- Email: [email protected]
GABAergic and NPY-Y1 network in the medial amygdala: a neuroanatomical basis for their functional interaction
Neuropharmacology 41 (2001) 639–642 www.elsevier.com/locate/neuropharm
Rapid communication
GABAergic and NPY-Y1 network in the medial amygdala: a neuroanatomical basis for their functional interaction A. Oberto
a, b
, G.C. Panzica c, F. Altruda d, C. Eva
a,*
a
c
Sezione di Farmacologia, Dipartimento di Anatomia, Farmacologia e Medicina Legale, Universita` di Torino, Via Pietro Giuria 13, 10125 Torino, Italy b Neurobiology Division, MRC Laboratory of Molecular Biology, MRC Center, Cambridge CB2 2QH, UK Sezione di Anatomia, Laboratorio di Neuroendocrinologia, Dipartimento di Anatomia, Farmacologia e Medicina Legale, Universita` di Torino, Torino, Italy d Dipartimento di Genetica, Biologia e Biochimica, Universita` di Torino, Torino, Italy Received 2 January 2001; received in revised form 8 June 2001; accepted 15 June 2001
Abstract We used Y1R/LacZ transgenic mice to investigate the interaction between NPY, GABA and Y1 receptors in the amygdala. Immunolabeling of GABA and NPY positive neurons and histochemical staining of β-galactosidase revealed NPY and GABA colocalization and close contacts of NPY-positive fibers with GABAergic neurons also expressing the Y1R/LacZ transgene. 2001 Elsevier Science Ltd. All rights reserved. Keywords: Neuropeptide Y; Y1 receptor; GABA; β-galactosidase; Amygdala; Transgenic mice
Neuropeptide Y (NPY) produces an anxiolytic-like action similar to that induced by benzodiazepines acting on the GABAA receptor. This effect is observed in a variety of paradigms including the elevated plus maze, the conflict test, the fear-potentiated startle paradigm and the social interaction test (for review see Griebel, 1999). The behavioral effects of NPY are probably mediated by the activation of Y1 receptors in different nuclei of the amygdala. Kask et al. (1996) showed that the benzodiazepine diazepam counteracts the anxiogenic effect of Y1 receptor selective antagonists, suggesting that the GABAA and Y1 receptor-mediated transmissions are closely coupled and may functionally interact in the regulation of anxiety. We previously generated ten independent transgenic mouse lines carrying the mouse Y1 receptor gene promoter fused to a LacZ reporter gene (Y1R/LacZ) (Oberto et al., 1998). With the use of this transgenic model, we recently showed that long-term treatment with allosteric modulators of GABAA receptors that act at the benzodiazepine or ω site affects the
* Corresponding author. Tel.: +39-011-6707718; fax: 39-0116707788. E-mail address: [email protected] (C. Eva).
Y1 receptor gene expression in the medial amygdala (Oberto et al., 2000). Here we used the Y1R/LacZ mice to study the neuroanatomical basis for the functional interaction between GABA and NPY-Y1 mediated transmissions in this brain area. Animal care and handling throughout the experimental procedure were in strict accordance with the European Community Council Directive, 24th November 1986 (86/609/EEC) and the protocol was approved by the Animal Investigation Committee of MURST. Transgenic Y1R/LacZ male mice (line 27) (Oberto et al., 1998) were anesthetized with chloral hydrate (300 mg/kg, ip.) and transcardiacally perfused with 20 ml of heparinized saline solution, followed by 20 ml of fixative (4% paraformaldehyde and 0.1% glutaraldehyde in 0.1 M phosphate buffer-saline (PBS) pH 7.2. Brains were dissected, postfixed for 2 h in 4% paraformaldehyde in PBS at 4°C, then rinsed in PBS, placed overnight at 4°C in 0.1 M PBS containing 30% sucrose, and frozen on dry ice. Coronal sections (40 µm-thick) obtained with a freezing microtome were collected and directly processed for Xgal histochemistry (Oberto et al., 1998). For double GABA and NPY immunostaining, after the histochemical reaction free floating sections were washed in PBS and then incubated for 30 min in 0.1 M PBS containing
0028-3908/01/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 8 - 3 9 0 8 ( 0 1 ) 0 0 1 0 9 - 5
