Terminal Abdominal Ganglion Research Articles

Different effects of the biogenic amines dopamine, serotonin and octopamine on the thoracic and abdominal portions of the escape circuit in the cockroach

1. The escape behavior of the cockroach, Periplaneta americana, is known to be modulated under various behavioral conditions (Camhi and Volman 1978; Camhi and Nolen 1981; Camhi 1988). Some of these modulatory effects occur in the last abdominal ganglion (Daley and Delcomyn 1981a, b; Libersat et al. 1989) and others in the thoracic ganglia (Camhi 1988). Neuromodulator substances are known to underlie behavioral modulation in various animals. Therefore, we have sought to determine whether topical application of putative neuromodulators of the escape circuit enhance or depress this circuit, and whether these effects differ in the last abdominal vs. the thoracic ganglia. 2. Topical application of the biogenic amines serotonin and dopamine to the metathoracic ganglion modulates the escape circuitry within this ganglion; serotonin decreases and dopamine enhances the response of leg motoneurons to activation of interneurons in the abdominal nerve cord by electrical or wind stimulation. 3. The neuropil of the thoracic ganglia contains many catecholamine-histofluorescent processes bearing varicosities, providing a possible anatomical substrate for dopamine release sites. 4. Topical application of octopamine to the terminal abdominal ganglion enhances the response of abdominal interneurons to wind stimulation of the cerci. In contrast, serotonin and dopamine have no effect at this site. 5. It is proposed that release of these biogenic amines may contribute to the known modulation of the cockroach escape response.

Corpus al latum regulation of copulatory behaviour in the male grasshopper, Melanoplus sanguinipes

Abstract The relationship between corpus allatum (CA) regulation of copulatory behaviour and the CA's influence on the development of the accessory reproductive glands was studied in the male grasshopper, Melanoplus sanguinipes (Fabr.). Allatectomy slowed the development of copulatory behaviour; ≤80% of control males 7 days and older mated with females, but allatectomized males did not show comparable levels of copulation until day 19. In a 3 h observation period, the time taken for 50% of males to initiate copulation was c. 60 min for allatectomized males and only c. 10 min for controls. At the age when 50% of males copulated, the accessory glands of allatectomized males were less developed than those of controls; the accessory gland weight was 65%, soluble protein was 72% and reserves of long hyaline protein I were 40% those of controls. Treatment with Juvenile Hormone III on day 2 stimulated accumulation of long hyaline protein I in 9‐day‐old allatectomized males to the level found in untreated 19‐day‐old allactec‐tomized males, but did not elicit heightened copulation. No positive feedback from the accessory glands appeared necessary to elicit copulation since vasectomy, ablation of the accessory glands or isolation of the terminal abdominal ganglion by ventral nerve cord transection did not inhibit copulatory behaviour in 7‐day‐old males. Because allatectomy inhibited copulatory behaviour in 7‐day‐old males in which the accessory glands were removed but not in 19‐day‐old males without accessory glands, the increased tendency of older allatectomized males to mate with females was not due to release of inhibition caused by continued growth of the accessory reproductive glands.

Physiology and Structure of Three New Uropod Proprioceptors in the Crayfish Procambarus Clarkii

ABSTRACT Three new chordotonal organs are described: APCO for the abdominal-proto-podite joint, PExCO for the protopodite-exopodite joint and PEnCO for the protopodite-endopodite joint of the crayfish uropod. The PEnCO is a distinct strand chordotonal organ, while the APCO and PExCO are webbed structures arising from peripheral nerve roots 2 and 3 of the terminal abdominal ganglion, in which some of their somata are located (‘root cells’). Physiological experiments showed that the organs monitor position and movement at all three joints. Position monitoring is limited to open angles of the exopodite and extended angles of the protopodite (no limits on endopodite position sensitivity). Distinct hysteresis is shown by most position-sensitive units. The abdomen-protopodite joint is monitored through four orders of velocity magnitude, while the exopodite and endopodite, which are involved in tailfan flare, are primarily monitored at high movement velocities. Large, phasic units in all three chordotonal organs (COs) can monitor continuous, high-velocity movement with little adaptation. These results are discussed in relation to known motor control mechanisms for crayfish uropods during swimming, walking, escape and righting behaviours.

