Group 1 metabotropic glutamate subtype 5 receptors (mGluR5) contribute to the control of motor behavior by regulating the balance between excitation and inhibition of outputs in the basal ganglia. The density of these receptors is increased in patients with Parkinson’s disease and motor complications. We hypothesized that similar changes may occur in Huntington’s disease (HD) and aimed at testing this hypothesis in a preliminary experimental series in postmortem human brain material obtained from HD patients. Using autoradiography, we analyzed mGluR5 density in the putamen, caudate nucleus and cerebellum (control region) in postmortem tissue samples from three patients with HD and three controls with two mGluR5-specific radioligands ([3H]ABP688 and [11C]ABP688). The density of enkephalin (Enk)- or substance P (SP)-containing neurons was assessed using immunohistochemical and cell-counting methods. [3H]ABP688 binding in HD was reduced in the caudate (−70.4 %, P < 0.001), in the putamen (−33.3 %, P = 0.053), and in the cerebellum (−8.79 %, P = 0.930) vs controls. Results with [11C]ABP688 were similar; there was good correlation between [11C]ABP688 and [3H]ABP688 binding ratios. Total cell density was similar in all three brain regions in HD patients and controls. Neuronal density was 69 % lower in the caudate (P = 0.002) and 64 % lower in the putamen (P < 0.001) of HD patients vs controls. Both direct and indirect pathways were affected, with ≥90 % decrease in the density of Enk- and SP-containing neurons in the caudate and putamen of HD patients vs controls (P < 0.001). In contrast to earlier observations in PD, in HD, compared to controls, the mGluR5 density was significantly lower in the caudate nucleus. The decrease in neuronal density suggests that neuronal loss was largely responsible for the observed decrease in mGluR5.

Alzheimer's disease is associated with a significant decrease in the cholinergic input to the neocortex. In a rat model of this depletion, we analyzed the subsequent long-term changes in cholinergic fiber density in two well-defined areas of the frontal and parietal cortices: Fr1, the primary motor cortex, and HL, the hindlimb area of the somatosensory (parietal) cortex, two cortical cholinergic fields that receive inputs from the nucleus basalis magnocellularis (nBM). A specific cholinergic lesion was induced by the intraparenchymal injection of 192 IgG-saporin into the nBM. Choline acetyltransferase (ChAT) immunohistochemistry was applied to identify the loss of cholinergic neurons in the nBM, while acetylcholinesterase (AChE) enzyme histochemistry was used to analyze the decreases in the number of cholinoceptive neurons in the nBM and the cholinergic fiber density in the Fr1 and HL cortical areas in response to the nBM lesion. The immunotoxin differentially affected the number of ChAT- and AChE-positive neurons in the nBM. 192 IgG-saporin induced a massive, irreversible depletion of the ChAT-positive (cholinergic) neurons (to 11.7% of the control level), accompanied by a less dramatic, but similarly persistent loss of the AChE-positive (cholinoceptive) neurons (to 59.2% of the control value) in the nBM within 2 weeks after the lesion. The difference seen in the depletion of ChAT- and AChE-positive neurons is due to the specificity of the immunotoxin to cholinergic neurons. The cholinergic fiber densities in cortical areas Fr1 and HL remained similarly decreased (to 62% and 68% of the control values, respectively) up to 20 weeks. No significant rebound in AChE activity occurred either in the nBM or in the cortices during the period investigated. This study therefore demonstrated that, similarly to the very extensive reduction in the number of ChAT-positive neurons in the nBM, cortical areas Fr1 and HL underwent long-lasting reductions in the number of AChE-positive fibers in response to specific cholinergic lesioning of the nBM.

The effect of neonatal capsaicin treatment, producing selective elimination of almost all unmyelinated C-fiber sensory axons, was studied on lesion-induced transganglionic labelling of the substantia gelatinosa of the spinal cord by choleragenoid. In both control and capsaicinpretreated rats, the injection of choleragenoid-horseradish peroxidase conjugate into the intact sciatic nerves resulted in intense labelling only of the deeper layers of the spinal dorsal horn. In the control but not the capsaicin-pretreated rats, the injection of the tracer into sciatic nerves transected 2 weeks previously produced an intense homogeneous labelling of the substantia gelatinosa. It is concluded that the uptake and axonal transport of choleragenoid by capsaicin-sensitive C-fiber afferents may be accounted for by the lesion-induced transganglionic labelling of the substantia gelatinosa, rather than by A-fiber sprouting. q 2003 Elsevier Ireland Ltd. All rights reserved.

Adult hippocampal slice cultures were used in the modeling of apoptotic aspects of neurodegeneration. Slice viability was determined by the use of trypan blue (TB) staining, and apoptosis was assessed by caspase-3 immunohistochemistry. A large number of pyramidal cells showed signs of degeneration 30 min after sectioning (58.4% of the total number of pyramidal cells), as they exhibited TB uptake, and about 71.6% of these neurons became stained by the third day in culture, when patches in the stratum oriens also demonstrated distinct TB staining. By the sixth day of culturing, almost all cells in the pyramidal cell layer became TB positive (88.4%). The caspase-3 immunoreactivity displayed a different pattern, as the most intense immunoreactivity, detected mainly in the pyramidal cells, peaked 6 h after culturing, and then decreased steadily. The present data show that in adult hippocampal slices a large number of pyramidal cells initiate apoptotic processes as a result of irreparable damage sustained during slice preparation and culture maintenance, and support the notion that apoptosis is an integral part of the neurodegenerative processes not only in vivo but also in vitro. Elucidation of mechanisms for the apoptotic processes in adult hippocampal slice cultures could lead to the development of new therapeutic strategies; moreover, the utilization of adult hippocampal slice cultures could be a viable alternative technique to in vivo experiments in studying the mechanisms responsible for neurodegeneration.

