Neuro~ience Letters, 32 (1982} 203-208 Elsevier Set.rifle Publishers ireland Ltd. 2~ EFFECTS: OF A LOW POWER LASER BEAM GUIDED ~Y OPTIC FIBER ON RAT B~AIN S~T &L MONOAMINES AND AMINO ACIDS SHEN-ZEN~*. XIAO-JIAN. LIN SHU-ZHI and WANG LI-HUA Depa~ment-of Psychotogy, Peking Uni~'~,sity, Peking (People's Republic of C'nina) (Received April 19th, I9o°2; Revised version receive~ July t4th, 1~82; Accepted July 20th, ~82) Key words: amino acids - cateeholam~.r.es - caudate nucleus -~ corpus striatu;n -. laser - optic fiber - rat - serotonht In vivo~ helium-neon and ni,'.rogen laser beams guided by optic fiber to rat caudat¢ nuc;eus decreased concentrations of dopamine ai~d serotonin, whil~ distant laser radiation to/'rontai ccrtex did not affect" stria+,al dopamine. In vitro, lat.~ radiation to pure monoamines and amino acids d~:crease~1 concentra- tions only of aspartie acid ant norepinephrine. The effe~.xs in vivo are attribnted to a combination of photoly~is and a,ered brain m,~.tabolism. Although lasers are beitig used increasingly in variou~ surgical procedures, their application to brain resea~'ch has been hampered by inadequate peaetration to s~::r~c .- tures of interest [2, 3, 5-7]. We i~ave ,.~vercorne this problem by irnpl~ntin~ optic fibers to guide the laser beams ard have used the technique to e×amir~.e t~e effc~:~; of laser radiation on rat brain concentrations of striatal mo~oamine~ and a~r~i~:~ acids. Laser light interacts with living tissue primarily in two ways: photochemicatly and thermMly [9, 10, 14]. Below the threshold fol- thermal reactions, the effects of ,laser application are mainly photochcartical. Because certain amino acid~ containing aromatic residues exhibit strong absorption of light radiation, we predicted that amino acids and putative monoamines, which 'also contain aromatic residues, might be Mtered t~y exposure to low power laser beams. We used two type~ of Iowopower ~iation. Oue i#a~ ~ ii:~i-him-nemx laser built by the Phys~c~ Depar~.raer~t at Pek~g University, the output of which was a continuous red Iase: oeam of 532.8 nm at 20 ,torn the Physics roW. The second was a nitrogen laser assembled with assista~ce # Department of Tsing Hua University; its output was an ultravic, let laser beam of 337.1 nm at ! mJ/pu~se with a pulse duratio~ of 5 ~.~ec, a~d a ~hythm of 10 pu!,~;e~ per see. Each Ias~ beam was focused by a lens coupled to aia optic fiber (~,7.~ #m ~: *'I'e whom cotr~ponden,~e should be addressed at: c/o Dept. ~f ~y-:hiatry (~-~.)3), U,~6versky ,.:;f CMi~brr.~a. ~ n D~ego~ La Jo~ia~ CA 926w~3. U.S.A. ~04.-3900182ftX~J)-O000t$ 02.75 cd.~ 1982 E!.~vier ~ientifT¢ F'~xb.ii.~;,,,rs Ireland Ltd.
Transcript
Neuro~ience Letters, 32 (1982} 203-208 Elsevier Se t . r i f le Publishers ireland Ltd.
2 ~
EFFECTS: OF A LOW POWER LASER BEAM GUIDED ~Y OPTIC FIBER ON RAT B~AIN S ~ T &L MONOAMINES AND AMINO ACIDS
SHEN-ZEN~*. XIAO-JIAN. LIN SHU-ZHI and WANG LI-HUA
Depa~ment-of Psychotogy, Peking Uni~'~,sity, Peking (People's Republic of C'nina)
(Received April 19th, I9o°2; Revised version receive~ July t4th, 1~82; Accepted July 20th, ~82)
In vivo~ helium-neon and ni,'.rogen laser beams guided by optic fiber to rat caudat¢ nuc;eus decreased concentrations of dopamine ai~d serotonin, whil~ distant laser radiation to/'rontai ccrtex did not affect" stria+,al dopamine. In vitro, lat.~ radiation to pure monoamines and amino acids d~:crease~1 concentra- tions only of aspartie acid an t norepinephrine. The effe~.xs in vivo are attribnted to a combination of photoly~is and a,ered brain m,~.tabolism.
