Peptide 19-immunoreactive primary sensory neurons in the rat trigeminal ganglion

Peptide 19-immunoreactivity (PEP 19-IR) was examined in the trigeminal ganglion (TG) of the adult rat. A half of TG neurons were immunoreactive(IR) for PEP 19. PEP 19-IR neurons were mostly medium-sized to large. 66% of TG neurons > 600 microm(2) and 38% of those in the range 300-600 microm(2) showed the IR. TG neurons <300 microm(2) were mostly devoid of PEP 19-IR (86%). A double immunofluorescence method revealed the coexpression of PEP 19 and calcium-binding proteins. 31% and 16% of PEP 19-IR neurons exhibited parvalbumin- and calbindin D-28k-IRs, respectively. Conversely, a half of parvalbumin- (53%) and calbindin D-28k-IR (55%) neurons coexpressed PEP 19-IR. PEP 19-IR neurons were mostly IR for S100 (91%) and 80% of S100-IR neurons showed PEP 19-IR. Virtually all (99%) PEP 19-IR neurons were devoid of calcitonin gene-related peptide (CGRP)-IR. The molar tooth pulp contained PEP 19-IR nerve fibers. In the root pulp, PEP 19-IR nerve fibers projected straight until they reached the coronal pulp. Accompanied by blood vessels, these nerve fibers ascended toward the pulp horn. They formed nerve plexuses in the subodontoblastic layer, and reached the base of the odontoblastic layer. However, PEP 19-IR nerve fibers could not be observed within the odontoblastic layer, predentine or dentine. The distribution of these nerve fibers was similar to that of parvalbumin-IR ones. In the TG, PEP 19-IR was found in 34% of primary sensory neurons retrogradely labeled from the molar tooth pulp. 80% of PEP 19-IR tooth pulp TG neurons coexpressed parvalbumin-IR. An immunoelectron microscopic method revealed that a half of radicular axons showed PEP 19-IR. 80% of myelinated axons exhibited PEP 19-IR, whereas 20% of unmyelinated ones showed the IR. In the subodontoblastic layer, PEP 19-IR nerve fibers mostly lost myelin sheath or Schwann cell ensheathment. At the base of the odontoblastic layer, PEP 19-IR neurites made close contact with odontoblasts. PEP 19-IR nerve endings could not be observed in other oro-facial tissues. The coexpression of PEP 19 and CaBPs suggests that low-threshold mechanoreceptors contain PEP 19-IR in the TG. It is also likely that PEP 19-IR TG neurons include myelinated nociceptors.     

Parvalbumin, calretinin and carbonic anhydrase in the trigeminal and spinal primary neurons of the rat

The cell-body size of parvalbumin-immunoreactive (-ir) primary neurons was measured in the trigeminal (TG) and lumber dorsal root ganglia (DRG). In the DRG, parvalbumin-ir was mostly detected in large cells (94% in the range of 600–2800 μm²). Parvalbumin-ir TG cells were smaller than similar DRG cells and yet parvalbumin-ir TG cells of < 400 μm² (2.86%) were rare. Trichrome stains for parvalbumin, calretinin (CR) and carbonic anhydrase (CA), and for parvalbumin, calcitonin gene-related peptide (CGRP) and CA were performed to estimate possible overlap of these substances. Virtually all parvalbumin-ir DRG cells contained CA activity while a small subpopulation (28.5%) of CR-ir DRG cells lacked CA activity. All the CR-ir DRG cells that exhibited CA were also ir for parvalbumin. 31.1% of parvalbumin-ir DRG cells exhibited CR-ir while 71.5% of CR-ir DRG cells showed parvalbumin-ir. All the CR-ir DRG cells of < 400 μm² lacked CA activity and parvalbumin-ir while all those of > 800 μm² exhibited both activities. 30% of CR-ir DRG cells in the size range of 400–800 μm² co-expressed CA. DRG cel co-expressing parvalbumin and CGRP were rare (1%). As was the case for the DRG, most of parvalbumin-ir TG cells exhibited CA activity (89.24%) and lacked CGRP-ir (96.6%). CR-ir TG cells were also subdivided into two groups; one with and the other without co-expression of CA. Unlike in the DRG, however, co-expression of parvalbumin and CR could never be detected in the TG.     

