Studies On The Peptidergic Nervous System In Cestodes

Recent years an interest in the neuropeptides in the platyhelminths is growing. There are no tine endocrine glands and a circulatory system in these organisms, and so the neurosecretory (peptidergic) component of the nervous system probably serves an important integrative role. It may be an exploitable target for chemotherapeutic evaluation. To our knowledge many researchers have accumulated attention to the morphological features of the electric dense vesicles. Little have been known about morphological and functional features of transport of messenger substances of neurosecretory cells to targets. Relatively few studies have been carried out to identify the neurosecretory/peptidergic molecules in 77 solium, 77 hydatigena, M expansa and plerocercoid of L. intesalis. In the present study, the structure of the nervous system, particularly neurosecretory components the presence and distribution of the regulatory peptides in the hitherto neglected group of cestodes were investigated using histological immunocytochemical techniques, transmission and scan electron microscope, PCR and western blot analysis. A wide range of nerve cells or stomata in multiple or bipolar form are distributed throughout both the CNS and PNS. The most striking ultrastructural feature of those worm neurons is that of a secretary cell engaged in the synthesis and export of material by axonal transport in vesicles. The neuronal some contained numerous clear vesicles(30 ?5Onm) and occasional dense-cored vesicles(50 1 OOnm). The basic components of neurosecretary cells were almost similar to those of neurons. There are, some differences, the most apparent of which was distinct existence of large dense-cored vesicles(lOO250nm) and a few electron dense- cored located eccentrically within the vesicles(70 l6Onm). Several types of true 86 chemical synapses have been observed in these tapeworms. The main types are axo- axonal, axo-dendritic, axo-somato and dendro-dendritic synapses that are symmetric or asymmetric. Neuromuscular synapses as otor end plates?of vertebrate skeletal muscles were not encountered in the morphological identification. Oftentimes, the axon merely passes close to the muscle cells. A close parallarity of the muscle cells and axonal membranes that are separated by space of 2Onm or less otherwise mark the myoneural junction. The relationship between neurosecretory processes and muscles were seen commonly in three ways: single neuro secretory axon contacts with several different cytoplasmic arms from myofibrils or a single arm contacts with several axons; secretory granules from peptidergic neurosecretory axons are released directly into extra cellular stroma close to muscles; axolemma of neurosecretory process contacts with membrane of muscle. The structure likes myelin sheaths surrounding axons was found in the CNS and PNS. PRL-IR was widely distributed in the CNS and PNS in the adult worms. PRL- IR perikarya occurred in the cerebral ganglia, around the basic area of sucker and the rostral border region between the rostellum and sucker. The PRL-IR fibres innervated the holdfast musculature of the scolex. There are a number of PRL-IR fibres in the main nerve cords and a few amounts in the transverse commissure. Numerous PRL-IR cells with processes occurred in the ootype/Mehlis?gland complex, oviduct, vetelline duct, uterum, seminal receptacle, also in vas efferent of testes and vas deferens. In the plerocercoid, PRL-IR were...