# Dorsal Horn Gastrin-Releasing Peptide Expressing Neurons Transmit Spinal Itch **URL:** \ **Category:** Journal Club\ **Created:** [March 21, 2019, 2:24am UTC](https://forum.painresearcher.net/t/dorsal-horn-gastrin-releasing-peptide-expressing-neurons-transmit-spinal-itch/575 "2019-03-21T02:24:18Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![achamess](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.painresearcher.net/achamess/32/534_2.png) [@achamess](https://forum.painresearcher.net/u/achamess)\ **Post date:** [March 21, 2019, 2:24am UTC](https://forum.painresearcher.net/t/dorsal-horn-gastrin-releasing-peptide-expressing-neurons-transmit-spinal-itch/575/1 "2019-03-21T02:24:18Z")
> **[Dorsal Horn Gastrin-Releasing Peptide Expressing Neurons Transmit Spinal Itch...](https://www.jneurosci.org/content/39/12/2238)** > > Gastrin-releasing peptide (GRP) is a spinal itch transmitter expressed by a small population of dorsal horn interneurons (GRP neurons). The contribution of these neurons to spinal itch relay is still only incompletely understood, and their potential... ---
**Author:** ![alex\_naka](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.painresearcher.net/alex_naka/32/215_2.png) [@alex\_naka](https://forum.painresearcher.net/u/alex_naka)\ **Post date:** [March 21, 2019, 2:30pm UTC](https://forum.painresearcher.net/t/dorsal-horn-gastrin-releasing-peptide-expressing-neurons-transmit-spinal-itch/575/2 "2019-03-21T14:30:14Z")
Pretty good read! Their results call the ‘leaky gate’ model proposed by [Sun et al. 2017](https://www.sciencedirect.com/science/article/pii/S0896627317300363?via%3Dihub) into question, will be interesting to see how things evolve from here ---
**Author:** ![achamess](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.painresearcher.net/achamess/32/534_2.png) [@achamess](https://forum.painresearcher.net/u/achamess)\ **Post date:** [March 21, 2019, 2:44pm UTC](https://forum.painresearcher.net/t/dorsal-horn-gastrin-releasing-peptide-expressing-neurons-transmit-spinal-itch/575/3 "2019-03-21T14:44:17Z")
Thanks for your thoughts @alex_naka. What do you think about conclusions in light of the relatively low overlap between _Cre_ and _Grp_+ neurons? More specifically, the fact that about 75% of _Grp_+ neurons are tdTom (and hence Cre) negative? ![00%20AM](https://canada1.discourse-cdn.com/flex030/uploads/painresearcher/original/1X/e4ee35d35ea438df46df3b383647a70300314993.png) Also, the ablation proportion was pretty weak, consistent with the low proportion of _Grp_+ neurons that express _Cre_. I need to dig in more but this caught my eye immediately. ![10%20AM](https://canada1.discourse-cdn.com/flex030/uploads/painresearcher/original/1X/75690210fe0a9f6958d9f2557529769252c688e0.png) On some other notes, things I was happy to see: - Use of Cre-dependent HSV129 for anterograde tracing from spinal cord. I think this is the first time this tool has been used in spinal cord. Glad to see it works. I tried from DRG retrogradely and it didn’t work for me. - CLARITY for imaging of complete morphology of DH neurons. This is nice. @RPSeal @tberta @liz @gcorder ---
**Author:** ![alex\_naka](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.painresearcher.net/alex_naka/32/215_2.png) [@alex\_naka](https://forum.painresearcher.net/u/alex_naka)\ **Post date:** [March 21, 2019, 3:37pm UTC](https://forum.painresearcher.net/t/dorsal-horn-gastrin-releasing-peptide-expressing-neurons-transmit-spinal-itch/575/4 "2019-03-21T15:37:24Z")
Good catch. Looking back at Sun et al. 2017 again, it looks like the correspondence is only okay between the GRP-eGFP and the GRP-Cre line as well. > GENSAT has another _Grp_ line with EGFP expression under the same promoter. Of neurons from the _Grp_ _EGFP_ line, 93% were reported to express _Grp_[mRNA](https://www.sciencedirect.com/topics/neuroscience/messenger-rna) ([Solorzano et al., 2015](https://www.sciencedirect.com/science/article/pii/S0896627317300363?via%3Dihub#bib43)). We crossed the EGFP line with _Grp_ _Cre_ _; ROSA26_ _LSL-tdTomato_ . 90.3% of _Grp_ _Cre_ -positive neurons also expressed _Grp_ _EGFP_ ([Figures 1](https://www.sciencedirect.com/science/article/pii/S0896627317300363?via%3Dihub#fig1)C and [S1](https://www.sciencedirect.com/science/article/pii/S0896627317300363?via%3Dihub#mmc1)), while 64.1% of _Grp_ _EGFP_ neurons colocalized with _Grp_ _Cre_ , showing that the _Grp_ _EGFP_ line labeled most _Grp_ _Cre_ -positive neurons. So I guess the takeaway is GRP-Cre more or less labels a subset of GRP-eGFP, which more or less labels a subset of the population of cells that have observable GRP transcripts in the adult. Not sure what to say about it, this is just one of the weaknesses of BAC transgenics I think - the patterns of labeling you get don’t necessarily have to recapitulate endogenous patterns of gene expression. I think the relatively low levels of efficiency in ablation might be a choice they’re making here > One potentially relevant difference in the experimental design, however, is the route of administration of DTX. In our experiments, we injected DTX locally into the intrathecal space of the lumbar spinal cord and in a hyperbaric solution to prevent diffusion to the brain. [S. Sun et al. (2017](http://www.jneurosci.org/content/39/12/2238.full#ref-32)), by contrast, applied DTX systemically via (intraperitoneal) injections. This difference may be relevant, as the presence of GRP neurons is not restricted to the spinal cord. But it does seem possible that maybe the discrepancies in their results could also just be from differences in how many GRP neurons are being ablated in the spinal cord. I did like the anterograde tracing. But I think people think the GRP neurons are all interneurons right? So the things they show must be at least two synapses away. Might have been interesting to do an earlier timepoint and see what the labeling looked like locally