Peripheral projections of calretinin-immunoreactive primary sensory neurons in chick hindlimbs

In chicken dorsal root ganglia, calretinin immunoreactivity is expressed by a subpopulation of large A-neurons, most of which co-express calbindin D-28k. The myelinated axons of these neurons selectively innervate all muscle spindles and most Herbst corpuscles associated to feathers in hindlimbs. It is suggested that the presence of calretinin in primary afferents may be correlated with the electrophysiological properties of rapidly adapting mechanoreceptors.     

Osteopontin-immunoreactive primary sensory neurons in the rat spinal and trigeminal nervous systems

1200 micrometer(2) and 9% of those in the range 600-1200 micrometer(2) showed the immunoreactivity (ir). DRG neurons <600 micrometer(2)800 micrometer(2) showed the ir and 21% of those in the range 400-800 micrometer(2) were immunoreactive for this protein. TG neurons <400 micrometer(2) were mostly devoid of OPN-ir (2%). Virtually all (99%) Mes5 primary sensory neurons exhibited the ir. Muscle spindles in the soleus and masseter muscles contained OPN-ir spiral axon terminals. In the hard palate and incisor periodontal ligament, unencapsulated corpuscular endings exhibited the ir. The co-expression of OPN with parvalbumin and calcitonin gene-related peptide (CGRP) was also examined in the DRG and TG. In the DRG, virtually all (97%) OPN-ir neurons exhibited parvalbumin-ir. Conversely, 66% of parvalbumin-ir DRG neurons co-expressed OPN-ir. In the TG, 81% of OPN-ir neurons exhibited parvalbumin-ir and 69% of parvalbumin-ir ones showed OPN-ir. Virtually all OPN-ir DRG and TG neurons were devoid of CGRP-ir. The present study indicates that OPN-ir primary sensory neurons in the DRG and Mes5 are spinal and trigeminal proprioceptors. OPN-ir TG neurons appear to include low-threshold mechanoreceptors.     

Peptide 19 in the dorsal root ganglion and the mesencephalic trigeminal tract nucleus of the adult rat

Peptide 19-immunoreactivity (PEP 19-ir) was examined in the dorsal root ganglion (DRG) and the mesencephalic trigeminal tract nucleus (Mes5) of the adult rat. Thirty-eight percent of DRG cells were immunoreactive (ir) for PEP 19. These neurons were small to large and measured 167-4583 micron2 (mean+/-S.D.=2048+/-913 micron2). Seventy-five percent of DRG cells >2000 micron2 and 15% of those <1000 micron2 exhibited PEP 19-ir. Thirty-six percent of DRG neurons in the range 1000-2000 micron2 showed the ir. In the Mes5, 87% of primary neurons were ir for this peptide. Muscle spindles in the soleus and masseter muscles contained PEP 19-ir spiral axon terminals. Double immunofluorescence methods revealed the co-expression of PEP 19 and calcium binding proteins. Eighty-six percent of parvalbumin-ir neurons exhibited PEP 19-ir. Conversely, 60% of PEP 19-ir neurons showed parvalbumin-ir. The cell size analysis revealed that 55% of PEP 19-ir neurons >600 micron2 showed parvalbumin-ir and that all PEP 19-ir neurons <600 micron2 were devoid of it. Ninety percent of PEP 19-ir DRG neurons showed S100-ir, whereas 60% of S100-ir ones co-expressed PEP 19-ir. In the Mes5, virtually all PEP 19-ir primary neurons exhibited parvalbumin-ir. The co-expression of PEP 19 and S100 could not be observed in the nucleus. The present study indicates that PEP 19-ir neurons which co-express parvalbumin-ir are proprioceptors in the spinal and the trigeminal systems. PEP 19-ir small DRG neurons without S100-ir are probably exteroceptors and may include unmyelinated nociceptors.     

