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Direct action of mazindol on guinea-pig ventromedial hypothalamic neurons: Intracellular studies in slice preparation
BrainResearch BuJJerin, Vol. 15, pp. 29-31, 1985. 0 Ankha International Inc. Printed in the U.S.A.
0361-9230/85. $3.00 + .OO
Direct Action of Mazindol on Guinea-Pig Ventromedial Hypothalamic Neurons: Intracellular Studies in Slice Preparation TAKETSUGU
MINAMI,
YUTAKA OOMURA,’ AND MARY HYNES
MUTSUYUKI
SUGI~ORI
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, 812 Japan and (MS.) Department of Physiology and Biophysics, New York University, Medical Center 550 First Avenue, New York, NY 10016 Received
4 April
1985
MINAMI, T., Y. OOMURA, M. SUGIMORI AND M. HYNES. Direct action of mazindoi on guinea-pig ventromedial hypothalamic neurons: Intracellular studies in slice preparation. BRAIN RES BULL 15(l) 29-31, 1985.-Neuronal responses in the ventromedi~ hy~th~~ic nucleus (VMH) to mazindol (MZD) were examined by int~cellular recordings in hy~th~amic slices in vitro. Bath application of MZD caused deflection of the membrane by 8.Ok3.4 mV (mean2S.D.) associated with an increase in the input membrane resistance (23.0~5.8%) among 20% of the cells examined. Current-voltage plots, obtained simultaneously, showed the reversal potential between -80 and -90 mV. These results indicate that MZD depolarizes VMH neurons by reducing the K+ conductance, through a mechanism similar to that of glucose, and the anorectic action of MZD can be explained by its direct effects on the VMH. Ventromedial hypothalamus Brain slice
Glucoreceptor
neuron
Mazindol
IT has been well documented that the lateral hypothalamic area (LHA) and the ventromedial hypothalamic nucleus (VMH) are important in the regulation of feeding [l 1, 12,131. These two regions are referred to as the feeding and satiety centers, respectively. About 25% of the neurons in each of these centers are chemosensitive, and their activity is intluenced by glucose, free fatty acids, insulin [l 1,121 and other endogenous metabolites [ 13, 15, 181. Glucoreceptor neurons in the VMH have been defined as those that increase in activity with a dose response manner under the influence of glucose. The existence of these neurons has been demonstrated from extracellular studies of single neuronal activity induced by direct microelectrophoretic application of glucose in vivo [14] and by bath applications to brain slices in vitro experiments [ 101. We recently reported details of VMH glucoreceptor neuron properties, such as the ionic mechanism, obtained by intracellular recording in hypothalamic slices in vitro [8]. In the last several years, mazindol (MZD), an imidazoisoindole derivative, has been used as an anorexic agent in humans [4,22]. A number of investigations have revealed that this anorexigenic agent may act in part through brain catecholamines or serotonine. However, its direct effects on the feeding and satiety centers in the central nervous system are obscure. It has recently been shown that electrophoretic application of MZD in anesthetized rats excited glucoreceptor neurons of the VMH in vivo [19]. The present
Anorexic agent
Intracellular recording
experiments were undertaken to investigate by intracellular recordings in hypothalamic slices in vitro, whether the mechanism of action of MZD on VMH neurons is similar to that of glucose. METHOD
The techniques used here are almost the same as those previously reported [7]. To prepare a hypothalamic tissue slice, the brain was quickly removed from 16 decapitated albino guinea-pigs (250-400 g) and placed in Krebs solution at 4°C. The solution contained (mM): NaCl, 124; KCI, 5; K2S04, 1.24; NaHCO,, 26; CaCl,, 2.4; MgSO,, 1.3; glucose, IO; and was equilibrated with 95% 0, and 5% CO*, at pH 7.4. Four-hundred pm thick, coronally-oriented hypothalamic VMH slices were sectioned and incubated at room temperature for about 1 hr in the same solution. The recording chamber (1 S-2 ml) was perfused by solution warmed at 34-36°C at a rate of 3-4 mllmin. Intracellular electrodes, filled with 1-3 M K acetate had an average DC resistance of 60-120 MC!. Electrophysiological properties of the VMH neurons were determined by means of a high input impedance bridge amplifier (Neuro Data IR-283). The location of the VMH was based on the stereotaxic atlas [21] and was easily determined by the fomix and the fasciculus mammillothalamicus. RESULTS In
order to obtain reliable analyses,
cells with membrane
‘Requests for reprints should be addressed to Professor Y. Oomura, Department of Physiology, Faculty of Medicine, Kyushu University 60, Fukuoka 812, Japan.
