A study of neuropeptide Y in brains of 'depressed' and healthy rats
Author: Jimenez Vasquez, Patricia A
Date: 2001-11-02
Location: Föreläsningssalen -1 tr., Psykiatriska Kliniken, St.Görans sjukhus, Stockholm
Time: 9.30
Department: Institutionen för klinisk neurovetenskap / Department of Clinical Neuroscience
Abstract
Neuropeptide Y (NPY), a 36-amino acid peptide that was originally
isolated from mammalian brain tissue, is widely distributed in both rat
and human brain. NPY has a number of physiological actions and affects
for example hypothalamic-pituitary-adrenal (HPA)-axis and circadian
rhythms, modulates memory processing and food intake. Also, emerging
evidence suggests that NPY may he involved in the pathophysiology of
depression. Chronic treatments with antidepressant drugs, lithium, as
well as repeated electroconvulsive stimuli (ECS), result in increased
NPY-LI concentrations in selected brain regions of rats. Thus, one of the
modes of action of ECT and antidepressants may be to elevate NPY in the
CNS. The hypothesis of a downregulation of NPY system in depression is in
part supported by human studies. Decreased NPY-LI concentrations in the
CSF and plasma of depressed patients compared to controls and low levels
of NPY-LI in the frontal cortex and caudate putamen in depressed suicide
victims have been reported. Recently it has been reported that NPY mRNA
was decreased in the prefrontal cortex of subjects affected with bipolar
disorder. In addition, repeated electroconvulsive treatment (ECT)
elevates NPY-LI in the CSF of depressed patients.
In this study, animal models of depression have been used to explore the possibility that NPY plays a role in depression. As a large body of evidence suggests that both genetic and environmental factors contribute to depressive disorders, we have used genetic animal models (the Fawn Hooded (FH) and the Flinders Sensitive Line (FSL) rats) and a stress model (maternal separation (MS)) of depression. Furthermore, as women are overrepresented in the depressed population, both male and female rats were included in some of our experiments. The respective "healthy" controls were Flinders Resistant Line (FRL), Wistar and non-maternally separated rats. Studies were conducted under baseline conditions and after repeated ECS or fluoxetine treatment. The present studies demonstrate that basal concentrations of NPY-LI in the hippocampus of the "depressed" FH, FSL and maternally separated (MS) rats are significantly lower than that of the controls. The alteration in NPY-Ll correlated well with the NPY mRNA expression. The basal NPYmRNA expression was lower in hippocampal CA and dentate gyrus of the FSL rats. We also found that Y1 binding sites are increased in the CA region of these animals. These results support our hypothesis that an NPY hypofunction, possibly secondary to decreased NPY synthesis, plays a role in depression. We also demonstrated that this deficit can he "normalized" by both repeated ECSs and fluoxetine treatments, probably by stimulating NPYergic neurotransmission in the limbic structures. Consequently, one heuristic hypothesis is that one of the modes of action of ECT and antidepressants may be to elevate NPY in the limbic system. Decreased basal NPY-LI levels in the "depressed" FSL and the FRL females as well as in the MS females compared to male controls were observed. It should be noted that the oestrous cycle did not modify NPY-LI levels in female FSL or FRL rats and thus it is not likely to be a confounding factor in obtained results. Whether the findings of lower NPY-LI levels in female compared to male "depressed" rats could explain increased rates of depression in women is purely speculative, but consistent with the results in present studies using different models of depression.
The work presented here adds further evidence for the involvement of NPY in depression and in the mechanisms of action of antidepressants.
