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Tachycardia, hypertension and decreased reflex bradycardia produced by striatal lesions induced by kainic acid
Neuropharmacology Vol. 23, No. II, pp. 1231-1235, 1984 Printed in Great Britain. All rights reserved
Copynght
0028.3908184 $3.00 + 0.00 ‘c 1984 Pergamon Press Ltd
TACHYCARDIA, HYPERTENSION AND DECREASED REFLEX BRADYCARDIA PRODUCED BY STRIATAL LESIONS INDUCED BY KAINIC ACID J. J. Wu*$,
C.-J. SHIH* and M.-T. LIN? of Physiology and Biophysics, National Defense
*Department of Surgery and tDepartment Medical Center and Tri-Service General
Hospital.
Taipei,
Taiwan,
Republic
of China
(Accepted 13 September 1983) Summary-The effects of intra-striatal injection of kainic acid on cardiovascular function were assessed in urethane-anesthetized rats. Intra-striatal administration of 2 pg of kainic acid (in a volume of 0.5 ~1) produced both tachycardia and hypertension. The tachycardia induced by intra-striatal injection of kainic acid was antagonized by either prior bilateral vagotomy or spinal transection of the animals (at C7). On the other hand, the hypertension induced by intra-striatal administration of kainic acid was antagonized by prior bilateral vagotomy, but not spinal transection. In addition, reflex bradycardia was produced by intravenous infusion of adrenaline in rats. Over the dose range (1.25-5.0pgg/kg, i.v.) of adrenaline used, a dose-dependent bradycardia was obtained. It was found that pretreatment of animals with intra-striatal injection of kainic acid, although causing no change in the adrenaline-induced pressor effect, did reduce the adrenaline-induced bradycardia. Intravenous administration of same dose of kainic acid had no effect on these cardiovascular responses. Thus, the data indicate that striatal neurones are involved in the central control of cardiovascular function. Key words: kainic spinal transection.
acid.
tachycardia,
hypertension,
consistent lesion in the choreic brain seems to be a disappearance of GABAergic-containing neurones from the basal ganglia, possibly also of cholinergic neurones (Enna, Stern, Wastek and Yamamura, 1977; Lloyd, 1980; Bird and Iversen. 1974; Coyle and Schwartz, 1976; Fibiger, 1978; McGeer and McGeer, 1976). Recently, it was found that injection of the glutamate analogue, kainic acid, into the striatum of the rat caused destruction of GABAergic and cholinergic cells and provided a model for Huntington’s disease (Enna et al., 1977; Lloyd, 1980; Bird and Iversen, 1974; Coyle and Schwartz, 1976; Fibiger. 1978; McGeer and McGeer, 1976). However, information is not available about the effects of intra-striatal injection of kainic acid on cardiovascular function. Therefore, the effects of injections of kainic acid into the striatum on the basal levels of both the heart rate and arterial pressure in rats were investigated. In addition, the effects on the reflex bradycardia in response to elevation of arterial pressure induced by intravenous infusion of adrenaline were also observed. The most
METHODS
Experimental Experiments Sprague-Dawley
animals were performed on male rats weighing between 250 and
IAddress correspondence and offprint requests to Dr Jionn-Jone Wu, Division of Neurosurgery, Department of Surgery, Far Eastern Memorial Hospital, Pan-Chiao, Taipei, Taiwan. Republic of China. N P 23’11 A
reflex bradycardia.
corpus
striatum.
vagotomy.
300 g. Before they were subjected to experiments, the animals were housed individually in wire mesh cages in a room maintained at a temperature of 22 + 1.0 C with a natural light-dark cycle. They were given free access to tap water and granular chicken feed supplied by Taiwan Sugar Corporation. Surgicul prepurution Each animal was anesthetized with pentobarbital sodium (6 mg/lOO g, i.p.) and placed in a Kopf stereotaxic apparatus. For the direct injection of kainic acid or control vehicle into the striatum (caudate-putamen complex), stainless steel cannulae, consisting of a guide tube with a snug fitting trocar, and a cannula insert, was introduced into the tube at the time of injection (Lin, Chandra, Tsay and Chern, 1982; Lin, Wu, Chandra and Tsay, 1981). The cannula guide tube with trocars was implanted using the stereotaxic atlas and co-ordinates of Kiinig and Klippel (1963). The following co-ordinates were used: A, 7.9-9.1 mm; L, 1.7-2.3 mm; and H, 1.4-0.6 mm. After appropriately-located craniotomy holes had been trephined, two self-tapping screws were attached to the calvarium of the parietal bones and the cannulae guide tubes were inserted to the desired depth through the craniotomy holes. They were anchored with fast-drying acrylic dental cement to the cranial surface that had been scraped clean of periosteum. The reflected skin was replaced around the acrylic mould containing the guide tubes and was sutured with chromic gut. At the time of injection. the cannula inserted was connected to a 10 p I Hamilton microsyringe by PE-10 polyethylene tubing, and the 1231
