Sensory neuron number in neonatal and adult rats estimated by means of stereologic and profile-based methods

Abstract

Postnatal neuron addition, if it occurred, would have profound implications both for the conceptualization of developmental processes and for efforts directed at replacing neurons that were lost to injury or disease. Although dorsal root ganglia (DRGs) offer the advantages of clear boundaries and functional homogeneity, studies comparing neuron number in the DRGs of animals of different ages or sizes have yielded conflicting results. In the present study, neuron number in DRGs L3-L6 was compared in neonatal (approximately 11 days old, mean weight of 24.5 g, mean volume of 25 cm3) and adult (approximately 80 days old, mean weight of 373.5 g, mean volume of 346 cm3) male Sprague-Dawley rats. Estimates of neuron number were derived by using both stereological (physical disector) and profile-counting (one or more nucleoli within a nucleus) methods. The reliability and validity of the two methods were evaluated by comparing estimates of neuron number with those derived from three-dimensional reconstruction of a subset of neurons. The recommended protocol for using the physical disector was found to give accurate estimates of neuron number, but the heterogeneous distribution of neurons in the ganglion led to sampling errors of up to 50%. Reliability was improved by increasing the number of disector pairs examined. Counts of nuclear/nucleolar profiles were more reliable, but introduced a bias that worked against the experimental hypothesis in that estimates of neuron number in neonates exceeded actual values. Nonetheless, both methods indicated that adult rats had more DRG neurons than did neonates. Profile counts were 19% higher in adults (P < .01, two-tailed t-test); and data obtained by using the physical disector showed that adult rats had 28% more neurons than did neonates (P < .05). The difference in neuron number between adults and neonates could be due either to neuron proliferation or to late differentiation of neurons that do not assume a typical appearance until adulthood.

Size and number of binucleate and mononucleate superior cervical ganglion neurons in young capybaras

“…In agreement with the results of Farel (2003), a greater number of neurons in the hypogastric ganglion of rats of 24 months than in rats of 4 months was reported by Warburton and Santer (1997) and a greater number of neurons in the dorsal root ganglia of rats of 80 days than rats of 11 days was also stated by Popken and Farel (1997). Similarly, Gagliardo et al (2005) have reported a significant 17· increase in the total number of dog's inferior mesenteric ganglion neurons during the post-natal development, i.e.…”

Evidence of Postnatal Neurogenesis in Dorsal Root Ganglion: Role of Nitric Oxide and Neuronal Restrictive Silencer Transcription Factor

“…However, there has been little investigation of neurogenesis and some is still controversial in DRG of PNS (Devor et al 1985;Devor and Govrin-Lippmann 1991;Farel 2002Farel , 2003Groves et al 2003;La Forte et al 1991;Namaka et al 2001;Popken and Farel 1997). We have demonstrated here, that inhibition of NO produced in DRG neurons-satellite glia (homologous to Schwann cells) co-cultures, in absence of NGF, has a direct effect on nestin + cell numbers in vitro and axotomized DRG in vivo.…”

“…Although the vast majority of neurons are differentiated before birth, there are a few special areas in the brain region, such as subventricular zone of the lateral ventricles and subgranular zone of the dentate gyrus, which generate large numbers of neurons during postnatal development (Alvarez-Buylla et al 2001;Gage 2000;Goldman and Luskin 1998;Zhu et al 2006). Postnatal neurogenesis in the peripheral nervous system (PNS) such as dorsal root ganglion (DRG) has been reported, but not as well defined as in the CNS (Devor et al 1985;Devor and Govrin-Lippmann 1991;Farel 2002Farel , 2003Groves et al 2003;La Forte et al 1991;Namaka et al 2001;Popken and Farel 1997). Postnatal neurogenesis in DRG occurs at various time points depending on the age and injury to their axons.…”

Impact of Treadmill Running and Sex on Hippocampal Neurogenesis in the Mouse Model of Amyotrophic Lateral Sclerosis

“…Because we were interested in relative differences and not necessarily an absolute value of BrdU-labeled cells in DG, BrdU positive cells in the entire DG were quantified by profile-sampling methods [47]. In the x-y plane, BrdU positive cells limited to the subgranule cell layer were manually counted in a blind fashion at 40× magnification (Olympus, BX60, Center Valley, USA).…”