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Effect of hypoxia combined with hypoglycemia on transmitter release from rat striatal slices
Pharmacological Research, Vol. 25, Supplement 2, 1992
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EFFECT OF HYPOXIA COMBINED WITH HYPOGLYCEMIA ON TRANSMITTER RELEASE FROM RAT STRIATAL SLICES Milusheva, E. *, Doda, M. **, Pasztor, E. ***, Lajtha, A . ****, Sershen, H. ****, and Vizi, E. S. ** ** Inst . of Experimental Medicine, Hungarian Academy of Sciences, H-1450, Budapest, POB 67, Hungary ; Inst . of Physiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria, * * National Inst . of Neurosurgery, Budapest, Hungary, and **** Center of Neurochemistry, Nathan S .Kline Institute for Psychiatric Research, Orangeburg, N .Y. 10962 Key Words : Hypoxia, hypoglycemia, striatum, transmitter release
Neuropathological studies clearly established that some brain regions are especially vulnerable to ischemic insult (1-3). The CA1 region of the hippocampus and the corpus striatum are areas particularly susceptible to transient ischemia . The effects of hypoxia on synaptic transmission and on neuronal damage were reviewed recently (3) . The effects of glucose deprivation on transmitter release have also been examined using microdialysis (4-6) and in vitro slice preparation (7) . Only a few authors, however, have analyzed the effects of combined oxygen and glucose withdrawal, a condition frequently occurring during ischemia . In this study the spontaneous and stimulation-evoked (2Hz, 360 pulses) release of tritiated dopamine, -aminobutyric acid, glutamate and acetylcholine (8) was measured in rat hippocampus slice preparation . Hypoxia increased the evoked release of glutamate and dopamine without effect on the resting release . In contrast, hypoglycemia itself increased the resting release of dopamine . Hypoxia in combination with hypoglycemia provoked a massive release of glutamate, dopamine and .~`-aminobutyric acid. The effect on acetylcholine release was less pronounced . Cat+ withdrawal partly reduced the effect of hypoxia combined with hypoglycemia on dopamine release and application of tetrodotoxin (1 AM) abolished it . MK-801 (3 AM), an NMDA-receptor antagonist, attenuated the effect of hypoxia and hypoglycemia on [ 3H]dopamine release . w-Conotoxin (0.1 AM) had similar effect on stimulation-evoked release in hypoxic condition . The D2-receptor antagonist sulpiride (100 AM) failed to enhance the release of [3H]acetylcholine in hypoxia combined with hypoglycemia . Since the application of 1 µM TTX inhibited the release of DA in response to hypoxic-hypoglycemic conditions, it is suggested that the release was associated with axonal firing . The fact that MK-801, an NMDA-receptor antagonist, attenuated the effect of hypoxia in combination with hypoglycemia on DA release and its effect was even more marked in the absence of Mgt' and TTX was not able to inhibit the effect of glutamate on DA release (9), indicates that the increased firing rate of glutamatergic neurons resulted in a mainly [Ca2+ J o -dependent release of glutamate, which in turn released DA from the axon terminals in a [Ca 2+ ] oindependent manner. It is suggested that in response to hypoxia combined with hypoglycemia there is a massive release of glutamate due to the increased firing rate which in turn releases dopamine from the axon terminals through stimulation of presynaptic 1043-6618/92/25110056-02/$03 .00/0
© 1992 The Italian Pharmacological Society
Pharmacological Research, Vol. 25, Supplement 2, 1992
NMDA receptors . Dopaminergic inhibitory control on ACh release seems to be not operative in conditions of hypoxia combined with hypoglycemia .
REFERENCES 1 . Pulsinelli WA . Selective neuronal vulnerability: morphological and molecular characteristics . Prog . Brain Res 1985, 63 :29-37 . 2 . Siesjo BK. Historical overview : calcium, ischemia, and death of brain cells . In: Vanhoutte DM, Paoletti R and Gononi S, eds . Pharmacology and Clinical Research :Calcium Antagonists. Ann. N.Y . Acad . Sci . 1988, 522 :638-661 . 3 . Schmidt-Kastner R and Freund TF . Selective vulnerability of the hippocampus in brain ischemia . Neurosci . 1991, 40:599-636. 4 . Lindvall 0, Auer RN, and Siesjo BK . Selective lesions of mesostriatal dopamine neurons ameliorate hypoglycemic damage in the caudate-putamem . Exp Brain Res 1986, 63 :382-386 . 5 . Tossman U, Wieloch T and Ungerstedt U. Gamma-aminobutyric acid and taurine release in the striatum of the rat during hypoglycemic coma, studied by microdialysis . Neurosci Lett . 1985, 62 :231-235 . 6 . Butcher S P, Sandberg M, Hagberg H and Hamberger A. Cellular origin of endogenous amino acids released into the extracellular fluid of the rat striatum during severe insulin-induced hypoglycemia . J . Neurochem . 1987, 48 :722-728 . 7 . Szerb JC . Changes in the relative amounts of aspartate and glutamate released and retained in hippocampal slices during stimulation . J . Neurochem . 1988,50 :219-224 . 8 . Milusheva E, Sperlagh B, Kiss B, Szporny L, Pasztor E, Papasova E and Vizi ES . Inhibitory effect of hypoxic condition on acetylcholine release is partly due to the effect of adenosine released from the tissue . Brain Res Bull 1990, 24 :369-373 . 9 . Cheramy A, Romo R, Godeheu G, Baruch P and Glowinski J . In vivo presynaptic control of dopamine release in the cat caudate nucleus . II Facilitory or inhibitory influence of L-Glutamate . Neurosci . 1986, 19:1081-1090 .