Co‐localization of FLRF‐ and vasopressin‐like immunoreactivity in a single pair of sexually dimorphic neurones in the nervous system of the locust

The distribution of Phe-Leu-Arg-Phe (FLRF)-like immunoreactivity is described in the brain and in the ganglia of the ventral nerve cord of the locust Schistocerca gregaria. A single homologous pair of immunoreactive cell bodies occurs ventrally and medially in the suboesophageal ganglion. Each cell sends a process dorsally which bifurcates into anteriorly and posteriorly running neurites. The single anterior neurite passes along the circumoesophageal connectives to the brain where it ascends in a posterior running tract, giving off branches to innervate the tritocerebral neuropile and ending in an extensive network of highly varicose immunoreactive processes in the protocerebral neuropile. No processes are seen in the optic lobes or associated with the structured neuropiles of the muschroom bodies. The single posterior neurite from each cell passes into the suboesophageal-prothoracic connectives. It runs in the lateral dorsal tract of each ganglion in the ventral nerve cord as a highly varicose process and in each ganglion gives rise to an ipsilateral network of varicose processes in the dorsal and lateral neuropiles. In the seventh and terminal abdominal ganglia the innervation pattern exhibits sexual dimorphism. Vasopressin-like immunoreactivity is co-localized in the same pair of suboesophageal neurones and their processes. A similar pair of ventral median neurones stains with both antibodies in the suboesophageal ganglion of another species of locust, Locusta migratoria. Although the basic distribution pattern of immunoreactive processes is similar in both species there are also marked species differences in the pattern.

Immunocytochemical localization of nicotinic acetylcholine receptors in the terminal abdominal ganglion of the cockroach (Periplaneta americana).

A polyclonal, monospecific antiserum raised against a nicotinic acetylcholine receptor protein affinity-purified from insect nervous tissue, was employed to demonstrate the localization of antigenic sites in the neuropile of the terminal (sixth) abdominal ganglion of the cockroach Periplaneta americana. In agreement with previously published autoradiographic mapping of specific [125I]alpha-bungarotoxin binding sites, specific areas of the central neuropile of this ganglion were densely stained, but not the cercal afferent axons. No staining was detected corresponding to the dense, peripheral, partly non-specific binding of alpha-bungarotoxin seen in autoradiographs of the same tissue. Certain peripherally located neuronal cell bodies, including the cell body of giant interneuron 2, contained intracellularly located antigenic sites.

Neural regulation of sex pheromone biosynthesis in Heliothis moths

Pheromone biosynthesis in females of Heliothis zea is regulated endogenously by a neuropeptide produced in the subesophageal ganglion. We have found that the ventral nerve cord must be intact for normal induction of pheromone biosynthesis and that pheromonotropic activity is associated with extracts of the abdominal nerve cord, but only during the period when pheromone is produced. We did not find evidence of pheromonotropic activity in hemolymph obtained from females that were producing pheromone. Extracts of the brain-subesophageal ganglion complex, which contain pheromone biosynthesis activating neuropeptide (PBAN), induced pheromone biosynthesis when applied to the terminal abdominal ganglion only if nerves from this ganglion to the pheromone gland were intact. Brain-subesophageal ganglion extracts did not induce biosynthesis when applied directly to the pheromone glands in vitro. From our results, we conclude that the target site of PBAN is not the pheromone gland but the terminal abdominal ganglion, and we hypothesize that the abdominal nerve cord transports PBAN to the terminal abdominal ganglion.

