Glutamate-like immunoreactivity in the leech central nervous system.

Using a monoclonal antibody for glutamate the distribution was determined of glutamate-like immunoreactive neurons in the leech central nervous system (CNS). Glutamate-like immunoreactive neurons (GINs) were found to be localized to the anterior portion of the leech CNS: in the first segmental ganglion and in the subesophageal ganglion. Exactly five pairs of GINs consistently reacted with the glutamate antibody. Two medial pairs of GINs were located in the subesophageal ganglion and shared several morphological characteristics with two medial pairs of GINs in the first segmental ganglion. An additional lateral pair of GINs was also located in segmental ganglion 1. A pair of glutamate-like immunoreactive neurons, which are potential homologs of the lateral pair of GINs in segmental ganglion 1, were occasionally observed in more posterior segmental ganglia along with a selective group of neuronal processes. Thus only a small, localized population of neurons in the leech CNS appears to use glutamate as their neurotransmitter.     

Initiation of swimming activity by trigger neurons in the leech subesophageal ganglion

In papers I and II of this series, we described two pairs of interneurons, Tr1 and Tr2, in the leech subesophageal ganglion which can trigger swimming activity in the isolated central nervous system (CNS). In this paper, we describe sensory inputs to these trigger neurons from previously identified mechanosensory neurons. We found that: Weak mechanical stimulation (stroking) of a body wall flap attached to a segmental ganglion in an otherwise isolated CNS excites the contralateral Tr1 slightly. Strong mechanical stimulation (pinching) of a mid-body wall flap evokes a burst of impulses in the contralateral Tr1. For both means of stimulation the effects on the ipsilateral Tr1 and on the Tr2 cell pair were much weaker. Stroking a body wall flap attached to the head ganglion (supra- and subesophageal ganglia) in an otherwise isolated CNS excites both Tr1s and both Tr2s, although the effect is weaker for the Tr2s. Pinching strongly excites both trigger neurons bilaterally. Pressure and nociceptive mechanosensory neurons (P and N cells) in the subesophageal ganglion and the first segmental ganglion appear to make direct excitatory synapses with the contralateral Tr1 and Tr2. Mechanosensory interactions with the ipsilateral trigger neurons appear to be indirect. Functional inactivation of Tr1 by hyperpolarization does not prevent swim initiation either by weak mechanical stimulation of a body-wall flap or by intracellular stimulation of P cells.2+ We conclude that the trigger neurons, Tr1 and Tr2, provide an excitatory pathway by which mechanosensory stimulation can initiate leech swimming activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Control of leech swimming activity by the cephalic ganglia

We investigated the role played by the cephalic nervous system in the control of swimming activity in the leech, Hirudo medicinalis, by comparing swimming activity in isolated leech nerve cords that included the head ganglia (supra- and subesophageal ganglia) with swimming activity in nerve cords from which these ganglia were removed. We found that the presence of these cephalic ganglia had an inhibitory influence on the reliability with which stimulation of peripheral (DP) nerves and intracellular stimulation of swim-initiating neurons initiated and maintained swimming activity. In addition, swimming activity recorded from both oscillator and motor neurons in preparations that included head ganglia frequently exhibited irregular bursting patterns consisting of missed, weak, or sustained bursts. Removal of the two head ganglia as well as the first segmental ganglion eliminated this irregular activity pattern. We also identified a pair of rhythmically active interneurons, SRN1, in the subesophageal ganglion that, when depolarized, could reset the swimming rhythm. Thus the cephalic ganglia and first segmental ganglion of the leech nerve cord are capable of exerting a tonic inhibitory influence as well as a modulatory effect on swimming activity in the segmental nerve cord.     

Localization of leech excitatory peptide, a member of the GGNG peptides, in the central nervous system of a leech (Whitmania pigra) by immunohistochemistry and in situ hybridization

We have recently isolated a myoactive peptide, called leech excitatory peptide, belonging to the GGNG peptide family from two species of leeches, Hirudo nipponia and Whitmania pigra. Immunohistochemistry and in situ hybridization were employed to localize leech excitatory peptide-like peptide(s) and its gene expression in the central nervous system of W. pigra. A pair of neuronal somata were stained by both immunohistochemistry and in situ hybridization in the supraesophageal, subesophageal, and segmental ganglia. In addition, several other neurons showed positive signals by either immunohistochemistry or in situ hybridization in these ganglia. An immunoreactive fiber was observed to run in the anterior root of segmental ganglion 6, which is known to send axons to the sexual organs, though we failed to detect immunoreactivity in possible target tissues. Antiserum specificity was established by enzyme-linked immunosorbent assay using different leech excitatory peptide-related peptides. Leech excitatory peptide elicited muscular contraction of isolated preparations of penis and intestine at concentrations of 10(-8 )M. These results suggest that leech excitatory peptide is a neuropeptide modulating neuromuscular transmission in multiple systems, including regulation of reproductive behavior.     

