Brain
Rexurch
Vol. 25. pp. 345-346. 0 Perpmon Press plc, 1990. Pnnted in the U.S.A
Bullrrin.
0361-9230190 $3.00 t .OO
RAPID COMMUNICATION
An Inexpensive Guide Cannula and Collar for Microdialysis Experiments PAUL
Department
of Psychology,
J. WELLMAN
Texas A&M Universi3,
Received
20 April
College Station, TX 77843
1990
WELLMAN, P. J. An inexpensive guide cannula and collar for microdialysis experiments. BRAIN RES BULL 25(2) 345-346, 1990. -Microdialysis experiments often require that a dialysis probe be fixed into position within the brain during a testing trial but that the probe be easily removed and precisely repositioned within the brain site on subsequent tests. The present paper describes an inexpensive guide cannula and locking collar that is easily fabricated for such experiments. Microdialysis
Guide cannula
Collar
Probe
laboratory and the improvised guide cannula and locking collar. The guide cannula is fashioned from a 20-mm length of thin-wall 20-gauge stainless steel tubing (Small Parts. Inc.). A l.O-mm diameter hole is drilled through the length of a stainless steel set screw (Small Parts: SSX-632/6) to form the outer body of the guide cannula. The guide shaft is soldered to the outer body at the base of the outer body. The guide cannula is then deburred and ground to length such that the guide shaft extends beyond the top of the outer body by 1 mm and from the base of the outer body by 6 mm. Each guide shaft is then sonicated in methanol to remove any metal filings and debris. The guide cannula collar is fashioned from a nylon acorn cap nut (Small Parts: CNN-632) by drilling a 1.5-mm hole through the center of the nut. The plastic collar is then slipped over the distal end of the microdialysis probe (relative to the CSF inlet tubing) and positioned over the PE-20 tubing near the junction of the inlet and outlet tubing (Fig. 1). Two rubber “0” rings (l/32” ID; Small Parts: DRB-001) are then slipped over the distal end of the microdialysis probe and positioned over the PE-20 tubing under the acorn nut. The PE-20 tubing of the probe body (which overlaps the 26-gauge tubing by 3 mm) serves as a stop to correctly position the probe beyond the distal end of the guide cannula. After positioning the probe within the guide shaft, the locking nut is screwed down onto the outer body of the guide cannula. As the “0” rings are compressed by the collar at the junction of the guide shaft and collar, the body of the probe is held in place and prevented from rotating within the brain site or from moving out of the brain site. The guide cannula and locking collar is constructed from inexpensive and readily available parts and requires only very simple tools (e.g., Dremel tool and soldering iron) for assembly. The cost of the guide cannula and locking collar at the time of this writing is approximately $0.25 which compares favorably with that of commercially available probe guide shafts and collars. One disadvantage, however, of the assembly is its size. If one wishes
THE in vivo procedure of microdialysis involves the insertion into brain, via a surgically implanted guide cannula, of a concentric probe capped with a semipermeable membrane (2,5). As artificial CSF flows inside along the membrane, neurochemicals within the extracellular space diffuse across the membrane and are collected for subsequent analysis using HPLC. This technique has achieved some popularity as a means to examine the dynamic changes in neurochemical activity with the extracellular space in response to either internal changes in motivation engendered by food reward (1) or to external stimulation (3). Various labs and commercial companies (Bioanalytical Systems, Lafayette, IN; Brain Research Instruments, Princeton, NJ) have devised novel solutions to the problems of probe design and construction (2,4). In the course of setting up a microdialysis lab, a problem was encountered related to reliably fixing the finished microdialysis probe within a guide cannula. Some investigators routinely implant a short length of 21-gauge tubing to be used as a guide cannula for subsequent insertion of the probe into brain. Various glues or dental acrylic are then used to fix the probe into place during sample collection. While this option prevents the probe from rotating in brain during sample collection, the nature of the solution often precludes easy removal and subsequent reinsertion of the microdialysis probe. Another solution, available from Bioanalytical Systems, involves a commercially prepared guide cannula that can be adapted to hold user-fabricated probes. Although this solution can minimize probe rotation and allows for multiple test insertions, its disadvantages are related to cost and to the difficulty in preventing rotation of the probe as the BAS locking collar is screwed into place. The present paper describes the fabrication of an inexpensive guide cannula and locking collar that allows for easy insertion and removal of the probe and that minimizes probe rotation. DESIGN AND CONSTRUCTION
Figure I depicts the microdialysis
probe presently used in this 345
346
WELLMA N
/
CSF
OUTLET
PE&lO
INLET
TUBING(l20
SILICA
to implant bilateral guide shafts aimed at a structure near the midline of the brain, the guide shafts will have to be implanted at an angle. However, this assembly is ideal for those applications in which a single guide cannula is required to sample the extracellular space of a brain region,
mm)
TUBING
(75
I IO mm)
U I D
ACKNOWLEDGEMENTS The author wishes to acknowledge the assistance of Brian Hutson and Sean McCollum for assistance in developing the guide cannula and locking collar and the helpful discussions with Dr. Susan Schenk regarding the collar.