29
30
MlNAMl
E7 AI..
3min 3XltPM
MZD
20mV 2omV
llil
,;,”
.-’
8,
l
I
.MZDi-100
FIG. 1.Depolarizing response of VMH neurons to mazindol(3 x lo-’ M MZD). A. annlication of MZD denolarized neuron and increased input membrane resistance measured by inward current pulse, duration 200 msec; intensity 0.07 nA. To ubtain current-voltage relations, various current pulses were applied before (a) and after MZD (b). Increase of input membrane resistance during response was clear by manual-clamping for 40 set at the resting membrane potential (c). B, current-voltage plots depicting voltage deflections to various current pulses applied before and after MZD. Open circles, control Krebs solution; filled circles, MZD solution. Apparent reversal potential in this cell is -84 mV.
FIG. 2. Hyperpolarizing response of VMH neuron to mazindol (3 x IO-’ M MZD). A, bath application of MZD hyperpolarized the neuron and decreased its input membrane resistance (measured by inward current pulse, duration 200 msec; intensity, 0.08 nA). To obtain current-voltage relations, current pulses were injected before (a) and after MZD (b). Decrease of input membrane resistance during response was cleared by manual-cl~ping for 55 set at resting membrane potential (c). B, current-voltage plots depicting voltage deflection to various current pulses applied before and after MZD. Apparent reversal potential in this cell is -90 mV.
potential less than 50 mV, spike amplitude less than 50 mV, input membrane resistance less than 80 MO, or stable recordings for less than 15 min were not accepted. Twenty-five neurons that satisfied these criteria were used for detailed analyses. The average spike amplitude was 60.3k5.9 mV (mean-cS.D.), input membrane resistance was 138.3t32.0 Ma and resting membrane potential was -61.4r6.2 mV. MZD was applied to the bath to produce concentrations of lO+ to 1O-6 M. MZD depolarized 5 cells (20%) by +8.0?3.4 mV and this response was accompanied by an increase in the input membrane resistance of the recorded neurons by 23.0t5.8%. An example is shown in Fig. 1. The actual increase in the membrane resistance by MZD was clearly indicated by the temporal manual-clamping of the membrane potential at the resting level in Fig. lA, c. The current-voltage (I-V) relations of a typical response is plotted in Fig. 1B. The membrane potential at the intersection of two curves describing the I-V relationship in normal Krebs solution and that in MZD solution is -84 mV, which indicates the reversal potential for MZD depolarization. The increased input membrane resistance and reversal potential between -80 and -90 mV suggests that the depolarization caused by MZD might be attributed to a reduction in the membrane KC conductance. Three cells (1%) were hyperpolarized by MZD (-3.82 1.0 mV), which was ~companied by a reduction (12.0t3.6%) in the input membrane resistance. Figure 2 shows one of these responses. Figure 2B shows a reversal potential of -90 mV for MZD hyperpolarization. These findings suggest that this hyperpolarization produced by MZD might contribute to the increased membrane K+ conductance. In two cells (8%), administration of MZD for about 2 minutes produced a biphasic response, short hy~~oI~ization (approximately 30 see) followed by a long depolarization (5-10 min). How-
ever, the main effect of this response polarization.
