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Neuro-immuno-pharmacological profile of dehydroepiandrosterone as a potential nootropic drug in model experiments with old rats
Poster C. Experimental-Animal studies
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treatments instead of solely examining the behavioural characteristics. Such biochemical and physiological factors have however to be investigated with several stress models and drugs.
Reference Willner, P., Towell, A., Sampson, D., Sophokleous, S., Muscat, R., 1987. Reduction of sucrose preference by chronic unpredictable mild stress, and its restoration by a tricyclic antidepressant. Psychopharmacology 93, 358-364.
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C-l 10
Neuro-immuno-pharmacological profile of dehydroepiandrosterone as a potential nootropic drug in modal experiments with old rats
0. BeneSov& H. TejkalovB, Z. KrigtofikovB, V. Panajotova”, P. Husek”. Prague Psychiatric Center, 18103 Prague 8; “Research Inst. for Pharmacy and Biochemistry, 13060 Prague 3: blnst. of Endocrinology, 11694 Prague I, Czech Republic Dehydroepiandrosterone (DHEA), the major steroid hormone synthetized in adrenals from cholesterol, reveals progresive decline with aging both in animals and man. DHEA concentration in the brain is higher than in adrenals, suggesting its role as a neuroactive steroidal hormone and its direct production by neurons. Plasma DHEA levels in nursing home patients were found to be inversely related to the presence of organic brain syndrome and its severity. DHEA in vitro enhanced neuronal and glial survival, in vivo improved memory and retention in senescent mice. It reduced age-related defects of immune reactivity and protected against hippocampal degeneration induced by stress released glucocorticoids. The mechanism of its action is explained by the inhibition of pentose cycle which may be the source of free radical generating processes, and by regulating interleukin IL-6 and IL-10 production which is increased in aging (Watson et al., 1996). Regarding the potential use of DHEA for the therapy of age-related cognitive decline, the present study was projected using animal model experiments simulating as close as possible the clinical condition of senile dementia treatment (i.e. long-term peroral drug administration in aging animals).
Methods: The experiments were carried out in female rats, strain Wistar, breed Kon&ovice, aged 17 months (N=18). The drug (DHEA sulphate) was administered for 10 weeks in the dose of 5 mglkglday given per OS as a mixture in the standard pellet diet, control age-matched rats received normal standard pellets. The consumption of the pellet portion alloted per rat was checked every day. At the end of the experiment, a set of tests was applied concerning behaviour (exploration and defecation rate in the ‘open field’), short-term memory (social recognition of conspecific juvenile), immune reactivity (cellular immune response) as well as brain biochemical analysis (concentration of monoamines and their metabolites in the hypothalamus and striatum, lipid peroxidation in the cortex and hippocampus). Results In comparison with age-matched controls, DHEA treated rats revealed higher exploratory activity, reduced emotional reactivity and improved short-term memory, but no difference in cellular immune response. Monoamine turnover in the hypothalamus and striatum was identical in both groups, the rate of lipid peroxidation in the cortex was increased in treated animals. Conclusion: Long-term treatment of aged rats with DHEA resulted in an improvement of behaviour and short-term memory without any change of cellular immune response and brain monoamine turnover. The rise of cortical peroxidation signals some negative action. Supported by the grant GA’?R No 309/95/1083.
Reference Watson, R.R., Huls, A., Araghinikuam, M., et al., 1996. Dehydroepiandrosterone and Diseases of Aging. Drugs and Aging 9, 274-29 1.