Although lasers are beitig used increasingly in variou~ surgical procedures, their application to brain resea~'ch has been hampered by inadequate peaetration to s~::r~c .- tures of interest [2, 3, 5-7]. We i~ave ,.~vercorne this problem by irnpl~ntin~ optic fibers to guide the laser beams ard have used the technique to e×amir~.e t~e effc~:~; of laser radiation on rat brain concentrations of striatal mo~oamine~ and a~r~i~:~ acids.
Laser light interacts with living tissue primarily in two ways: photochemicatly and thermMly [9, 10, 14]. Below the threshold fol- thermal reactions, the effects of ,laser application are mainly photochcartical. Because certain amino acid~ containing aromatic residues exhibit strong absorption of light radiation, we predicted that amino acids and putative monoamines, which 'also contain aromatic residues, might be Mtered t~y exposure to low power laser beams. We used two type~ of Iowopower ~ i a t i o n . Oue i#a~ ~ ii:~i-him-nemx laser built by the Phys~c~ Depar~.raer~t at Pek~g University, the output of which was a continuous red Iase: oeam of 532.8 nm at 20
,torn the Physics roW. The second was a nitrogen laser assembled with assista~ce # Department of Tsing Hua University; its output was an ultravic, let laser beam of 337.1 nm at ! mJ/pu~se with a pulse duratio~ of 5 ~.~ec, a~d a ~hythm of 10 pu!,~;e~ per see. Each Ias~ beam was focused by a lens coupled to aia optic fiber (~,7.~ #m ~:
*'I'e whom cotr~ponden,~e should be addressed at: c/o Dept. ~f ~y-:hiatry (~-~.)3), U,~6versky ,.:;f CMi~brr.~a. ~ n D~ego~ La Jo~ia~ CA 926w~3. U.S.A.
diameter. A laser power meter measured light intensity at the distal end of the fiber. Fifty rats weighing 200-300 g each were divided randorrdy into 5 groups of 10 as
follows: (I) controls (optic fibers implanted to the caudate m~c!eus through the fron- tal cortex); (2) helium-neon laser radiation to the frontal cortex; (3) helium-neon laser radiation to the caudate nucleus; (4)nitrogen laser radiation to the frontal cor- tex, and (5) nitrogen laser radiation to the caudate nucleus.
After anesthesia with Nembutal (50 mg/kg i.p.) and stereotaxic immobilization [11], a nylon cannu!a (outer diameter, 0.5 mm; inner diameter, 0.12 mm; length, 5 ram) was implanted through a drill hole in the cranium and fixed with dental ce- ment. On the fifth day following surgery, each rat was restrained on an experimental stage. Coupled optic fi0ers were inserted bi!aterally through the cannula into the caudate nucleus or frontal cortex and fixed to the skull with cIoth tape.
Either a helium-neor~: beam (0.04 mW) or a nitrogen laser beam (0.(34 m J/pulse, 10/see) wa.~; ~uided along the optic fiber into the caudate nucleus or frontal torte×. Laser energies were considered to be localized because of the weak penetrability of low power laser beam Urazaev et al. [15] found that the helit:m-neon laser (500, mW/cm ~) penetrated into rat brain tissue by 0.42 _+ 0.02 mm. We calculated that our laser beam in rat brain may have an effective penetration of 1 ram. After 3 rain of radiation, the rat wa~ decapitated, and the corpus striatum was removed, weigh- ed, and homogenized with acidified n-butanol. Dopamine (DA), norepinepbrine (NE), 5-hydroxytryptamine (5-HT, seIotonin), and 5-hydroxyir~d~ieacetic acid (5-HIAA) were analyze~t by Miller's fiuorospectrometric techniw.- [112]. Aspa~tic acid (Asp), glutamic acid (GA), and -~-aminobutyric acid (GABA) were uetermir~ed by Atfield's method [1]. Results were compared to the control by Student's t-tc:~t.