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A. Oberto et al. / Neuropharmacology 41 (2001) 639–642
0.02% Triton X-100 at room temperature followed by 30 min at room temperature in 20% normal goat serum. They were placed for 48 h at 4°C in a mixture of primary polyclonal antisera — guinea pig anti-GABA IgG, 1:500 (Chemicon International, CA, USA) and rabbit anti-NPY IgG 1:1000 (a gift by H. Vaudry, Rouen, France) — diluted in 0.1 M PBS containing 0.1% normal goat serum and 0.02% Triton X-100. After several rinses in PBS, sections were further incubated in a mixture of rhodamine (TRITC)-conjugated anti-guinea pig IgG and fluorescein (FITC)-conjugated anti-rabbit IgG (Autogen Bioclear UK Ltd, UK), diluted to 1:50 in 0.1 M PBS, for 1 h in the dark at room temperature, then washed in five changes of PBS for 10 min each. Sections were mounted with Vectashield (Vector Laboratories, CA, USA) on gelatin-coated slides and analyzed on a Biorad (MRC-1024) confocal microscope. To increase the number of in-focus-IR structures, we employed the features of the Biorad software to merge several focus layers in a single one. To test the specificity of the immunoreaction, control reactions were performed by replacing the antisera with normal serum. The production of the antibody against NPY and the results of the assays performed to control its specificity and cross-reactivity have been previously described (Pelletier et al., 1984). The histochemical detection of the β-galactosidase (βgal) activity confirmed a high expression of the Y1R/LacZ transgene in the medial amygdala (Oberto et al., 1998). Immunocytochemical detection of NPY-positive elements demonstrated a wide network of beaded fibers covering the whole extension of the medial amygdala, with a few stained cell bodies mainly located in the central portion of the medial amygdala (Fig. 1(A) and (D)). GABA-IR cell bodies were observed in large number within the medial amygdala as well as in the whole amygdaloid complex. The neuropil of the medial amygdala was characterized by a diffuse immunoreactivity, probably corresponding to GABA-ergic endings (Fig. 1(C) and (F)). The confocal analysis of sections treated for the simultaneous detection of β-gal staining, GABA and NPY revealed a high degree of colocalization for GABA or NPY and the Y1R/LacZ transgene. At the same time the majority of NPY-IR cell bodies were also positive for GABA (yellow cells in Fig. 1(E) and (H)). A few of them were also showing the β-gal histochemical activity (asterisk in Fig. 1(H)). In some cases we observed the coexistence of GABA and NPY within the same nerve fibers (Fig. 1(A)–(C)). GABAergic elements showing transgene expression were usually in close contact with NPY-IR fibers that were surrounding or covering the cell bodies (Fig. 1(B), (E), (G) and (H)). Similar close contacts were also observed for GABA-ergic elements non-reactive for LacZ expression. NPY-fibers were also seen in close contact with elements showing only β-gal staining. Lastly, we have also observed NPY-IR fibers in close contact with NPY-
GABA-Y1R/LacZ transgene positive elements (asterisk in Fig. 1(H)). The use of confocal-merged images was important to understand the entity of distribution of immunoreactive fibers around and in the proximity of GABA-ergic elements. However, the merging process ended in a masking of β-gal histochemical labeling and reduced the number of positive elements detected in the final image (compare Fig. 1(H) and (E) for the number of cells showing the histochemical labeling). Experimental evidence from our and other laboratories has suggested the existence of a functional interaction between GABA and NPY in the amygdala that may be important in the regulation of anxiety-like behavior (Kask et al., 1996; Oberto et al., 2000). Here we provide the first morphological evidence in support of a possible interrelationship between GABA and NPY-Y1 mediated transmission, suggesting that this interconnectivity may be an important regulatory mechanism within the medial amygdala that may contribute to NPY’s effects on anxious behavior. NPY