In this study, animal models of depression have been used to explore the possibility that NPY plays a role in depression. As a large body of evidence suggests that both genetic and environmental factors contribute to depressive disorders, we have used genetic animal models (the Fawn Hooded (FH) and the Flinders Sensitive Line (FSL) rats) and a stress model (maternal separation (MS)) of depression. Furthermore, as women are overrepresented in the depressed population, both male and female rats were included in some of our experiments. The respective "healthy" controls were Flinders Resistant Line (FRL), Wistar and non-maternally separated rats. Studies were conducted under baseline conditions and after repeated ECS or fluoxetine treatment. The present studies demonstrate that basal concentrations of NPY-LI in the hippocampus of the "depressed" FH, FSL and maternally separated (MS) rats are significantly lower than that of the controls. The alteration in NPY-Ll correlated well with the NPY mRNA expression. The basal NPYmRNA expression was lower in hippocampal CA and dentate gyrus of the FSL rats. We also found that Y1 binding sites are increased in the CA region of these animals. These results support our hypothesis that an NPY hypofunction, possibly secondary to decreased NPY synthesis, plays a role in depression. We also demonstrated that this deficit can he "normalized" by both repeated ECSs and fluoxetine treatments, probably by stimulating NPYergic neurotransmission in the limbic structures. Consequently, one heuristic hypothesis is that one of the modes of action of ECT and antidepressants may be to elevate NPY in the limbic system. Decreased basal NPY-LI levels in the "depressed" FSL and the FRL females as well as in the MS females compared to male controls were observed. It should be noted that the oestrous cycle did not modify NPY-LI levels in female FSL or FRL rats and thus it is not likely to be a confounding factor in obtained results. Whether the findings of lower NPY-LI levels in female compared to male "depressed" rats could explain increased rates of depression in women is purely speculative, but consistent with the results in present studies using different models of depression.
The work presented here adds further evidence for the involvement of NPY in depression and in the mechanisms of action of antidepressants.
List of papers:
I. Mathe AA, Jimenez PA, Theodorsson E, Stenfors C (1998). "Neuropeptide Y, neurokinin A and neurotensin in brain regions of Fawn Hooded "depressed", Wistar, and Sprague Dawley rats. Effects of electroconvulsive stimuli. " Prog Neuropsychopharmacol Biol Psychiatry 22(3): 529-46
Pubmed
II. Jimenez-Vasquez PA, Overstreet DH, Mathe AA (2000). "Neuropeptide Y in male and female brains of Flinders Sensitive Line, a rat model of depression. Effects of electroconvulsive stimuli. " J Psychiatr Res 34(6): 405-12
Pubmed
III. Jimenez-Vasquez PA, Diaz-Cabiale Z, Caberlotto L, Bellido I, Fuxe K, Mathe AA (2001). "Electroconvulsive stimuli affect neuropeptide Y (NPY) gene expression and NPY Y1 receptor binding and gene expression in brain of Flinders Sensitive Line rats, an animal model of depression." (Manuscript)
IV. Caberlotto L, Jimenez PA, Overstreet DH, Hurd YL, Mathe AA, Fuxe K (1999). "Alterations in neuropeptide Y levels and Y1 binding sites in the Flinders Sensitive Line rats, a genetic animal model of depression." Neurosci Lett 263: 191.4
V. Jimenez-Vasquez PA, Mathe AA, Thomas J, Riley EP, Ehlers CL (2001). "Early maternal separation alters neuropeptide Y concentrations in selected brain regions in adult rats." Developmental Brain Research (Submitted)
I. Mathe AA, Jimenez PA, Theodorsson E, Stenfors C (1998). "Neuropeptide Y, neurokinin A and neurotensin in brain regions of Fawn Hooded "depressed", Wistar, and Sprague Dawley rats. Effects of electroconvulsive stimuli. " Prog Neuropsychopharmacol Biol Psychiatry 22(3): 529-46
Pubmed
II. Jimenez-Vasquez PA, Overstreet DH, Mathe AA (2000). "Neuropeptide Y in male and female brains of Flinders Sensitive Line, a rat model of depression. Effects of electroconvulsive stimuli. " J Psychiatr Res 34(6): 405-12
Pubmed
III. Jimenez-Vasquez PA, Diaz-Cabiale Z, Caberlotto L, Bellido I, Fuxe K, Mathe AA (2001). "Electroconvulsive stimuli affect neuropeptide Y (NPY) gene expression and NPY Y1 receptor binding and gene expression in brain of Flinders Sensitive Line rats, an animal model of depression." (Manuscript)
IV. Caberlotto L, Jimenez PA, Overstreet DH, Hurd YL, Mathe AA, Fuxe K (1999). "Alterations in neuropeptide Y levels and Y1 binding sites in the Flinders Sensitive Line rats, a genetic animal model of depression." Neurosci Lett 263: 191.4
V. Jimenez-Vasquez PA, Mathe AA, Thomas J, Riley EP, Ehlers CL (2001). "Early maternal separation alters neuropeptide Y concentrations in selected brain regions in adult rats." Developmental Brain Research (Submitted)
Issue date: 2001-10-12
Publication year: 2001
ISBN: 91-7349-060-1
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