Absolute Number Of Neurons Research Articles

Lateral fluid percussion injury in the developing rat causes an acute, mild behavioral dysfunction in the absence of significant cell death

Lateral fluid percussion injury (LFP), a model of mild–moderate concussion, leads to the temporary loss of the capacity for experience-dependent plasticity in developing rats. To determine if this injury-induced loss in capacity for plasticity is due to cell death, we conducted stereological measurements within the cerebral cortex and CA3 of the hippocampus 2 weeks following mild, moderate or severe LFP in the post-natal day 19 (P19) rat. Results indicated that there was no significant change in the absolute number of neurons, regardless of injury severity, in either the ipsilateral cortex (sham = 10.6 ± 1.7, mild = 11.5 ± 2.1, moderate = 10.0 ± 1.0, severe = 10.9 ± 1.3 million neurons) or CA3 region of the hippocampus (sham = 251 ± 38, mild = 289 ± 2, moderate = 245 ± 48, severe = 255 ± 62 thousand neurons). Even though there was no evidence of a significant degree of injury-induced cell death, animals exhibited cognitive deficits as revealed in a Morris water maze task (MWM). The MWM results indicated that regardless of injury severity, P19-injured rats exhibited a significant increase in escape latency compared to age-matched shams (injury by day; P < 0.001) and a significant increase in the number of trials needed to reach criterion ( P < 0.05). Analysis of a probe trial one week post-MWM training, however, indicated that there was no deficit in storage or recall of the learned behavior as analyzed by platform hits (sham = 2.9 ± 0.37, mild = 2.0 ± 0.40, moderate = 1 ± 0, severe = 2.8 ± 0.62) or percent time spent in, or immediately surrounding, the platform area (sham = 13.5 ± 1.71, mild = 10.8 ± 2.32, moderate = 12.7 ± 0, severe = 13.5 ± 1.69). Taken together, these results indicate that while LFP in P19-injured animals does not lead to significant cell death, it does generate acute, mild deficits in MWM performance.

Proliferation of cerebellar neurons induced by astrocytes treated with thyroid hormone is mediated by a cooperation between cell contact and soluble factors and involves the epidermal growth factor‐protein kinase a pathway

Cerebellar development is fully dependent on thyroid hormone (T3) levels. We have previously demonstrated a glia-mediated effect of T3 on cerebellar neurons. We have reported that cerebellar astrocytes treated with thyroid hormone secrete epidermal growth factor (EGF), which directly induces neuronal proliferation and, indirectly, by increasing synthesis of extracellular matrix proteins, induces neurite outgrowth in vitro. Here, by using a neuron-astrocyte coculture model, we investigated the involvement of cell contact on neuronal proliferation. Culturing of cerebellar neurons on T3-treated astrocyte carpets or conditioned medium derived from them (T3CM) yielded similar results, revealed by a 60% increase in cell population. However, the absolute number of neurons in coculture assays was greatly enhanced in comparison with that in CM assays (3.5-4-fold). Bromodeoxyuridine (BrdU) incorporation assays revealed that such an increase was due mainly to proliferation of precursors cells. BrdU incorporation was three times higher in cell carpet (31%) than in CM (13%). Treatment of astrocytes by T3 increased neuronal proliferation either by T3CM (2.5 times) or by contact with T3-treated astrocytes (1.5 times). Neuronal death was not affected by T3 treatment of astrocytes as revealed by either trypan blue viability assays or active caspase-3 labeling. Treatment of astrocytes by EGF mimicked T3 effects on neuronal proliferation. Addition of the EGF receptor tyrosine kinase inhibitor genistein and the protein kinase A (PKA) inhibitor KT5720 to cocultutres and T3CM completely reversed neuronal proliferation. Our results implicate EGF and the PKA pathway in the proliferation induced by T3-treated astrocytes. Furthermore, the fact that cocultures potentiate the effect of T3 on neuronal proliferation suggests that neuron-astrocyte contact may cooperate with astrocyte soluble factors to enhance neuronal population. Our data reveal an important role of astrocytes as mediators of T3-induced cerebellar development and partially elucidate the role of cell contact and soluble factors on this process.