has frequently been observed in GABAergic neurons in the cerebral cortex, basolateral amygdala, hippocampus and the hypothalamus (Hendry et al., 1984; Ko¨ hler et al., 1986; McDonald and Pearson, 1989; Pu et al., 1999). Using immunolabeling for NPY and GABA and histochemical labeling of Y1R/LacZ transgene expression we now have extended these studies showing that in the medial amygdala: (i) NPY and GABA coexist within the same neurons; (ii) NPY producing neurons make close contacts with GABA-containing neurons; (iii) several GABA-IR neurons display β-gal staining and (iv) few NPY-IR cell bodies also show the β-gal histochemical activity. These findings suggest that a network of axons from NPY neurons innervate GABAergic neurons that also express the Y1 receptor gene; and that NPY might inhibit GABA release by the activation of this receptor subtype. However, other mechanisms might also be involved. Several GABA producing neurons, which are surrounded by NPY positive fibers, do not display β-gal positive staining, indicating that not all GABAergic neurons are regulated by Y1 receptors. On the other hand the expression of Y1R/LacZ within the NPY containing neurons suggests a possible role of the Y1 receptor as an auto-receptor regulating the NPY release in this brain area. This is consistent with previous studies showing that the Y1 receptor subtype can act as an autoreceptor in the hippocampus and in the suprachiasmatic nucleus (Chen and van den Pol, 1996; St-Pierre et al., 2000). These observations, together with those showing that most of the NPY-containing neurons also contain GABA, could account for a complex response to NPY in the medial amygdala. As a working hypothesis, we suggest that the NPY-Y1-mediated transmission and the GABAergic system may act together on the same postsynaptic target sites to decrease anxiety and that the Y1 receptors might also play a role in controlling both the NPY and GABA
A. Oberto et al. / Neuropharmacology 41 (2001) 639–642
641
Fig. 1. Confocal images illustrating the coexistence and close relationships among NPY, GABA, and Y1R/LacZ expressing elements. In green the immunolabeling for NPY, in red the immunolabeling for GABA, in dark blue the histochemical staining for β-gal. Yellow cells or fibers are elements where NPY (green) and GABA (red) coexist. (A)–(F): confocal images obtained merging several focus planes. Bar in A represents 30 µm. (G) and (H): single, not merged confocal images. The bar in (G) represents 30 µm. In (A) and (C), the arrow points to the same fiber recognizable for its characteristic shape showing NPY (A) and GABA (C) immunoreactivity. The same fiber is stained in yellow in (B). In (D) and (F) the arrows point to numerous co-existent NPY- and GABA-IR cell bodies which are yellow in (E). In (G) and (H) the arrowheads indicate a few of the numerous elements showing also the histochemical staining for β-gal. In (H) the arrow point to NPY-IR cell bodies showing also β-gal activity. The asterisk indicates one yellow cell body positive for β-gal. The same cell is clearly identifiable in (E) (asterisk), the image reconstructed from the series to which (H) is belonging.
presynaptic release. We have recently demonstrated that chronic treatment with positive modulators of the GABAA receptor complex increases, and negative modulators decrease, Y1R/LacZ transgene expression in the
medial amygdala (Oberto et al., 2000). We now propose that chronic potentiation (or inhibition) of GABAA receptor function in the medial amygdala may induce compensatory changes in the activity of the GABA- and
642
A. Oberto et al. / Neuropharmacology 41 (2001) 639–642
NPY-containing neurons and, in turn, in gene expression of presynaptic and/or postsynaptic Y1 receptors.
Acknowledgements This work was supported by Grant 9905045782 from MURST to C.E. (Projects of National Relevance, Article 65DPR 382/80). A.O. was supported by a Marie Curie Research EC Training Grant No ERB4001GT980563. We thank Dr W. Wisden (MRC, Cambridge, UK) for helpful discussion and critical reading of the manuscript.
