EurekaMag.com logo
+ Translate

Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. II. The AP and AE neurons


, : Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. II. The AP and AE neurons. Journal of Neurobiology 18(3): 295-313

To assess the generality of our previous finding (Gao and Macagno, 1987) that segmental homologues play a role in the establishment of the pattern of axonal projections of the heart accessory HA neurons, we have extended our studies to two other identified leech neurons: the anterior pagoda (AP) neurons and the annulus erector (AE) motor neurons. Bilateral pairs of AP neurons are found in the first through the twentieth segmental ganglia (SG1 through SG20) of the leech ventral nerve cord. All AP neurons initially extend axonal projections to the contralateral periphery as well as longitudinal projections along the contralateral interganglionic connective nerves toward anterior and posterior neighboring ganglia. Although the peripheral projections are maintained by all AP neurons throughout the life of the animal, the longitudinal projections disappear in all but two segments: the AP neurons in SG1 maintain their anterior projections and extend them into the head ganglion, and those in SG20 maintain their posterior projections and extend them into SG21 and the tail ganglion. When single AP neurons are deleted anywhere along the nerve cord before processes begin to atrophy, however, the longitudinal projections are retained by their ipsilateral homologues in adjacent ganglia. The rescued processes appear to take over the projections of the deleted neurons. In cases where two or more AP neurons on the same side of the nerve cord are deleted from adjacent ganglia, a contralateral homologue sometimes extends projections to the periphery ipsilaterally or on both sides. We obtained similar results when we deleted single AE neurons from midbody ganglia. Thus, our experiments with three different identified neurons consistently show that the initial pattern of projections is the same in all ganglia, but that the existence of homologues in adjacent ganglia leads to the pruning of some of the initial projections. A consequence of this homologue-dependent process retraction is that neurons normally lacking neighboring homologues will have patterns of projections different from those neurons that do have such neighbors. Process loss by the HA, AP, and AE neurons may be the result either of competition for targets, inputs, or growth factors or of direct interactions among homologous cells.

Accession: 005432783

PMID: 3298543

DOI: 10.1002/neu.480180305

Download PDF Full Text: Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. II. The AP and AE neurons


Submit PDF Full Text

No spam - Every submission is manually reviewed

Due to poor quality, we do not accept files from Researchgate

Submitted PDF Full Texts will always be free for everyone
(We only charge for PDFs that we need to acquire)

Select a PDF file:
Close
Close

Related references

Gao, W.Q.; Macagno, E.R., 1987: Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. I. The HA cells. The role of homologues in the establishment of the pattern of axonal projections of identified segmentally homologous neurons was investigated by means of selective cell ablation and dye injection. The cells studied were the bilateral pairs of hea...

Gao, W.Q.; Macagno, E.R., 1988: Axon extension and retraction by leech neurons: severing early projections to peripheral targets prevents normal retraction of other projections. During leech embryogenesis, interactions between homologous neurons in neighboring segments lead to the selective retraction of longitudinal axonal projections by midbody AP and AE neurons, which maintain lateral axonal projections to the peripher...

Johansen, J.; Hockfield, S.; McKay, R.D., 1984: Axonal projections of mechanosensory neurons in the connectives and peripheral nerves of the leech, Haemopis marmorata. The axonal projections of the seven mechanosensory neurons in the connectives and peripheral nerves were examined by horseradish peroxidase (HRP) injections. In the connective the closely functionally related mechanosensory neurons travel in two b...

Alonso, G.; Bribes, E.; Chauvet, N., 1996: Survival and regeneration of neurons of the supraoptic nucleus following surgical transection of neurohypophysial axons depend on the existence of collateral projections of these neurons to the dorsolateral hypothalamus. The aim of the present study was to compare the postlesional responses of vasopressin-producing (VP) and oxytocin-producing (OT) neurons of the supraoptic nucleus (SON) to transection of neurohypophysial axons. At different times after sectioning...

Gershon, T.R.; Baker, M.W.; Nitabach, M., 1998: Two receptor tyrosine phosphatases of the LAR family are expressed in the developing leech by specific central neurons as well as select peripheral neurons, muscles, and the other cells. Journal of Neuroscience 18(8): 91-3002

Gershon, T.R.; Baker, M.W.; Nitabach, M.; Wu, P.; Macagno, E.R., 1998: Two receptor tyrosine phosphatases of the LAR family are expressed in the developing leech by specific central neurons as well as select peripheral neurons, muscles, and other cells. Receptor protein tyrosine phosphatases (rPTPs) are thought to play a crucial role in neuronal development, particularly in pathfinding by growing processes. We have cloned and sequenced two Hirudo medicinalis rPTPs that are homologous to the Droso...

Wong, V.Y.; Wang, H.J.; Macagno, E., 1996: Expression of Dfd homologues in identifiable neurons of leech. Society for Neuroscience Abstracts 22(1-3): 528

Dolbeare, D.; Houle, J.D., 2003: Restriction of axonal retraction and promotion of axonal regeneration by chronically injured neurons after intraspinal treatment with glial cell line-derived neurotrophic factor (GDNF). The response of supraspinal neurons to acute or delayed treatment with GDNF following a spinal cord injury was examined. A cervical level 3 hemisection lesion cavity was created by tissue aspiration in adult, female rats. In one experiment gel foa...

Wilcox J.N.; Chronwall B.M.; O'donohue T.L.; Roberts J.L., 1985: Localization of pro opiomelanocortin messenger rna in related neurons functionally defined by their axonal projections combining in situ hybridization with fluorescent axonal tracing. Society for Neuroscience Abstracts 11(1): 143

Lillesaar, C.; Stigloher, C.; Tannhäuser, B.; Wullimann, M.F.; Bally-Cuif, L., 2008: Axonal projections originating from raphe serotonergic neurons in the developing and adult zebrafish, Danio rerio, using transgenics to visualize raphe-specific pet1 expression. Serotonin is a major central nervous modulator of physiology and behavior and plays fundamental roles during development and plasticity of the vertebrate central nervous system (CNS). Understanding the developmental control and functions of seroto...