Parvalbumin- and calretinin-immunoreactive trigeminal neurons innervating the rat molar tooth pulp

Calcium-binding proteins and neuropeptides were examined in trigeminal neuronal cell bodies retrogradely labeled with Fast blue (FB) from the maxillary molar tooth pulp of the rat. FB-labeled cells were located in the maxillary division of the trigeminal ganglion. 30 and 50% of the labeled cells were immunoreactive for parvalbumin and calcitonin gene-related peptide (CGRP), respectively. The coexpression of these substances was observed in 9.5% of FB-labeled cells. On the other hand, 2.4% of FB-labeled cells exhibited calretinin-immunoreactivity (CR-ir) and 20% tachykinin (TK)-ir. The coexpression of CR and TK was observed in 1.9% of FB-labeled cells, i.e., most of CR-ir FB-labeled neurons coexpressed TK-ir. An immuno-EM method revealed that all parvalbumin-ir nerve fibers in the root pulp were myelinated and that CGRP-ir nerve fibers were both myelinated (15%) and unmyelinated (85%). The present study indicated that primary nociceptors innervating the rat molar both pulp contained parvalbumin and CR and coexpressed these calcium-binding proteins and neuropeptides. It was suggested that peripheral axons of parvalbumin-ir tooth pulp primary neurons are all myelinated. Most peripheral CR-ir axons are probably unmyelinated because TK-ir myelinated axons have never been demonstrated in any peripheral organ.     

Co-expression of VRL-1 and calbindin D-28k in the rat sensory ganglia

The co-expression of vanilloid receptor 1-like receptor (VRL-1), a newly cloned capsaicin-receptor homologue, with calbindin D-28k was examined in the rat sensory ganglia. The co-expression was rare in the dorsal root, trigeminal and jugular ganglia and abundant in the petrosal and nodose ganglia. In the dorsal root ganglion, none of VRL-1-immunoreactive (ir) neuron co-expressed calbindin D-28k-immunoreactivity (ir). Of the VRL-1-ir neurons, 9 and 5% showed calbindin D-28k ir in the trigeminal and jugular ganglia, respectively. On the other hand, 35 and 63% of VRL-1-ir neurons in the petrosal and nodose ganglia, respectively, co-expressed these substances. The retrograde tracing method indicated that petrosal neurons which co-expressed VRL-1-and calbindin D-28k-ir innervated taste buds in the circumvallate papilla. The present findings may suggest that VRL-1 is associated with chemosensory functions in visceral sensory neurons.     

Partial coexistence of neuropeptide Y and calbindin D28k in the trigeminal ganglion following peripheral axotomy of the inferior alveolar nerve in the rat

Immunohistochemistry was applied to examine the correlation between neuropeptide Y (NPY) and the two calcium binding proteins (CaBPs) parvalbumin (PV) and calbindin D28k (CB) in the trigeminal ganglion following peripheral axotomy of the inferior alveolar nerve (IAN) in the rat. Five days following transection and application of FluoroGold (FG) to the cut end of the IAN, approximately 14.8% (80/539) and 18.6% (90/483) of FG-labeled IAN neurons in the trigeminal ganglion showed PV-like immunoreactivity (-LI) and CB-LI, respectively. The mean ± S.D. area of FG-labeled PV-like immunoreactive (-IR) cells (FG/PV-IR cells) and FG/CB-IR cells were 835.9 ± 303.1 μm² and 712.7 ± 246.0 μm², respectively. FG/PV-IR cells were significantly larger than FG/CB-IR cells. Fourteen days following peripheral axotomy of the IAN, NPY-LI appeared in the medium- to large-sized cells. Double immunostaining revealed that approximately 3.3% (52/1569) of NPY-IR cells in the axotomized trigeminal ganglion displayed PV-LI, while approximately 26.7% (371/1392) of NPY-IR cells displayed CB-LI. The mean ± S.D. cross-sectional areas of PV-IR and CB-IR trigeminal ganglion cells displaying NPY-LI were 819.5 ± 265.6 μm² and 766.5 ± 279.7 μm², respectively. There were no significant differences in the cross-sectional areas either between NPY/PV-IR cells and NPY/CB-IR cells, or between FG/PV-IR cells and NPY/PV-IR cells, or between FG/CB-IR cells and NPY/CB-IR cells. The present results indicate that injury-evoked medium- to large-sized NPY neurons were a different population from large-sized PV neurons, and NPY was partly co-localized with CB.     

