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Immunohistochemical evidence for a crossed cholecystokinin corticostriatal pathway in the rat
Neuroscience Letters, 148 (1992) 133 136 © 1992 Elsevier Scientific Publishers Ireland Ltd. All rights reserved 0304-3940/92/$ 05.00
133
NSL 09172
Immunohistochemical evidence for a crossed cholecystokinin corticostriatal pathway in the rat Patrizia M o r i n o a, M a r i o H e r r e r a - M a r s c h i t z b, J. Javier M e a n a b, U r b a n U n g e r s t e d t b a n d T o m a s HOkfelt" Departments of"Histology and Neurobiology and ~Pharmacology, Karolinska Institute, Stockholm (Sweden) (Received 17 August 1992; Revised version received 25 September 1992; Accepted 25 September 1992)
Key words: Neuropeptide; Excitatory transmitter; Basal Ganglia; Caudate nucleus; Patch Using the indirect immunofluorescence technique, the effects of decortication and callosotomy on the pattern of cholecystokinin (CCK)-like immunoreactivity were studied in the striatum of the rat. Decortication plus callosotomy, but not decortication alone, caused a strong decrease in the immunoreactivity on the side ipsilateral to the lesion. An almost complete disappearance of CCK immunoreactive patches in the medial-dorsal aspects of the striatum was observed. These results indicate that part of the striatal CCK immunoreactive fibres are of cortical origin, to a considerable extent from the contralateral side.
Vanderhaeghen et al. [24] first demonstrated the presence of gastrin/cholecystokinin (CCK)-like immunoreactivity (LI) in the rat brain, subsequently shown to represent mainly CCK octapeptide (CCK-8) [5]. Radioimmunoassay studies have revealed high concentrations of CCK-8 in cortex [1], but detailed immunohistochemical analysis only visualize few C C K positive cell bodies in cortical areas, presumably representing interneurons [10, 15, 20]. More recently in situ hybridization studies have, however, shown that a large proportion of the cortical neurons express CCK m R N A [3, 13, 14, 23, 26]. Furthermore, Burgunder and Young [2] have demonstrated, using combined retrograde tracing and in situ hybridization, that some of these cortical CCK m R N A positive neurons project to the striatum. This is in agreement with the previous neuroanatomical demonstration of ipsilateral and contralateral corticostriatal projection neurons [17]. Also the striatum contains CCK-LI, although in lower concentrations than cortex [1]. Immunohistochemical studies have revealed the presence of several C C K systems in the striatum [12], and some of these fibres may have a cortical origin as shown with radioimmunological studies combined with lesions experiments [18, 19]. In the present study we have attempted to further define the origin of striatal CCK positive fibres combining the indi-
Correspondence: P. Morino, Department of Histology and Neurobiology, Karolinska Institutet, Box 60400, S-10401 Stockholm, Sweden.