Proctolinergic innervation of the accessory gland in male crickets ( Gryllus bimaculatus): Detection of proctolin and some pharmacological properties of myogenically and neurogenically evoked contractions

Spontaneous contractions were observed in the cricket male accessory gland which is innervated by dorsal unpaired median neurones (DUMR7 neurones) and paired neurones (LC neurones) arising from the terminal abdominal ganglion. These contractions were myogenic: identical mechanical activity was observable in a transplanted accessory gland which lacked innervation. Selective antidromic electrical stimulation of the DUMR7 neurones evoked a contraction of the accessory gland, which was graded and dependent upon both frequency and duration of stimulation. Glutamate at 10 −4 M, and proctolin, at low concentrations of 10 −9 M, produced sustained contractions of the accessory gland. These drugs at higher concentrations (glutamate, > 10 −4 M; proctolin, > 10 −8 M) reduced the amplitude of neurogenically evoked contractions and increased the basal tonus. Octopamine, at 10 −7 M, increased the frequency of myogenically evoked contractions. Application of serotonin, at 10 −5 M, reduced the amplitude of neurally evoked contractions and also resulted in a lowering of the basal tonus. By use of high-performance liquid chromatoraphy and bioassay we have found that proctolin was present in the accessory gland, and it was released from the accessory gland in response to the application of high K + saline. No proctolin was detected in the transplanted accessory gland.

The uropod righting reaction of the crayfishProcambarus clarkii (Girard): an equilibrium response driven by two largely independent reflex pathways

1. The uropod righting reaction of the crayfish,Procambarus clarkii, was investigated in response to stimulation of proprioceptors at the bases of the walking legs and to stimulation of the balance organs, the statocysts. 2. Tilting a platform beneath the legs of crayfish elicited movements of the exopodites of the uropods in the horizontal plane. These were produced by activity only in the slow opener and closer muscles of the exopodites, the fast muscles not being involved in the formation of the uropod pattern. Platform tilts (±20°) with the axis of rotation parallel to the transverse axis of the body elicited a symmetrical closing of the exopodites when the anterior leg groups were depressed, and a symmetrical opening when the same leg groups were levated. 3. Platform tilts parallel to the longitudinal axis of the body elicited asymmetrical movements of the uropods with the exopodite ipsilateral to the levated legs opening and the contralateral exopodite closing. In all experiments the responses of the uropods were only reliably elicited when accompanied by extension of the abdomen. 4. The influence of input from various leg groups was examined by raising them from the oscillating platform in various combinations. The strongest reflex drive came from the 4th and 5th pairs of walking legs. The major source of input came from the coxo-basipodite (C-B) joint of the walking legs. Blocking other leg joints (mero-carpopodite (M-C) and carpo-propodite (C-P)) had no obvious effects on the normal response. 5. Tilting animals in the roll plane (±20°), with no leg contact, produced an opening of the exopodite on the upward side and a closing of the exopodite on the downward side. Responses were again only reliably elicited when accompanied by abdominal extension, and were produced by activity only in the slow opener and closer muscles. 6. Previously identified statocyst interneurones (C1 and C2) were recorded in the circumoesophageal commissures. No modulation of their spontaneous activity by leg input could be detected. 7. Results suggest that separate pathways from the leg proprioceptors and the statocyst organs to the uropods exist and converge at a late stage in the pathway, within the terminal (6th) abdominal ganglion.

Epiphallic Afferent Projections into the Terminal Abdominal Ganglion of the CricketsAcheta domesticusandGryllue bimaculatus

Summary The sensilla on the epiphallus of male crickets are necessary for the correct transfer of spermatophores to females during copulatory behaviour. This report identifies, for the first time, a specific region within the terminal abdominal ganglion that is likely to process sensory information received from the epiphallus during copulatory activity.

