Interactive and individual effects of sensory potentiation and region-specific changes in excitability after spinal cord injury

Altered GABA and somatostatin modulation of proprioceptive feedback after spinal cord injury in lamprey

“…The bending point was thus approximately 0.5 cm below the lesion site. A syringe tip (25-gauge) was attached to a vertical arm connected to a custom made motor that moved the vertical arm sinusoidally 1 cm to the left and right of center (this displacement was comparable to previously used bending parameters; Kiemel and Cohen, 2001;Tytell and Cohen, 2008;McClellan and Sigvardt, 1988;Hoffman and Parker, 2011). We have only used 1 Hz stimulation here as a previous study showed that 0.1-1 Hz stimulation revealed little frequency-dependent effect on bending responses in control and lesioned animals (Hoffman and Parker, 2011).…”

“…A syringe tip (25-gauge) was attached to a vertical arm connected to a custom made motor that moved the vertical arm sinusoidally 1 cm to the left and right of center (this displacement was comparable to previously used bending parameters; Kiemel and Cohen, 2001;Tytell and Cohen, 2008;McClellan and Sigvardt, 1988;Hoffman and Parker, 2011). We have only used 1 Hz stimulation here as a previous study showed that 0.1-1 Hz stimulation revealed little frequency-dependent effect on bending responses in control and lesioned animals (Hoffman and Parker, 2011). 1 Hz stimulation also provided a physiologically-relevant stimulus within 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 7 Extracellular recordings were made from the surface of the lateral tract using glass suction electrodes to monitor movement-related sensory feedback (see Grillner et al, 1982;McClellan and Sigvardt, 1988).…”

“…As the edge cells are stretch-sensitive the activation of edge cells with contralateral or ipsilateral projecting axons (Vianan di Prisco et al, 1990) can be determined from the response to stretch (ipsilateral axon) or compression (contralateral axon) relative to the side that the recording is made from. Recordings were made approximately 7 segments caudal to the bending point (we have seen no difference in effects at 3, 7, and 12 segments caudal to the bending point; Hoffman and Parker, 2011). The edge cells also have ascending axons (see Tang and Selzer, 1979).…”

“…We have used this system to examine changes below lesion sites, and have shown an increase in spinal cord excitability associated with changes in cellular and synaptic properties and synaptic ultrastructure (Cooke and Parker, 2009), and an increase in the strength of proprioceptive feedback (Hoffman and Parker, 2011). The proprioceptive system offers a particularly tractable model system for analyzing functional changes after lesioning, as the proprioceptive edge cells that are depolarized by stretch of the body during swimming are located on the lateral margin of the spinal cord and can be examined in response to imposed movements of the isolated spinal cord (Rovainen, 1979;Grillner et al, 1982Grillner et al, , 1984McClellan and Sigvardt, 1988).…”

“…Locomotor function in unlesioned and lesioned animals was assessed from video and electromyogram recordings and scored according to a six-point scale (see Cooke and Parker, 2009;Hoffman and Parker, 2011). EMG recordings were made by inserting bipolar teflon insulated electrodes (0.075 mm in diameter) into the muscle under MS-222 anesthesia.…”