rect immunofluorescence technique with various types of cortical lesions. Male Sprague-Dawley rats (b. wt. 450-550 g, ALAB) were used for this study. Fifteen rats received 1 pl of kainic acid stereotaxically injected in 16 locations in the frontoparietal cerebral cortex [1 l]. Twelve of these rats were also callosotomised by using a surgical blade attached to a stereotaxic holder [11]. One week to 10 days following the lesions, these animals and eight untreated rats were deeply anaesthetized and fixed by formalin perfusion [12]. After rinsing the brains were cut at 14 pm in a cryostat (Microm) and processed for the indirect immunofluorescence technique. The sections were incubated for 24 h at 4°C with a polyclonal rabbit antiserum (R-18) to the non-sulphated C-terminal octapeptide of CCK-33 [8], rinsed, incubated with fluorescein isothiocyanate-conjugated goat anti-rabbit antibodies (1:80; Boehringer Mannheim Scandinavia), rinsed, mounted and examined in a fluorescence microscope. Antiserum preabsorbed with an excess of CCK-8 (10 6 M) (Peninsula) was used as a control. In untreated rats a weakly fluorescent, dot-like plexus of CCK positive structures was observed in the nucleus caudatus. In addition patches of fibres were found mainly in medial aspects of the striatum, usually in close relation to the fibre bundles of the internal capsule. More strongly immunoreactive fibres formed a band along the ventricle (Fig. I B,C). Unilateral decortication did not affect significantly the pattern of CCK-LI. However, when decortication was followed by callosotomy, a strong de-
134
Fig. 1. lmmunofluorescence micrographs of caudate nucleus (A C) and corpus callosum (D -G) of rat with unilateral decortication plus callosotomy after incubation with C C K antiserum. A -C: strongly immunoreactive patches of fibres (arrows) can be seen on the side contralateral (B,C) but not ipsilateral (A) to the decortication. Stars indicate lateral ventricle. D: low-power micrograph of the corpus callosum (co) at the lenel of the knife cut (arrowheads). Note accumulation of CCK-like material along the knife cut, contralateral to the decortication and that knife cut is slightly parasagittal to the midline (star in D indicates longitudinal sulcus). E G: a dense accumulation of CCK-immunoreactive elements is seen after caltosotomy on the side contralateral to the decortication (F,G), while only few such structures are seen on the lesioned side (E,G). Arrowheads m (; indicate knifecut. Bars ~ 50/./m.
135
crease in immunoreactivity was seen ipsilateral to the lesion. On this side, in fact, the patches of fibres had almost completely disappeared (Fig. 1A), while they seemed unaffected on the contralateral side (Fig. 1B,C). In the corpus callosum at the level of the transection a dense accumulation of strongly CCK-immunoreactive elements was seen on the intact side (Fig. 1D), with numerous swollen fiber profiles, filled with CCK-LI (Fig. 1F,G). On the side ipsilateral to the cortical lesion only few thin fibrous elements were observed (Fig. 1E,G). None of the above mentioned fluorescent structures were seen after incubation with control serum. The present results demonstrate that a unilateral extensive kainate lesion of the frontal parietal cortex combined with a callosotomy causes a virtual disappearance of the strongly fluorescent immunoreactive patches in the medial caudate nucleus of the lesion side. However, no certain effect could be observed on the contralateral side or ipsilaterally after decortication alone. In general terms these findings indicate the presence of a crossed cortico-striatal CCK pathway. This is in agreement with earlier radioimmunological studies showing that destruction of the cortical areas alone does not reduce CCK-LI in the ipsilateral striatum, but that a significant decrease in CCK-LI could only be obtained after additional parasagittal severance of the corpus callosum [18, 19]. Thus contralateral cortical areas seem to provide an important CCK input to the striatum, presumably entering the striatum via the capsula externa, since lesion of this structure diminishes the CCK in the striatum [18]. The present immunohistochemical analysis of