The coexistence of TrkA with putative transmitter agents and calcium-binding proteins in the vagal and glossopharyngeal sensory neurons of the adult rat

The presence of the neurotrophin receptor, TrkA, in neurochemically identified vagal and glossopharyngeal sensory neurons of the adult rat was examined. TrkA was colocalized with calcitonin gene-related peptide (CGRP), parvalbumin, or calbindin D-28k in neurons of the nodose, petrosal and/or jugular ganglia. In contrast, no TrkA-immunoreactive (ir) neurons in these ganglia colocalized tyrosine hydroxylase-ir. About one-half of the TrkA-ir neurons in the jugular and petrosal ganglia contained CGRP-ir, whereas only a few of the numerous TrkA-ir neurons in the nodose ganglion contained CGRP-ir. Although 43% of the TrkA-ir neurons in the nodose ganglion contained calbindin D-28k-ir, few or no TrkA-ir neurons in the petrosal or jugular ganglia were also labeled for either calcium-binding protein. These data show distinct colocalizations of TrkA with specific neurochemicals in vagal and glossopharyngeal sensory neurons, and suggest that nerve growth factor (NGF), the neurotrophin ligand for TrkA, plays a role in functions of specific neurochemically defined subpopulations of mature vagal and glossopharyngeal sensory neurons.     

Kv1.2-immunoreactive primary sensory neurons in the rat trigeminal ganglion

Immunohistochemistry for Kv1.2, a subunit of voltage-gated K(+) channels, was performed on the trigeminal ganglion (TG). Immunoreactivity (ir) was detected in half (48%) the TG neurons. These neurons were mostly medium-sized to large (range 137.6-2664.8 microm(2), mean+/-S.D. 892.6+/-413.3 microm(2)). A double immunofluorescence method also revealed co-expression of Kv1.2 and parvalbumin. Half (54%) the Kv1.2-immunoreactive (ir) neurons exhibited parvalbumin-ir, and parvalbumin-ir neurons mostly showed Kv1.2-ir (95%). Kv1.2-ir neurons which co-expressed CGRP-ir were rare in this ganglion. Some 40% of TG neurons retrogradely labeled from the facial skin exhibited Kv1.2-ir, whereas ir was detected in 16% of those labeled from the tooth pulp. The present study indicates that Kv1.2-ir TG neurons include low-threshold mechanoreceptors and nociceptors which innervate the facial skin and tooth pulp, respectively.     

Aspartate-immunoreactive primary sensory neurons in the mouse trigeminal ganglion

Aspartate-immunoreactivity (ir) was examined in the mouse trigeminal ganglion (TG). The ir was detected in 34% of TG neurons and their cell bodies were of various sizes (mean +/- S.D. = 1,234 +/- 543 microm(2)). A triple immunofluorescence method revealed the co-expression of aspartate with calcitonin gene-related peptide (CGRP) and parvalbumin; 22% and 14% of aspartate-immunoreactive (ir) neurons were also immunoreactive for CGRP and parvalbumin, respectively. The co-expression of aspartate with both CGRP and parvalbumin was very rare in the TG. By retrograde tracing method, half and 66% of TG neurons which innervate the vibrissa and palate, respectively, contained aspartate-ir. The co-expression of aspartate with CGRP was more common among palatal neurons (36%) compared to vibrissal neurons (22%). Aspartate-ir neurons which co-expressed parvalbumin-ir were numerous in the vibrissa (17%) but not in the palate (4%). These findings may suggest that the function of aspartate-containing TG neurons is correlated with their peripheral receptive fields.     