is thought to be de-
DISCUSStON
Brain cate~holamines have previously been shown to be affected by MZD administration. Specifically, noradrenaline uptake was inhibited [3,5]. However, controversial results were shown with regard to dopamine (DA), with an increase in turnover [2] or a decrease in uptake [S]. Alhskog [l] has shown that selective destruction of the ventral noradrenergic bundle with 6-hydroxydop~ine produces hyperphagia in rat, while Samanin et ai. [ 171and Leibowitz et al. [6] showed that electrolytic lesion of this bundle decreased anorexic efficacy of MZD. From the above findings, it appears that the action of MZD might be mediated indirectly through neurotransmitters. Intra-third ventricle injections of MZD in rats however decreased meal size (mount of food intake) and prolonged postprandial intermeal intervals f 161. Continuous infusion of MZD into the median eminence near the VMH caused the greatest reduction of food intake [9]. ‘It has been speculated that these anorectic actions of MZD are mediated by its direct action on the hypothalamic feeding control mechanism. Studies in our laboratory showed that MZD, when electrophoretically applied in anesthetized rats, selectively inhibited the activity of glucose-sensitive neurons in LHA [20]. Electrophoretically applied DA blocker attenuated the DA suppression caused by electrophoretic application of DA but not the MZD suppression. Ouabain, a Na-K pump inhibitor, attenuated MZD induced suppression of the neuronal activity. Further, intracellular recordings revealed hype~ola~zation of the membrane with no change in membrane conductance when rat brain slice was perfused with
~AZIN~L
MZD. This effect was similar to that of glucose. These results indicate that the inhibitory action of MZD is mediated by the activation of the Na-K pump. Our preliminary studies showed the excitatory effect of electrophoretically applied MZD on the glucoreceptor neurons of VMH that were excited by glucose application. Shiraishi [191 also reported a similar finding, In our intracellular studies, MZD mainly depolarized 20% of VMH neurons by reducing the K+ conductance, a mechanism similar to that of glucose [8]. These findings strongly indicate that MZD action on the glucosesensitive and glucoreceptor neurons mimics glucose. Thus, the anorexigenic action of MZD might be brought by its direct effects on the hypothalamus. MZD had either an inhibitory effect or an inhibitory effect followed by an excitation
1. Ahlskog, J. E. Food intake and amphetamine anorexia after selective forebrain norepinephrine loss. Brain Res 82: 21.i-240, 1974. 2. Carruba, M. O., A. Groppetti, P. Mantegazza, L. Vicentini and F. Zambotti. Effects of mazindol, a non-phenylethylamine anorexigenic agent, on biogenic amine levels and turnover rate. Br J ~~u~~u~o~ 56: 431-436, 1976. 3. Engstrom, R. G., L. A. Kelly and J. H. Gogerty. The effects of 5-hydroxy-5-(4’-chlorophenyl)-2,3-dihydro-5H-imidazo(Z,la) isoindole (m~~ndol. SaH 42-548) on the meta~lism of brain norepinephrine.ArchfnrPharmacudyn Ther214: 30%321,197s. 4. Gogerty, J. H., C. Penberthy, L. C. Iorio and J. Trapold. Pharmacological analysis of a new anorexic substance: 5-dihydroxyd-(~-chlorophenyl)-2,3-dihydro-5H-imidazo-(2, l-a) isoindole fmazindol). Arch int Pharmucodyn Ther 214: 284-307, 1975. 5. Heikkila, R. E., F. S. Cabbat and C. Mytilineou. Studies on the capacity of mazindol and dita to act as uptake inhibitors releasing agents for 3H-biogenic amines in rat brain tissue slices. EttrJ Pharmucol45: 329-333, 1977. 6. Leibowitz, S. F., N. J. Hammer and L. L. Brown. Analysis of
7. 8.
9.
10.
31
AND VMH NEURONS
behavioral deficits produced by lesions in the dorsal and ventral rn~db~~n te8mentum. Physi[~/ Behav 25: 829-843, 1980. Minami, T., Y. Oomura and M. Sugimori. Electrophysiological properties of guinea-pig ventromedial hypothalamic neurones: an in vitro study. J Physju~, submitted. Minami, T., Y. Gomura, M. Sugimori and R. R. Llinas. Electrophysiological properties of ventromedial hypothalamic neurons in guinea pig and their response to glucose: a vitro study. Sot Netrrosci Abstr 10:612, 1984. Nagai, K., T. Mori, M. Ookura, H. Tujimoto, S. Takagi and H. Nakagawa. Pharmacological effects of the mazindol on the behaviors and metabolism of rats. J Obesity Weight Regut, in press, 1985. Ono, T., H. Nishino, M. Fukuda, K. Sasaki, K. Muramoto and Y. Oomura. Clucoresponsive neurons in rat ventromedial hypothalamic tissue slice in vitro. Brain Res 232:494-499, 1982.
on 12% and 8% of VMH neurons tested respectively. These might be due to an indirect effect of MZD from the glucoreceptor neurons because of the bath application of MZD. The exact mechanism of these neurons on food intake is not clear at present.