Initiation of swimming activity by trigger neurons in the leech subesophageal ganglion

The aim of this study was to identify neurons in the subesophageal ganglion of the medicinal leech which initiate swimming activity and to determine their output connections. We found two bilaterally symmetrical pairs of interneurons, Tr1 and Tr2, located in the first division of the subesophageal ganglion which initiate swimming activity in the isolated nervous system when depolarized with brief (1-3 s) current pulses. Tr1 and Tr2 are considered trigger neurons because elicited swimming episodes outlast the stimulus duration, and because the length of elicited swim episodes is nearly independent of the intensity with which Tr1 and Tr2 are stimulated. Tr1 and Tr2 have similar morphologies. The neurites of both cells cross contralaterally in the subesophageal ganglion, project posteriorly, and exit the subesophageal ganglion in the contralateral connective. The axons of Tr1 and Tr2 extend as far posterior as segmental ganglion 18 of the ventral nerve cord. Tr1 provides direct excitatory drive to three groups of segmental neurons which are capable of initiating swimming: swim-initiating interneurons (cells 204 and 205), serotonin-containing interneurons (cells 61 and 21), and the serotonergic Retzius cells. In addition, all Retzius cells in the subesophageal ganglion are excited directly by Tr1. These three groups of neurons are excited even if Tr1 stimulation is subthreshold for swim initiation. In contrast to Tr1, Tr2 stimulation evokes transient inhibition in swim-initiating and serotonin-containing interneurons, and has little immediate effect on Retzius cells. In addition, Tr2 indirectly inhibits several oscillator neurons, including cells 208, 33, and 60. When Tr1 is stimulated during a swimming episode the swim period decreases for several cycles, while stimulation of Tr2 during swimming episodes reliably resets the ongoing swimming rhythm. Our findings indicate that Tr1 and Tr2 are trigger neurons which initiate swimming activity by different pathways. These neurons also have functional interactions with the swim oscillator network since either Tr1 or Tr2 stimulation during swimming can modulate the ongoing swimming rhythm.     

Pyrokinin/PBAN-like peptides in the central nervous system of mosquitoes

The pyrokinin/pheromone biosynthesis activating neuropeptide (PBAN) family of peptides is characterized by a common C-terminal pentapeptide, FXPRLamide, which is required for diverse physiological functions in various insects. Polyclonal antisera against the C-terminus was utilized to determine the location of cell bodies and axons in the central nervous systems of larval and adult mosquitoes. Immunoreactive material was detected in three groups of neurons in the subesophageal ganglion of larvae and adults. The corpora cardiaca of both larvae and adults contained immunoreactivity indicating potential release into circulation. The adult and larval brains had at least one pair of immunoreactive neurons in the protocerebrum with the adult brain having additional immunoreactive neurons in the dorsal medial part of the protocerebrum. The ventral ganglia of both larvae and adults each contained one pair of neurons that sent their axons to a perisympathetic organ associated with each abdominal ganglion. These results indicate that the mosquito nervous system contains pyrokinin/PBAN-like peptides and that these peptides could be released into the hemolymph. The peptides in insects and mosquitoes are produced by two genes, capa and pk/pban. Utilizing PCR protocols, we demonstrate that products of the capa gene could be produced in the abdominal ventral ganglia and the products of the pk/pban gene could be produced in the subesophageal ganglion. Two receptors for pyrokinin peptides were differentially localized to various tissues.     