the lesioned corpus callosum shows a dramatic accumulation of CCK-LI in transected fibers on the contralateral side, but only few fibers on the side with cortical lesion, providing direct evidence that the crossed CCK pathway runs through the corpus callosum. In agreement, Vanderhaeghen et al. [25] showed CCK-positive fibers in the corpus callosum of colchicine-treated rats. Since no apparent decrease was observed after callosotomy in the contralateral side, it is apparent that a combined lesion is needed to produce immunohistochemically and biochemically [19] detectable decreases in CCK-LI. It is possible that the density of fibres in these patches is so high that even a 50% decrease, hypothetically obtained by the ipsilateral decortication, may not be detected immunohistochemically. However, it is surprising that under these circumstances also the radioimmunoassay quantitative determination did not reveal any reductions, but in fact an increase in C C K - L | on the ipsilateral side [19]. The question may therefore be raised whether or not compensatory mechanisms, initiated in CCK terminals of contralateral origin in animals with decortication
alone, may disguise degenerative decreases in ipsilateral CCK systems. In a parallel study we have analysed rats with the same type of lesions with regard to striatal release of CCK and some neurotransmitters using in vivo microdialysis [11]. No significant effect on basal or potassium induced CCK release was found after unilateral decortication alone. However, in rats with combined decortication and callosotomy there was a marked reduction in basal and potassium induced CCK release, in agreement with our immunohistochemical studies. Moreover, also glutamate release was reduced, with a stronger reduction after combined decortication and callosotomy than after decortication alone. This is in agreement with earlier descriptions of the presence of cortico-striatal pathways in rats containing glutamate [7, 16, 21, 22]. Functionally, the corticostriatal glutamate pathway may interact with striatal dopamine nerve terminals, perhaps to control the state of DARPP-32 phosphorylation [9], and may be of clinical significance in central nervous system diseases such as schizophrenia and Parkinson's disease (see ref 4). It is an interesting question to what extent the CCK peptide could coexist with this excitatory amino acid. It was early established [6] that CCK exerts excitatory effects and has thus an action that is synergistic to that of excitatory amino acids. This study was supported by grants from the Swedish Medical Research Council (2887, 8669), Karolinska Institutets Fonder, Loo och Hans Ostermans fond, Ake Wibergs and Magnus Bergvalls Stiftelser, and the N I M H (MH43230). J.J.M. was a recipient o f a Hezkuntza Unibersitate eta Ikerketa Saila (Basque Government, Spain) fellowship. RM. was a recipient of a Wenner-Gren Center Foundation fellowship. We thank Dr. P. Frey for the generous gift of CCK antiserum and Ms. W. Hiort ['or skillful technical assistence. 1 Beinfeld. M.C., Meyer, D.K., Eskey, R.L., Jensen, R.T. and Brownstein, M.J.. The distribution of cholecystokinin immunoreactivity in the central nervous system of the rat as determined by radioimmunoassay, Brain Res., 212 (1981) 51 57. 2 Burgunder, J.-M. and Young l, W.S., Cortical neurons expressing the eholecystokinin gene in the rat: distribution in the adult brain, ontogeny, and some of their projections, J. Comp. Neurol., 300 (1990) 26 46. 3 Burgunder, J.M. and Young 1, W.S., The distribution of thalamic projection neurons containing cholecystokinin messenger RNA, using in situ hybridization histochemistry and retrograde labeling, Mol. Brain Res., 4 (1988) 179 189. 4 Carlsson, M. and Carlsson, A., Interactions between glutamatergic and monoaminergic systems within the basal ganglia implications Ik/r schizophrenia and Parkinson's disease, Trends Neurosci. 13 (1990) 272 276.
