We have investigated the role of the metabotropic glutamate receptor 7 (mGluR7) and the gastrin releasing peptide receptor (Grpr) population that are involved at different levels of itch transmission. We found that mGuR7 deficient mice displayed an anaphylaxis-like behavior when provoked with histamine. Analysis of blood revealed elevated plasma levels of histamine and mouse mast cell protease-1 (mMCP1), two indicators of anaphylaxis, in mGluR7 deficient mice compared with control mice. Inhibition of the neurokinin 1 receptor, by preventing binding of the corresponding ligand substance P (SP), prior to provocation with histamine prevented the development of anaphylaxis in mGluR7 deficient animals. However, blocking GRPR (gastrin releasing peptide receptor) only resulted in decreased itch levels in mGluR7 deficient mice but did not prevent the systemic anaphylaxis-like behavior. Our findings indicate that mGluR7 normally functions as a brake on histaminergic itch that is mediated through GRPR as well as anaphylaxis through Substance P. Grpr has previously been shown to mediate both histaminergic and non-histaminergic itch but little is known about the GRPR neuronal population. We used a BAC cloning strategy to construct a Grpr-Cre line, which we crossed with the reporter lines tdTomato and Viaat-egfp as well as with Vglut2-lox. We could conclude that Grpr-Cre neurons are mainly excitatory interneurons located in lamina II-IV, that convey itch using VGLUT2-mediated glutamatergic transmission to the next, currently unknown, step in the labeled line of chemical itch. To eventually deduce the function of the endogenous opioids dynorphin and enkephalin, which are hypothesized to be involved in gating pain and itch in the spinal cord, we constructed two Cre lines using BAC cloning that targeted the precursor proteins preprodynorphin and preproenkephalin, respectively. Preprodynorphin-Cre neurons were mainly located in lamina II-IV and overlapped to 47% with Vglut2 mRNA, while the co-expression with the inhibitory markers Viaat-egfp and PAX2 was 13% and 28% respectively in the spinal cord. Preproenkephalin neurons were more localized to lamina III in the dorsal horn, furthermore single cell analysis showed that they overlapped to 94% with Vglut2 mRNA while 7% and 13% expressed Viaat-egfp and PAX2 respectively.

Background: Glomerular filtration rate (GFR) is a clinically important measurement of kidney function and estimating the GFR is of great importance in healthcare. Methods available today either lack in precision or are overly time consuming. Proenkephalin (PENK) has been shown to correlate well with the GFR and has therefore been proposed as a novel biomarker for kidney function. Aim: To evaluate a new point-of-care test for measuring PENK in blood and to assess its correlation to GFR measured by iohexol plasma clearance (mGFRiohexol). Materials and methods: Blood was collected from 21 patients with varying indications for the iohexol plasma clearance test. PENK was measured with IB10 Sphingotest penKid in whole blood, plasma and serum respectively. The concentration was correlated to the mGFRiohexol and results were compared to those from measurement of the routine markers for kidney function, i.e. creatinine and cystatin C. Results: Fourteen men and seven women were included. The median age was 57 years. PENK in plasma correlated weakly with mGFRiohexol (R2=0.22, p=0.042). No significant correlation was shown for PENK in whole blood or serum. Creatinine also showed a weak correlation with mGFRiohexol (R2=0.35, p=0.0046). In contrast, cystatin C was strongly correlated with mGFRiohexol (R2= 0.87, p<0.0001). Conclusion: Our results indicate that PENK is a biomarker of low clinical value for estimating the GFR. However, further studies are needed before this can be assured. Cystatin C, on the contrary, seems to be an accurate biomarker for estimating the GFR.