A new model of experimental hemispherotomy in young adult Rattus norvegicus: a neural tract tracing and SPECT in vivo study

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>The objective of this study was to describe a new experimental model of hemispherotomy performed on laboratory animals.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>Twenty-six male young adult Wistar rats were distributed into two groups (surgery and control). The nonfluorescent anterograde neurotracer biotinylated dextran amine (BDA; 10,000 MW) was microinjected into the motor cortex area (M1) according to <jats:italic>The Rat Brain in Stereotaxic Coordinates</jats:italic> atlas to identify pathways and fibers disconnected after the experimental hemispherectomy. SPECT tomographic images of <jats:sup>99m</jats:sup>Tc hexamethylpropyleneamine oxime were obtained to verify perfusion in functioning areas of the disconnected and intact brain. A reproducible and validated surgical procedure is described in detail, including exact measurements and anatomical relationships. An additional 30 rodents (n = 10 rats per group) were divided into naïve, sham, and hemispherotomy groups and underwent the rotarod test.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>Cortico-cortical neural pathways were identified crossing the midline and contacting neuronal perikarya in the contralateral brain hemisphere in controls, but not in animals undergoing hemispherotomy. There was an absence of perfusion in the left side of the brain of the animals undergoing hemispherotomy. Motor performance was significantly affected by brain injuries, increasing the number of attempts to maintain balance on the moving cylinder in the rotarod test at 10 and 30 days after the hemispherotomy, with a tendency to minimize the motor performance deficit over time.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>The present findings show that the technique reproduced neural disconnection with minimal resection of brain parenchyma in young adult rats, thereby duplicating the hemispherotomy procedures in human patients.</jats:p></jats:sec>

Lateralization in Hemiparkinsonian Rats Is Affected by either Deep Brain Stimulation or Glutamatergic Neurotransmission in the Inferior Colliculus

“…Indeed, the neural tract tracings performed in this study demonstrated connections between the IC and both dorsal (deep layers of the superior colliculus and dorsal columns of the periaqueductal gray matter) and ventral (SNpl) midbrain structures. Both the deep layers of the superior colliculus and the dorsolateral columns of the periaqueductal gray matter are interconnected ( Ribeiro et al, 2005 ; Freitas et al, 2005 ), receive inputs from the substantia nigra ( Eichenberger et al, 2002 ; Ribeiro et al, 2005 ; Castellan-Baldan et al, 2006 ), a ventral midbrain structure also connected to the neostriatum ( Castellan-Baldan et al, 2006 ; Matias et al, 2019 ), and send projections to the deep midbrain and pontine reticular formation ( Coimbra et al, 2006 ). These former areas also include the mesencephalic locomotor region (MLR; Sébille et al, 2017 ), an important midbrain structure implicated in commands for movement initiation and gait selection ( Jordan et al, 2008 ; Takakusaki, et al, 2016 ).…”