J. J. Wu et ui.
1232
0.9 % saline
90
min
after
kalnic
acid
600
Heart rate beats/min
400
-_
7-
200
Arterial blood pressure mmHg
OL
t-l adrenaline
25pg/
kg, i.v.
adrenaline
2.5 pg/
kg, Iv.
Fig. 1. The cardiovascular responses induced by intravenous administration (iv.) of adrenaline in urethane-anesthetized rats both before and after an intra-striatal injection of 2 pg of kainic acid.
syringe and tubing were filled with silicone fluid to act as a piston. A volume of 0.5 ~1 was infused into the striatum over a period of I min. In preparing spinal animals, the cervical vertebrae was exposed and complete transection was made with a spatula at the seventh cervical segment of the spinal cord (C7). Bilateral vagotomy were made at the neck region (Chai and Lin, 1977).
by irradiation with infra-red light. The trachea was cannulated and the femoral artery catheterized. The femoral arterial pressure was monitored with a Stathan P23AC transducer, and heart rate was monitored with a Grass 7C tachometer triggered by arterial pulses. The right femoral vein was cannulated for intravenous injection. All recordings were made on a four-channel Grass 7C polygraph.
Drug solution
Histological
All drug solutions were prepared in pyrogen-free glassware baked for 5 hr at 180°C before use. The drug kainic acid (Sigma Chemical Co., St Louis, Missouri) was freshly made up as a stock solution by dissolving certain amount in 0.9D/ saline. Adrenaline (epinephrine. USP) (Retired Servicemen’s Pharmaceutical Plant of Taiwan) was administered intravenously by way of the femoral vein. In the present study, the reflex bradycardia was induced by intravenous infusion of adrenaline in rats (Lin and Chern, 1979).
After the experiments were completed, the animals were killed with an overdose of sodium pentobarbital and the cerebral circulation was perfused with 0.9”,, saline, followed by 10% (v/v) formalin solution. Later, sections of the fixed brain were cut at a 40 itrn section and stained with thionin so that the stereotaxic co-ordinates of the cannulae were verified.
Physiological
Table 1 shows (2 pg in 0.5 ~1) caused a rise in arterial pressure
mensurements
The animals were anesthetized with urethane (1.2 g/kg, i.p.). Rectal temperature was maintained at 37 k 0S”C throughout the course of the experiments Table
I.
Effects
of intra-striatal
Treatments Mean arterial pressure I. Saline 0.996 2. Kainic acid I pg 3. Kainic acid 2bg Heart rate (beatslmin) I. Saline 0.9>,, 2. Kainic acid I pg 3. Kainic acid 2pg
oer@cation
RESULTS
l@cts of‘intra-striatal injection of kainic acid on the basal leaels of heart rate and urteriul pressure
administration
of saline vehicle or urethane-anesthetized rats
kainic
that a direct injection of kainic acid into the caudate-putamen complex both the heart rate and the mean in urethane-anesthetized animals.
acid
on
cardiovascular
responses
m
Time of reCW0-y (“II”)
Maximal
n
Control values
values
Difference
Time to maximal rise C”““)
X 4 R
104 * 15.8 IO1 i 16.7 102 2 17.8
104 f 14.9 IO1 t 17.2 178&179
0 0 16 f 6.96’
0 0 32.8 + I .74*
0 0 ho*5
8 4 8
399 * 13.5 404 f 16.9 402 + 12.2
399 + 15.5 404 f 17.8 592 + 12.9
0 0 190 f 20.8’
0 0 54.6 k 2.37”
0 0 X9 k 6.3l*
(mmHg)
‘Difference is statistically significant from corresponding as mean +SE: n = numbers of animals tested
control values. P c 0.05 (Student’s
14*
r-test). The values are expressed
Striatal lesions on cardiovascular functions Table
2. Effects
of bilateral
vagotomy
and spinal transection on the cardiovascular kainic acid in urethane-anesthetized Mean arterial
Treatments
n
Sham operation 2. Bilateral vagotomy 3. Spinal transection
8 8 8
I.