Blastomere ablation and the developmental origin of identified monoamine-containing neurons in the leech

Ablation of different identifiable blastomeres of the early embryo of the leech Helobdella triserialis was found to lead to the absence of different sets of segmentally iterated monoamine-containing neurons in subsequent development. Thus the ablation of one of the paired N ectoteloblasts leads to the absence of one member of each of the three bilateral pairs of serotonin-containing neurons (one of which is the Retzius cell) from each segmental ganglion. The ablation of one of the paired OP blastomeres (precursors of the paired O and P ectoteloblasts) leads to the absence of one member of each of the two bilateral pairs of lateral dopamine-containing neurons that lie in the body wall of each segment. And the ablation of one of the paired Q ectoteloblast leads to the absence of one member of the bilateral pair of medial dopamine-containing neurons that lie in the body wall of each segment. These results suggest that each of these sets of monoamine-containing neurons is derived from a particular blastomere. Upon ablation of that blastomere the set does not develop from any other source.     

Blockade of the release of the neuropeptide leucokinin to determine its possible functions in fly behavior: Chemoreception assays

Previous studies have revealed leucokinin (LK) expression in the brain and ventral ganglion of Drosophila CNS. One pair of protocerebrum neurons located in the lateral horn area (LHLK) surrounds the peduncles of the mushroom bodies while two pairs of subesophageal neurons (SELKs) project extended processes to the tritocerebrum and through a cervical connection to the ventral ganglion. There, axons of eight or nine pairs of abdominal (ABLK) neurons leave the CNS through the abdominal nerves and processes connecting each other ipsilaterally and contralaterally. The neural functions of LK remain largely unknown, especially those related to Drosophila behavior. Here, we have studied the role of LK in olfactory and gustatory perception by keeping the LK neurons electrically silent through targeted expression of inward rectifier K⁺ channels. In order to examine the effects of LK failure, we first analyzed the dehydration response, comparing the leucokinin-silent individuals with their parents as a control. Our results showed significant differences that demonstrate the effectiveness of the method. We then tested the olfactory behavioral response to a set of odorants over a range of concentrations in a T-maze paradigm in which flies were allowed to choose between the odorant and solvent compartments. The feeding preference assays were carried out on microplates in which flies were allowed to choose between two colored tastes. Our results show that the blockade of LK release alters both olfactory and gustatory responses, and are therefore evidence that this neuropeptide also modulates chemosensory responses through LHLK and SELK neurons.     

Neurons with histaminelike immunoreactivity in the segmental and stomatogastric nervous systems of the crayfishPacifastacus leniusculus and the lobsterHomarus americanus

Summary We used a polyclonal antiserum against histamine to map histaminelike immunoreactivity (HLI) in whole mounts of the segmental ganglia and stomatogastric ganglion of crayfish and lobster. Carbodiimide fixation permitted both HRP-conjugated and FITC-conjugated secondary antibodies to be used effectively to visualize HLI in these whole mounts. Two interneurons that send axons through the inferior ventricular nerve (ivn) and the stomatogastric nerve to the stomatogastric ganglion had strong HLI, both in crayfish and in lobster. These ivn interneurons were known from other evidence to be histaminergic. The neuropil of the stomatogastric ganglion in both crayfish and lobster contained brightly labeled terminals of axons that entered the ganglion from the stomatogastric nerve. No neuronal cell bodies in this ganglion had HLI. Each segmental ganglion contained at least one pair of neurons with HLI. Some neurons in the subesophageal ganglion and in each thoracic ganglion labeled very brightly. Axons of projection interneurons with strong HLI occurred in the dorsal lateral tracts of each segmental ganglion, and sent branches to the lateral neuropils and tract neuropils of each ganglion. All the labeled neurons were interneurons; no HLI was observed in peripheral nerves.     

The caudal ganglion of the leech,with particular reference to homologues of segmental touch receptors

The caudal ganglion of the leech, which provides sensory and motor innervation to the posterior sucker, represents the fusion of seven embryonic segmental ganglia. Although fused, each of the seven contributing ganglia (“subganglia”) of the caudal ganglion can be distinguished morphologically and functionally. The roots from each subganglion carry the axons of mechanoreceptors homologous to “touch” cells found in the segmental ganglia and the subesophageal compound ganglion. The receptive fields supplied by the touch cells of the caudal ganglion are uniquely arranged and reveal the modified segmentation of the circular posterior sucker. Extensive overlap of sensory innervation occurs between adjacent segments of the sucker, beyond the overlap characteristic of the homologous cells of body segments. It thus appears that the touch receptors of the caudal ganglion are less restricted than receptors of the segmental ganglia with regard to their territories of innervation. The caudal ganglion has additional unique properties that establish it as a distinct integrative center of the leech CNS.     