References Chen, G., van den Pol, A.N., 1996. Multiple NPY receptors coexist in pre- and postsynaptic sites: inhibition of GABA release in isolated self-innervating SCN neurons. Journal of Neuroscience 16, 7711–7724. Griebel, G., 1999. Is there a future for neuropeptide receptor ligands in the treatment of anxiety disorders? Pharmacology and Thereapeutics 82, 1–61. Hendry, S.H., Jones, E.G., DeFelipe, J., Schmechel, D., Brandon, C., Emson, P.C., 1984. Neuropeptide-containing neurons of the cerebral cortex are also GABAergic. Proceedings of the National
Academy of Sciences of the United States of America 81, 6526– 6530. Kask, A., Rago, L., Harro, J., 1996. Anxiogenic-like effect of the neuropeptide Y Y1 receptor antagonist BIBP3226: antagonism with diazepam. European Journal of Pharmacology 317, R3–4. Ko¨ hler, C., Eriksson, L., Davies, S., Chan-Palay, V., 1986. Neuropeptide Y innervation of the hippocampal region in the rat and monkey brain. Journal of Comparative Neurology 244, 384–400. McDonald, A.J., Pearson, J.C., 1989. Coexistence of GABA and peptide immunoreactivity in non-pyramidal neurons of the basolateral amygdala. Neuroscience Letters 100, 53–58. Oberto, A., Panzica, G., Altruda, F., Eva, C., 2000. Chronic modulation of GABAA receptor complex regulates Y1 receptor gene expression in the medial amygdala of transgenic mice. Neuropharmacology 39, 227–234. Oberto, A., Tolosano, E., Brusa, R., Altruda, F., Panzica, G., Eva, C., 1998. The murine Y1 receptor 5⬘ upstream sequence directs cellspecific and developmentally regulated LacZ expression in transgenic mice CNS. European Journal of Neuroscience 10, 3257– 3268. Pelletier, G., De´ sy, L., Kerkee´ rian, L., Cote´ , J., 1984. Immunocytochemical localization of neuropeptide Y (NPY) in the human hypothalamus. Cell Tissue Research 238, 203–205. Pu, S., Jain, M.R., Horvath, T.L., Diano, S., Kalra, P.S., Kalra, S.P., 1999. Interactions between neuropeptide Y and γ-aminobutyric acid in stimulation of feeding: a morphological and pharmacological analysis. Endocrinology 140, 933–940. St-Pierre, J.A., Nouel, D., Dumont, Y., Beaudet, A., Quirion, R., 2000. Association of neuropeptide Y Y1 receptors with glutamate-positive and NPY-positive neurons in rat hippocampal cultures. European Journal of Neuroscience 12, 1319–1330.
Rapid communication
GABAergic and NPY-Y1 network in the medial amygdala: a neuroanatomical basis for their functional interaction A. Oberto
a, b
, G.C. Panzica c, F. Altruda d, C. Eva
a,*
a
c
Sezione di Farmacologia, Dipartimento di Anatomia, Farmacologia e Medicina Legale, Universita` di Torino, Via Pietro Giuria 13, 10125 Torino, Italy b Neurobiology Division, MRC Laboratory of Molecular Biology, MRC Center, Cambridge CB2 2QH, UK Sezione di Anatomia, Laboratorio di Neuroendocrinologia, Dipartimento di Anatomia, Farmacologia e Medicina Legale, Universita` di Torino, Torino, Italy d Dipartimento di Genetica, Biologia e Biochimica, Universita` di Torino, Torino, Italy Received 2 January 2001; received in revised form 8 June 2001; accepted 15 June 2001
Abstract We used Y1R/LacZ transgenic mice to investigate the interaction between NPY, GABA and Y1 receptors in the amygdala. Immunolabeling of GABA and NPY positive neurons and histochemical staining of β-galactosidase revealed NPY and GABA colocalization and close contacts of NPY-positive fibers with GABAergic neurons also expressing the Y1R/LacZ transgene. 2001 Elsevier Science Ltd. All rights reserved. Keywords: Neuropeptide Y; Y1 receptor; GABA; β-galactosidase; Amygdala; Transgenic mice
Neuropeptide Y (NPY) produces an anxiolytic-like action similar to that induced by benzodiazepines acting on the GABAA receptor. This effect is observed in a variety of paradigms including the elevated plus maze, the conflict test, the fear-potentiated startle paradigm and the social interaction test (for review see Griebel, 1999). The behavioral effects of NPY are probably mediated by the activation of Y1 receptors in different nuclei of the amygdala. Kask et al. (1996) showed that the benzodiazepine diazepam counteracts the anxiogenic effect of Y1 receptor selective antagonists, suggesting that the GABAA and Y1 receptor-mediated transmissions are closely coupled and may functionally interact in the regulation of anxiety. We previously generated ten independent transgenic mouse lines carrying the mouse Y1 receptor gene promoter fused to a LacZ reporter gene (Y1R/LacZ) (Oberto et al., 1998). With the use of this transgenic model, we recently showed that long-term treatment with allosteric modulators of GABAA receptors that act at the benzodiazepine or ω site affects the
* Corresponding author. Tel.: +39-011-6707718; fax: 39-0116707788. E-mail address: [email protected] (C. Eva).