Involvement of the Terminal Abdominal Ganglion in Neuroendocrine Regulation of Integumentary Water Loss in the Cockroach Periplaneta Americana L

ABSTRACT Neuroendocrine secretions from the terminal abdominal ganglion (TAG) augment the cephalic neuroendocrine regulation of integumentary water loss in the cockroach. As with the cephalic system, the TAG produces both promoting (TAGP) and restricting (TAGR) secretions which, respectively, lead to an increase or a decrease in the rate of integumentary water loss. The promoting factor (TAGP) requires priming by the cephalic promoting factor (BHP) before it is activated, and it probably acts by stimulating release of more BHP which in turn increases water loss through the integument. The restricting factor (TAGR) is autoactive and exerts its effects even in the absence of the cephalic neuroendocrine system or its secretions. It provides additional, independent restriction of integumentary water loss in adverse (desiccating) ambient conditions. Its action accounts for the longer-term decrease in water loss found in decapitated cockroaches. These effects parallel closely the effects of the diuretic and antidiuretic hormones produced by the TAG. Measurement of faecal product demonstrates that the changes in overall water loss are not primarily due to changes in excretory loss but are due to regulation of integumentary permeability.

Analysis of synaptic integration using the laser photoinactivation technique

Crickets (and many other insects) have two antenna-like appendages at the rear of their abdomen, each of which is covered with hundreds of ‘filiform’ hairs resembling the bristles on a bottle brush. Deflection of these filiform hairs by wind currents activates mechanosensory neurons at the base of the hairs. The axons from these sensory neurons project into the terminal abdominal ganglion to form a topographic representation (or “map”) containing information about the direction, velocity and acceleration of wind currents around the animal. Information is extracted from this map by primary sensory interneurons that are also located within the terminal abdominal ganglion. In this paper, we review the progress that has been made toward understanding the mechanisms underlying directional sensitivity of an identified sensory interneuron in the cricket,Acheta domesticus. The response properties of the cell have been found to depend to a large extent upon the structure of its dendritic branches, which determines its synaptic connectivity with the sensory afferents in the map of wind space and the relative efficacy of its different synaptic inputs.

The central projections of the stretch receptor neurons of crayfish: structure, variation, and postembryonic growth

Each stretch receptor neuron (SR) of the crayfish abdomen projects from its peripherally located soma an axon that enters the CNS through the second nerve (N2) of its segmental ganglion. Co2+ backfills of N2 revealed that this axon bifurcates, sending one branch to the brain and the other to the terminal abdominal ganglion. Each axon makes many short lateral branches as it traverses each of the other segmental ganglia, and has 2 major arborizations--one in the tritocerebrum of the brain and the other in the terminal abdominal ganglion, G6. These projections to G6 are described in detail. Individual SR axons from different segments were impaled in G6 with a Lucifer yellow-filled microelectrode, identified physiologically, and then filled to discover their structures. In a sample of more than 50 SR neurons, no systematic structural differences between the projections of phasic SR neurons and tonic SR neurons were observed. Three kinds of structural variability occurred in these projections to G6: unusual primary axon shape, long primary axon, and large terminal varicosities. Comparisons of SR neurons that originated in different segments revealed a segmental gradient in the probability of each structural variant. SR neurons from more anterior segments were more likely to show these structural variations. Comparisons of these variations in crayfish of different sizes showed that unusual primary axon shape and long primary axons were more probable in large crayfish than in small ones. Therefore, these variations are probably the products of postembryonic growth of the nervous system.

Control mechanisms of calling behaviour in Lymantria dispar: An electrophysiological investigation on the role of the terminal abdominal ganglion

Using a modified “grease electrode”, we recorded extracellular spike activity from either member of each of the six pairs of peripheral nerves of the terminal abdominal ganglion in the female gypsy moth. Our results show that the three most caudally located nerve pairs (nerve pairs IV, V and VI) carry most of the spike activity related to the ovipositor movements associated with calling. The spike trains from nerve pair VI presented a temporal pattern which correlated most closely to the extension and retraction of the ovipositor during calling. Transection of the ventral nerve cord anterior to the terminal ganglion stopped neither the spike activity nor the calling behaviour, but some slight changes in both the spike frequency patterns and the duration of ovipositor extension and retraction were detected. We conclude that the terminal abdominal ganglion exhibits a considerable degree of autonomy in its control of the calling behaviour in the female gypsy moth.

