Go Sinoaortic Nerve In The Rat Brain Cardiovascular Nuclei Of Fos And Nadph-d Expression

Objective: 1. To investigate whether the neuronal nitric oxide synthase(nNOS) is involved in the component of arterial baroreceptor reflex (ABR)transmission pathway in the rats; 2. To investigate whether the nNOS neuronsin these nuclei are abnormal under normal living condition in the rats on whichsinoaortic denervation (SAD) was performed in a preliminary operationsequentially a recovery period of seven days.Methods: 1. The distribution of activated neurons was investigated bymapping immunoreactivity of Fos protein in the medulla and supramedullaryregions 2 h and 1 w following SAD respectively; 2. The colocalization of Fosimmunoreactive (Fos-IR) neurons and the nNOS-containing neurons wasmapped in these nuclei using nicotinamide adenine dinucleotide phosphatediaphorase (NADPH-d) histochemistry combined with Fosimmunohistochemistry 2 h and 1 w following SAD respectively.Results:1. There was a specific pattern of Fos protein expression in cardiovascularnuclei 2 h following SAD.(1) Fos-IR neurons were identified in specific subnuclei of the NTS and therostral ventrolateral medulla (RVLM). The overwhelming number of Fos-IRneurons was present bilaterally at the level of the area postrema (AP), mainlylocated in the dorsomedial (Sdm), medial (Sm) and dorsolateral subnuclei (Sdl)of the NTS. Moderate number of Fos-IR cells was also detected at the obex level of the NTS, which were mainly located in the commissural nucleus(Com). In addition, sparse Fos-IR cells were scattered in the ventrolateralsubnucleus (Svl) of the NTS.(2) A specific subnuclei localization of Fos-IR neurons was detected in theparabrachial nucleus (PBN). A large number of Fos-IR neurons wereparticularly located in the external lateral subnucleus (el) of the PBN. Amoderate number of Fos-IR neurons were present at the dorsolateralsubnucleus (dl), the extreme medial subnucleus (exm), K-F subnucleus and thesuperior lateral subnucleus (sl). Nearly no Fos-IR cells were found in themedial PBN (MPBN).(3) There were a large number of Fos-IR neurons in the the supraopticnucleus (SON) and the hypothalamic paraventricular nucleus (PVN), denselydistributed in the medial parvocellular division (mp) and the dorsalparvocellular division (dp), sparsely distributed in the lateral magnocellulardivision (lm) and the posterior magnocelluar division (pm).(4) A large number of Fos-IR neurons were also observed in the centralnucleus of the amygdale (CeA) in basal forebrain.2. NADPH-d/Fos double-staining neurons were specificly distributed insome cardiovascular nuclei 2 h following SAD. In the medulla, double-labeledcells were mainly distributed in the Sm subnucleus of the NTS at the level ofAP and the Com subnucleus at the obex level of the NTS. In the pons,NADPH-d/Fos neurons were mainly distributed in the dl subnucleus of the PBN. Intensive NADPH-d positive fiber terminals were intermingled with theFos-IR neurons in the el subnucleus of the PBN. No double-labeled neuronswere observed in the K-F nucleus and other subnuclei. In the hypothalamus,distinct proportional NADPH-d/Fos double-staining neurons were distributedin the parvocellular division, magnocelluar division of the PVN and the SON.The percent of double-labeled neurons in the above regions was 6.8％, 72.1％and 47.1％, respectively. There were no NADPH-d/Fos neurons in the RVLMand CeA.3. Increased Fos-IR neurons were observed in several cardiovascular nucleiin the rats which SAD was performed in a preliminary operation following arecovery period of seven days under normal living condition. In the medulla,Fos-IR neurons were mainly distributed in the Sm and the Com subnuclei ofthe NTS. In addition, there were a large number of Fos-IR neurons in theRVLM. In the pons, Fos-IR neurons mainly distributed in the el and slsubnuclei of the PBN. In the hypothalamus, Fos-IR neurons were denselydistributed in the mp and dp of the PVN, moderately distributed in the SON.However, there were no Fos-IR neurons in the CeA in the basal forebrain.4. There were extensive amount of NADPH-d/Fos double-staining neuronsin the sl subnucleus of the PBN, only a small amount of sparse double-stainingneurons were also found in the SON and magnocelluar division of the PVN.No double-staining neurons were found in other subnuclei of the PBN, NTS,RVLM and CeA. Conclusions: 1. SAD evoked a reproducible pattern of Fos proteinexpression that conformed in the NTS to the termination patterns of primarybaroreceptor and in the RVLM to the important efferent region. SAD alsoresulted in a distinctive pattern of Fos expression in some supramedullaryregions such as the pontine LPBN, the PVN and SON in the hypothalamus andthe CeA in the basal forebrain. The distribution of nNOS-containing neuronswas topographically specific, and they may be involved in the modulation ofbaroreflex signal transmission.2. The neurons in partial cardiovascular nuclei in the SAD rats brain werealso able to be activated abnormally in the SAD rats under normal livingcondition, and partial nNOS neurons may participate in this process. Thisabnormal central cardiovascular regulation may involve the physiopathologicprocess which caused cardiovascular target organs damage.