Localization of leucokinin VIII in the cockroach,Leucophaea maderae,using an antiserum directed against an achetakinin-I analog

An antiserum against an achetakinin analog selectively localized leucokinin VIII (LKVIII) in the CNS ofLeucophaea maderae. Preabsorption studies of the achetakinin antiserum with either preimmune serum or LKVIII prevented a positive reaction in both ELISA and immunocytochemical procedures. LKVIII immunoreactive neurons were found in the brain, frontal, and subesophageal ganglion, all 3 thoracic ganglia and the terminal ganglion. Nerves originating from the thoracic and terminal abdominal ganglia contain LKVIII material. Lateral and medial neurosecretory cells synthesizing LKVIII-like products contribute axons to the nervi corporis cardiaci that terminate in neurohemal sites in the corpora cardiaca and nervi corporis allati. Thus, leucokinin VIII, like leucokinin I (LKI) and leucomyosuppressin (LMS), appears to have both a neurohemal and neurotransmitter mode of regulating target cells inL. maderae.     

Immunocytochemical studies on the central nervous system of the earthworm, Lumbricus terrestris

There are numerous aldehyde fuchsin (AF)-positive, neurosecretory cells of medium size (A cells) and a small number of large, AF-negative neurons (B cells) in the cortical layer of the cerebral ganglion. In the subesophageal ganglion, symmetrical groups of AF-positive cells lie ventrally. The peroxidase--antiperoxidase (PAP) method was used for the immunocytochemical study of substance P and ACTH in these ganglia. In addition, the presence of L-enkephalin and alpha endorphin could be confirmed. Using rabbit antibodies to substance P we found small immunoreactive neurons among negative A and B cells in the cerebral ganglion. The processes of these immunoreactive cells could be traced to the subcortical synaptic neuropil. With antibodies to ACTH, activity was visible in perikarya similar in size to A neurons. A part of the nerve terminals of the synaptic zone, some of the B neurons and further several nerve cells of the subesophageal ganglion reacted positively. Successive demonstration of substance P and ACTH on the same section showed that the two materials occurred in different cell types. Using antiopsin antibody in an indirect immunocytochemical test we observed strong reaction in numerous medium-sized perikarya and in nerve fibres of the synaptic zone of the cerebral ganglion, further in some neurons of the subesophageal and abdominal ganglia. In contrast to this result, the photoreceptor cells of the prostomium and cerebral ganglion were negative. Presumably, substance P is present in a perikaryon type hitherto unrecognized while ACTH and antiopsin reactions seem to be located first of all in A cells.     

Distribution of Eisenia tetradecapeptide immunoreactive neurons in the nervous system of earthworms

A detailed mapping of Eisenia-tetradecapeptide-immunoreactive neurons in the central and peripheral nervous system combined with quantitative morphological measurements was performed in Eisenia fetida and Lumbricus terrestris. In Eisenia, most labelled neurons were observed in the ganglia of the ventral cord (20.38% of the total cell number of the ganglion) and 15.67% immunoreactive cells occurred in the brain, while 6% of the neurons could be shown in the subesophageal ganglion. In the case of Lumbricus, most immunoreactive cells were found in the subesophageal ganglion (16.17%) and in the ventral ganglia (12.54%). The brain contained 122 ETP-immunoreactive cells (5.6%). The size of the immunoreactive cells varied between 35-75 microm. A small number of Eisenia-tetradecapeptide immunoreactive fibres were seen to leave the ventral ganglia via segmental nerves, and labelled processes could also be observed in the stomatogastric system and the body wall. Labelled axon branches originating from the segmental nerves formed an immunoreactive plexus both between the circular and longitudinal muscle layer and on the inner surface of the longitudinal muscle layer. This inner plexus was especially rich in the setal sac. Among the superficial epithelial cells the body wall contained a significant number of immunoreactive cells. Only a few Eisenia-tetradecapeptide immunoreactive neurons and fibres occurred in the stomatogastric ganglia. In the enteric plexus the number of immunoreactive neurons and fibres decreased along the cranio-caudal axis of the alimentary tract. Eisenia-tetradecapeptide immunoreactive cells were also present among the epithelial cells in the alimentary canal. Some of these cells resembled sensory neurons in the foregut, while others showed typical secretory cell morphology in the midgut and hindgut.     