Control 103 f 15.8 128 i_ 12.1 80 k 7.5
*Significantly different from corresponding n = numbers of animals tested.
control
pressure
responses rats
178 i 13.7 I81 * 11.3 160 f 14.2
75 i 5.12 53 f 3.25’ 80 + 7.91
Table 3 summarizes the vasopressor and bradycardic responses to intravenous infusion of adrenaline in urethane-anesthetized animals before and after an intra-striatal injection of 2 pg of kainic acid. Over the dose range (1.2-5.0 pg/kg, i.v.) of adrenaline, a dose-dependent response was obtained. Before the injection of kainic acid, the administration of adrenaline (e.g. 2.5 pgg/kg, i.v.) induced an average increase in mean arterial pressure of 75 f 12.1 mmHg and an average decrease in heart rate of 90 ) 8.9 beats/min. Ninety minutes after the injection of kainic acid, the basal levels of both mean arterial pressure and heart rate had already recovered, the animals were subjected to injection of adrenaline. It was found that the bradycardic effects induced by adrenaline were greatly reduced by pretreatment of animals with intra-striatal administration of kainic acid. However, the vasopressor effects induced by adrenaline were not significantly affected by pretreatment with intra-striatal administration of kainic acid. Either intrastriatal administration of control vehicle solution or intravenous administration of kainic acid (2~0 had no significant effects on the cardiovascular responses induced by intravenous infusion of adrenaline. DISCUSSION It has been well established that dopamine is a transmitter in neurones arising in the pars compacta of substantia nigra and projecting to the striatum
of 2 fig of
After kainic
P c 0.05 (Student’s
Eflects of intra-striatal injection of kainic acid on the reflex bradycardia induced by adrenaline
injection
Heart rate (beats:min)
Difference
After an intra-striatal injection of 2 pg of kainic acid, the heart rate rose almost immediately and reached the maximum level (e.g. 190 beats/min) at about 50min. The trachycardia responses recovered at 90 min after the injection of kainic acid. On the other hand, the mean arterial pressure also rose immediately and reached the maximum level (e.g. 76 mmHg) at about 30 min. The pressor responses recovered at 60 min after the injection of kainic acid. Table 2 shows that the tachycardia induced by intra-striatal injection of kainic acid was antagonized by either prior spinal transection (at C7) or bilateral vagotomy of the animals. However, the hypertension induced by kainic acid was antagonized by prior bilateral vagotomy, but not spinal transection in urethane-anesthetized animals.
induced by intra-striatal
(mmHg)
After kainic acid
values,
1233
l-test).
