RESUMO
Palatine tonsils (PTs), together with ileal Peyer's patches, rank among the first colonization sites for infectious prions. After replicating in these lymphoid tissues, prions undertake the process of "neuroinvasion," which is likely mediated by the peripheral nerves connecting lymphoid tissues to the central nervous system (CNS). To study the connections between the tonsils and the CNS, we injected fluorescent tracers into the PTs of lambs; the highest number of Fast Blue (FB)-labeled neurons was found in cranial cervical ganglia (CCG), whereas a progressively decreasing number of cells were detected in proximal glossopharyngeal, proximal vagal, trigeminal, pterygopalatine, and cervicothoracic ganglia. Immunohistochemistry was carried out on tonsil and ganglia cryosections. Immunoreactivity (IR) for tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), neuronal nitric oxide synthase (nNOS), calcitonin gene-related peptide (CGRP), substance P (SP), and calcium-binding protein S100 (S100), was observed in the fibers around and within PT lymphoid nodules. In the trigeminal, proximal glossopharyngeal and vagal ganglia the retrogradely-labeled neurons showed nNOS-, SP- and CGRP-IR. In all ganglia some retrogradely-labeled neurons showed nNOS-, SP- and CGRP-IR co-localization. It is worth noting that only 66+/-19% and 75+/-13% of retrogradely-labeled neurons in CCG showed TH- and DBH-IR, respectively. The present results allow us to attribute PT innervation mainly to the sympathetic component and to the glossopharyngeal, vagal and trigeminal cranial nerves. Furthermore, these data also provide a plausible anatomic route through which infectious agents, such as prions, may access the CNS, i.e. by traveling along several cranial and sympathetic nerves, as well as by migration via glial cells.
Assuntos
Gânglios Sensitivos/anatomia & histologia , Gânglios Simpáticos/anatomia & histologia , Tonsila Palatina/inervação , Ovinos/anatomia & histologia , Animais , Sistema Nervoso Autônomo/anatomia & histologia , Sistema Nervoso Autônomo/metabolismo , Peptídeo Relacionado com Gene de Calcitonina/metabolismo , Tamanho Celular , Dopamina beta-Hidroxilase/metabolismo , Feminino , Gânglios Sensitivos/metabolismo , Gânglios Simpáticos/metabolismo , Linfonodos/anatomia & histologia , Linfonodos/inervação , Linfonodos/metabolismo , Vias Neurais/anatomia & histologia , Vias Neurais/metabolismo , Neurônios/metabolismo , Óxido Nítrico Sintase Tipo I/metabolismo , Tonsila Palatina/anatomia & histologia , Tonsila Palatina/metabolismo , Proteínas S100/metabolismo , Medula Espinal/anatomia & histologia , Medula Espinal/metabolismo , Substância P/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
The purpose of this investigation was to determine the central distribution of the efferent neurons of the recurrent laryngeal nerve (RLN) in the sheep by the use of the retrograde transport of the fluorescent tracer Fast Blue. The distribution of the RLN neurons was also compared with that of the neurons simultaneously labelled by injection of another tracer, Diamidino Yellow dihydrochloride, into the cervical trunk of the vagus nerve (CTV). Injections of the tracer into the CTV resulted in heavy retrograde labelling of neurons in the ipsilateral dorsal motor nucleus of the vagus nerve, in the nucleus ambiguus, in the nucleus retroambigualis and in the reticular formation surrounding the nucleus ambiguus. Following injections of the tracer into the RLN, labelling of neurons was seen over a wide area of the ipsilateral nucleus ambiguus and in the nucleus retroambigualis. Species differences in the distribution of the efferent component of the RLN are discussed, in particular ruminants compared to nonruminants.