| Figure 8. |
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| Schematic of the use of local drug microinfusion combined with stimulation recording in vivo to trace functional circuitry. In this case, the sciatic nerve was stimulated electrically and impulse activity of LC neurons was recorded extracellularly with a glass micropipette. A composite recording/injection pipette was placed in a major afferent to the LC, the nucleus paragigantocellularis (PGi). The smaller central barrel (dark shading) was used to record neuronal activity to aid in the proper placement of the injection assembly. In this case, two drug barrels (unshaded area) are glued adjacent to the recording pipette. Drug solutions were injected there using pneumatic pressure. Inactivation of the PGi via local microinfusions of lidocaine, GABA, or a synaptic decoupling solution blocked or attenuated responses of LC neurons to sciatic stimulation, indicating that the PGi is a synaptic relay for sciatic influences on LC neurons (43). |
published 2000