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Neuroactive steroid-mediated modulation of two native GABA, receptor subtypes in the brain of aduR rat
G. Schmid, R. Sala, G. Bonanno, M. Raiteri. Istituto di Farmacologia e Tossicologia, Universit2 di Geneva, Viale Cembrano 4, 16148 Genova, Ita1.y Nerve ending preparations
isolated from rat hippocampus
and cerebellum
contain, respectively, noradrenergic and glutamatergic nerve terminals endowed with presynaptic receptors of the GABA,, type, which modulate the basal release of noradrenaline (NA) and the depolarisation-evoked overflow of glutamic acid (GLU), respectively. It was recently found that the hippocampal receptor is sensitive to benzodiazepine agonists, whereas the cerebellar receptor is benzodiazepine-insensitive, suggesting that the two receptors represent native subtypes of the GABA, receptor present in the adult brain (S&mid et al., 1996). Using transmitter release from superfused synaptosomes as a functional response, we here tested the effects of naturally occurring neurosteroids on these two native GABA, receptors. Hippocampal synaptosomes were labelled, 15 min at 37”C, with [‘H]NA; cerebellar synaptosomes with [‘HID-ASP. After incubation with the radioactive tracers, synaptosomes were layered on microporous filters in parallel superfusion chambers and exposed to the various substances in superfusion. Allopregnanolone (3c&-P), at nanomolar concentrations, potentiated the GABA-induced [3H]-NA release from superfused hippocampal synaptosomes; in the absence of GABA, the steroid was ineffective up to 10 PM. The enhancement by GABA of the K’-evoked [3H]-D-asprutate release from cerebellar synaptosomes also was potentiated by nanomolar 3o1,5a-P; in addition, at l-10 PM, the steroid increased [‘HI-D-ASP release in the absence of GABA. Both in hippocampus and cerebellum the potentiation of the GABA effects produced by nanomolar 3a,5u-P were abolished by dehydroepiandrosterone sulphate (DHEAS). Added up to 10 PM, DHEAS could not inhibit the effects of GABA alone. The enhancement of [3H]-D-ASP release elicited by 3 p,M 3a,5a-P from cerebellar synaptosomes in the absence of added GABA was antagonised completely by bicuculline and picrotoxin and halved by DHEAS. To conclude, 3a,5a-P, at nanomolar concentrations, behaves as a positive allosteric GABA modulator at both the GABA, receptors under study. Low micromolar 3a;5a-P can directly activate the cerebellar receptor, whereas the hippocampal GABA, receptor is insensitive to the neurosteroid alone. DHBAS appears to be a pure antagonist at the neurosteroid allosteric site. Along with the previously observed differential sensitivity to benzodiazepines, the present data strengthen the idea that the two receptors investigated represent native subtypes of the GABA, receptor having distinct pharmacology, neuronal localisation and function. Supported
by Italian MURST
Reference Schmid, G., Bonanno, G., Raiteri, M., 1996. Functional evidence for two native GABA, receptor subtypes in adult rat hippocampus and cerebellum. Neuroscience 73, 697-704.
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Effect of imipramine on forced swim test performance of female wistar rats exposed to variable vs fixed schedule of inescapable tones
T. Celikel, D. Schulz, S. Alkan, F. Balkanli, C. Diinmez, B. Gent, H. Kaygun, A. YalGin and R. Canbeyli. Department of Psychology, Bosphorus University, Istanbul, Turkey Exposure to inescapable aversive stimuli induces learned helplessness in many species including rats. Rats also display learned despair in the form of longer immobility in the second of two forced swim tests separated by 24 hours. These procedures have been used as animal models of depression and are known to respond positively to antidepressants (including imipramine) used in treating depression in humans. The two methods were combined in an effort to develop a behavioral method for prevention of depression despite repeated exposure to enescapable aversive stimuli in rats. Rats were exposed to a series of loud, inescaple tones and depression was assessed by means of immobility in two forced two swim tests. Previous work in our laboratory has shown that exposing rats to inescapable tones that were both uncontrollable and unpredictable in terms of onset and duration significantly impaired performance in subsequent forced swim tests compared to control animals that were not exposed to tones and are immunized against the debilitating effect of behavioral immunization and pharmacological therapy inescapable toneinduced depression as evaluated by performance in forced swim tests. Female Wistar rats were exposed to 60 inescapable tones (2000 HZ, 120 dB) of either varying duration (3 to 7 set; mean duration 5 set) and
s40
treatments instead of solely examining the behavioural characteristics. Such biochemical and physiological factors have however to be investigated with several stress models and drugs.