136 5 Dockray, G.J., Gregory, R.A., Hutchinson, J.B., Harris, J.l. and Runswick, M.J., Isolation, structure and biological activity of two cholecystokinin octapeptides from sheep brain, Nature, 274 (1978) 711 713. 6 Dodd, J. and Kelly, J.S., The action of cholecystokinin and related peptides on pyramidal neurons of the mammalian hippocampus, Brain Res., 205 (1981) 337-350. 7 Fonnum, F., Storm-Mathisen, J. and Divac, 1., Biochemical evidence for glutamate as neurotransmitter in corticostriatal and corticothalamic fibres in rat brain, Neuroscience, 6 (1981) 863 873. 8 Frey, P., Cholecystokinin octapeptide (CCK 2(~33), nonsulfated octapeptide and tetrapeptide (CCK 30-33) in rat brain: analysis by high pressure liquid chromatography (HPLC) and radioimmunoassay (RIA), Neurochem. Int., 5 (1983) 811-815. 9 Halpain, S., Girault, J.-A. and Greengard, R, Activation of NMDA receptors induces dephosphorylation of DARPP-32 in rat striatal slices, Nature, 343 (1990) 369-372. 10 Hendry, S.H.C., Jones, E.G. and Beinfeld, M.C., Cholecystokininimmunoreactive neurons in rat and monkey cerebral cortex make symmetric synapses and have intimate associations with blood vessels, Proc. Natl. Acad. Sci. USA, 80 (1983) 2400-2404. 11 Herrera-Marschitz, M., Meana, J.J., H/Skfelt, T., You, Z.-B., Morino, R, Brodin, E. and Ungerstedt, U., Cholecystokinin is released from a crossed corticostriatal pathway, NeuroReport, 3 (1992) 905-908. 12 H6kfelt, T., Herrera-Marschitz, M., Seroogy, K., Gong, J., Staines, W.A., Holets, V., Schalling, M., Ungerstedt, U., Post, C., Rehfeld, J.F., Frey, R, Fischer, J., Dockray, G., Hamaoka, T., Walsh, H.H. and Goldstein, M., Immunohistochemical studies on cholecystokinin (CCK)-immunoreactive neurons in the rat using sequence specific antisera and with special reference to the caudate nucleus and primary sensory neurons, J.Chem. Neuroanat., 1 (1988) I1 -52. 13 Ingram, S.M., Krause, R.G., Baldino, I.F., Jr., Skeen, L.C. and Lewis, M.E., Neuronal localization of cholecystokinin mRNA in the rat brain by using in situ hybridization histochemistry, J. Comp. Neurol., 287 (1989) 260 272. 14 Lanaud, R, Popovici, T., Normand, E., Lemoine, C., Block, B. and Rocques, B.R, Distribution of CCK mRNA in particular regions (hippocampus, periaqueductal grey and thalamus) of the rat by in situ hybridization, Neurosci. Lett., 104 (1989) 38M2.
15 McDonald, J.K., Parnavelas, J.G., Karamanlidis, A., Brecha, N. and Rosenquist, G., The morphology and distribution of peptidecontaining neurons in the adult and developing visual cortex of the rat. lIl. Cholecystokinin, J. Neurocytol., 11 (1982) 881 895. 16 McGeer, RE., McGeer, E.G., Scherer, V. and Singh, K., A glutamatergic corticostriatal pathway, Brain Res., 128 (1977) 369 373. 17 McGeorge, A.J. and Faull, R i . M . , The organization of the projection from the cerebral cortex to the striatum in the rat, Neuroscience, 29 (1989) 503--538. 18 Meyer, D.K., Beinfeld, M.C., Oertel, W.H. and Brownstein, M.J.. Origin of the cholecystokinin-containing fibers in the rat caudatoputamen, Science, 215 (1982) 187188. 19 Meyer, D.K. and Protopapas, Z.. Studies on cholecystokinin-containing neuronal pathways in rat cerebral cortex and striatum, Ann. N.Y. Acad. Sci., 448 (1985) 133 143. 20 Peters, A., Miller, M. and Kimere, L.M., Cholecystokinin-like immunoreactive neurons in rat cerebral cortex, Neuroscience, 8 (l 983) 431 448. 21 Reubi, J.C. and Cu6nod, M., Glutamate release in vitro from cortico-striatal terminals, Brain Res., 170 (1980) 185 -188. 22 Rowlands, G.J. and Roberts, RJ., Specific calcium-dependent release of endogenous glutamate from rat striatum is reduced by destruction of the cortico-striatal tract, Exp. Brain Res,, 39 (t980) 239 240. 23 Savasta, M., Palacios, J.M. and Mengod, G., Regional localization of the mRNA coding for the neuropeptide cholecystokinin in the rat brain studied by in situ hybridization, Neurosci. Lett., 93 (1988) 132- 138. 24 Vanderhaeghen, J.J., Signeau, P. and Gepts, W., New peptide in the vertebrate CNS reacting with antigastrin antibodies, Nature, 257 (1975) 604~605. 25 Vanderhaeghen, J.J., Lotstra, F., De Mey, J. and Gilles, C., Immunohistochemical localization of cholecystokinin- and gastrin-like peptides in the brain and hypophysis of the rat, Proc. Natl. Acad. Sci. USA, 77 (1980) 1190--1194. 26 Voigt, M.M. and Uhl, G.R., Preprocholecystokinin mRNA in the rat brain: regional expression includes thalamus, Mol. Brain Res., 4 (1988) 247 253.