ACKNOWLEDGEMENTS We thank Professor A. Simpson and Dr. K. P. Puthuraya for their help in preparing this manuscript. This work was partly supported by grants (Y-0.) 588,700118,5744,0085 from the Ministry of Education, Science and Culture and (Y.O. and M.S.) the Japan-U.S. cooperative research program. Mazindol was donated by Sandoz Pharmaceuticals, Ltd., Japan.
11. Oomura, Y. Significance of glucose, insulin, and free fatty acid on the hy~thalamus feeding and satiety neurons. in: Hunger: Basic Mechan~sm.~ und Clinical fmp~ications, edited by D. Novin, W. Wyrwicka and G. A. Bray. New York: Raven Press, 1976, pp. 145-157. 12. Oomura, Y. Input-output organization in the hypothalamus relating to food intake behavior. In: handbook ofthe Hypotbalamus, vof 2, Physiology of the Hypotba~am~s, edited by P. J. Morgane and J. Panksepp. New York: Marcel Dekker, 1980, pp. 557-620. 13. Oomura, Y. Feeding control through bioassay of body chemistry. Jpn J Physiol 3% l-19, 1985. 14. Oomura. Y.. T. Ono. H. Oovama and M. J. Wavner. Glucose and osmosensitive neurones of the rat hy~thalamus. Nature 222: 282-284, 1%9. 15. Pnthuraya, K. P., Y. Oomura and N. Shim&. Effects of endogenous sugar acids on the ventromedial hypothalamic nucleus of the rat. Brain Res 33% 165-168, 1985. 16. Sakata, T., K. Fujimoto, K. Terada, K. Arase and M. Fukushima. Changes in meal pattern and endogenous feeding related substances following mazindol administration. Arch Int Pharmacody~ Ther 270: 1l-28, 1984. 17. Samanin, R., C. Bendotti, S. Bemasconi, E. Borroni and S. Garattini. Role of brain monoamines in the anorectic activity of mazindol and d-amphetamine in the rat. Em J Pharmacot*O: 117-124, 1977. 18. Shimizu, N., Y I Oomura and T. Sakata. Moduration of feeding
by endogenous sugar acids acting as hunger or satiety factors. Am J Physioi 246: R542-550, 1984. 19. Shiraishi, T. Mazindol effects on the salivary and gastric acid secretory mechanism. Inr J Obesity, in press, 1985. 20. Sikdar, S. K., Y. Oomura and A. Inokuchi. Effects of mazindol on rat lateral hypothalamic neurons. Brain Res Bull 15: 33-38, 1985. 21. Tindal, J. S. The forebrain of the guinea-pig in stereotaxic coordinates. J Comp Neurol 124: 259-266, 1965. 22. Wallance, A. G. and B. Chir. An 448 Sandoz (mazindol) in the treatment of obesity. Med J Aust 1: 343-345, 1976.
0361-9230/85. $3.00 + .OO
Direct Action of Mazindol on Guinea-Pig Ventromedial Hypothalamic Neurons: Intracellular Studies in Slice Preparation TAKETSUGU
MINAMI,
YUTAKA OOMURA,’ AND MARY HYNES
MUTSUYUKI
SUGI~ORI
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, 812 Japan and (MS.) Department of Physiology and Biophysics, New York University, Medical Center 550 First Avenue, New York, NY 10016 Received
4 April
1985
MINAMI, T., Y. OOMURA, M. SUGIMORI AND M. HYNES. Direct action of mazindoi on guinea-pig ventromedial hypothalamic neurons: Intracellular studies in slice preparation. BRAIN RES BULL 15(l) 29-31, 1985.-Neuronal responses in the ventromedi~ hy~th~~ic nucleus (VMH) to mazindol (MZD) were examined by int~cellular recordings in hy~th~amic slices in vitro. Bath application of MZD caused deflection of the membrane by 8.Ok3.4 mV (mean2S.D.) associated with an increase in the input membrane resistance (23.0~5.8%) among 20% of the cells examined. Current-voltage plots, obtained simultaneously, showed the reversal potential between -80 and -90 mV. These results indicate that MZD depolarizes VMH neurons by reducing the K+ conductance, through a mechanism similar to that of glucose, and the anorectic action of MZD can be explained by its direct effects on the VMH. Ventromedial hypothalamus Brain slice
Glucoreceptor
neuron
Mazindol
