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Polyamines attenuate the catalepsy elicited by haloperidol
ATTENUATE THE CATALEPSY E L I C I T E D BY H A L O P E R I D O L K. Szczawifiska D.Cenajek-Musial, P.Kwiatkowski. Department of Pharmacology, Karol Marcinkowski University of Medical Sciences, 10 Fredry Str., 61-701 Poznafi, Poland. POLYAMINES
The N-methyl-D-aspartate (NMDA) receptor is believed to be implicated in psychiatric disorders. Polyamines (PA): spermidine (SPD) and spermine (SPM), but not putrescine (PUT) bind to a specific polyamine site on this receptor molecule. Furthermore, PA have modulatory effects on dopaminergic systems (Genedani, 1994) and interact with GABAA receptor (Doyle, 1992). Ifenpredil, the polyaminesensitive sites antagonist may label sigma receptors in rat brain, too (Hashimoto, 1994). Haloperidol (HAL) beside the more selective blockade of D2 than D1 receptor has a weak affinity for 5-HT2 and alphai-receptors. In addition is not devoid of potential sigma antagonist activity. We examined the effect of SPD and SPM on the behavioural response to HAL in rats. Catalepsy and the locomotor activity was measured in animals after both acute and subchronic administration of HAL in combination with a single dose of PA. To assess the interaction with HAL a combination of SPD (40 mg/kg) i.p. + HAL (1.0 mg/kg) i.p. for 1 or 14 days was administered. This resulted in a significant attenuation of catalepsy evoked by single or multiple HAL injections. Accordingly, an acute and subchronic treatment with HAL joint with SPM (20 mg/kg) i.p. markedly alleviated the catalepsy elicited by HAL. Increased locomotor activity in rats treated subchronically with HAL was potently diminished only by SPM. There findings indicate that PA may alter the behavioural response to HAL.
EFFECTS OF SODIUM H Y D R O X Y B U T I R A T E ('/-OH) ON SPINAL VISCERO-SOMATIC CONVERGENT NEURONS IN CATS AND RATS S.Kasparov, V.Petrov and D.Kharkevich Department of Pharmacology, Moscow Sechenov Medical Academy, B.Pirogovskaya 2/6, 119 8 8 i, Moscow, Russia The effects of T-OH on the activity of the dorsal horn neurons receiving noxious afferent inputs from both cutaneous (peroneus) and visceral (pelvic) nerves were investigated. Cats and rats were anesthetized with chloralose, spinalized and single units were recorded extracellularly in the lumbar dorsal horn. In cats, supramaximal electrical stimuli were applied to small isolated branches of the nerves. T-OH (50 - 100 mg/kg i.v.) suppressed the discharges, carried by the fast A~3-cutaneous fibers less than those conducted by C-fiberS. However, the responses to the visceral and to the cutaneous AS+C-fibers stimulation were inhibited to similar degree (78 ± 9 and 70 ± 11, correspondingly; n = 7). The estimated conduction velocity of the pelvic afferents was 2 - 7 m/see, i.e. in the range, typical to the A8 fibers of the cutaneous nerves. In the rats, the responses of the convergent units were evoked by pressure appli&l to the skin of the dorsal paw or colorectal distention. In these experiments T-OH suppressed the activity evoked by cutaneous stimulation less, than that of visceral origin (54 =k 10% and 81 ± 13% at 50 mg/kg and 36 i 9 and 60 ± 5% at 100 mg/kg, correspondingly; n = 6. P < 0.01 at 100 mg/kg). Thus, y-OH suppresses spinal nociceptive transmission and cutaneous afferent valleys are inhibited more than the visceral ones. The difference may reflect different afferent fiber composition of the pelvic and peroneous nerves~
-- 340-
FUNCTIONAL MATURATION OF HYPOTHALAMIC GABAERGIC NEURONES; EVIDENCE FOR THE EMERGENCE OF A GABAA-RECEPTOR MEDIATED INHIBITION OF GABA SECRETION.