133
NSL 09172
Immunohistochemical evidence for a crossed cholecystokinin corticostriatal pathway in the rat Patrizia M o r i n o a, M a r i o H e r r e r a - M a r s c h i t z b, J. Javier M e a n a b, U r b a n U n g e r s t e d t b a n d T o m a s HOkfelt" Departments of"Histology and Neurobiology and ~Pharmacology, Karolinska Institute, Stockholm (Sweden) (Received 17 August 1992; Revised version received 25 September 1992; Accepted 25 September 1992)
Key words: Neuropeptide; Excitatory transmitter; Basal Ganglia; Caudate nucleus; Patch Using the indirect immunofluorescence technique, the effects of decortication and callosotomy on the pattern of cholecystokinin (CCK)-like immunoreactivity were studied in the striatum of the rat. Decortication plus callosotomy, but not decortication alone, caused a strong decrease in the immunoreactivity on the side ipsilateral to the lesion. An almost complete disappearance of CCK immunoreactive patches in the medial-dorsal aspects of the striatum was observed. These results indicate that part of the striatal CCK immunoreactive fibres are of cortical origin, to a considerable extent from the contralateral side.
Vanderhaeghen et al. [24] first demonstrated the presence of gastrin/cholecystokinin (CCK)-like immunoreactivity (LI) in the rat brain, subsequently shown to represent mainly CCK octapeptide (CCK-8) [5]. Radioimmunoassay studies have revealed high concentrations of CCK-8 in cortex [1], but detailed immunohistochemical analysis only visualize few C C K positive cell bodies in cortical areas, presumably representing interneurons [10, 15, 20]. More recently in situ hybridization studies have, however, shown that a large proportion of the cortical neurons express CCK m R N A [3, 13, 14, 23, 26]. Furthermore, Burgunder and Young [2] have demonstrated, using combined retrograde tracing and in situ hybridization, that some of these cortical CCK m R N A positive neurons project to the striatum. This is in agreement with the previous neuroanatomical demonstration of ipsilateral and contralateral corticostriatal projection neurons [17]. Also the striatum contains CCK-LI, although in lower concentrations than cortex [1]. Immunohistochemical studies have revealed the presence of several C C K systems in the striatum [12], and some of these fibres may have a cortical origin as shown with radioimmunological studies combined with lesions experiments [18, 19]. In the present study we have attempted to further define the origin of striatal CCK positive fibres combining the indi-
Correspondence: P. Morino, Department of Histology and Neurobiology, Karolinska Institutet, Box 60400, S-10401 Stockholm, Sweden.
rect immunofluorescence technique with various types of cortical lesions. Male Sprague-Dawley rats (b. wt. 450-550 g, ALAB) were used for this study. Fifteen rats received 1 pl of kainic acid stereotaxically injected in 16 locations in the frontoparietal cerebral cortex [1 l]. Twelve of these rats were also callosotomised by using a surgical blade attached to a stereotaxic holder [11]. One week to 10 days following the lesions, these animals and eight untreated rats were deeply anaesthetized and fixed by formalin perfusion [12]. After rinsing the brains were cut at 14 pm in a cryostat (Microm) and processed for the indirect immunofluorescence technique. The sections were incubated for 24 h at 4°C with a polyclonal rabbit antiserum (R-18) to the non-sulphated C-terminal octapeptide of CCK-33 [8], rinsed, incubated with fluorescein isothiocyanate-conjugated goat anti-rabbit antibodies (1:80; Boehringer Mannheim Scandinavia), rinsed, mounted and examined in a fluorescence microscope. Antiserum preabsorbed with an excess of CCK-8 (10 6 M) (Peninsula) was used as a control. In untreated rats a weakly fluorescent, dot-like plexus of CCK positive structures was observed in the nucleus caudatus. In addition patches of fibres were found mainly in medial aspects of the striatum, usually in close relation to the fibre bundles of the internal capsule. More strongly immunoreactive fibres formed a band along the ventricle (Fig. I B,C). Unilateral decortication did not affect significantly the pattern of CCK-LI. However, when decortication was followed by callosotomy, a strong de-
134
Fig. 1. lmmunofluorescence micrographs of caudate nucleus (A C) and corpus callosum (D -G) of rat with unilateral decortication plus callosotomy after incubation with C C K antiserum. A -C: strongly immunoreactive patches of fibres (arrows) can be seen on the side contralateral (B,C) but not ipsilateral (A) to the decortication. Stars indicate lateral ventricle. D: low-power micrograph of the corpus callosum (co) at the lenel of the knife cut (arrowheads). Note accumulation of CCK-like material along the knife cut, contralateral to the decortication and that knife cut is slightly parasagittal to the midline (star in D indicates longitudinal sulcus). E G: a dense accumulation of CCK-immunoreactive elements is seen after caltosotomy on the side contralateral to the decortication (F,G), while only few such structures are seen on the lesioned side (E,G). Arrowheads m (; indicate knifecut. Bars ~ 50/./m.