Y1 receptor gene expression in the medial amygdala (Oberto et al., 2000). Here we used the Y1R/LacZ mice to study the neuroanatomical basis for the functional interaction between GABA and NPY-Y1 mediated transmissions in this brain area. Animal care and handling throughout the experimental procedure were in strict accordance with the European Community Council Directive, 24th November 1986 (86/609/EEC) and the protocol was approved by the Animal Investigation Committee of MURST. Transgenic Y1R/LacZ male mice (line 27) (Oberto et al., 1998) were anesthetized with chloral hydrate (300 mg/kg, ip.) and transcardiacally perfused with 20 ml of heparinized saline solution, followed by 20 ml of fixative (4% paraformaldehyde and 0.1% glutaraldehyde in 0.1 M phosphate buffer-saline (PBS) pH 7.2. Brains were dissected, postfixed for 2 h in 4% paraformaldehyde in PBS at 4°C, then rinsed in PBS, placed overnight at 4°C in 0.1 M PBS containing 30% sucrose, and frozen on dry ice. Coronal sections (40 µm-thick) obtained with a freezing microtome were collected and directly processed for Xgal histochemistry (Oberto et al., 1998). For double GABA and NPY immunostaining, after the histochemical reaction free floating sections were washed in PBS and then incubated for 30 min in 0.1 M PBS containing
0028-3908/01/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 8 - 3 9 0 8 ( 0 1 ) 0 0 1 0 9 - 5
640
A. Oberto et al. / Neuropharmacology 41 (2001) 639–642
0.02% Triton X-100 at room temperature followed by 30 min at room temperature in 20% normal goat serum. They were placed for 48 h at 4°C in a mixture of primary polyclonal antisera — guinea pig anti-GABA IgG, 1:500 (Chemicon International, CA, USA) and rabbit anti-NPY IgG 1:1000 (a gift by H. Vaudry, Rouen, France) — diluted in 0.1 M PBS containing 0.1% normal goat serum and 0.02% Triton X-100. After several rinses in PBS, sections were further incubated in a mixture of rhodamine (TRITC)-conjugated anti-guinea pig IgG and fluorescein (FITC)-conjugated anti-rabbit IgG (Autogen Bioclear UK Ltd, UK), diluted to 1:50 in 0.1 M PBS, for 1 h in the dark at room temperature, then washed in five changes of PBS for 10 min each. Sections were mounted with Vectashield (Vector Laboratories, CA, USA) on gelatin-coated slides and analyzed on a Biorad (MRC-1024) confocal microscope. To increase the number of in-focus-IR structures, we employed the features of the Biorad software to merge several focus layers in a single one. To test the specificity of the immunoreaction, control reactions were performed by replacing the antisera with normal serum. The production of the antibody against NPY and the results of the assays performed to control its specificity and cross-reactivity have been previously described (Pelletier et al., 1984). The histochemical detection of the β-galactosidase (βgal) activity confirmed a high expression of the Y1R/LacZ transgene in the medial amygdala (Oberto et al., 1998). Immunocytochemical detection of NPY-positive elements demonstrated a wide network of beaded fibers covering the whole extension of the medial amygdala, with a few stained cell bodies mainly located in the central portion of the medial amygdala (Fig. 1(A) and (D)). GABA-IR cell bodies were observed in large number within the medial amygdala as well as in the whole amygdaloid complex. The neuropil of the medial amygdala was characterized by a diffuse immunoreactivity, probably corresponding to GABA-ergic endings (Fig. 1(C) and (F)). The confocal analysis of sections treated for the simultaneous detection of β-gal staining, GABA and NPY revealed a high degree of colocalization for GABA or NPY and the Y1R/LacZ transgene. At the same time the majority of NPY-IR cell bodies were also positive for GABA (yellow cells in Fig. 1(E) and (H)). A few of them were also showing the β-gal histochemical activity (asterisk in Fig. 1(H)). In some cases we observed the coexistence of GABA and NPY within the same nerve fibers (Fig. 1(A)–(C)). GABAergic elements showing transgene expression were usually in close contact with NPY-IR fibers that were surrounding or covering the cell bodies (Fig. 1(B), (E), (G) and (H)). Similar close contacts were also observed for GABA-ergic elements non-reactive for LacZ expression. NPY-fibers were also seen in close contact with elements showing only β-gal staining. Lastly, we have also observed NPY-IR fibers in close contact with NPY-