INDICATES EPOXY
NYLON
ACORN
RUBBER
CAP
O-RINGS
26 GAUGE STAINLESS (0018 OD. 0004’WALL
OUTER
P -_(6
20
GAUGE
BODY
(l/32
STEEL
(6132
STAINLESS (17
(6/32)
I D 1
TUBING 22 mm)
thread
STEEL
IO mmj
TUBING
mm)
mm)
FIG. 1. Schematic illustrating the details of the concentric microdialysis probe and locking collar (top) and the guide cannula (bottom).
REFERENCES 1. Hernandez, L.; Hoebel, B. G. Food reward and cocaine increase extracellular dopamine in the nucleus accumbens as measured by microdialysis. Life Sci. 42:1705-1712; 1988. 2. Hernandez, L.; Stanley, B. G.; Hoebel, B. G. A small, removable micmdialysis probe. Life Sci. 39:2629-2637; 1986. 3. Myers, R. D.; Knott, P. D. Neurochemical analysis of the conscious brain: Voltammetry and push-pull perfusion. Ann. NY Acad. Sci. 473; 1986.
4. Robinson, T. E.; Whishaw, I. Q. Normalization of extracellular dopamine in striatum following recovery from a partial unilateral 6-OHDA lesion of the substantia nigm: A micrudialysis study in freely moving rats. Brain Res. 450~209-224; 1988. 5. Ungerstedt, U. Measurement of neumtransmitter release by intracranial dialysis. In: Mar&en, C. A., ed. Measurement of neurotransmitter release in vivo. New York: Wiley; 1984~81-105.
Rexurch
Vol. 25. pp. 345-346. 0 Perpmon Press plc, 1990. Pnnted in the U.S.A
Bullrrin.
0361-9230190 $3.00 t .OO
RAPID COMMUNICATION
An Inexpensive Guide Cannula and Collar for Microdialysis Experiments PAUL
Department
of Psychology,
J. WELLMAN
Texas A&M Universi3,
Received
20 April
College Station, TX 77843
1990
WELLMAN, P. J. An inexpensive guide cannula and collar for microdialysis experiments. BRAIN RES BULL 25(2) 345-346, 1990. -Microdialysis experiments often require that a dialysis probe be fixed into position within the brain during a testing trial but that the probe be easily removed and precisely repositioned within the brain site on subsequent tests. The present paper describes an inexpensive guide cannula and locking collar that is easily fabricated for such experiments. Microdialysis
Guide cannula
Collar
Probe
laboratory and the improvised guide cannula and locking collar. The guide cannula is fashioned from a 20-mm length of thin-wall 20-gauge stainless steel tubing (Small Parts. Inc.). A l.O-mm diameter hole is drilled through the length of a stainless steel set screw (Small Parts: SSX-632/6) to form the outer body of the guide cannula. The guide shaft is soldered to the outer body at the base of the outer body. The guide cannula is then deburred and ground to length such that the guide shaft extends beyond the top of the outer body by 1 mm and from the base of the outer body by 6 mm. Each guide shaft is then sonicated in methanol to remove any metal filings and debris. The guide cannula collar is fashioned from a nylon acorn cap nut (Small Parts: CNN-632) by drilling a 1.5-mm hole through the center of the nut. The plastic collar is then slipped over the distal end of the microdialysis probe (relative to the CSF inlet tubing) and positioned over the PE-20 tubing near the junction of the inlet and outlet tubing (Fig. 1). Two rubber “0” rings (l/32” ID; Small Parts: DRB-001) are then slipped over the distal end of the microdialysis probe and positioned over the PE-20 tubing under the acorn nut. The PE-20 tubing of the probe body (which overlaps the 26-gauge tubing by 3 mm) serves as a stop to correctly position the probe beyond the distal end of the guide cannula. After positioning the probe within the guide shaft, the locking nut is screwed down onto the outer body of the guide cannula. As the “0” rings are compressed by the collar at the junction of the guide shaft and collar, the body of the probe is held in place and prevented from rotating within the brain site or from moving out of the brain site. The guide cannula and locking collar is constructed from inexpensive and readily available parts and requires only very simple tools (e.g., Dremel tool and soldering iron) for assembly. The cost of the guide cannula and locking collar at the time of this writing is approximately $0.25 which compares favorably with that of commercially available probe guide shafts and collars. One disadvantage, however, of the assembly is its size. If one wishes