Local circuit neurons in the medial prefrontal cortex (areas 24a,b,c, 25 and 32) in the monkey: II. Quantitative areal and laminar distributions

The companion paper (Gabbott and Bacon [1996] J. Comp. Neurol.) describes the morphology of calretinin (CR)-, parvalbumin (PV)-, calbindin (CB)-, and GABA-immunoreactive neurons, and NADPH diaphorase-reactive cells, in the medial prefrontal cortex (mPFC; areas 24a, 24b, 24c, 25 and 32) of the adult monkey. Since these local circuit neurons play crucial functional roles, the aim of this study was to provide supportive quantitative data defining their areal and laminar distribution in mPFC. The numerical densities of neurons (Nv, number of cells per mm3) in each area and layer were calculated stereologically. The mean total neuronal Nv estimates across mPFC was 55,727 ± 3,319 per mm3 (mean ± S.D.; n = 3); values ranged from 50,489 ± 8,374 per mm3 (area 24a) to 59,938 ± 7,214 per mm3 (area 24c). Interareal differences were not significant. Cortical depth measurements and neuronal Nv estimates for each area allowed the absolute number of neurons in a column of cortex under 1 mm2 of surface to be calculated; values varied between 86,457 ± 15,063 (area 24a) and 128,464 ± 24,050 (area 24c). Using immunolabelled Nissl-stained sections of mPFC, CR+ neurons constituted 11.2%, PV+ neurons 5.9%, and CB+ neurons 5.0% of the total neuron population. GABA+ neurons represented an overall 24.9% (23.5–27.3%) of neurons in the mPFC. Differences between areas were not significant. The cortical depth distribution histograms of CR+, PV+, CB+, and GABA+ cell populations in each area were derived and the percentage of a given cell population in each layer subsequently calculated. Peaks in the cortical depth distributions of CR+ and CB+ neurons occurred in layer 2 and upper layer 3, respectively; the peak distribution of PV+ neurons occurred between lower layer 3 and upper layer 5. The depth distribution of GABA+ cells reflected the combined distributions of CR+, PV+ and CR+ neurons. In all areas, the majority (74.4–84.0%) of the GABA cell population was located in layers 2/3. The depth distributions for each cell type were similar between areas. Diaphorase-reactive neurons accounted for 0.25% (0.2–0.32%) of all cortical neurons in mPFC and were distributed in two horizontal strata, in midlayer 3 and in mid/upper layer 6. A large population of diaphorase-reactive cells was present in the white matter. The absolute numbers of CR+, PV+, CB+ and GABA+ neurons within individual layers in a column of cortex under 1 mm2 and 50 × 50 μm of cortical surface have been derived. The data presented provide the basis for a quantitative definition of cortical circuits in monkey mPFC. © 1996 Wiley-Liss, Inc.

Local circuit neurons in the medial prefrontal cortex (areas 24a,b,c, 25 and 32) in the monkey: II. Quantitative areal and laminar distributions