Neurons projecting to the retrocerebral complex of the adult blow fly, Protophormia terraenovae

Anatomical study of neurons projecting to the retrocerebral complex of the adult blow fly, Protophormia terraenovae, was done by NiCl2 filling and immunocytochemistry. Retrograde filling through the cardiac-recurrent nerve labeled three groups of neurons in the brain/subesophageal ganglion: (1) paramedial clusters of the pars intercerebralis, (2) neurons in each pars lateralis, and (3) neurons in the subesophageal ganglion. The pars intercerebralis neurons send prominent axons into the median bundle and exit from the brain via the contralateral nervus corporis cardiaci. Based on the projection pattern, two types of the pars lateralis neurons can be distinguished: the most lateral pairs of neurons contralaterally extend through the posterior lateral tract and the remainder ipsilaterally extend through the posterior lateral tract. The neurons in the subesophageal ganglion run through the contralateral nervus corporis cardiaci. The dendritic arborization of the pars intercerebralis and pars lateralis neurons is restricted to the superior protocerebral neuropil and to the anterior neuropil of the subesophageal ganglion where the neurons in the subesophageal ganglion also project. Retrograde filling from the corpus allatum indicated that the pars lateralis neurons and a few pars intercerebralis neurons project to the corpus allatum, but that the neurons in the subesophageal ganglion do not. Orthograde filling from the pars intercerebralis and staining by paraldehyde-thionin/paraldehyde-fuchsin indicated that the pars intercerebralis neurons project primarily to the corpus cardiacum/hypocerebral ganglion complex. Immunostaining with a polyclonal antiserum against diapause hormone, a member of the FXPRLamide family, suggests that some of the subesophageal ganglion neurons contain FXPRLamide-like peptides.     

Microstructural organization of the central nervous system in the harvestman Leiobunum japonicum (Arachnida: Opiliones)

Although the order Opiliones constitutes the third‐largest group of arachnids, this creature is still mysterious and has a rich unexplored field compared to what is known about insects and crustaceans. The order Opiliones is traditionally regarded as a close relative of mites, mainly because of morphological similarities in external body structure; however microstructural organization of the ganglionic neurons and nerves in the harvestman Leiobunum japonicum is quite similar to the central nervous system (CNS) in all extant arachnids. The CNS consists of a large neural cluster with paired appendicular nerves. The esophagus passes through the neural cluster and divides it into the upper supraesophageal ganglion (SpG) and the lower subesophageal ganglion (SbG). The dorsal part of the SpG has a quite condensed cell body compared with other parts of the CNS and has two main components, the protocerebrum and the cheliceral ganglion. The protocerebrum receives the optic nerves and has four main groups of neuropiles from the optic lobes, the superior central body, the lateral neuropils (corpora pedunculata) and the inferior neuropil. However, a pair of pedipalpal and four pairs of appendage nerves including several pairs of abdominal nerves arise from the nerve masses of the SbG.     

<Emphasis Type="Italic">Hau-Pax6A</Emphasis> expression in the central nervous system of the leech embryo

The leech Helobdella sp. (Austin) has two genes of the Pax6 subfamily, one of which is characterized in detail. Hau-Pax6A was expressed during embryonic development in a pattern similar to other bilaterian animals. RNA was detected in cellular precursors of the central nervous system (CNS) and in peripheral cells including a population associated with the developing eye. The CNS of the mature leech is a ventral nerve cord composed of segmental ganglia, and embryonic Hau-Pax6A expression was primarily localized to the N teloblast lineage that generates the majority of ganglionic neurons. Expression began when the ganglion primordia were four cells in length and was initially restricted to a single cell, n_s.a, whose descendants will form the ganglion’s anterior edge. At later stages, the Hau-Pax6A expression pattern expanded to include additional CNS precursors, including some descendants of the O teloblast. Expression persisted through the early stages of ganglion morphogenesis but disappeared from the segmented body trunk at the time of neuronal differentiation. The timing and iterated pattern of Hau-Pax6A expression in the leech embryo suggests that this gene may play a role in the segmental patterning of CNS morphogenesis.     