IT has been well documented that the lateral hypothalamic area (LHA) and the ventromedial hypothalamic nucleus (VMH) are important in the regulation of feeding [l 1, 12,131. These two regions are referred to as the feeding and satiety centers, respectively. About 25% of the neurons in each of these centers are chemosensitive, and their activity is intluenced by glucose, free fatty acids, insulin [l 1,121 and other endogenous metabolites [ 13, 15, 181. Glucoreceptor neurons in the VMH have been defined as those that increase in activity with a dose response manner under the influence of glucose. The existence of these neurons has been demonstrated from extracellular studies of single neuronal activity induced by direct microelectrophoretic application of glucose in vivo [14] and by bath applications to brain slices in vitro experiments [ 101. We recently reported details of VMH glucoreceptor neuron properties, such as the ionic mechanism, obtained by intracellular recording in hypothalamic slices in vitro [8]. In the last several years, mazindol (MZD), an imidazoisoindole derivative, has been used as an anorexic agent in humans [4,22]. A number of investigations have revealed that this anorexigenic agent may act in part through brain catecholamines or serotonine. However, its direct effects on the feeding and satiety centers in the central nervous system are obscure. It has recently been shown that electrophoretic application of MZD in anesthetized rats excited glucoreceptor neurons of the VMH in vivo [19]. The present
Anorexic agent
Intracellular recording
experiments were undertaken to investigate by intracellular recordings in hypothalamic slices in vitro, whether the mechanism of action of MZD on VMH neurons is similar to that of glucose. METHOD
The techniques used here are almost the same as those previously reported [7]. To prepare a hypothalamic tissue slice, the brain was quickly removed from 16 decapitated albino guinea-pigs (250-400 g) and placed in Krebs solution at 4°C. The solution contained (mM): NaCl, 124; KCI, 5; K2S04, 1.24; NaHCO,, 26; CaCl,, 2.4; MgSO,, 1.3; glucose, IO; and was equilibrated with 95% 0, and 5% CO*, at pH 7.4. Four-hundred pm thick, coronally-oriented hypothalamic VMH slices were sectioned and incubated at room temperature for about 1 hr in the same solution. The recording chamber (1 S-2 ml) was perfused by solution warmed at 34-36°C at a rate of 3-4 mllmin. Intracellular electrodes, filled with 1-3 M K acetate had an average DC resistance of 60-120 MC!. Electrophysiological properties of the VMH neurons were determined by means of a high input impedance bridge amplifier (Neuro Data IR-283). The location of the VMH was based on the stereotaxic atlas [21] and was easily determined by the fomix and the fasciculus mammillothalamicus. RESULTS In
order to obtain reliable analyses,
cells with membrane
‘Requests for reprints should be addressed to Professor Y. Oomura, Department of Physiology, Faculty of Medicine, Kyushu University 60, Fukuoka 812, Japan.
29
30
MlNAMl
E7 AI..
3min 3XltPM
MZD
20mV 2omV
llil
,;,”
.-’
8,
l
I
.MZDi-100
FIG. 1.Depolarizing response of VMH neurons to mazindol(3 x lo-’ M MZD). A. annlication of MZD denolarized neuron and increased input membrane resistance measured by inward current pulse, duration 200 msec; intensity 0.07 nA. To ubtain current-voltage relations, various current pulses were applied before (a) and after MZD (b). Increase of input membrane resistance during response was clear by manual-clamping for 40 set at the resting membrane potential (c). B, current-voltage plots depicting voltage deflections to various current pulses applied before and after MZD. Open circles, control Krebs solution; filled circles, MZD solution. Apparent reversal potential in this cell is -84 mV.
FIG. 2. Hyperpolarizing response of VMH neuron to mazindol (3 x IO-’ M MZD). A, bath application of MZD hyperpolarized the neuron and decreased its input membrane resistance (measured by inward current pulse, duration 200 msec; intensity, 0.08 nA). To obtain current-voltage relations, current pulses were injected before (a) and after MZD (b). Decrease of input membrane resistance during response was cleared by manual-cl~ping for 55 set at resting membrane potential (c). B, current-voltage plots depicting voltage deflection to various current pulses applied before and after MZD. Apparent reversal potential in this cell is -90 mV.