Coexistence of calbindin D-28k and NADPH-diaphorase in vagal and glossopharyngeal sensory neurons of the rat

The presence and coexistence of calbindin D-28k-immunoreactivity (ir) and nicotinamide adenosine dinucleotide phosphate (NADPH)-diaphorase activity (a marker of neurons that are presumed to convert L-arginine to L-citrulline and nitric oxide) were examined in the glossopharyngeal and vagal sensory ganglia (jugular, petrosal and nodose ganglia) of the rat. Calbindin D-28k-ir nerve cells were found in moderate and large numbers in the petrosal and nodose ganglia, respectively. Some calbindin D-28k-ir nerve cells were also observed in the jugular ganglion. NADPH-diaphorase positive nerve cells were localized to the jugular and nodose ganglia and were rare in the petrosal ganglion. A considerable portion (33–51%) of the NADPH-diaphorase positive neurons in these ganglia colocalized calbindin D-28k-ir. The presence and colocalization of calbindin D-28k-ir and NADPH-diaphorase activity in neurotransmitter-identified subpopulations of visceral sensory neurons were also studied. In all three ganglia, calcitonin gene-related peptide (CGRP)-ir was present in many NADPH-diaphorase positive neurons, a subset of which also contained calbindin D-28k-ir. In the nodose ganglion, many (42%) of tyrosine hydroxylase (TH)-ir neurons also contained NADPH diaphorase activity but did not contain calbindin D-28k-ir. These data are consistent with a potential co-operative role for calbindin D-28k and NADPH-diaphorase in the functions of a subpopulation of vagal and glossopharyngeal sensory neurons.     

Distribution of neurons immunoreactive for calcium-binding proteins varies across areas of cat primary somatosensory cortex

The primary somatosensory (SI) cortex in the cat contains four cytoarchitectonic areas that appear to contain separate body representations and have different functions. We tested whether functional differences among these areas are reflected in the densities of neurons containing each of three calcium-binding proteins: parvalbumin (PV), calbindin (CB), and calretinin (CR). Colocalization experiments revealed that CR was localized in a population of neurons distinct from those containing PV or CB. The general laminar distributions of the three calcium-binding proteins were similar to those described in other species and cortical areas, but there were significant density differences in layers II and III across SI. The density of PV-immunoreactive neurons was higher in areas 3b and 1 than in areas 3a and 2. CB-immunoreactive neurons were found in higher densities in anterior SI than in posterior SI, and the pattern of CR-immunoreactive neurons was reciprocal to that of CB, with significantly higher densities in posterior regions of SI. Since the firing characteristics of nonpyramidal neurons appear to be related to their calcium-binding protein content, differences in regional distributions of these neurons in layers II and III may contribute to functional differences between the cytoarchitectonic areas of SI cortex.     

The difference of osteocalcin-immunoreactive neurons in the rat dorsal root and trigeminal ganglia: co-expression with nociceptive transducers and central projection

The co-expression of osteocalcin (OC) with the capsaicin receptor (VR1) and vanilloid receptor 1-like receptor (VRL-1) was examined in the dorsal root (DRG) and trigeminal ganglia (TG). Virtually all OC-immunoreactive (ir) DRG neurons were devoid of VR1- and VRL-1-immunoreactivity (ir). In the TG, 14.1% of OC-ir neurons were also immunoreactive for VR1. Only 1.7% of OC-ir TG neurons co-expressed VRL-1-ir. The distribution of OC-ir was also examined in the spinal cord and trigeminal sensory nuclei. In the spinal cord, the superficial laminae of the dorsal horn were devoid of OC-ir. The neuropil was weakly stained in other regions of the spinal horns. The medullary dorsal horn (MDH) contained numerous OC-ir varicose fibers in laminae I and II. These fibers were occasionally observed originating from the spinal trigeminal tract. The neuropil was weakly stained in deeper laminae of the MDH, and the rostral parts of the trigeminal sensory nuclei. The present study suggests that OC-ir TG nociceptors send their unmyelinated axons to the superficial laminae of the MDH.     

