Viral strategies for targeting spinal neuronal subtypes in adult wild-type rodents

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.

Soft monolithic infrared neural interface for simultaneous neurostimulation and electrophysiology

“…The multifunctional neural interface was inserted sequentially in the different regions at a depth of >1 mm, using a single smooth motion to avoid additional damage to the tissue, to perform the simultaneous INS and EE experiments at different powers. At the end of the experiments, the rats were deeply anesthetized by an intraperitoneal injection of pentobarbital, followed by transcardial perfusion 54 , 55 with a solution of 4% paraformaldehyde (PFA) in PBS.…”

Opsin-free optical neuromodulation and electrophysiology enabled by a soft monolithic infrared multifunctional neural interface

“…The multifunctional neural interface was inserted sequentially in the different regions at a depth of ∼1 mm, using a single smooth motion to avoid additional damage to the tissue, to perform the simultaneous INM and EE experiments at different powers. At the end of the experiments, the rats were deeply anesthetized by an intraperitoneal injection of pentobarbital, followed by transcardial perfusion [51, 52] with a solution of 4% paraformaldehyde (PFA) in PBS.…”

Pedunculopontine-stimulation obstructs hippocampal theta rhythm and halts movement

“…After confirming the motor arrest, a second surgery was performed where 4 tungsten electrodes were implanted in the primary motor cortex (AP =1.56-2.52, ML =2.2-2.3 and DV=2.0-2.3) and 4 in the hippocampus (AP = -3.3-3.6, ML = 2.0 and DV= 3.0-3.4) together with 1 reference silver and 1 ground silver electrodes. Post-surgical care was given as reported by 65 .…”