135
crease in immunoreactivity was seen ipsilateral to the lesion. On this side, in fact, the patches of fibres had almost completely disappeared (Fig. 1A), while they seemed unaffected on the contralateral side (Fig. 1B,C). In the corpus callosum at the level of the transection a dense accumulation of strongly CCK-immunoreactive elements was seen on the intact side (Fig. 1D), with numerous swollen fiber profiles, filled with CCK-LI (Fig. 1F,G). On the side ipsilateral to the cortical lesion only few thin fibrous elements were observed (Fig. 1E,G). None of the above mentioned fluorescent structures were seen after incubation with control serum. The present results demonstrate that a unilateral extensive kainate lesion of the frontal parietal cortex combined with a callosotomy causes a virtual disappearance of the strongly fluorescent immunoreactive patches in the medial caudate nucleus of the lesion side. However, no certain effect could be observed on the contralateral side or ipsilaterally after decortication alone. In general terms these findings indicate the presence of a crossed cortico-striatal CCK pathway. This is in agreement with earlier radioimmunological studies showing that destruction of the cortical areas alone does not reduce CCK-LI in the ipsilateral striatum, but that a significant decrease in CCK-LI could only be obtained after additional parasagittal severance of the corpus callosum [18, 19]. Thus contralateral cortical areas seem to provide an important CCK input to the striatum, presumably entering the striatum via the capsula externa, since lesion of this structure diminishes the CCK in the striatum [18]. The present immunohistochemical analysis of the lesioned corpus callosum shows a dramatic accumulation of CCK-LI in transected fibers on the contralateral side, but only few fibers on the side with cortical lesion, providing direct evidence that the crossed CCK pathway runs through the corpus callosum. In agreement, Vanderhaeghen et al. [25] showed CCK-positive fibers in the corpus callosum of colchicine-treated rats. Since no apparent decrease was observed after callosotomy in the contralateral side, it is apparent that a combined lesion is needed to produce immunohistochemically and biochemically [19] detectable decreases in CCK-LI. It is possible that the density of fibres in these patches is so high that even a 50% decrease, hypothetically obtained by the ipsilateral decortication, may not be detected immunohistochemically. However, it is surprising that under these circumstances also the radioimmunoassay quantitative determination did not reveal any reductions, but in fact an increase in C C K - L | on the ipsilateral side [19]. The question may therefore be raised whether or not compensatory mechanisms, initiated in CCK terminals of contralateral origin in animals with decortication
alone, may disguise degenerative decreases in ipsilateral CCK systems. In a parallel study we have analysed rats with the same type of lesions with regard to striatal release of CCK and some neurotransmitters using in vivo microdialysis [11]. No significant effect on basal or potassium induced CCK release was found after unilateral decortication alone. However, in rats with combined decortication and callosotomy there was a marked reduction in basal and potassium induced CCK release, in agreement with our