Serotonergic fibers distribution in the midline and intralaminar thalamic nuclei in the rock cavy (Kerodon rupestris)


The thalamic midline/intralaminar complex is part of the higher-order thalamus, which receives little sensory input, and instead forms extensive cortico-thalamo-cortical pathways. The midline thalamic nuclei connect with the medial prefrontal cortex and the medial temporal lobe. On the other hand, the intralaminar nuclei connect with the fronto-parietal cortex. Taking into account this connectivity pattern, it is not surprising that the midline/intralaminar complex has been implicated in a broad variety of cognitive functions, including memory process, attention and orientation, and also reward-based behavior. Serotonin (5-HT) is a neurotransmitter that exerts different post-synaptic roles. Serotonergic neurons are almost entirely restricted to the raphe nuclei and the 5-HT fibers are distributed widely throughout the brain, including the midline/intralaminar complex. The present study comprises a detailed description of the morphologic features and semiquantitative analysis of 5-HT fibers distribution in the midline/intralaminar complex in the rock cavy, a typical rodent of the Northeast region of Brazil, which has been used by our group as an anatomical model to expand the comprehension about phylogeny on the nervous system. The 5-HT fibers in the midline/intralaminar nuclei of the rock cavy were classified into three distinct categories: (1) beaded fibers, which are relatively fine and endowed with large varicosities; (2) fine fibers, with thin axons and small varicosities uniformly distributed in whole axon; and (3) stem axons, showing thick non-varicose axons. Moreover, the density of 5-HT fibers is variable among the analyzed nuclei. On the basis of this diversity of the morphological fibers and the differential profile of optical density among the midline/intralaminar nuclei of the rock cavy, we conclude that the serotonergic system uses a diverse morphologic apparatus to exert a large functional repertory in the midline/intralaminar thalamic nuclei.

DOI: 10.1016/j.brainres.2014.08.047

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@article{Silva2014SerotonergicFD, title={Serotonergic fibers distribution in the midline and intralaminar thalamic nuclei in the rock cavy (Kerodon rupestris)}, author={Alane de Medeiros Silva and Melquisedec Abiar{\'e} Dantas de Santana and Paulo Leonardo Ara{\'u}jo de G{\'o}is Morais and Twyla Barros de Sousa and Rovena Clara Galv{\~a}o Janu{\'a}rio Engelberth and Eudes Euler de Souza Lucena and Clarissa Loureiro das Chagas Camp{\^e}lo and Jeferson de Sousa Cavalcante and Judney Cley Cavalcante and Miriam Stela Maris de Oliveira Costa and Expedito Silva do Nascimento}, journal={Brain Research}, year={2014}, volume={1586}, pages={99-108} }