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Viral strategies for targeting spinal neuronal subtypes in adult wild-type rodents. Sci Rep 2022; 12:8627. [PMID: 35606530 PMCID: PMC9126985 DOI: 10.1038/s41598-022-12535-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 05/12/2022] [Indexed: 12/02/2022] Open
Abstract
Targeting specific subtypes of interneurons in the spinal cord is primarily restricted to a small group of genetic model animals. Since the development of new transgenic model animals can be expensive and labor intensive, it is often difficult to generalize these findings and verify them in other model organisms, such as the rat, ferret or monkey, that may be more beneficial in certain experimental investigations. Nevertheless, endogenous enhancers and promoters delivered using an adeno-associated virus (AAV) have been successful in providing expression in specific subtypes of neurons in the forebrain of wildtype animals, and therefore may introduce a shortcut. GABAergic interneurons, for instance, have successfully been targeted using the mDlx promoter, which has recently been developed and is now widely used in wild type animals. Here, we test the specificity and efficiency of the mDlx enhancer for robust targeting of inhibitory interneurons in the lumbar spinal cord of wild-type rats using AAV serotype 2 (AAV2). Since this has rarely been done in the spinal cord, we also test the expression and specificity of the CamKIIa and hSynapsin promoters using serotype 9. We found that AAV2-mDlx does in fact target many neurons that contain an enzyme for catalyzing GABA, the GAD-65, with high specificity and a small fraction of neurons containing an isoform, GAD-67. Expression was also seen in some motor neurons although with low correlation. Viral injections using the CamKIIa enhancer via AAV9 infected in some glutamatergic neurons, but also GABAergic neurons, whereas hSynapsin via AAV9 targets almost all the neurons in the lumbar spinal cord.
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Seo S, Sizemore RJ, Reader KL, Smither RA, Wicky HE, Hughes SM, Bilkey DK, Parr-Brownlie LC, Oorschot DE. A schizophrenia risk factor induces marked anatomical deficits at GABAergic-dopaminergic synapses in the rat ventral tegmental area: Essential evidence for new targeted therapies. J Comp Neurol 2021; 529:3946-3973. [PMID: 34338311 DOI: 10.1002/cne.25225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/07/2021] [Accepted: 07/26/2021] [Indexed: 11/09/2022]
Abstract
To develop new therapies for schizophrenia, evidence accumulated over decades highlights the essential need to investigate the GABAergic synapses that presynaptically influence midbrain dopaminergic neurons. Since current technology restricts these studies to animals, and evidence accumulated in recent decades indicates a developmental origin of schizophrenia, we investigated synaptic changes in male rat offspring exposed to maternal immune activation (MIA), a schizophrenia risk factor. Using a novel combination of lentiviruses, peroxidase-immunogold double labeling, three-dimensional serial section transmission electron microscopy and stereology, we observed clear anatomical alterations in synaptic inputs on dopaminergic neurons in the midbrain posterior ventral tegmental area (pVTA). These changes relate directly to a characteristic feature of schizophrenia: increased dopamine release. In 3-month-old and 14-month-old MIA rats, we found a marked decrease in the volume of presynaptic GABAergic terminals from the rostromedial tegmental nucleus (RMTg) and in the length of the synapses they made, when innervating pVTA dopaminergic neurons. In MIA rats in the long-term, we also discovered a decrease in the volume of the postsynaptic density (PSD) and in the maximum thickness of the PSD at the same synapses. These marked deficits were evident in conventional GABA-dopamine synapses and in synaptic triads that we discovered involving asymmetric synapses that innervated RMTg GABAergic presynaptic terminals, which in turn innervated pVTA dopaminergic neurons. In triads, the PSD thickness of asymmetric synapses was significantly decreased in MIA rats in the long-term cohort. The extensive anatomical deficits provide a potential basis for new therapies targeted at synaptic inputs on midbrain pVTA dopaminergic neurons, in contrast to current striatum-targeted antipsychotic drugs.
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Affiliation(s)
- Steve Seo
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - Rachel J Sizemore
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - Karen L Reader
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
| | - Roseanna A Smither
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand.,Brain Research, New Zealand
| | - Hollie E Wicky
- Brain Health Research Centre, University of Otago, Dunedin, New Zealand.,Brain Research, New Zealand.,Department of Biochemistry, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Stephanie M Hughes
- Brain Health Research Centre, University of Otago, Dunedin, New Zealand.,Brain Research, New Zealand.,Department of Biochemistry, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - David K Bilkey
- Brain Health Research Centre, University of Otago, Dunedin, New Zealand.,Department of Psychology, University of Otago, Dunedin, New Zealand
| | - Louise C Parr-Brownlie
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand.,Brain Research, New Zealand
| | - Dorothy E Oorschot
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, University of Otago, Dunedin, New Zealand
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