Neurocalcin-immunoreactive primary sensory neurons in the trigeminal ganglion provide myelinated innervation to the tooth pulp and periodontal ligament

The distribution of neurocalcin-immunoreactive (NC-ir) primary sensory neurons was examined in the trigeminal ganglion (TG), mesencephalic trigeminal tract nucleus (Mes5) and intraoral structures. NC-ir primary sensory neurons were located in the TG but not the Mes5. The coexpression study demonstrated that virtually all NC-ir TG neurons exhibited S100-immunoreactivity (-ir). In the tooth pulp, NC-ir nerve fibers were observed in the subodontoblastic and odontoblastic layers. Immunoelectron microscopic and retrograde tracing methods revealed that myelinated pulpal axons derived from the TG mostly exhibited the ir. In the periodontal ligament, bush-like endings showed NC-ir. These endings were morphologically identical to Ruffini-like endings. The present study suggests that NC-ir trigeminal primary sensory neurons have their cell bodies in the TG. Their peripheral axons are probably myelinated. Such neurons include pulpal nociceptors and low-threshold mechanoreceptors.     

Calretinin and calbindin D-28k delay the onset of cell death after excitotoxic stimulation in transfected P19 cells

In some neurological diseases, injury to neurones reflects an over-stimulation of their receptors for excitatory amino acids. This response may disturb the Ca(2+)-homeostasis and lead to a pronounced and sustained increase in the intracellular concentration of this ion. On the basis of data derived from correlative studies, calcium-binding proteins have been postulated to play a protective role in these pathologies. We tested, directly, the capacity of the three calcium-binding proteins calretinin (CR), calbindin D-28k (CB) and parvalbumin (PV) to buffer [Ca(2+)], and to protect cells against excitotoxic death. We used P19 murine embryonic carcinoma cells, which can be specifically induced (by retinoic acid) to transform into nerve-like ones. The differentiated cells express functional glutamate-receptors and are susceptible to excitotoxic shock. Undifferentiated P19-cells were stably transfected with the cDNA for CR, CB or PV, induced to differentiate, and then exposed to NMDA, a glutamate-receptor agonist. The survival rates of clones expressing CR, CB or PV were compared with those of untransfected P19-cells using the lactate-dehydrogenase assay. CR- and CB-expressing cells were protected from death during the first 2 h of exposure to NMDA. This protection was, however, transient, and did not suffice to rescue P19-cells after prolonged stimulation. Two of the three PV-transfected clones raised were vulnerable to NMDA-induced excitotoxicity; the third, which expressed the lowest level of PV, was protected to a similar degree as that found for the CR- and CB-transfected clones. Our results indicate that in the P19-cell model, CR and CB can help to delay the onset of cell death after excitotoxic stimulation.     

Brain-derived neurotrophic factor-immunoreactive primary sensory neurons in the rat trigeminal ganglion and trigeminal sensory nuclei

Immunohistochemistry for brain-derived neurotrophic factor (BDNF) was performed on the rat trigeminal ganglion (TG). The immunoreactivity (IR) was detected in 46% of TG neurons. These neurons were mostly small- or medium-sized (range, 149.7-1246.3 microm2; mean +/- SD = 373.4 +/- 151.6 microm2). A double immunofluorescence method also revealed that 54% of BDNF-immunoreactive (IR) neurons were immunoreactive for calcitonin-gene-related peptide. In addition, 93% of BDNF-IR TG neurons contained vanilloid receptor subtype 1. However, the co-expression of BDNF and vanilloid receptor 1-like receptor was very rare (less than 1%). In the trigeminal sensory nuclei, laminae II of the medullary dorsal horn was abundant in presumed BDNF-IR axon terminals. Such profiles were also detected in the dorsolateral part of the subnucleus oralis. The retrograde tracing and immunohistochemical methods demonstrated that BDNF-IR was common among cutaneous TG neurons (47%) but not tooth pulp TG neurons (13%). The present study indicates that BDNF-IR TG neurons have unmyelinated axons and project to the superficial medullary dorsal horn. It is likely that BDNF-containing neurons in both the trigeminal and spinal sensory systems have similarities in morphology and function. However, the content of BDNF in TG neurons probably depends on their peripheral targets. BDNF seems to convey nociceptive cutaneous input to the trigeminal sensory nuclei.     