Bilateral local non-spiking interneurons in the terminal (sixth) abdominal ganglion of the crayfish,Procambarus clarkii

The function of local bilateral non-spiking interneurons (BNSs) in the crayfish terminal (sixth) abdominal ganglion has been studied using intracellular recording and staining techniques. The results show that BNSs function not only in sensory processing but also in motor control. 1. One identified BNS, LDS (Reichert et al. 1983), is connected to the ascending interganglionic interneurons that carry sensory information from the tailfan to rostral ganglia, but not to the uropod motoneurons. Other BNSs have measurable postsynaptic effects upon the motoneurons. 2. Depolarizing current injected into BNSs affects the spike activity of uropod motoneurons in a graded manner. Hyperpolarization of BNSs, however, has no effect upon motoneurons. 3. BNSs have a small diameter (less than 5 μm) transverse process across the ganglionic midline and thin branches emerging from it. LDS has a large diameter (more than 15 μn) transverse process with thick branches. 4. The branches of BNSs have both input and output connections in each hemiganglion, though in LDS the input (soma side) and output (contralateral side) branches are separated. 5. The voltage change elicited on one side of LDS is conducted to the opposite side with a decrement in amplitude of only 10–20%. This indicates that LDS operates as a single functional unit. 6. Injection of a small amount of depolarizing current into BNSs can affect the motoneurons on the same side only. This suggests that the branches of BNSs on each side might function as local processing sites of neural information that operate independent of each other.

Proctolin potentiates synaptic transmission in the central nervous system of an insect

1. 1. Bursts of spike activity in the ventral nerve cord of the cockroach were elicited by mechanically stimulating the cercal organs. 2. 2. In the presence of micromolar proctolin, the peak frequency and the duration of a burst were slowly but significantly increased. 3. 3. In contrast, carbachol produced an immediate enhancement of spontaneous activity, but a potentiation of bursts was not seen. 4. 4. It is proposed that proctolin functions as a neuromodulator in the terminal abdominal ganglion of the cockroach.

Synapse formation by sensory neurons after cross-species transplantation in crickets: The role of positional information

The role of positional information in synapse formation was studied in the cricket cercal sensory system by transplanting epidermis from one species of cricket to another. Strips of cercal epidermis containing identified sensory neurons were transplanted from a black donor species to a tan host species; the color difference was used to distinguish between donor and host tissue in adults. Transplanted sensory neurons regenerated axons into the host terminal abdominal ganglion where they formed functional chimeric synapses. These methods were used to test the role of positional information in central synapse formation. Newly generated sensory neurons, formed by the donor tissue at the border between graft and host, were examined to test the idea that their position would determine their structure, function, and projection pattern. These “intercalated” sensory neurons support the positional information hypothesis. First, they had directional sensitivities which were appropriate to their location on the cercus; receptors of this directionality would never be made by the donor tissue if left in its original position. Second, these sensory neurons projected to regions of the CNS known to be appropriate for their directionality. Finally, simultaneous recordings from these ectopic sensory neurons and host interneurons demonstrated the expected synaptic connection, based on the overlap of pre-and postsynaptic cells. Thus three aspects of receptor function, directionality, afferent projection, and choice of synaptic partners, appeared to be controlled by positional information.

Opposing parallel connections through crayfish local nonspiking interneurons.

