Mice devoid of glial fibrillary acidic protein (GFAP), an intermediate filament protein specifically expressed in astrocytes, develop normally and do not show any detectable abnormalities in the anatomy of the brain. In the cerebellum, excitatory synaptic transmission from parallel fibers (PFs) or climbing fibers (CFs) to Purkinje cells is unaltered, and these synapses display normal short-term synaptic plasticity to paired stimuli in GFAP mutant mice. In contrast, long-term depression (LTD) at PF-Purkinje cell synapses is clearly deficient. Furthermore, GFAP mutant mice exhibited a significant impairment of eyeblink conditioning without any detectable deficits in motor coordination tasks. These results suggest that GFAP is required for communications between Bergmann glia and Purkinje cells during LTD induction and maintenance. The data support the notion that cerebellar LTD is a cellular mechanism closely associated with eyeblink conditioning, but is not essential for motor coordination tasks tested.

1. We investigated the role of nitric oxide (NO) in the induction of long-term potentiation (LTP) in slices prepared from the rat auditory cortex. 2. Tetanic stimulation of layer IV elicited LTP of field potentials in layer II-III (LTPII-III) and in layer V (LTPV). The magnitude of LTPII-III measured at 30 min after tetanic stimulation was 171 ± 9% (n = 15, mean ± s.e.m.) of the control measured before tetanic stimulation, while that of LTPV was 138 ± 3% (n = 17). 3. NO synthase (NOS) inhibitors had no apparent effect on LTPII-III, but LTPV was significantly suppressed (P < 0·001). This suppression of LTPV was significantly antagonized by a NO donor (P < 0·001) or a cGMP analogue (P < 0·001). 4. Small non-pyramidal neurones in the auditory cortex were stained with an anti-neuronal NOS antibody. More neurones were stained with the antibody in the deeper cortical layers. 5. We measured neocortical NO release with electrochemical NO probes. Layer IV stimulation elicited significantly more NO release in layer V than in layer II-III (P < 0·001). The amplitude of the increase in NO concentration elicited by stimulation at 20 Hz for 5 s was 380 ± 14 pÒ (n = 55) in layer V and 55 ± 8 pÒ (n = 5) in layer II-III. 6. NO release in layer V was partially but significantly suppressed by non-NMDA (P < 0·002) or NMDA (P < 0·002) receptor antagonists. Simultaneous application of the antagonists of the two types blocked NO release almost completely. 7. These results clearly indicate the NO dependence of the induction of LTPV, and the greater NO release in the deeper layer of the rat auditory cortex.8152

Carbon monoxide (CO) suppresses brain functions at doses lower than that suppressing oxygen (O(2)) supply to the brain, and the cerebellum is one of the sites most susceptible to the neurotoxic effects of CO. We investigated the effects of CO on the induction of cerebellar long-term depression (LTD) in the synapses between parallel fibres (PFs) and Purkinje cells. CO, at concentrations between 8 nM and 5 microM, exhibited almost no effect on synaptic responses in Purkinje cells, O(2) consumption and NO release from PFs in rat cerebellar slices. However, the induction of LTD was significantly suppressed by CO at concentrations between 40 and 200 nM. The suppressive effect of 40 nM CO was antagonized by 10 microM NOR3, an NO donor. In contrast, CO exhibited no clear effect on the induction of LTD at concentrations between 1 and 5 microM. The induction of LTD, suppressed by 10 microM N(G)-nitro-L-arginine, an inhibitor of NO synthase, was not restored by 5 microM CO. CO is not only a neurotoxic substance but also a candidate for an intercellular messenger. delta-Aminolevulinate (30 microM), a substance facilitating endogenous CO production, suppressed the induction of LTD, and the effect of delta-aminolevulinate was antagonized by 10 microM NOR3. These findings suggest that CO may have a suppressive effect on the induction of cerebellar LTD at nanomolar concentrations, probably via its effects on NO/cGMP signalling.

Introduction Triamcinolone acetonide (TA), a steroid, is often used clinically to prevent dysfunctions associated with fibrosis. The objective of this study was to examine whether TA can be suspended in a gelatin sheet for tissue engineering using a mouse skin wound model. Methods TA was suspended in biodegradable gelatin and freeze-dried in a sheet form. The sheet was analyzed for homogeneity and controlled release of TA by high-performance liquid chromatography. We made two skin wounds on the dorsal side of mice. Gelatin sheets with TA (TA sheet) and without TA (control sheet) were attached to each skin wound. To determine the efficacy of the prepared TA sheet on the skin wounds, TA-sheet versus TA-injection experiments were conducted. Hematoxylin and eosin staining was performed to assess the grade of epithelialization and alpha smooth muscle actin (α-SMA) immunohistochemical staining was conducted to evaluate myofibroblast infiltration. Results In the TA-release test in vitro , 7.7 ± 2.3% of TA was released from the sheet by 24 h. After replacing the initial phosphate-buffered saline (PBS) with collagenase PBS, the amount of released TA increased over time. The wound area/original skin wound area after 15 days with the TA sheet was significantly larger than that with the control sheet (26.9 ± 5.5% vs 10.7 ± 2.6%, p = 0.023). The α-SMA positive area/whole area with the TA sheet was significantly lower than that with the control sheet (4.65 ± 0.66% vs 7.24 ± 0.7%, p = 0.023). Furthermore, the α-SMA positive area/whole area with the TA sheet was significantly lower than that with TA injection (5.32 ± 0.45% vs 7.93 ± 0.75%, p = 0.013). Conclusions We developed a TA sheet and confirmed both the homogeneity of the suspended TA and controlled-release of the TA in the presence of collagenase in vitro . The TA sheet caused less myofibroblast infiltration into the tissue than the control sheet or TA injection did.

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