 12 μ m). The visceral motor and vasomotor nerves, however, contain hundreds of thousands of minute fibres (< 3 μ m). The significance of these numerous small fibres can hardly be to obtain great resolution of movement in such acts as secretion of saliva. Presumably the great number has a special significance. The fibres to the muscles of the buccal mass are more numerous and smaller than the somatic motor fibres, but fewer and larger than those for the viscera. The muscles of the arms and suckers have 3.0 x 10 6 fibres, all < 6 μ m, originating from neurons within the arms. They are controlled from the brain by relatively few but large fibres (32000, < 26 μ m). There is also a reduction of 100 times on the afferent pathway of the arms, from some 18 x 10 6 receptors at the periphery of the suckers to 140000 fibres entering the brain. The brain thus serves for major decisions, whose detailed execution is left to peripheral reflex centres in the arms. The optic nerve fibres are very numerous, and all small (20 x 10 6 , < 1.3 μ m) presumably for economy of space and material. By contrast the static nerves, although they are short, contain a small number of large fibres (1400 between 6 and 22 μ m) as well as several thousand smaller ones. The presence of sets of fibres with their distinctive diameters, conduction velocities and other properties is evidently a fundamental feature of the design of the nervous system of cephalopods as it is of vertebrates, although the significance of many features remains to be explored.

Co-localization of ecdysteroid receptors and c-fos-like protein in the brain of Manduca sexta larvae

1991 ◽  
Vol 200 (3) ◽  
pp. 149-155 ◽  
Author(s):  
Hans-J�rgen Bidmon ◽  
Noelle Audrey Granger ◽  
Walter Erich Stumpf
Keyword(s):  
Manduca Sexta ◽  
Manduca Sexta Larvae ◽  
The Brain ◽  
Ecdysteroid Receptors

Physiology of Insect Ecdysis

1973 ◽  
Vol 58 (3) ◽  
pp. 821-829
Author(s):  
JAMES W. TRUMAN
Keyword(s):  
Nervous System ◽  
Manduca Sexta ◽  
Hormone Activity ◽  
Hormonal Factors ◽  
Corpora Cardiaca ◽  
Eclosion Hormone ◽  
Neural Input ◽  
The Brain ◽  
Pupal Cuticle

1. In pharate Manduca sexta moths eclosion hormone activity was present in the brain and corpora cardiaca. Bursicon activity was confined to the abdominal nervous system, and was most concentrated in the abdominal perivisceral organs (PVOs). 2. When newly emerged moths were given access to suitable wing-spreading sites, bursicon activity was depleted from the PVOs and appeared in the blood within 15 min after eclosion. This hormone was responsible for the tanning and hardening of the wings. 3. Bursicon release could be delayed for at least 24 h by forcing the newly emerged moth to dig. Secretion then occurred swiftly upon giving the moth a suitable wing-spreading site. 4. The pupal cuticle was removed from pharate Manduca approximately 7 h before their normal eclosion gate, and the peeled moths were provided with a wing-spreading site. These moths did not then secrete bursicon until after their normal time of eclosion. 5. Injection of the eclosion hormone into pharate moths caused early eclosion followed by precocious bursicon secretion. 6. It was concluded that bursicon release is regulated by both neural and hormonal factors. The eclosion hormone triggers a program of neural output which includes the secretion of bursicon. This release, however, can be delayed by neural input which is associated with the digging behaviour of the moth.

scholarly journals The initiation of pre-ecdysis and ecdysis behaviors in larval Manduca sexta: the roles of the brain, terminal ganglion and eclosion hormone.

1996 ◽  
Vol 199 (8) ◽  
pp. 1757-1769 ◽  
Author(s):  
A Novicki ◽  
J C Weeks
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Manduca Sexta ◽  
Brain Neurons ◽  
Eclosion Hormone ◽  
Terminal Ganglion ◽  
The Central Nervous System ◽  
Time Required ◽  
The Brain ◽  
Larval Molt

Each larval molt of Manduca sexta culminates in the sequential performance of pre-ecdysis (cuticle loosening) and ecdysis (cuticle shedding) behaviors. Both behaviors are thought to be triggered by the release of a peptide, eclosion hormone (EH), from brain neurons whose axons extend the length of the nervous system. EH bioactivity appears in the hemolymph at the onset of pre-ecdysis behavior, and EH injection can trigger pre-ecdysis and ecdysis behaviors prematurely. The present study examined the effects of removing or disconnecting portions of the central nervous system prior to the time of EH release on the initiation of pre-ecdysis and ecdysis behaviors at the final larval molt. We found that the initiation of pre-ecdysis abdominal compressions at the appropriate time required the terminal abdominal ganglion (AT) but not the brain; the initiation of pre-ecdysis proleg retractions at the appropriate time required neither the AT nor the brain; the initiation of ecdysis at the appropriate time usually required the brain but did not require the AT; and premature pre-ecdysis (but not ecdysis) could be elicited in isolated abdomens by injection of EH. Finally, pre-ecdysis behavior performed by brainless larvae was not associated with the normal elevation of EH bioactivity in the hemolymph or the normal loss of EH immunoreactivity from peripheral neurohemal release sites.

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