K. Davidson. H.E. Murray & G.E. Gillies Department of Pharmacology, Charing Cross & Westminster Medical School, London W6 8RF. During a critical perinatal period organisational events occur within the neuroendocrine hypothalamus which set the sexually dimorphic post-pubertal patterns of anterior pituitary hormone secretion. The mechanisms which bring about these events remain to be determined, but GABAergic systems intrinsic to the hypothalamus have been implicated in mediating the actions of gonadal steroids which influence the development and function of the neuroendocrine system. In this study, we have extended our earlier observations 1 on the maturation of GABAergic neurones in primary hypothalamic cultures initiated from tissue at embryonic day 18 and maintained in defined medium. Using [3HI GABA, the apparent kinetic parameters for uptake suggested that the neurones rapidly achieved maturity by 7 days in Yi[r9 (DIV) [Km (gM) = 2.3+0.4, 1.0-2:0.14 and 0.9:k-0.19 and Vmax (nmoles/min/well of cells) = 6.622:1.-0.213, 10.85+9..9 and 11.64+2.1 on DIV 3, 7 and 14 respectively]. When the release of endogenous GABA was measured both an inherent and a depolarisation-dependent maturation of the secretory capacity of the GABAergic neurones was observed over 24 DIV. On DIV 11 and 17, but not DIV 5, a progressive ability of bieuculline (10-5M) to increase GABA release was observed (9.0+0.47 vs control 3.7+0.17 ng/hypothalamus and 20.2+1.2 vs control 8.3:k-0.07 ng/hypothalamus on DIV 11 and 17 respectively, P<0.002, n=6, Student's t test). This effect was reversed by muscimol (10-5M) which, at later stages in vitro inhibited GABA release. In conclusion, these results confirm the capacity of hypothalamic GABAergic neurones to mature in vitro. They also provide evidence for the development of GABAAmediated (auto) regulatory inhibition of GABA release. 1. Hoffman et al. (1994), Br. J. Pharmacol. 112: (Suppl). 265P Acknowledgements: We are grateful to the Wellcome Trust for financial support of this work.
THIOCOLCHICOSIDE ACTS AT THE GLYCINE-SITE OF THE STRYCHNINE-SENSITIVE GLYCINE RECEPTOR IN RAT SPINAL CORD AND BRAINSTEM. P. Marini, M. Andena~ M. Cimino, S. Malandrino and F. Cattabeni. Inst. of Pharmacological Sciences, University of Milano, 20133 Milano and I N D E N A S.p.A, Milano.
Glycine and 7-aminobutyric ( G A B A ) are major inhibitory neurotransmitters of the vertebrate CNS. Synaptic inhibition in the spinal cord and brainstem is primarily mediated by glycine, whereas G A B A is the predominant neurotransmitter in other areas of the brain. T h i o c o l c h i c o s i d e is a potent and therapeutically useful muscle-relaxant which is c o m m o n l y believed to act as GABA-agonist, but with an affinity which is not compatible with therapeutically active doses. In this study we test the action of thiocolchicoside and its metabolite on the glycine-gated chloride channel in the rat spinal cord and brainstem. Using 3H-Strychnine displacement analysis we found that thiocolchicoside and metabolite are able to interact with pharmacological rank order of potency of 10 -7-10-6M on the glycine receptor. The displacement of 3H-Strychnine binding by thiocolchicoside and its metabolite cannot be explained by a simple c o m p e t i t i v e interaction; therefore m i m i c k i n g the b e h a v i o u r of g l y c i n e this binding is not completely inhibited by these drugs and the Hill coefficient is less than 1. These properties are consistent with a mathematical model of two mutually interacting binding sites for strychnine and glycine. These studies then suggest the selective action of thiocolchicoside and its metabolite at the glycine site, but not at the strychnine-site, o f the g l y c i n e receptor. M o r e o v e r autoradiographic studies show specific displacement of 3HStrychnine binding by thi0colchicoside and methabolite in many a r e a s o f the b r a i n s t e m and the d i s t r i b u t i o n o f thiocolchicoside/metabolite sensitive sites overlaps that of glycine-sites not only in spinal cord but also in brainstem.