Reference Willner, P., Towell, A., Sampson, D., Sophokleous, S., Muscat, R., 1987. Reduction of sucrose preference by chronic unpredictable mild stress, and its restoration by a tricyclic antidepressant. Psychopharmacology 93, 358-364.
I
C-l 10
Neuro-immuno-pharmacological profile of dehydroepiandrosterone as a potential nootropic drug in modal experiments with old rats
0. BeneSov& H. TejkalovB, Z. KrigtofikovB, V. Panajotova”, P. Husek”. Prague Psychiatric Center, 18103 Prague 8; “Research Inst. for Pharmacy and Biochemistry, 13060 Prague 3: blnst. of Endocrinology, 11694 Prague I, Czech Republic Dehydroepiandrosterone (DHEA), the major steroid hormone synthetized in adrenals from cholesterol, reveals progresive decline with aging both in animals and man. DHEA concentration in the brain is higher than in adrenals, suggesting its role as a neuroactive steroidal hormone and its direct production by neurons. Plasma DHEA levels in nursing home patients were found to be inversely related to the presence of organic brain syndrome and its severity. DHEA in vitro enhanced neuronal and glial survival, in vivo improved memory and retention in senescent mice. It reduced age-related defects of immune reactivity and protected against hippocampal degeneration induced by stress released glucocorticoids. The mechanism of its action is explained by the inhibition of pentose cycle which may be the source of free radical generating processes, and by regulating interleukin IL-6 and IL-10 production which is increased in aging (Watson et al., 1996). Regarding the potential use of DHEA for the therapy of age-related cognitive decline, the present study was projected using animal model experiments simulating as close as possible the clinical condition of senile dementia treatment (i.e. long-term peroral drug administration in aging animals).
Methods: The experiments were carried out in female rats, strain Wistar, breed Kon&ovice, aged 17 months (N=18). The drug (DHEA sulphate) was administered for 10 weeks in the dose of 5 mglkglday given per OS as a mixture in the standard pellet diet, control age-matched rats received normal standard pellets. The consumption of the pellet portion alloted per rat was checked every day. At the end of the experiment, a set of tests was applied concerning behaviour (exploration and defecation rate in the ‘open field’), short-term memory (social recognition of conspecific juvenile), immune reactivity (cellular immune response) as well as brain biochemical analysis (concentration of monoamines and their metabolites in the hypothalamus and striatum, lipid peroxidation in the cortex and hippocampus). Results In comparison with age-matched controls, DHEA treated rats revealed higher exploratory activity, reduced emotional reactivity and improved short-term memory, but no difference in cellular immune response. Monoamine turnover in the hypothalamus and striatum was identical in both groups, the rate of lipid peroxidation in the cortex was increased in treated animals. Conclusion: Long-term treatment of aged rats with DHEA resulted in an improvement of behaviour and short-term memory without any change of cellular immune response and brain monoamine turnover. The rise of cortical peroxidation signals some negative action. Supported by the grant GA’?R No 309/95/1083.
Reference Watson, R.R., Huls, A., Araghinikuam, M., et al., 1996. Dehydroepiandrosterone and Diseases of Aging. Drugs and Aging 9, 274-29 1.