Immunohistochemical localization of calretinin in the dorsal root ganglion and spinal cord of the rat

Calretinin (CR). a recently identified calcium-binding protein, is present in nervous tissue, including sensory pathways, where it may play an important role in regulation of cellular activity. Using immunocytochemistry, we examined the cellular localization of CR in dorsal root ganglia (DRG) and spinal cord of normal rats and after multiple unilateral dorsal root ganglionectomies. In DRG, CR-immunoreactive cell bodies and axons were a small subpopulation (10%) of medium- to large-sized neurons. In the spinal cord, CR-like immunoreactivity (LI) in neurons and fibers was found in all laminae except motoneurons. Dense fiber networks were also found in Clarke's column. The densest staining of both cell bodies and fibers was in the superficial laminae, especially lamina II, and in the lateral spinal and lateral cervical nuclei. CR-immunoreactive fibers were also observed in the fasciculi cuneatus and gracilis. Fasciculus gracilis exhibited the greatest number of labeled axons at the lumbosacral levels, but few labeled axons were found at the rostral thoracic and cervical levels. In contrast, the corticospinal tract at the base of the dorsal column was devoid of CR-immunoreactive fibers. Unilateral multiple lumbar ganglionectomies resulted in a loss of CR-LI in the dorsal columns ipsilateral to the surgery. In the spinal gray matter ipsilateral to the ganglionectomies, CR-LI was reduced in Clarke's column and slightly enhanced in the medial third of lamina II. Our observations demonstrate a unique distribution pattern of CR-LI compared to other calcium-binding proteins in the spinal cord, and suggest a role for CR in nociceptive and proprioceptive pathways.     

VR1-immunoreactive primary sensory neurons in the rat trigeminal ganglion

Immunohistochemistry for VR1, a nociceptive transducer for vanilloid compounds, protons and heat (>43°C), was performed on the rat trigeminal ganglion (TG). The immunoreactivity (IR) was detected in 20% of TG cells and these neurons were mostly small- to medium-sized (mean±S.D. 427±189 μm²). Twenty-six percent of the TG neurons retrogradely labeled from the facial skin exhibited VR1-IR, while the IR was detected in only 8% of those labeled from the tooth pulp. Co-expression of VR1 was common among the calcitonin gene-related peptide-immunoreactive cutaneous neurons (63%) but not among the similar tooth pulp neurons (20%). The present study indicates that primary nociceptive neurons which respond to vanilloid compounds, protons and heat are abundant in the facial skin but not in the tooth pulp.     

Poor correlation between delayed neuronal death induced by transient forebrain ischemia,and immunoreactivity for parvalbumin and calbindin D-28k in developing gerbil hippocampus

In the normal developing hippocampus of the gerbil, parvalbumin-immunoreactive neurons first appear in the stratum pyramidale of CA3 at postnatal day 15 (P15), and in CA2 and hilus of the dentate gyrus from P21 onwards. Immunoreactive terminals also follow the same sequence from CA3 to CA1 to reach adult patterns by the end of the 1st month. Calbindin D-28k immunoreactivity is seen in the external part of the upper blade of the dentate gyrus at P5, and progresses to the granule cell and molecular layers of the whole gyrus by P15, except for a thin band of immature cells located at the base of the granule cell layer which are calbindin negative. Calbindin immunoreactivity in mossy fibers progresses from the external to the hilar region of CA3 during the same period. A few immunoreactive cells are also found in the stratum radiatum/lacunare of the CA3, but no calbindin-immunoreactive cells are observed in the CA1 and CA2 subfields. The adult pattern of calbindin immunoreactivity is reached at P21. Vulnerability following transient forebrain ischemia for 20 min was examined in the hippocampal formation of gerbils during postnatal development. No cellular damage was seen in animals aged 7 days. Dying cells were observed at the base of the granule cell layer of the dentate gyrus in animals aged 15, 21 and 30 days. Pyramidal cells in the CA3 subfield were also sensitive to ischemia in gerbils aged 15 days, and less frequently in animals aged 21 days. The adult pattern of cellular damage, characterized by selective vulnerability of the CA1 subfield, was seen from day 30 onwards. These findings show that the pattern of selective vulnerability following transient forebrain ischemia is different in young and adult gerbils, and suggest that little, if any, correlation exists between resistance to delayed cellular damage and parvalbumin and calbindin D-28k content in the hippocampus of young gerbils.Supported in part by grant FIS 93-131 and a grant from the Fundacio Pi i Synyer (to A.T.)