The N-methyl-D-aspartate (NMDA) receptor is believed to be implicated in psychiatric disorders. Polyamines (PA): spermidine (SPD) and spermine (SPM), but not putrescine (PUT) bind to a specific polyamine site on this receptor molecule. Furthermore, PA have modulatory effects on dopaminergic systems (Genedani, 1994) and interact with GABAA receptor (Doyle, 1992). Ifenpredil, the polyaminesensitive sites antagonist may label sigma receptors in rat brain, too (Hashimoto, 1994). Haloperidol (HAL) beside the more selective blockade of D2 than D1 receptor has a weak affinity for 5-HT2 and alphai-receptors. In addition is not devoid of potential sigma antagonist activity. We examined the effect of SPD and SPM on the behavioural response to HAL in rats. Catalepsy and the locomotor activity was measured in animals after both acute and subchronic administration of HAL in combination with a single dose of PA. To assess the interaction with HAL a combination of SPD (40 mg/kg) i.p. + HAL (1.0 mg/kg) i.p. for 1 or 14 days was administered. This resulted in a significant attenuation of catalepsy evoked by single or multiple HAL injections. Accordingly, an acute and subchronic treatment with HAL joint with SPM (20 mg/kg) i.p. markedly alleviated the catalepsy elicited by HAL. Increased locomotor activity in rats treated subchronically with HAL was potently diminished only by SPM. There findings indicate that PA may alter the behavioural response to HAL.
EFFECTS OF SODIUM H Y D R O X Y B U T I R A T E ('/-OH) ON SPINAL VISCERO-SOMATIC CONVERGENT NEURONS IN CATS AND RATS S.Kasparov, V.Petrov and D.Kharkevich Department of Pharmacology, Moscow Sechenov Medical Academy, B.Pirogovskaya 2/6, 119 8 8 i, Moscow, Russia The effects of T-OH on the activity of the dorsal horn neurons receiving noxious afferent inputs from both cutaneous (peroneus) and visceral (pelvic) nerves were investigated. Cats and rats were anesthetized with chloralose, spinalized and single units were recorded extracellularly in the lumbar dorsal horn. In cats, supramaximal electrical stimuli were applied to small isolated branches of the nerves. T-OH (50 - 100 mg/kg i.v.) suppressed the discharges, carried by the fast A~3-cutaneous fibers less than those conducted by C-fiberS. However, the responses to the visceral and to the cutaneous AS+C-fibers stimulation were inhibited to similar degree (78 ± 9 and 70 ± 11, correspondingly; n = 7). The estimated conduction velocity of the pelvic afferents was 2 - 7 m/see, i.e. in the range, typical to the A8 fibers of the cutaneous nerves. In the rats, the responses of the convergent units were evoked by pressure appli&l to the skin of the dorsal paw or colorectal distention. In these experiments T-OH suppressed the activity evoked by cutaneous stimulation less, than that of visceral origin (54 =k 10% and 81 ± 13% at 50 mg/kg and 36 i 9 and 60 ± 5% at 100 mg/kg, correspondingly; n = 6. P < 0.01 at 100 mg/kg). Thus, y-OH suppresses spinal nociceptive transmission and cutaneous afferent valleys are inhibited more than the visceral ones. The difference may reflect different afferent fiber composition of the pelvic and peroneous nerves~
-- 340-
FUNCTIONAL MATURATION OF HYPOTHALAMIC GABAERGIC NEURONES; EVIDENCE FOR THE EMERGENCE OF A GABAA-RECEPTOR MEDIATED INHIBITION OF GABA SECRETION.