~4i':~t:fiogical examina~:ion o~ the rat's brain afttr laser radiatio~l revealed no da~:~:: at the end of the optic fiber, but hemorrhage was occasionaliy observe8 al~n~3 the tract.
Helium-neon laser radiation in the caudate nucleons decreased concentrations of striatal DA, 5-HT, 5-HIAA and GA, and increa:eci striatal GABA concentration (P<0.01). It did not change striatal NE or Asp. Distant radiation to the.. frontal cor- tex decreased 5-HT and 5-HIAA and increased Asp and GABA concentrations (P<0.01). It did not change striatal DA concentration (Table [).
Nitrogen laser radiation in the caudate nucleus decreased concentrations of DA and 5-HT, and increased Asp ant 5-HIAA concentrations (P < 0.01). Distant radia- tion to the frontal cortez decrease~ 5-HT and NE concentrations and ir~.cre~sed con- centrations of 5-HIAA, Asp ~r~d C ABA, but did not change striatat DA concentra- tion (Table II~. No obvious sr~onto, c~us behavioral cha~geg were ob~erved i, ta~ rats following laser radiation.
To determine whether or not the effects of ia~e; radiation en striatat monoamine'z and amino acids might be ~lue to a photochemca, reaction, reagent gra.~e ~.,.~_~ (Fe~a-
C " biochemica, Heidelberg, F..R.G.), DA, 5-HT, 5-EIA_A (Calbiochem, La Jolia, ..A), GA, GABA and Asp (Feki~chemca, Peking~ C?~ina) were mixed and dissolved ir~
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vitro in concentrations:corresponding to those found in rat co~us striatum in vi¥o byus _anc? others-[8, 13];Mixed:samples were divided into three equal series: (1) not ~obe irradiated;-(2) to be irradiated fo:: 3-rain With helium-neon laser, 0.04 roW; and!_(3)to be irradiated for 3 ~ with r:itrogen laser, 0.04 mJ/pulse, lO/sec. After irradiation, the samp!es were assayed by the methc, ds used in the in vivo ex- periments, Nitrogen: laser radiation caused a decrease of hie in vitro; both lasers caused a mild decrease of: Asl,'concentratiou (Table HI),
The f'mding that st,.iatal concentrations of DA and 5-NT were both decreased by either laser but striatalNE was not ¢har~ged may have been due to the much lower concentration of NE, :which was found to be 0.I-0.01 times that of DA and 5-HT, a level consistent with other reports [4, 13].
Although the patterns and intensities of laser radiation were identical, our fin- dings in vivo versus in vitro were differer~t. In vitro, laser radiation caused decreases in a few substances, but in vivo it caused decreases in some and increases in o:-'.her~:° An explanation might be found in different mechanisms of laser action. In vitro, the beams directlyaffected the target substancesand caused a photochemical reac-. tion - photolysis. In vivo, the radiation may not only have directly affected the 7 substances we measured; i t probably also acted on enzymes involved in their metabolism, affecting their degradation and/or synthe.~is. Thus differences between results in v:~vo and in vitro suggest that the former effects by either laser on concen- trations of the 7 substances may Je due to influences on the brain's metabolic proce~ses.
We fouad, as others have [9, 15], that the shorter the wavelength of laser radia- tion, the easier it is absorbed by the molecules of the irradiated substance.. ~n our experiment, the shorter wavelength of the nitrogen laser aN:ears to have a s~ronger action in vitro; it decreased both NE and Asp while the ae~mmoneo ~ laser only decreased Asp.
Although there are a few differences between the two lasers' effects in~ vivo (for instance, helium-neon decreased stdatal 5-HIAA while nitrogen increased it), both lasers decreased striatal 5-HT. It is difficult to say which laser's effect here is stronger', but the phenomenon could be explained by different sites of action on the serotonergic metabolic process. Helium-neon radiation decreased both 5-t.FI and its metgbolic product 5-HIAA; therefore it may have acted to reduce the synthesis of 5-HT. On the other hand, nitrogen laser radiation decreased 5-HT and increased 5,.HIAA, so it may have been acting on the degradation of 5-HT.
We appreciate the help of Michael Blackburn, Barbara Blomgren a~d Barbara Baehr with the revision of the manuscript.
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