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EFFECT OF HYPOXIA COMBINED WITH HYPOGLYCEMIA ON TRANSMITTER RELEASE FROM RAT STRIATAL SLICES Milusheva, E. *, Doda, M. **, Pasztor, E. ***, Lajtha, A . ****, Sershen, H. ****, and Vizi, E. S. ** ** Inst . of Experimental Medicine, Hungarian Academy of Sciences, H-1450, Budapest, POB 67, Hungary ; Inst . of Physiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria, * * National Inst . of Neurosurgery, Budapest, Hungary, and **** Center of Neurochemistry, Nathan S .Kline Institute for Psychiatric Research, Orangeburg, N .Y. 10962 Key Words : Hypoxia, hypoglycemia, striatum, transmitter release
Neuropathological studies clearly established that some brain regions are especially vulnerable to ischemic insult (1-3). The CA1 region of the hippocampus and the corpus striatum are areas particularly susceptible to transient ischemia . The effects of hypoxia on synaptic transmission and on neuronal damage were reviewed recently (3) . The effects of glucose deprivation on transmitter release have also been examined using microdialysis (4-6) and in vitro slice preparation (7) . Only a few authors, however, have analyzed the effects of combined oxygen and glucose withdrawal, a condition frequently occurring during ischemia . In this study the spontaneous and stimulation-evoked (2Hz, 360 pulses) release of tritiated dopamine, -aminobutyric acid, glutamate and acetylcholine (8) was measured in rat hippocampus slice preparation . Hypoxia increased the evoked release of glutamate and dopamine without effect on the resting release . In contrast, hypoglycemia itself increased the resting release of dopamine . Hypoxia in combination with hypoglycemia provoked a massive release of glutamate, dopamine and .~`-aminobutyric acid. The effect on acetylcholine release was less pronounced . Cat+ withdrawal partly reduced the effect of hypoxia combined with hypoglycemia on dopamine release and application of tetrodotoxin (1 AM) abolished it . MK-801 (3 AM), an NMDA-receptor antagonist, attenuated the effect of hypoxia and hypoglycemia on [ 3H]dopamine release . w-Conotoxin (0.1 AM) had similar effect on stimulation-evoked release in hypoxic condition . The D2-receptor antagonist sulpiride (100 AM) failed to enhance the release of [3H]acetylcholine in hypoxia combined with hypoglycemia . Since the application of 1 µM TTX inhibited the release of DA in response to hypoxic-hypoglycemic conditions, it is suggested that the release was associated with axonal firing . The fact that MK-801, an NMDA-receptor antagonist, attenuated the effect of hypoxia in combination with hypoglycemia on DA release and its effect was even more marked in the absence of Mgt' and TTX was not able to inhibit the effect of glutamate on DA release (9), indicates that the increased firing rate of glutamatergic neurons resulted in a mainly [Ca2+ J o -dependent release of glutamate, which in turn released DA from the axon terminals in a [Ca 2+ ] oindependent manner. It is suggested that in response to hypoxia combined with hypoglycemia there is a massive release of glutamate due to the increased firing rate which in turn releases dopamine from the axon terminals through stimulation of presynaptic 1043-6618/92/25110056-02/$03 .00/0
© 1992 The Italian Pharmacological Society
Pharmacological Research, Vol. 25, Supplement 2, 1992
NMDA receptors . Dopaminergic inhibitory control on ACh release seems to be not operative in conditions of hypoxia combined with hypoglycemia .
REFERENCES 1 . Pulsinelli WA . Selective neuronal vulnerability: morphological and molecular characteristics . Prog . Brain Res 1985, 63 :29-37 . 2 . Siesjo BK. Historical overview : calcium, ischemia, and death of brain cells . In: Vanhoutte DM, Paoletti R and Gononi S, eds . Pharmacology and Clinical Research :Calcium Antagonists. Ann. N.Y . Acad . Sci . 1988, 522 :638-661 . 3 . Schmidt-Kastner R and Freund TF . Selective vulnerability of the hippocampus in brain ischemia . Neurosci . 1991, 40:599-636. 4 . Lindvall 0, Auer RN, and Siesjo BK . Selective lesions of mesostriatal dopamine neurons ameliorate hypoglycemic damage in the caudate-putamem . Exp Brain Res 1986, 63 :382-386 . 5 . Tossman U, Wieloch T and Ungerstedt U. Gamma-aminobutyric acid and taurine release in the striatum of the rat during hypoglycemic coma, studied by microdialysis . Neurosci Lett . 1985, 62 :231-235 . 6 . Butcher S P, Sandberg M, Hagberg H and Hamberger A. Cellular origin of endogenous amino acids released into the extracellular fluid of the rat striatum during severe insulin-induced hypoglycemia . J . Neurochem . 1987, 48 :722-728 . 7 . Szerb JC . Changes in the relative amounts of aspartate and glutamate released and retained in hippocampal slices during stimulation . J . Neurochem . 1988,50 :219-224 . 8 . Milusheva E, Sperlagh B, Kiss B, Szporny L, Pasztor E, Papasova E and Vizi ES . Inhibitory effect of hypoxic condition on acetylcholine release is partly due to the effect of adenosine released from the tissue . Brain Res Bull 1990, 24 :369-373 . 9 . Cheramy A, Romo R, Godeheu G, Baruch P and Glowinski J . In vivo presynaptic control of dopamine release in the cat caudate nucleus . II Facilitory or inhibitory influence of L-Glutamate . Neurosci . 1986, 19:1081-1090 .
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