Control 401 f 14.5 485 + 17.9 350 rt 15.4 The values
acid
DilTerence
588 f 14.6 524 * 14.5 382 f I I .7
187 i 17.6 39 + 7.12’ 32 k 2.51*
are expressed
as the means
+SE;
(caudate nucleus plus putamen or caudate-putamen complex) (Anden, Carlsson, Dahlstrom, Fuxe, Hillarp and Larsson, 1964; Anden, Dahlstrom, Fuxe and Larsson, 1965; Dahlstrom and Fuxe, 1964; Faull and Laverty, 1969; Gumulka, Ramirez-Del Angel, Samanin and Valzelli, 1970; Hornykiewicz, 1966; Poirier and Sourkes, 1965). In addition, there is a glutamic acid-containing corticostriatal connection (Divac, Fonnum and Storm-Mathiesen, 1977; McGeer, McGeer, Scherer and Singh, 1977; Spencer, 1976) and a cholinergic thalmostriatal projection (Simke and Saelens, 1977). On the other hand, it is believed that y-aminobutyric acid (GABA) is the transmitter for the strionigral and striopallidal efferent systems (Kim, Bak, Hassler and Okada, 1971; Okada and Hassler, 1973; Feltz, 1971; Obata and Yoshida. 1973). Moreover, a possible correlation between nigrostriatal dopaminergic, striatal cholinergic and strionigral GABAergic reverberating neurone circuit has been described (Di Chiara, Corsini, Mereu, Tissari and Gessa, 1978). In fact, the role played by the nigrostriatal dopaminergic pathway, one of the three main dopamine pathways in the brain, in the central control of the arterial baroreflex had been assessed in rats (Lin, Tsay and Chen, 1982; Chen, and Lin, 1980). It was demonstrated that inhibiting the nigrostriatal dopamine pathway with the electrolytic lesions in the substantia nigra, depressed reflex bradycardia. In contrast, activating the nigrostriatal dopamine pathway with electrical stimulation in the substantia nigra, facilitated reflex bradycardia in rats. Furthermore, local administration of apomorphine (a dopamine receptor agonist) into the caudate-putamen complex facilitated reflex bradycardia, while local administration of dopaminergic receptor antagonists such as haloperidol and pimozide into the same site depressed reflex bradycardia in the rat. Moreover, the facilitation in the reflex bradycardia induced by local administration of apomorphine into the caudateputamen complex could be readily abolished by pretreatment of animals with administration of either haloperidol or pimozide in the striatum. Thus. it appears that a dopaminergic synapse exists in the caudate-putamen complex which mediates reflex bradycardia in the rat. The present results also showed that lesion of striatal neurones (Enna et a/., 1977; Lloyd, 1980; Bird and Iversen, 1974; Coyle and Schwartz, 1976; Fibiger, 1978; McGeer and McGeer, 1976) with intrastriatal administration of kainic acid
1234
J. J. WU et al.
depressed reflex bradycardia in the rat. These observations prompted the idea that intra-striatal administration of kainic acid would destroy the dopaminergic receptors which are located on these neurones within the striatum and depress reflex bradycardia, mediated through baroreceptor reflexes in response to an acute increase in arterial pressure. In addition, the present results showed that lesion of striatal neurones with kainic acid caused both tachycardia and hypertension in urethaneanesthetized animals. The tachycardia induced by intra-striatal administration of kainic acid was antagonized by either prior spinal transection (at C7) or bilateral vagotomy of the animals. This indicates that the induced tachycardia is brought about by both an increase in sympathetic efferent activity and a decrease in vagal efferent activity. On the other hand. the hypertension induced by intra-striatal administration of kainic acid was antagonized by prior bilateral vagotomy, but not spinal transection, This strongly suggests that, in addition to a decrease in vagal efferent activity, certain unknown neurochemical factors (e.g. vasopressin), released from the brain following the intra-striatal administration of kainic acid, may also be responsible for the development of hypertension in the animal. Of course. this hypothesis needs further verification. In summary, the present results show that intrastriatal administration of kainic acid caused tachycardia, hypertension and suppressed reflex bradycardia. The induced tachycardia may be due to both increased sympathetic efferent activity and decreased vagal tone, whereas the induced hypertension may be due to decreased vagal tone and enhanced release ol certain unknown neurohumoral factors from the brain. The data indicate that strtatal neurones are involved in central control of cardiovascular functions. Acknowledgements-The work reported here was supported by a grant from the National Science Council of the Republic of China. The authors wish to thank Miss Ba-Ling Tsay for her excellent technical assistance. We are grateful to Professor J. S. Kuo for his comments during the preparation of this paper.