The companion paper (Gabbott and Bacon [1996] J. Comp. Neurol.) describes the morphology of calretinin (CR)-, parvalbumin (PV)-, calbindin (CB)-, and GABA-immunoreactive neurons, and NADPH diaphorase-reactive cells, in the medial prefrontal cortex (mPFC; areas 24a, 24b, 24c, 25 and 32) of the adult monkey. Since these local circuit neurons play crucial functional roles, the aim of this study was to provide supportive quantitative data defining their areal and laminar distribution in mPFC. The numerical densities of neurons (Nv, number of cells per mm3) in each area and layer were calculated stereologically. The mean total neuronal NV estimates across mPFC was 55,727 +/- 3,319 per mm3 (mean +/- S.D.; n = 3); values ranged from 50,489 +/- 8,374 per mm3 (area 24a) to 59,938 +/- 7,214 per mm3 (area 24c). Interareal differences were not significant. Cortical depth measurements and neuronal NV estimates for each area allowed the absolute number of neurons in a column of cortex under 1 mm2 of surface to be calculated; values varied between 86,457 +/- 15,063 (area 24a) and 128,464 +/- 24,050 (area 24c). Using immunolabelled Nissl-stained sections of mPFC, CR+ neurons constituted 11.2%, PV+ neurons 5.9%, and CB+ neurons 5.0% of the total neuron population. GABA+ neurons represented an overall 24.9% (23.5-27.3%) of neurons in the mPFC. Differences between areas were not significant. The cortical depth distribution histograms of CR+, PV+, CB+, and GABA+ cell populations in each area were derived and the percentage of a given cell population in each layer subsequently calculated. Peaks in the cortical depth distributions of CR+ and CB+ neurons occurred in layer 2 and upper layer 3, respectively; the peak distribution of PV+ neurons occurred between lower layer 3 and upper layer 5. The depth distribution of GABA+ cells reflected the combined distributions of CR+, PV+ and CR+ neurons. In all areas, the majority (74.4-84.0%) of the GABA cell population was located in layers 2/3. The depth distributions for each cell type were similar between areas. Diaphorase-reactive neurons accounted for 0.25% (0.2-0.32%) of all cortical neurons in mPFC and were distributed in two horizontal strata, in midlayer 3 and in mid/upper layer 6. A large population of diaphorase-reactive cells was present in the white matter. The absolute numbers of CR+, PV+, CB+ and GABA+ neurons within individual layers in a column of cortex under 1 mm2 and 50 x 50 microns of cortical surface have been derived. The data presented provide the basis for a quantitative definition of cortical circuits in monkey mPFC.

Layer V pyramidal cells in the adult human cingulate cortex. A quantitative Golgi-study.

The anterior and posterior parts of the human cingulate cortex differ in their absolute number of neurons per unit volume, with fewer neurons in the anterior part. To test the hypothesis that lower absolute number and packing density of neurons in the anterior cingulate cortex are associated with an increased complexity in the neuropil compartment, dendritic arborizations of layer V neurons in both cingulate parts were analyzed in a Golgi study. Results show that these neurons in the anterior cingulate cortex have more primary and secondary basal dendrites than those in the posterior cingulate cortex. This establishes an association of a higher complexity of the dendritic arborization in the anterior cingulate cortex with a lower cell number per unit volume and larger neuropil compartment. The significant lower degree of dendritic arborization in the posterior cingulate cortex is accompanied by a higher cell packing density. These structural differences are associated with functional differences between the two parts of the human cingulate cortex.

Effect of dark rearing on the volume of visual cortex (areas 17 and 18) and number of visual cortical cells in young kittens.

The surface area, total volume, and total number of neurons of areas 17 and 18 in one hemisphere of dark-reared (DR), dark-reared and light-exposed (DRL), and normally reared (NR) kittens were studied at the age of 6 weeks. The thickness of the visual cortex was lower by 13% and 11% (area 17) and by 17% and 16% (area 18) in DR and DRL groups, respectively, when compared with similar cortical areas in NR kittens. The surface area values of area 17 were nearly the same in DR and DRL kittens, both being, however, 37% smaller than in NR animals. The surface area of area 18 was significantly smaller than that of area 17 in each group, and was also lower in DR (by 27%) and DRL (by 21%) groups when compared with the NR group. As a consequence of dark rearing, the numerical density of cortical neurons in area 17 amounted to about double of the value observed in normally reared kittens and was also significantly higher in area 18. The numerical density of nerve cells of DRL kittens fell between the DR and NR groups. The total cortical volume of area 17 was similar in DR and DRL groups but it was by 46% (DR) and by 44% (DRL) smaller than in NR kittens. In each experimental group, the total volume of area 18 was significantly smaller than that of area 17. The cortical volume of area 18 was also smaller than in the NR group by 39% and 34% in DR and DRL groups, respectively. In DR and NR kittens, the total numbers of neurons in areas 17 (DR = 26.4 million, NR = 25.7 million) and 18 (DR = 8.5 million, NR = 9.0 million) were essentially similar. In the DRL groups a significantly smaller number of cortical neurons was found both in area 17 (21.5 million) and in area 18 (6.8 million). It is concluded that, in spite of considerable differences in the cortical thickness, surface area, numerical density, and total cortical volume, the absolute numbers of neurons in area 17 and 18 of visually deprived (DR) and NR kittens do not differ at 6 weeks of age. The main deficit in cortical organization following dark rearing, therefore, appears to be confined mainly to the neuropil, as a result of an underdevelopment of neuronal processes and of depressed synaptic organization.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of systemic androgen treatment on androgen accumulation in song control regions of the adult female canary brain