A lezarult OTKA tamogatassal vegzett kutatasi periodus főbb eredmenyeinek a kovetkezőket tartom: 1) Elsőkent allapitottuk meg es tovabbi adatokat szolgaltattunk arra vonatkozoan, hogy a periferias idegek seruleset kovető un. gerincvelői sprouting jelenseg morfologiai szubsztratumat nem a vastag myelinhuvelyes spinalis afferens rostok ill. azok burjanzasa, hanem a velőtlen, nociceptiv capsaicin-erzekeny C-tipusu afferensek kepezik. Ezzel jelentősen hozzajarultunk a fajdalomkutatasban mintegy egy evtizedig uralkodo dogma megdontesehez; 2) Kvantitativ in situ hibridizacios es immunhisztokemiai vizsgalatainkban kimutattuk, hogy a capsaicin receptor feherje expressziojanak tartos, es a TRPV1 mRNS reszleges es tranziens down-regulacioja szerepet jatszhat a capsaicin es mas vanilloidok, mint a resiniferatoxin antinociceptiv hatasaban; 3) Elektrofiziologiai es immunhisztokemiai modszerekkel karakterizaltuk az inzulin receptor-pozitiv ganglionsejtek uj populacioit; 4) Felismertuk, hogy a glukozilceramide-szintaz gatlasa jelentősen befolyasolja a nociceptiv erző ganglionsejtek capsaicin-erzekenyseget. Megfigyelesunk utat nyithat egy uj kutatasi terulethez, a glykolipideknek fajdalomerzes modulaciojaban betoltott szerepenek tanulmanyozasahoz. | The main findings of the past research period may be summarized as follows: 1) We provided evidence for the first time for unmyelinated nociceptive C-fibre afferents being the anatomical substrate of nerve lesion induced increased transganglionic transport of choleratoxin B subunit, a highly specific marker and receptor of GM1 ganglioside and membrane lipid rafts. This observation disproved the decade old dogma of pain research which suggested that myelinated primary afferent sprouting may be responsible for this phenomenon which, in turn, may play a role in the development of chronic pain states; 2) Using quantitative immunohistochemistry and in situ hybridization techniques we demonstrated that permanent elimination of the TRPV1 (capsaicin) receptor protein and transient and partial down regulation of TRPV1 mRNA may significantly contribute to the antinociceptive, pain relieving effect of perineurally administered capsaicin and similar vanilloids such as resiniferatoxin; 3) By using electrophysiological and immunohistochemical techniques we characterized new populations of primary sensory neurons which express the insulin receptor; 4) We demonstrated that inhibition of neuronal glucosylceramide synthase markedly reduced the sensitivity of cultured dorsal root ganglion cells to capsaicin. This finding may lead to new observations concerning pain modulation and pain relief.

Dithranol has been used to treat psoriasis for decades. Although its beneficial effect may involve the induction of cutaneous inflammation, and inflammation often leads to damages in nerve fibers, these alterations are not well documented. Therefore, we investigated the effects of dithranol on the immunohistochemical characteristics of the cutaneous nerve fibers in the rat skin. Epidermal nerve fiber staining was achieved with ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) immunohistochemistry in the orofacial skin of control rats, rats treated with (a) dithranol for 5 days, (b) corticosteroid for 5 days following dithranol treatment for 5 days, and (c) corticosteroid for 5 days. The results revealed a complete loss of UCH-L1 immunoreactivity in the dithranol-treated animals. Topical application of corticosteroid onto the inflamed skin for 5 days reversed this effect: the UCH-L1 immunoreactivity was almost completely restored. Steroid treatment for 5 days did not change the appearance of the UCH-L1-immunoreactive nerve fibers. These findings were supported by Western blot analyses. We conclude that dithranol, incidentally similarly to psoriasis, causes inflammation and abolishes UCH-L1 immunoreactivity in the rat orofacial skin in a corticosteroid-reversible manner. This phenomenon may be due to the ability of dithranol to cause oxidative damage to the UCH-L1 protein, and to the antioxidant activity of the corticosteroids countering this effect.

We compared two in situ hybridization protocols for the detection of low- abundance calmodulin (CaM) I mRNA populations in the lipid-rich white matter of the rat lumbar spinal cord. Digoxigenin-labeled, CaM I gene-specific antisense and sense cRNA probes were used in these experiments. Although microwave heating followed by chloroform and 0.1% triton X-100 treatment resulted in the specific labeling of several cells in the gray matter of the spinal cord with a low nonspecific signal, it did not detect any CaM I expressing cells in the white matter. The protocol involving a hybridization solution adjusted to a slightly alkaline pH (pH 8.0), however, resulted in the detection of a large number of CaM-expressing cells not only in the gray matter, but also in the white matter of the spinal cord, with a nonspecific hybridization signal that was essentially identical to that of the background, and it also retained a much better overall tissue quality as compared with the protocol involving microwave heating and triton X-100 treatment. Numerous medium-sized astrocyte-like cells and smaller cells resembling oligodendrocytes were detected that expressed CaM I mRNAs throughout the white matter of the lumbar spinal cord. Thus, in situ hybridization carried out at a slightly alkaline pH is a far superior method for the detection of low-abundance mRNA populations in lipid-rich regions of the central nervous system, such as the white matter areas, as compared with microwave heating combined with triton X-100 treatment.