Unilateral local nonspiking interneurons in the terminal (sixth) abdominal ganglion of crayfish (Procambarus clarkii Girard) can be classified into two major groups of PL and AL types by their gross morphology and somatic position. These premotor interneurons are the neural components of uropod motor pattern formation. They receive sensory input from the exopodite of the contralateral side as well as that of the ipsilateral side. Small fluctuations in their membrane potentials cause sustained change in activity of the motoneurons innervating the uropod muscles. PL interneurons, which make noninverting connections to an identified closer, the reductor motoneuron No. 1, mainly receive excitatory input from the afferents of the contralateral exopodite, whereas inverting PL interneurons receive inhibitory input. AL interneurons receive distinctly different input from the afferents. Noninverting AL interneurons mainly receive inhibitory input, whereas inverting AL interneurons receive excitatory input. The rate of discharge of the reductor motoneurons is increased by sensory stimulation. The PL interneurons form either excitatory or disinhibitory pathways, which are relevant in function to the observed increase of the motoneuron. Conversely, the AL interneurons form either inhibitory or disfacilitatory pathways. Thus, the PL and the AL interneurons are fractionated in function and distinguishable in terms of their physiology by their input and output correlations. Functional meaning of the presence of these two types of unilateral local nonspiking interneurons of opposing connections in the uropod motor control system is discussed.

Neural control of rhythmic pheromone gland exposure in Utetheisa ornatrix (Lepidoptera: Arctiidae)

The rhythmic exposure of the sex pheromone gland during calling in female Utetheisa ornatrix (L.) (Lepidoptera: Arctiidae) is under neural control. Two lines of evidence support this conclusion. (1) Bisection of the ventral nerve cord of adult females prevented calling while sham-operations had little effect. (2) Brief electrical stimulation of the ventral nerve cord in isolated abdomens elicited extended trains of regularly spaced gland exposures indistinguishable from normal calling behaviour. The coordination of calling behaviour is localized in the terminal abdominal ganglion and the peripheral structures that it innervates. Removal of the corpora allata and corpora cardiaca, neurohaemal organs previously implicated in calling control, did not affect calling behaviour.

Role of the fat body in the regulation of host-seeking behaviour in the mosquito, Aedes aegypti

Following a blood meal that initiates oöcyte development, the host-seeking behaviour of Aedes aegypti mosquitoes is inhibited by a haemolymph-borne factor that is released in response to a humoral signal from a vitellogenic ovary. This inhibition is accompanied by a decrease in the sensitivity of the peripheral lactic acid receptors. Implantation of corpora allata, medial neurosecretory cells, or terminal abdominal ganglia from blood-fed donors could not induce the inhibition in sugar-fed recipients. However, fat body transplanted from blood-fed into sugar-fed females suppressed host-seeking behaviour as well as the sensitivity of lactic acid receptors, suggesting that the source of the behavioural inhibitor is the fat body. Resting-stage ovaries from other mosquito species inhibited host-seeking after the A. aegypti host was fed on blood only if the fat body was activated by the donor ovary.

Effect of allatectomy and ventral nerve cord transection on calling, pheromone emission and pheromone production in Lymantria dispar

The physiological control mechanisms of calling, pheromone production, and pheromone release in female gypsy moths were investigated. No involvement of the corpora allata was found since mean pheromone emission rates from females allatectomized as larvae (14.1 ng/h) were not significantly different from sham-operated (16.4 ng/h), anaesthetized (13.1 ng/h), or untreated controls (13.1 ng/h). Neural input from the brain or other higher centres of the nervous system, however, appeared critical since females which received ventral nerve cord transection anterior to the terminal abdominal ganglion between 0 and 24 h after pupation showed significant reductions in both gland-extractable pheromone ( x = 8.7 ng) and pheromone emission rate ( x = 2.1 ng/h) compared with controls ( x = 25.0 ng and x = 13.1 ng/h, respectively). Differences in calling behaviour were also observed; in control females, the duration of ovipositor protraction was about 16.5 s and retraction about 1.3 s, in ventral nerve cord-transected females the ovipositor was maintained in a full or partially protruded state for periods longer than 300 s. Post-operative inspection of the terminal abdominal ganglion revealed fewer descending nerve branches in ventral nerve cord-transected females compared to controls.