Ecdysteroid binding sites localized by autoradiography in the central nervous system of precommitment fifth-stadium Manduca sexta larvae

1991 ◽  
Vol 263 (1) ◽  
pp. 183-194 ◽  
Author(s):  
Hans -J. Bidmon ◽  
Walter E. Stumpf ◽  
Noelle A. Granger
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Manduca Sexta ◽  
Binding Sites ◽  
The Central Nervous System ◽  
Manduca Sexta Larvae

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.

Adipokinetic hormone stimulates neurones in the insect central nervous system.

1995 ◽  
Vol 198 (6) ◽  
pp. 1307-1311
Author(s):  
J J Milde ◽  
R Ziegler ◽  
M Wallstein
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Manduca Sexta ◽  
Central Action ◽  
Adipokinetic Hormone ◽  
Metabolic Functions ◽  
Simple Preparation ◽  
Pressure Injection ◽  
The Central Nervous System ◽  
Insect Central Nervous System

A simple preparation designed to screen and compare the central action of putative neuroactive agents in the moth Manduca sexta is described. This approach combines microinjections into the central nervous system with myograms recorded from a pair of spontaneously active mesothoracic muscles. Pressure injection of either octopamine or Manduca adipokinetic hormone (M-AKH) into the mesothoracic neuropile increases the monitored motor activity. Under the conditions used, the excitatory effects of M-AKH exceed those of the potent neuromodulator octopamine. This suggests that M-AKH plays a role in the central nervous system in addition to its known metabolic functions and supports recent evidence that neuropeptides in insects can be multifunctional.

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