REFERENCES Anden N. E., Carlsson A., Dahlstrom A.. Fuxe K., Hillarp N. A. and Larsson K. (I 964) Demonstrating and mapping out of nigrostriatal dopamine neurons. Lifi, Sci. 3: 5233530. Anden N. E., Dahlstrom A., Fuxe K. and Larsson K. ( 1965) Further evidence for the presence of nigro-striatal dopamine neurons in the rat. Am. J. Anat. 116: 329-333. Bird E. D. and Iversen L. L. (1974) Huntington’s chorea: post-mortem measurement of glutamic acid decarboxylase, choline acetylase and dopamine in basal ganglia. Brain 97: 457472. Chai C. Y. and Lin M. T. (1977) The enhancement of chlorpromazine-induced hypothermia by lesions in the anterior hypothalamus. Br. J. Pharmac. 61: 77-82. Chen F. F. and Lin M. T. (1980) Effects of dopamine. apomorphine. gamma-hydroxybutyric acid. haloperidol
Striatal
lesions
on cardiovascular
and pimozide on reflex bradycardia in rats. J. Pharmac. exp. Ther. 214: 421432. Coyle J. T. and Schwartz R. (1976) Lesion of striatal neurons with kainic acid orovides a model for Huntinaton’s chorea. Nature 26j: 244246. Dahistrom A. and Fuxe K. (1964) Evidence for the existence of monoamine containing neurons in the central nervous system. I. Demonstrati& of monoamines in the cell bodies of brain stem neurons. Acta physiol. stand. (suppl. 232) 62: l-55. Di Chara G., Corsini G. U., Mereu G. P., Tissari A. and Gessa G. L. (1978) Self-inhibitory dopamine receptors: Their role in the biochemical and behavioral effects of low doses of apomorphine. Adr. Biochem. Psychopharmac. 19: 275-292. Divac I.. Fonnum F. and Storm-Mathisen J. (1977) Hieh affinity uptake of glutamate in terminals of corticostria& axons: Nature 266: 317-378. Enna S. J.. Stern L. Z.. Wastek G. J. and Yamamura H. I. (I 977) Minireview: neurobiology and pharmacology of Huntington’s disease. Life Sci. 20: 205-212. Faull R. L. M. and Laverty R. (1969) Changes in dopamine levels in the corpus striatum following lesions in the substantia nigra. Expl Neural. 23: 332-340. Feltz P. (1971) Gamma-aminobutyric acid and a caudatoinhibition. Can. J. Physiol. Pharmac. 49: nigral 1113-1115. Fibiger H. C. (1978) Kainic acid lesions of the striatum: a pharmacological and behavioral model of Huntington’s disease. In: Kainic Acid as a Tool in Neurology, pp. 161-176. Raven Press. New York. Gumulka W., Ramirez-Del Angel A., Samanin R. and Valzelli L. (1970) Lesion of the substantia niera: bio/ chemical and behavioral effects in rats. Eur. J. Pharmac. lo: 79982. Hornykiewicz 0. (1966) Dopamne (3-hydroxytryramine) and brain function. Pharmac. Rev. 18: 925-964. Kim J. S., Bak 1. J., Hassler R. and Okada Y. (1971) Role of gamma-aminobutyric acid (GABA) in the extrapyramidal motor system. 2. Some evidence for the existence of a type of GAMA-rich strionigral neurons. Expl Brain Res. 14: 95-104.
functions
1235
Kiinig J. F. R. and Klippel R. A. (1963) The Rat Brain: A Stereolaxic Atlas of the Forebrain and Lower Parts of the Brain Stem. Williams & Wilkins, Maryland. Lin M. T. and Chem S. I. (1979) Effects of brain 5-hydroxytryptamine alterations on reflex bradycardia in rats. Am. J. Physiol. 236: R302-R306. Lin M. T., Wu J. J., Chandra A. and Tsay B. L. (1981) Activation of striatal dopamine receptors induces pain inhibition in rats. J. Neural Trans. 51: 213-222. Lin M. T., Chandra A., Tsay B. L. and Chern Y. F. (1982) Hypothalamic and striatal dopamine receptor activation inhibits heat production in the rat. Am. J. Physiol. 242: R47l-R481. Lin M. T., Tsay B. L. amd Chen F. F. (1982) Activation of dopaminergic receptors within the caudate-putamen complex facilitates reflex bradycardia in the rat. Jup. J. Physiol. 32: 431-442. Lloyd K. G. (1980) Indications for GABA dysfunction in mental disease. In: Enzymes and Neurotransmitters in Mental Disease. Raven Press, New York. McGeer E. G. and McGeer P. L. (1976) Duplication of biochemical changes of Huntington’s chorea by intrastriatal injections of kainic acid. Nature 263: 517-519. McGeer P. L.. McGeer E. G.. Scherer U. and Sineh K. (1977) A glutamatergic corticostriatal path? Brain Res. 128: 369-373. Obata K. and Yoshida M. (1973) Caudate-evoked inhibition and action of GABA and other substances on cat pallidal neurons. Bruin Res. 64: 455459. Okada Y. and Hassler R. (1973) Uptake and release of GABA in slices of substantia nigra of rat. Brain Res. 49: 214-217. Poirier L. J. and Sourkes T. R. (1965) Influence of the substantia nigra on the catechdlamine content of the striatum. Brain 88: 181-192. Simke J. P. and Saelens J. K. (1977) Evidence for a cholinergic fiber tract connecting the thalamus with the head of the striatum of the rat. Brain Res. 126: 487495. Spencer H. J. (1976) Antagonism of cortical excitation of striatal neurons by glutamic acid diethyl ester: Evidence for glutamic acid as an excitatory transmitter in the rat striatum. Brain Res. 102: 91-101.
