A simple and reliable method for delivering small fluid volumes to the brain of a freely moving rat

RETRACTED: A flexible system for hands-free intracranial microinjection

“…It does not require grease to seal a rotating piston against a fluid-filled plastic block as in our system's design (Hesse et al, 1997). Using a 10 L microsyringe, the volume of a single step is small (2.19 nL), allowing precise selection of volume and infusion time through digital control of the stepper motor.…”

“…One way around this problem is to use a fluid swivel with IC microinfusion delivery from a remotely placed pump (Swanson et al, 1972;Wirth et al, 1977;Goeders and Smith, 1987;Parada et al, 1993Parada et al, , 1994. However, it has been noted previously (Hesse et al, 1997) that such a system is vulnerable to small fluid leaks in the swivel and unintended fluid motion generated by animal movement from peristaltic forces induced on the long tubing connecting the fluid swivel to the behaving animal. These complications are troublesome when microinfusing small volumes.…”

“…One was a screw-drive plunger system we designed previously (Hesse et al, 1997), which was used to study amphetamine intracranial self-administration (ICSA) into the nucleus accumbens and the amygdala (Chevrette et al, 2002). This system featured a stepper motor connected to an electrical swivel and delivered the fluid injectant directly to the IC microinfusion site through short tubes.…”

“…Another idea described previously used electrolysis to generate pressure in a sealed, head-mounted chamber that was directly coupled to chronically implanted IC cannulae (Bozarth and Wise, 1980;Yamamoto et al, 1985). This method produced variable infusion volumes in our hands (Hesse et al, 1997). A final method (Ikemoto and Sharpe, 2001) used the same screwdrive plunger concept employed by our old system (Hesse et al, 1997), but mounted the apparatus on the animal's head.…”

“…This method produced variable infusion volumes in our hands (Hesse et al, 1997). A final method (Ikemoto and Sharpe, 2001) used the same screwdrive plunger concept employed by our old system (Hesse et al, 1997), but mounted the apparatus on the animal's head. The unit eliminates use of long tubing, but does not free the animal from attachment, as a power-and control-carrying cable remains necessary for device operation.…”