K. Davidson. H.E. Murray & G.E. Gillies Department of Pharmacology, Charing Cross & Westminster Medical School, London W6 8RF. During a critical perinatal period organisational events occur within the neuroendocrine hypothalamus which set the sexually dimorphic post-pubertal patterns of anterior pituitary hormone secretion. The mechanisms which bring about these events remain to be determined, but GABAergic systems intrinsic to the hypothalamus have been implicated in mediating the actions of gonadal steroids which influence the development and function of the neuroendocrine system. In this study, we have extended our earlier observations 1 on the maturation of GABAergic neurones in primary hypothalamic cultures initiated from tissue at embryonic day 18 and maintained in defined medium. Using [3HI GABA, the apparent kinetic parameters for uptake suggested that the neurones rapidly achieved maturity by 7 days in Yi[r9 (DIV) [Km (gM) = 2.3+0.4, 1.0-2:0.14 and 0.9:k-0.19 and Vmax (nmoles/min/well of cells) = 6.622:1.-0.213, 10.85+9..9 and 11.64+2.1 on DIV 3, 7 and 14 respectively]. When the release of endogenous GABA was measured both an inherent and a depolarisation-dependent maturation of the secretory capacity of the GABAergic neurones was observed over 24 DIV. On DIV 11 and 17, but not DIV 5, a progressive ability of bieuculline (10-5M) to increase GABA release was observed (9.0+0.47 vs control 3.7+0.17 ng/hypothalamus and 20.2+1.2 vs control 8.3:k-0.07 ng/hypothalamus on DIV 11 and 17 respectively, P<0.002, n=6, Student's t test). This effect was reversed by muscimol (10-5M) which, at later stages in vitro inhibited GABA release. In conclusion, these results confirm the capacity of hypothalamic GABAergic neurones to mature in vitro. They also provide evidence for the development of GABAAmediated (auto) regulatory inhibition of GABA release. 1. Hoffman et al. (1994), Br. J. Pharmacol. 112: (Suppl). 265P Acknowledgements: We are grateful to the Wellcome Trust for financial support of this work.
THIOCOLCHICOSIDE ACTS AT THE GLYCINE-SITE OF THE STRYCHNINE-SENSITIVE GLYCINE RECEPTOR IN RAT SPINAL CORD AND BRAINSTEM. P. Marini, M. Andena~ M. Cimino, S. Malandrino and F. Cattabeni. Inst. of Pharmacological Sciences, University of Milano, 20133 Milano and I N D E N A S.p.A, Milano.
Glycine and 7-aminobutyric ( G A B A ) are major inhibitory neurotransmitters of the vertebrate CNS. Synaptic inhibition in the spinal cord and brainstem is primarily mediated by glycine, whereas G A B A is the predominant neurotransmitter in other areas of the brain. T h i o c o l c h i c o s i d e is a potent and therapeutically useful muscle-relaxant which is c o m m o n l y believed to act as GABA-agonist, but with an affinity which is not compatible with therapeutically active doses. In this study we test the action of thiocolchicoside and its metabolite on the glycine-gated chloride channel in the rat spinal cord and brainstem. Using 3H-Strychnine displacement analysis we found that thiocolchicoside and metabolite are able to interact with pharmacological rank order of potency of 10 -7-10-6M on the glycine receptor. The displacement of 3H-Strychnine binding by thiocolchicoside and its metabolite cannot be explained by a simple c o m p e t i t i v e interaction; therefore m i m i c k i n g the b e h a v i o u r of g l y c i n e this binding is not completely inhibited by these drugs and the Hill coefficient is less than 1. These properties are consistent with a mathematical model of two mutually interacting binding sites for strychnine and glycine. These studies then suggest the selective action of thiocolchicoside and its metabolite at the glycine site, but not at the strychnine-site, o f the g l y c i n e receptor. M o r e o v e r autoradiographic studies show specific displacement of 3HStrychnine binding by thi0colchicoside and methabolite in many a r e a s o f the b r a i n s t e m and the d i s t r i b u t i o n o f thiocolchicoside/metabolite sensitive sites overlaps that of glycine-sites not only in spinal cord but also in brainstem.