Ontogenesis of the snail,Helix aspersa: Embryogenesis timetable and ontogenesis of GABA-like immunoreactive neurons in the central nervous system

Late stages of embryogenesis in the terrestrial snail Helix aspersa L. were studied and a developmental timetable was produced. The distribution of gamma-aminobutyric acid-like immunoreactive (GABA-ir) elements in the CNS of the snail was studied from embryos to adulthood in wholemounts. In adults, approximately 226 GABA-ir neurons were located in the buccal, cerebral and pedal ganglia. The population of GABA-ir cells included four pairs of buccal neurons, three neuronal clusters in the pedal ganglia, two clusters and six single neurons in the cerebral ganglia. GABA-ir fibers were observed in all ganglia and in some nerves. The first detected pair of GABA-ir cells in the embryos appeared in the buccal ganglia at about 63–64% of embryonic development. Five pairs of GABA-ir cell bodies were observed in the cerebral ganglia at about 64–65% of development. During the following 30% of development three more pairs of GABA-ir neurons were detected in the buccal ganglia and over fifteen cells were detected in each cerebral ganglion. At the stage of 70% of development, the first pair of GABA-ir neurons was found in the pedal ganglia. In the suboesophageal ganglion complex, GABA-ir fibers were first detected at about 90% of embryonic development. In the posthatching period, the quantity of GABA-ir neurons reached the adult status in four days in the cerebral ganglia, and in three weeks in the pedal ganglia. In juveniles, transient expression of GABA was found in the pedal ganglia (fourth cluster).     

Formation and specification of neurons during the development of the leech central nervous system

In the leech embryo, neurogenesis takes place within the context of a stereotyped cell lineage. The prospective germ layers are formed during the early cleavage divisions by the reorganization and segregation of circumscribed domains within the cytoplasm of the fertilized egg. The majority of central neurons arise from the ectoderm, and central neuroblasts are distributed throughout both the length and width of each ectodermal hemisegment. Much of the segmental ganglion arises from medial neuroblasts, but there are also lateral ectodermal neuroblasts and mesodermal neuroblasts that migrate into the nascent ganglion from peripheral sites of origin. Some of these migratory cells are committed to neurogenesis prior to reaching their central destination. In addition, the leech embryo exhibits a secondary phase of neurogenesis that is restricted to the two sex segment ganglia. Secondary neurogenesis requires that a mitogenic or trophic signal be conveyed from the peripherally located male sex organ to a particular set of centrally located neuroblasts, apparently via already differentiated central neurons that innervate the sex organ. The differential specification of neuronal phenotypes within the leech central nervous system occurs in multiple steps. Some aspects of a neuron's identity are already specified at the time of its terminal cell division and would seem to involve the lineal inheritance of developmental commitments made by one of the neuron's progenitors. This lineage-based identity can then be modified by interactions between the postmitotic neuron and other neurons or non-neuronal target cells encountered during its terminal differentiation. © 1995 John Wiley & Sons, Inc.     

Distribution and characterization of Corazonin in the central nervous system of Triatoma infestans (Insecta: Heteroptera)

The distribution of corazonin in the central nervous system of the heteropteran insect Triatoma infestans was studied by immunohistochemistry. The presence of corazonin isoforms was investigated using MALDI-TOF mass spectrometry in samples containing the brain, the subesophageal ganglion, the corpora cardiaca-corpus allatum complex and the anterior part of the aorta. Several groups of immunopositive perikarya were detected in the brain, the subesophageal ganglion and the thoracic ganglia. Regarding the brain, three clusters were observed in the protocerebrum. One of these clusters was formed by somata located near the entrance of the ocellar nerves whose fibers supplied the aorta and the corpora cardiaca. The remaining groups of the protocerebrum were located in the lateral soma cortex and at the boundary of the protocerebrum with the optic lobe. The optic lobe housed immunoreactive somata in the medial soma layer of the lobula and at the level of the first optic chiasma. The neuropils of the deutocerebrum and the tritocerebrum were immunostained, but no immunoreactive perikarya were detected. In the subesophageal ganglion, immunostained somata were found in the soma layers of the mandibular and labial neuromeres, whereas in the mesothoracic ganglionic mass, they were observed in the mesothoracic, metathoracic and abdominal neuromeres. Immunostained neurites were also found in the esophageal wall. The distribution pattern of corazonin like immunoreactivity in the central nervous system of this species suggests that corazonin may act as a neurohormone. Mass spectrometric analysis revealed that [Arg⁷]-corazonin was the only isoform of the neuropeptide present in T. infestans tissue samples.