potential less than 50 mV, spike amplitude less than 50 mV, input membrane resistance less than 80 MO, or stable recordings for less than 15 min were not accepted. Twenty-five neurons that satisfied these criteria were used for detailed analyses. The average spike amplitude was 60.3k5.9 mV (mean-cS.D.), input membrane resistance was 138.3t32.0 Ma and resting membrane potential was -61.4r6.2 mV. MZD was applied to the bath to produce concentrations of lO+ to 1O-6 M. MZD depolarized 5 cells (20%) by +8.0?3.4 mV and this response was accompanied by an increase in the input membrane resistance of the recorded neurons by 23.0t5.8%. An example is shown in Fig. 1. The actual increase in the membrane resistance by MZD was clearly indicated by the temporal manual-clamping of the membrane potential at the resting level in Fig. lA, c. The current-voltage (I-V) relations of a typical response is plotted in Fig. 1B. The membrane potential at the intersection of two curves describing the I-V relationship in normal Krebs solution and that in MZD solution is -84 mV, which indicates the reversal potential for MZD depolarization. The increased input membrane resistance and reversal potential between -80 and -90 mV suggests that the depolarization caused by MZD might be attributed to a reduction in the membrane KC conductance. Three cells (1%) were hyperpolarized by MZD (-3.82 1.0 mV), which was ~companied by a reduction (12.0t3.6%) in the input membrane resistance. Figure 2 shows one of these responses. Figure 2B shows a reversal potential of -90 mV for MZD hyperpolarization. These findings suggest that this hyperpolarization produced by MZD might contribute to the increased membrane K+ conductance. In two cells (8%), administration of MZD for about 2 minutes produced a biphasic response, short hy~~oI~ization (approximately 30 see) followed by a long depolarization (5-10 min). How-
ever, the main effect of this response polarization.
is thought to be de-
DISCUSStON
Brain cate~holamines have previously been shown to be affected by MZD administration. Specifically, noradrenaline uptake was inhibited [3,5]. However, controversial results were shown with regard to dopamine (DA), with an increase in turnover [2] or a decrease in uptake [S]. Alhskog [l] has shown that selective destruction of the ventral noradrenergic bundle with 6-hydroxydop~ine produces hyperphagia in rat, while Samanin et ai. [ 171and Leibowitz et al. [6] showed that electrolytic lesion of this bundle decreased anorexic efficacy of MZD. From the above findings, it appears that the action of MZD might be mediated indirectly through neurotransmitters. Intra-third ventricle injections of MZD in rats however decreased meal size (mount of food intake) and prolonged postprandial intermeal intervals f 161. Continuous infusion of MZD into the median eminence near the VMH caused the greatest reduction of food intake [9]. ‘It has been speculated that these anorectic actions of MZD are mediated by its direct action on the hypothalamic feeding control mechanism. Studies in our laboratory showed that MZD, when electrophoretically applied in anesthetized rats, selectively inhibited the activity of glucose-sensitive neurons in LHA [20]. Electrophoretically applied DA blocker attenuated the DA suppression caused by electrophoretic application of DA but not the MZD suppression. Ouabain, a Na-K pump inhibitor, attenuated MZD induced suppression of the neuronal activity. Further, intracellular recordings revealed hype~ola~zation of the membrane with no change in membrane conductance when rat brain slice was perfused with
~AZIN~L
MZD. This effect was similar to that of glucose. These results indicate that the inhibitory action of MZD is mediated by the activation of the Na-K pump. Our preliminary studies showed the excitatory effect of electrophoretically applied MZD on the glucoreceptor neurons of VMH that were excited by glucose application. Shiraishi [191 also reported a similar finding, In our intracellular studies, MZD mainly depolarized 20% of VMH neurons by reducing the K+ conductance, a mechanism similar to that of glucose [8]. These findings strongly indicate that MZD action on the glucosesensitive and glucoreceptor neurons mimics glucose. Thus, the anorexigenic action of MZD might be brought by its direct effects on the hypothalamus. MZD had either an inhibitory effect or an inhibitory effect followed by an excitation
1. Ahlskog, J. E. Food intake and amphetamine anorexia after selective forebrain norepinephrine loss. Brain Res 82: 21.i-240, 1974. 2. Carruba, M. O., A. Groppetti, P. Mantegazza, L. Vicentini and F. Zambotti. Effects of mazindol, a non-phenylethylamine anorexigenic agent, on biogenic amine levels and turnover rate. Br J ~~u~~u~o~ 56: 431-436, 1976. 3. Engstrom, R. G., L. A. Kelly and J. H. Gogerty. The effects of 5-hydroxy-5-(4’-chlorophenyl)-2,3-dihydro-5H-imidazo(Z,la) isoindole (m~~ndol. SaH 42-548) on the meta~lism of brain norepinephrine.ArchfnrPharmacudyn Ther214: 30%321,197s. 4. Gogerty, J. H., C. Penberthy, L. C. Iorio and J. Trapold. Pharmacological analysis of a new anorexic substance: 5-dihydroxyd-(~-chlorophenyl)-2,3-dihydro-5H-imidazo-(2, l-a) isoindole fmazindol). Arch int Pharmucodyn Ther 214: 284-307, 1975. 5. Heikkila, R. E., F. S. Cabbat and C. Mytilineou. Studies on the capacity of mazindol and dita to act as uptake inhibitors releasing agents for 3H-biogenic amines in rat brain tissue slices. EttrJ Pharmucol45: 329-333, 1977. 6. Leibowitz, S. F., N. J. Hammer and L. L. Brown. Analysis of
7. 8.