Systemic treatment of adult female canaries (Serinus canarius) with testosterone (T) induces song and increases the size of song control regions (SCRs) in the brain. We used autoradiographic techniques to determine whether systemic T treatment also changes the accumulation of tritiated T or its metabolites by SCR cells. T treatment did not change the proportion of T target cells in SCRs, nor did it change the degree of cellular accumulation of T or its metabolites. Neuronal density was not altered by T treatment in any SCR sampled. In HVc (caudal nucleus of the ventral hyperstriatum) and RA (robust nucleus of the archistriatum), cell size did not differ between T-treated and control females. However, systemic T did increase the mean sizes of labelled cells and of all cells sampled in MAN (magnocellular nucleus of the anterior neostriatum). The results support the hypothesis that the induction of song in female canaries by T relates to increases in the absolute numbers of neurons and of T target neurons in SCRs.

The impact of sexual dimorphism on neuron numbers in the superior cervical ganglion of the rat

Other workers have reported a sexual dimorphism in the number of neurons that project from the rat superior cervical ganglion (SCG) via the internal carotid nerve (ICN). We have re-examined this situation by comparing ganglionic neuron numbers as well as the number of neurons labelled retrogradely from the iris and the pineal gland, in age-matched adult male and female rats. No significant dimorphism was seen in total cell numbers or in the cell populations supplying iris or pineal gland, although there was a trend towards more neurons in male animals. From evaluation of our results and the published data, we suggest that the variation in absolute numbers of neurons counted in the SCG is so wide, within genders, that any impact of gender differences on cell numbers is of little significance.

Murine strain differences in taste responsivity and organization of the rostral nucleus of the solitary tract

Taste responsivity and organization of fungiform papillae, geniculate ganglion neurons and gustatory recipient zones of the nucleus of the solitary tract (NST) were examined in C57BL/6NCrlBR (C57) mice, BALB/c6NCrlBR (BALB/c) mice and CB6Fl/CrlBr (CB6) mice, an F1 hybrid cross between BALB/c and C57 mice. Results from behavioral studies confirm that C57 and CB6 mice exhibit higher preferences to sucrose and lower preferences to NaCl, as compared to BALB/c mice. No strain differences were confirmed for aversion responses to citric acid or quinine HC1 taste stimuli. Anatomical analyses show that the number and organization of fungiform papillae do not reliably differ between C57, BALB/c, and CB6 mice, nor do volumes of glossopharyngeal terminal fields in the NST. However, strain-specific differences exist in the number of neurons contained in the geniculate ganglion, volume of chorda tympani (CT) terminal fields in the rostral NST, and number of NST neurons contained in CT terminal fields. BALB/c and CB6 mice possess a greater number of geniculate ganglion neurons and larger CT terminal fields, as compared to C57 mice. However, strain differences in the number of geniculate ganglion neurons and terminal field volume are not obviously correlated with strain differences in gustatory responsivity. The only reliable relationship confirmed between taste responsivity and neuroanatomical organization of the rostral NST relates to the absolute number of neurons contained in CT terminal fields, and corresponding neuronal density within CT terminal fields. Chorda tympani terminal fields of C57 and CB6 mice contain an average of 379 neurons, whereas CT terminal fields of BALB/c mice contain an average of 531 neurons. Chorda tympani terminal fields of C57 and CB6 mice contain an average of 1.14 neurons/10 4 cubic microns, whereas CT terminal fields of BALB/c mice contain an average of 1.679 neurons/10 4 cubic microns. These results confirm that genetic factors contribute to a wide range of anatomical differences at the level of the geniculate ganglion and rostral gustatory NST, and suggest that murine strain differences in taste responsivity may at least partially relate to strain differences in populations of NST neurons contained in CT terminal fields.