immunohistochemical studies. Moreover, also glutamate release was reduced, with a stronger reduction after combined decortication and callosotomy than after decortication alone. This is in agreement with earlier descriptions of the presence of cortico-striatal pathways in rats containing glutamate [7, 16, 21, 22]. Functionally, the corticostriatal glutamate pathway may interact with striatal dopamine nerve terminals, perhaps to control the state of DARPP-32 phosphorylation [9], and may be of clinical significance in central nervous system diseases such as schizophrenia and Parkinson's disease (see ref 4). It is an interesting question to what extent the CCK peptide could coexist with this excitatory amino acid. It was early established [6] that CCK exerts excitatory effects and has thus an action that is synergistic to that of excitatory amino acids. This study was supported by grants from the Swedish Medical Research Council (2887, 8669), Karolinska Institutets Fonder, Loo och Hans Ostermans fond, Ake Wibergs and Magnus Bergvalls Stiftelser, and the N I M H (MH43230). J.J.M. was a recipient o f a Hezkuntza Unibersitate eta Ikerketa Saila (Basque Government, Spain) fellowship. RM. was a recipient of a Wenner-Gren Center Foundation fellowship. We thank Dr. P. Frey for the generous gift of CCK antiserum and Ms. W. Hiort ['or skillful technical assistence. 1 Beinfeld. M.C., Meyer, D.K., Eskey, R.L., Jensen, R.T. and Brownstein, M.J.. The distribution of cholecystokinin immunoreactivity in the central nervous system of the rat as determined by radioimmunoassay, Brain Res., 212 (1981) 51 57. 2 Burgunder, J.-M. and Young l, W.S., Cortical neurons expressing the eholecystokinin gene in the rat: distribution in the adult brain, ontogeny, and some of their projections, J. Comp. Neurol., 300 (1990) 26 46. 3 Burgunder, J.M. and Young 1, W.S., The distribution of thalamic projection neurons containing cholecystokinin messenger RNA, using in situ hybridization histochemistry and retrograde labeling, Mol. Brain Res., 4 (1988) 179 189. 4 Carlsson, M. and Carlsson, A., Interactions between glutamatergic and monoaminergic systems within the basal ganglia implications Ik/r schizophrenia and Parkinson's disease, Trends Neurosci. 13 (1990) 272 276.
136 5 Dockray, G.J., Gregory, R.A., Hutchinson, J.B., Harris, J.l. and Runswick, M.J., Isolation, structure and biological activity of two cholecystokinin octapeptides from sheep brain, Nature, 274 (1978) 711 713. 6 Dodd, J. and Kelly, J.S., The action of cholecystokinin and related peptides on pyramidal neurons of the mammalian hippocampus, Brain Res., 205 (1981) 337-350. 7 Fonnum, F., Storm-Mathisen, J. and Divac, 1., Biochemical evidence for glutamate as neurotransmitter in corticostriatal and corticothalamic fibres in rat brain, Neuroscience, 6 (1981) 863 873. 8 Frey, P., Cholecystokinin octapeptide (CCK 2(~33), nonsulfated octapeptide and tetrapeptide (CCK 30-33) in rat brain: analysis by high pressure liquid chromatography (HPLC) and radioimmunoassay (RIA), Neurochem. Int., 5 (1983) 811-815. 9 Halpain, S., Girault, J.-A. and Greengard, R, Activation of NMDA receptors induces dephosphorylation of DARPP-32 in rat striatal slices, Nature, 343 (1990) 369-372. 10 Hendry, S.H.C., Jones, E.G. and Beinfeld, M.C., Cholecystokininimmunoreactive neurons in rat and monkey cerebral cortex make symmetric synapses and have intimate associations with blood vessels, Proc. Natl. Acad. Sci. USA, 80 (1983) 2400-2404. 