Postnatal Generation of Neurons in the Ventrobasal Nucleus of the Rat Thalamus

Abstract

Most CNS systems, including the trigeminal-somatosensory system, develop via a hierarchical order (from the periphery and up the neuraxis). We tested the hypothesis that development of the trigeminal system can proceed via a nonhierarchical mechanism (i.e., that neuronogenesis can occur postnatally). Preweanling rats were perfused, and brain sections were stained with cresyl violet or immunolabeled with NeuN (for neuronal counts), or processed for acetylcholinesterase (AChE) activity or p75 immunoreactivity [to identify boundaries of the ventrobasal nucleus (VB)]. Neuronal number decreased during the first postnatal week but increased 2.5-fold over the next 3 weeks. To determine whether this remarkable rise resulted from the generation of new neurons, preweanlings were given injections of bromodeoxyuridine (BrdU) on postnatal day 6 (P6) or P21. BrdU-positive VB cells were apparent on both days. Cumulative BrdU labeling showed that the cell cycle was 17.3 h on P6. Moreover, Ki-67, a protein elaborated throughout the cell cycle, was expressed by 25.8 -29.3% of all VB cells on P6 -P15, falling to 7.7% by P21. BrdU-positive VB cells coexpressed neuronal markers: NeuN, HuC/D, microtubule-associated protein 2, and a dextran placed in the somatosensory cortex. Note that postnatal neuronal generation was also evident in other thalamic nuclei (e.g., the lateral geniculate nucleus). Thus, the developing VB experiences two periods of neuronal generation. Prenatal neuronogenesis is part of hierarchical trigeminal-somatosensory development. Postnatal nonhierarchical neuronogenesis is intrathalamic and matches changes in neuromodulatory systems (exemplified by AChE activity and p75) and the arrival of corticothalamic afferents.

Role of neurotrophins on postnatal neurogenesis in the thalamus: prenatal exposure to ethanol

“…Interestingly, the postnatal period of neuronal generation in the VB coincides with upregulation of neurotrophin receptors. That is, both Trk (data not shown) and p75 (Crockett et al, 2000; Mooney and Miller, 2007b) are highly expressed in the neonate and are downregulated by the middle of the first postnatal month. Furthermore, the decrease in Ki-67 immunolabeling during the third postnatal week (Mooney and Miller, 2010) parallels the losses of p75 and Trk expression.…”

“…The VB is distinctive within the developing CNS; it is one of the few structures that experiences postnatal neuronogenesis (Mooney and Miller, 2007b). It is unique in that this occurs in situ and not within a distinct generative population.…”

Oscillatory Entrainment of Thalamic Neurons by Theta Rhythm in Freely Moving Rats

“…Then the recorded area is a cylinder with volume V s ϭ 0.0471 mm 3 for the small-diameter and V l ϭ 0.0804 mm 3 for the large-diameter electrode. The average density of rodent dorsal thalamus is ϳ23,000 neurons per mm 3 (Mooney and Miller 2007;Ramos et al 1995), which translates to ϳ1,083 local neurons that contribute to LFP s and ϳ1,849 neurons to LFP l , respectively. Our model is coherent with the passive neuronal electrical parameters known to undergo fast amplitude decay, which is proportional to the square of the distance to the point source (Pettersen and Einevoll 2008).…”

“…A similar exponential rule is used to identify extracellular spike signals (Henze et al 2000). A cylinder with a radius of 47 m contains on average 1,083 neurons in rat thalamus (Mooney and Miller 2007;Ramos et al 1995), which is the maximum number of possible recordable cells by a single small-diameter electrode. In this case, the total number of AV theta cells (23.7%) contributing to the LFP s will be ϳ257.…”

The Role of Cell Fusion in Physiological and Reparative Regeneration of the Cerebral Cortex

“…Today the majority of scientists regard proliferation and differentiation of neural stem cells into neurons as the main and even the only mechanism of the nervous system regeneration, including regeneration of its highest compartments [8,9]. However, this opinion is often disputed.…”