Stability of neuron number in cortical barrels of aging mice.

The question of whether age-related neuron loss occurs in the cerebral cortex of rodents, as it apparently does in humans, has not been directly answered by previous studies. The barrel, a discrete morphological and functional unit in rodent somatosensory cortex, is a favorable system in which to address the problem of neuron loss during senescence. The numerical density and absolute number of neurons as well as barrel volume were determined from a computer-assisted three-dimensional reconstruction of thick (100 microns) and semithin (1 micron) sections through a single barrel, C3, from inbred mice (C57Bl/6NNia) at 4, 12, 22, 26, 30, and 33 months of age. The number and density of neuron and glial cells and the volume of the barrel did not change significantly with age. These data indicate that neuron loss is not a universal phenomenon in senescence and that there may be significant species differences in the aging of laboratory rodents and humans.

Depopulation of the ventromedial hypothalamic nucleus in the diabetic Chinese hamster.

The relationship between diabetes and the size, density and area of the ventromedial hypothalamic nucleus (VMH) was studied in the genetically diabetic Chinese hamster. Matched diabetic and non-diabetic control chinese hamsters were perfused, the hypothalamus collected, sectioned and stained for light microscopy. The mid-point of each VMH nucleus was located, photographed and enlarged for morphometric analysis. Each neuron that possessed a nucleolus and was located within the confines of a VMH was counted, and subsequently the area of each nucleus and the density of neurons per area of VMH were calculated. The results indicated that both the area and absolute number of neurons within the VMH of diabetic hamsters were significantly reduced compared to control values (P less than 0.01) The density of neurons per unit area of VMH was similar in both groups. These data suggest that the VMH experiences a neuronal depopulation in diabetic hamsters which may have a functional influence on the hypothalamic-pancreatic axis in this species.

Quantitative cytoarchitectonic distribution of neurons, glia, and DNa in rat cerebral cortex.

AbstractA new technique combining microfluorometric DNA assays with differential cell counts was used to quantitate the intralaminar distribution of neuronal and non‐neuronal cells (chiefly glial) in rat somatosensory cortex (Charles River 250 gm males, C D® strain). The intracortical amounts of DNA per unit fresh volume were calculated from the DNA contents of serial frozen slices of known volume sampled serially from the pial surface to white matter in frozen cortical cylinders; respective amounts per unit solids were calculated from predetermined dry weights of the slices. Cell counts were performed on serial horizontal sections from formalin‐fixed cylinders stained by Nissl's method. Neuronal DNA and glial DNA were calculated based on the percentages of the respective cells counted.Total DNA averaged 5.43 μg/mg dry weight (1.19 μg mm3 fresh volume). Values were highest in layers II and IV. Neuronal DNA paralleled total DNA in its intracortical distribution and showed distinct peaks in layers II and IV. Glial DNA showed an even distribution. Glia exceeded neurons only in layers I and VIc. The mean neuron/glia ratio was 2.5. This method gives a more precise estimate of the absolute numbers of neurons and glia than can be obtained by histological methods alone, since DNA assays eliminate the need to correct the histological counts for volume changes during fixation and staining.