9.
10.
31
AND VMH NEURONS
behavioral deficits produced by lesions in the dorsal and ventral rn~db~~n te8mentum. Physi[~/ Behav 25: 829-843, 1980. Minami, T., Y. Oomura and M. Sugimori. Electrophysiological properties of guinea-pig ventromedial hypothalamic neurones: an in vitro study. J Physju~, submitted. Minami, T., Y. Gomura, M. Sugimori and R. R. Llinas. Electrophysiological properties of ventromedial hypothalamic neurons in guinea pig and their response to glucose: a vitro study. Sot Netrrosci Abstr 10:612, 1984. Nagai, K., T. Mori, M. Ookura, H. Tujimoto, S. Takagi and H. Nakagawa. Pharmacological effects of the mazindol on the behaviors and metabolism of rats. J Obesity Weight Regut, in press, 1985. Ono, T., H. Nishino, M. Fukuda, K. Sasaki, K. Muramoto and Y. Oomura. Clucoresponsive neurons in rat ventromedial hypothalamic tissue slice in vitro. Brain Res 232:494-499, 1982.
on 12% and 8% of VMH neurons tested respectively. These might be due to an indirect effect of MZD from the glucoreceptor neurons because of the bath application of MZD. The exact mechanism of these neurons on food intake is not clear at present.
ACKNOWLEDGEMENTS We thank Professor A. Simpson and Dr. K. P. Puthuraya for their help in preparing this manuscript. This work was partly supported by grants (Y-0.) 588,700118,5744,0085 from the Ministry of Education, Science and Culture and (Y.O. and M.S.) the Japan-U.S. cooperative research program. Mazindol was donated by Sandoz Pharmaceuticals, Ltd., Japan.
11. Oomura, Y. Significance of glucose, insulin, and free fatty acid on the hy~thalamus feeding and satiety neurons. in: Hunger: Basic Mechan~sm.~ und Clinical fmp~ications, edited by D. Novin, W. Wyrwicka and G. A. Bray. New York: Raven Press, 1976, pp. 145-157. 12. Oomura, Y. Input-output organization in the hypothalamus relating to food intake behavior. In: handbook ofthe Hypotbalamus, vof 2, Physiology of the Hypotba~am~s, edited by P. J. Morgane and J. Panksepp. New York: Marcel Dekker, 1980, pp. 557-620. 13. Oomura, Y. Feeding control through bioassay of body chemistry. Jpn J Physiol 3% l-19, 1985. 14. Oomura. Y.. T. Ono. H. Oovama and M. J. Wavner. Glucose and osmosensitive neurones of the rat hy~thalamus. Nature 222: 282-284, 1%9. 15. Pnthuraya, K. P., Y. Oomura and N. Shim&. Effects of endogenous sugar acids on the ventromedial hypothalamic nucleus of the rat. Brain Res 33% 165-168, 1985. 16. Sakata, T., K. Fujimoto, K. Terada, K. Arase and M. Fukushima. Changes in meal pattern and endogenous feeding related substances following mazindol administration. Arch Int Pharmacody~ Ther 270: 1l-28, 1984. 17. Samanin, R., C. Bendotti, S. Bemasconi, E. Borroni and S. Garattini. Role of brain monoamines in the anorectic activity of mazindol and d-amphetamine in the rat. Em J Pharmacot*O: 117-124, 1977. 18. Shimizu, N., Y I Oomura and T. Sakata. Moduration of feeding
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