11 Herrera-Marschitz, M., Meana, J.J., H/Skfelt, T., You, Z.-B., Morino, R, Brodin, E. and Ungerstedt, U., Cholecystokinin is released from a crossed corticostriatal pathway, NeuroReport, 3 (1992) 905-908. 12 H6kfelt, T., Herrera-Marschitz, M., Seroogy, K., Gong, J., Staines, W.A., Holets, V., Schalling, M., Ungerstedt, U., Post, C., Rehfeld, J.F., Frey, R, Fischer, J., Dockray, G., Hamaoka, T., Walsh, H.H. and Goldstein, M., Immunohistochemical studies on cholecystokinin (CCK)-immunoreactive neurons in the rat using sequence specific antisera and with special reference to the caudate nucleus and primary sensory neurons, J.Chem. Neuroanat., 1 (1988) I1 -52. 13 Ingram, S.M., Krause, R.G., Baldino, I.F., Jr., Skeen, L.C. and Lewis, M.E., Neuronal localization of cholecystokinin mRNA in the rat brain by using in situ hybridization histochemistry, J. Comp. Neurol., 287 (1989) 260 272. 14 Lanaud, R, Popovici, T., Normand, E., Lemoine, C., Block, B. and Rocques, B.R, Distribution of CCK mRNA in particular regions (hippocampus, periaqueductal grey and thalamus) of the rat by in situ hybridization, Neurosci. Lett., 104 (1989) 38M2.
15 McDonald, J.K., Parnavelas, J.G., Karamanlidis, A., Brecha, N. and Rosenquist, G., The morphology and distribution of peptidecontaining neurons in the adult and developing visual cortex of the rat. lIl. Cholecystokinin, J. Neurocytol., 11 (1982) 881 895. 16 McGeer, RE., McGeer, E.G., Scherer, V. and Singh, K., A glutamatergic corticostriatal pathway, Brain Res., 128 (1977) 369 373. 17 McGeorge, A.J. and Faull, R i . M . , The organization of the projection from the cerebral cortex to the striatum in the rat, Neuroscience, 29 (1989) 503--538. 18 Meyer, D.K., Beinfeld, M.C., Oertel, W.H. and Brownstein, M.J.. Origin of the cholecystokinin-containing fibers in the rat caudatoputamen, Science, 215 (1982) 187188. 19 Meyer, D.K. and Protopapas, Z.. Studies on cholecystokinin-containing neuronal pathways in rat cerebral cortex and striatum, Ann. N.Y. Acad. Sci., 448 (1985) 133 143. 20 Peters, A., Miller, M. and Kimere, L.M., Cholecystokinin-like immunoreactive neurons in rat cerebral cortex, Neuroscience, 8 (l 983) 431 448. 21 Reubi, J.C. and Cu6nod, M., Glutamate release in vitro from cortico-striatal terminals, Brain Res., 170 (1980) 185 -188. 22 Rowlands, G.J. and Roberts, RJ., Specific calcium-dependent release of endogenous glutamate from rat striatum is reduced by destruction of the cortico-striatal tract, Exp. Brain Res,, 39 (t980) 239 240. 23 Savasta, M., Palacios, J.M. and Mengod, G., Regional localization of the mRNA coding for the neuropeptide cholecystokinin in the rat brain studied by in situ hybridization, Neurosci. Lett., 93 (1988) 132- 138. 24 Vanderhaeghen, J.J., Signeau, P. and Gepts, W., New peptide in the vertebrate CNS reacting with antigastrin antibodies, Nature, 257 (1975) 604~605. 25 Vanderhaeghen, J.J., Lotstra, F., De Mey, J. and Gilles, C., Immunohistochemical localization of cholecystokinin- and gastrin-like peptides in the brain and hypophysis of the rat, Proc. Natl. Acad. Sci. USA, 77 (1980) 1190--1194. 26 Voigt, M.M. and Uhl, G.R., Preprocholecystokinin mRNA in the rat brain: regional expression includes thalamus, Mol. Brain Res., 4 (1988) 247 253.