C 111 I_
Neuroactive steroid-mediated modulation of two native GABA, receptor subtypes in the brain of aduR rat
G. Schmid, R. Sala, G. Bonanno, M. Raiteri. Istituto di Farmacologia e Tossicologia, Universit2 di Geneva, Viale Cembrano 4, 16148 Genova, Ita1.y Nerve ending preparations
isolated from rat hippocampus
and cerebellum
contain, respectively, noradrenergic and glutamatergic nerve terminals endowed with presynaptic receptors of the GABA,, type, which modulate the basal release of noradrenaline (NA) and the depolarisation-evoked overflow of glutamic acid (GLU), respectively. It was recently found that the hippocampal receptor is sensitive to benzodiazepine agonists, whereas the cerebellar receptor is benzodiazepine-insensitive, suggesting that the two receptors represent native subtypes of the GABA, receptor present in the adult brain (S&mid et al., 1996). Using transmitter release from superfused synaptosomes as a functional response, we here tested the effects of naturally occurring neurosteroids on these two native GABA, receptors. Hippocampal synaptosomes were labelled, 15 min at 37”C, with [‘H]NA; cerebellar synaptosomes with [‘HID-ASP. After incubation with the radioactive tracers, synaptosomes were layered on microporous filters in parallel superfusion chambers and exposed to the various substances in superfusion. Allopregnanolone (3c&-P), at nanomolar concentrations, potentiated the GABA-induced [3H]-NA release from superfused hippocampal synaptosomes; in the absence of GABA, the steroid was ineffective up to 10 PM. The enhancement by GABA of the K’-evoked [3H]-D-asprutate release from cerebellar synaptosomes also was potentiated by nanomolar 3o1,5a-P; in addition, at l-10 PM, the steroid increased [‘HI-D-ASP release in the absence of GABA. Both in hippocampus and cerebellum the potentiation of the GABA effects produced by nanomolar 3a,5u-P were abolished by dehydroepiandrosterone sulphate (DHEAS). Added up to 10 PM, DHEAS could not inhibit the effects of GABA alone. The enhancement of [3H]-D-ASP release elicited by 3 p,M 3a,5a-P from cerebellar synaptosomes in the absence of added GABA was antagonised completely by bicuculline and picrotoxin and halved by DHEAS. To conclude, 3a,5a-P, at nanomolar concentrations, behaves as a positive allosteric GABA modulator at both the GABA, receptors under study. Low micromolar 3a;5a-P can directly activate the cerebellar receptor, whereas the hippocampal GABA, receptor is insensitive to the neurosteroid alone. DHBAS appears to be a pure antagonist at the neurosteroid allosteric site. Along with the previously observed differential sensitivity to benzodiazepines, the present data strengthen the idea that the two receptors investigated represent native subtypes of the GABA, receptor having distinct pharmacology, neuronal localisation and function. Supported
by Italian MURST
Reference Schmid, G., Bonanno, G., Raiteri, M., 1996. Functional evidence for two native GABA, receptor subtypes in adult rat hippocampus and cerebellum. Neuroscience 73, 697-704.
C 112 I
Effect of imipramine on forced swim test performance of female wistar rats exposed to variable vs fixed schedule of inescapable tones
T. Celikel, D. Schulz, S. Alkan, F. Balkanli, C. Diinmez, B. Gent, H. Kaygun, A. YalGin and R. Canbeyli. Department of Psychology, Bosphorus University, Istanbul, Turkey Exposure to inescapable aversive stimuli induces learned helplessness in many species including rats. Rats also display learned despair in the form of longer immobility in the second of two forced swim tests separated by 24 hours. These procedures have been used as animal models of depression and are known to respond positively to antidepressants (including imipramine) used in treating depression in humans. The two methods were combined in an effort to develop a behavioral method for prevention of depression despite repeated exposure to enescapable aversive stimuli in rats. Rats were exposed to a series of loud, inescaple tones and depression was assessed by means of immobility in two forced two swim tests. Previous work in our laboratory has shown that exposing rats to inescapable tones that were both uncontrollable and unpredictable in terms of onset and duration significantly impaired performance in subsequent forced swim tests compared to control animals that were not exposed to tones and are immunized against the debilitating effect of behavioral immunization and pharmacological therapy inescapable toneinduced depression as evaluated by performance in forced swim tests. Female Wistar rats were exposed to 60 inescapable tones (2000 HZ, 120 dB) of either varying duration (3 to 7 set; mean duration 5 set) and