GABA-Y1R/LacZ transgene positive elements (asterisk in Fig. 1(H)). The use of confocal-merged images was important to understand the entity of distribution of immunoreactive fibers around and in the proximity of GABA-ergic elements. However, the merging process ended in a masking of β-gal histochemical labeling and reduced the number of positive elements detected in the final image (compare Fig. 1(H) and (E) for the number of cells showing the histochemical labeling). Experimental evidence from our and other laboratories has suggested the existence of a functional interaction between GABA and NPY in the amygdala that may be important in the regulation of anxiety-like behavior (Kask et al., 1996; Oberto et al., 2000). Here we provide the first morphological evidence in support of a possible interrelationship between GABA and NPY-Y1 mediated transmission, suggesting that this interconnectivity may be an important regulatory mechanism within the medial amygdala that may contribute to NPY’s effects on anxious behavior. NPY has frequently been observed in GABAergic neurons in the cerebral cortex, basolateral amygdala, hippocampus and the hypothalamus (Hendry et al., 1984; Ko¨ hler et al., 1986; McDonald and Pearson, 1989; Pu et al., 1999). Using immunolabeling for NPY and GABA and histochemical labeling of Y1R/LacZ transgene expression we now have extended these studies showing that in the medial amygdala: (i) NPY and GABA coexist within the same neurons; (ii) NPY producing neurons make close contacts with GABA-containing neurons; (iii) several GABA-IR neurons display β-gal staining and (iv) few NPY-IR cell bodies also show the β-gal histochemical activity. These findings suggest that a network of axons from NPY neurons innervate GABAergic neurons that also express the Y1 receptor gene; and that NPY might inhibit GABA release by the activation of this receptor subtype. However, other mechanisms might also be involved. Several GABA producing neurons, which are surrounded by NPY positive fibers, do not display β-gal positive staining, indicating that not all GABAergic neurons are regulated by Y1 receptors. On the other hand the expression of Y1R/LacZ within the NPY containing neurons suggests a possible role of the Y1 receptor as an auto-receptor regulating the NPY release in this brain area. This is consistent with previous studies showing that the Y1 receptor subtype can act as an autoreceptor in the hippocampus and in the suprachiasmatic nucleus (Chen and van den Pol, 1996; St-Pierre et al., 2000). These observations, together with those showing that most of the NPY-containing neurons also contain GABA, could account for a complex response to NPY in the medial amygdala. As a working hypothesis, we suggest that the NPY-Y1-mediated transmission and the GABAergic system may act together on the same postsynaptic target sites to decrease anxiety and that the Y1 receptors might also play a role in controlling both the NPY and GABA
A. Oberto et al. / Neuropharmacology 41 (2001) 639–642
641
Fig. 1. Confocal images illustrating the coexistence and close relationships among NPY, GABA, and Y1R/LacZ expressing elements. In green the immunolabeling for NPY, in red the immunolabeling for GABA, in dark blue the histochemical staining for β-gal. Yellow cells or fibers are elements where NPY (green) and GABA (red) coexist. (A)–(F): confocal images obtained merging several focus planes. Bar in A represents 30 µm. (G) and (H): single, not merged confocal images. The bar in (G) represents 30 µm. In (A) and (C), the arrow points to the same fiber recognizable for its characteristic shape showing NPY (A) and GABA (C) immunoreactivity. The same fiber is stained in yellow in (B). In (D) and (F) the arrows point to numerous co-existent NPY- and GABA-IR cell bodies which are yellow in (E). In (G) and (H) the arrowheads indicate a few of the numerous elements showing also the histochemical staining for β-gal. In (H) the arrow point to NPY-IR cell bodies showing also β-gal activity. The asterisk indicates one yellow cell body positive for β-gal. The same cell is clearly identifiable in (E) (asterisk), the image reconstructed from the series to which (H) is belonging.