THE in vivo procedure of microdialysis involves the insertion into brain, via a surgically implanted guide cannula, of a concentric probe capped with a semipermeable membrane (2,5). As artificial CSF flows inside along the membrane, neurochemicals within the extracellular space diffuse across the membrane and are collected for subsequent analysis using HPLC. This technique has achieved some popularity as a means to examine the dynamic changes in neurochemical activity with the extracellular space in response to either internal changes in motivation engendered by food reward (1) or to external stimulation (3). Various labs and commercial companies (Bioanalytical Systems, Lafayette, IN; Brain Research Instruments, Princeton, NJ) have devised novel solutions to the problems of probe design and construction (2,4). In the course of setting up a microdialysis lab, a problem was encountered related to reliably fixing the finished microdialysis probe within a guide cannula. Some investigators routinely implant a short length of 21-gauge tubing to be used as a guide cannula for subsequent insertion of the probe into brain. Various glues or dental acrylic are then used to fix the probe into place during sample collection. While this option prevents the probe from rotating in brain during sample collection, the nature of the solution often precludes easy removal and subsequent reinsertion of the microdialysis probe. Another solution, available from Bioanalytical Systems, involves a commercially prepared guide cannula that can be adapted to hold user-fabricated probes. Although this solution can minimize probe rotation and allows for multiple test insertions, its disadvantages are related to cost and to the difficulty in preventing rotation of the probe as the BAS locking collar is screwed into place. The present paper describes the fabrication of an inexpensive guide cannula and locking collar that allows for easy insertion and removal of the probe and that minimizes probe rotation. DESIGN AND CONSTRUCTION
Figure I depicts the microdialysis
probe presently used in this 345
346
WELLMA N
/
CSF
OUTLET
PE&lO
INLET
TUBING(l20
SILICA
to implant bilateral guide shafts aimed at a structure near the midline of the brain, the guide shafts will have to be implanted at an angle. However, this assembly is ideal for those applications in which a single guide cannula is required to sample the extracellular space of a brain region,
mm)
TUBING
(75
I IO mm)
U I D
ACKNOWLEDGEMENTS The author wishes to acknowledge the assistance of Brian Hutson and Sean McCollum for assistance in developing the guide cannula and locking collar and the helpful discussions with Dr. Susan Schenk regarding the collar.
INDICATES EPOXY
NYLON
ACORN
RUBBER
CAP
O-RINGS
26 GAUGE STAINLESS (0018 OD. 0004’WALL
OUTER
P -_(6
20
GAUGE
BODY
(l/32
STEEL
(6132
STAINLESS (17
(6/32)
I D 1
TUBING 22 mm)
thread
STEEL
IO mmj
TUBING
mm)
mm)
FIG. 1. Schematic illustrating the details of the concentric microdialysis probe and locking collar (top) and the guide cannula (bottom).
REFERENCES 1. Hernandez, L.; Hoebel, B. G. Food reward and cocaine increase extracellular dopamine in the nucleus accumbens as measured by microdialysis. Life Sci. 42:1705-1712; 1988. 2. Hernandez, L.; Stanley, B. G.; Hoebel, B. G. A small, removable micmdialysis probe. Life Sci. 39:2629-2637; 1986. 3. Myers, R. D.; Knott, P. D. Neurochemical analysis of the conscious brain: Voltammetry and push-pull perfusion. Ann. NY Acad. Sci. 473; 1986.
4. Robinson, T. E.; Whishaw, I. Q. Normalization of extracellular dopamine in striatum following recovery from a partial unilateral 6-OHDA lesion of the substantia nigm: A micrudialysis study in freely moving rats. Brain Res. 450~209-224; 1988. 5. Ungerstedt, U. Measurement of neumtransmitter release by intracranial dialysis. In: Mar&en, C. A., ed. Measurement of neurotransmitter release in vivo. New York: Wiley; 1984~81-105.