presynaptic release. We have recently demonstrated that chronic treatment with positive modulators of the GABAA receptor complex increases, and negative modulators decrease, Y1R/LacZ transgene expression in the
medial amygdala (Oberto et al., 2000). We now propose that chronic potentiation (or inhibition) of GABAA receptor function in the medial amygdala may induce compensatory changes in the activity of the GABA- and
642
A. Oberto et al. / Neuropharmacology 41 (2001) 639–642
NPY-containing neurons and, in turn, in gene expression of presynaptic and/or postsynaptic Y1 receptors.
Acknowledgements This work was supported by Grant 9905045782 from MURST to C.E. (Projects of National Relevance, Article 65DPR 382/80). A.O. was supported by a Marie Curie Research EC Training Grant No ERB4001GT980563. We thank Dr W. Wisden (MRC, Cambridge, UK) for helpful discussion and critical reading of the manuscript.
References Chen, G., van den Pol, A.N., 1996. Multiple NPY receptors coexist in pre- and postsynaptic sites: inhibition of GABA release in isolated self-innervating SCN neurons. Journal of Neuroscience 16, 7711–7724. Griebel, G., 1999. Is there a future for neuropeptide receptor ligands in the treatment of anxiety disorders? Pharmacology and Thereapeutics 82, 1–61. Hendry, S.H., Jones, E.G., DeFelipe, J., Schmechel, D., Brandon, C., Emson, P.C., 1984. Neuropeptide-containing neurons of the cerebral cortex are also GABAergic. Proceedings of the National
Academy of Sciences of the United States of America 81, 6526– 6530. Kask, A., Rago, L., Harro, J., 1996. Anxiogenic-like effect of the neuropeptide Y Y1 receptor antagonist BIBP3226: antagonism with diazepam. European Journal of Pharmacology 317, R3–4. Ko¨ hler, C., Eriksson, L., Davies, S., Chan-Palay, V., 1986. Neuropeptide Y innervation of the hippocampal region in the rat and monkey brain. Journal of Comparative Neurology 244, 384–400. McDonald, A.J., Pearson, J.C., 1989. Coexistence of GABA and peptide immunoreactivity in non-pyramidal neurons of the basolateral amygdala. Neuroscience Letters 100, 53–58. Oberto, A., Panzica, G., Altruda, F., Eva, C., 2000. Chronic modulation of GABAA receptor complex regulates Y1 receptor gene expression in the medial amygdala of transgenic mice. Neuropharmacology 39, 227–234. Oberto, A., Tolosano, E., Brusa, R., Altruda, F., Panzica, G., Eva, C., 1998. The murine Y1 receptor 5⬘ upstream sequence directs cellspecific and developmentally regulated LacZ expression in transgenic mice CNS. European Journal of Neuroscience 10, 3257– 3268. Pelletier, G., De´ sy, L., Kerkee´ rian, L., Cote´ , J., 1984. Immunocytochemical localization of neuropeptide Y (NPY) in the human hypothalamus. Cell Tissue Research 238, 203–205. Pu, S., Jain, M.R., Horvath, T.L., Diano, S., Kalra, P.S., Kalra, S.P., 1999. Interactions between neuropeptide Y and γ-aminobutyric acid in stimulation of feeding: a morphological and pharmacological analysis. Endocrinology 140, 933–940. St-Pierre, J.A., Nouel, D., Dumont, Y., Beaudet, A., Quirion, R., 2000. Association of neuropeptide Y Y1 receptors with glutamate-positive and NPY-positive neurons in rat hippocampal cultures. European Journal of Neuroscience 12, 1319–1330.