Copynght
0028.3908184 $3.00 + 0.00 ‘c 1984 Pergamon Press Ltd
TACHYCARDIA, HYPERTENSION AND DECREASED REFLEX BRADYCARDIA PRODUCED BY STRIATAL LESIONS INDUCED BY KAINIC ACID J. J. Wu*$,
C.-J. SHIH* and M.-T. LIN? of Physiology and Biophysics, National Defense
*Department of Surgery and tDepartment Medical Center and Tri-Service General
Hospital.
Taipei,
Taiwan,
Republic
of China
(Accepted 13 September 1983) Summary-The effects of intra-striatal injection of kainic acid on cardiovascular function were assessed in urethane-anesthetized rats. Intra-striatal administration of 2 pg of kainic acid (in a volume of 0.5 ~1) produced both tachycardia and hypertension. The tachycardia induced by intra-striatal injection of kainic acid was antagonized by either prior bilateral vagotomy or spinal transection of the animals (at C7). On the other hand, the hypertension induced by intra-striatal administration of kainic acid was antagonized by prior bilateral vagotomy, but not spinal transection. In addition, reflex bradycardia was produced by intravenous infusion of adrenaline in rats. Over the dose range (1.25-5.0pgg/kg, i.v.) of adrenaline used, a dose-dependent bradycardia was obtained. It was found that pretreatment of animals with intra-striatal injection of kainic acid, although causing no change in the adrenaline-induced pressor effect, did reduce the adrenaline-induced bradycardia. Intravenous administration of same dose of kainic acid had no effect on these cardiovascular responses. Thus, the data indicate that striatal neurones are involved in the central control of cardiovascular function. Key words: kainic spinal transection.
acid.
tachycardia,
hypertension,
consistent lesion in the choreic brain seems to be a disappearance of GABAergic-containing neurones from the basal ganglia, possibly also of cholinergic neurones (Enna, Stern, Wastek and Yamamura, 1977; Lloyd, 1980; Bird and Iversen. 1974; Coyle and Schwartz, 1976; Fibiger, 1978; McGeer and McGeer, 1976). Recently, it was found that injection of the glutamate analogue, kainic acid, into the striatum of the rat caused destruction of GABAergic and cholinergic cells and provided a model for Huntington’s disease (Enna et al., 1977; Lloyd, 1980; Bird and Iversen, 1974; Coyle and Schwartz, 1976; Fibiger. 1978; McGeer and McGeer, 1976). However, information is not available about the effects of intra-striatal injection of kainic acid on cardiovascular function. Therefore, the effects of injections of kainic acid into the striatum on the basal levels of both the heart rate and arterial pressure in rats were investigated. In addition, the effects on the reflex bradycardia in response to elevation of arterial pressure induced by intravenous infusion of adrenaline were also observed. The most
METHODS
Experimental Experiments Sprague-Dawley
animals were performed on male rats weighing between 250 and
IAddress correspondence and offprint requests to Dr Jionn-Jone Wu, Division of Neurosurgery, Department of Surgery, Far Eastern Memorial Hospital, Pan-Chiao, Taipei, Taiwan. Republic of China. N P 23’11 A
reflex bradycardia.
corpus
striatum.
vagotomy.
300 g. Before they were subjected to experiments, the animals were housed individually in wire mesh cages in a room maintained at a temperature of 22 + 1.0 C with a natural light-dark cycle. They were given free access to tap water and granular chicken feed supplied by Taiwan Sugar Corporation. Surgicul prepurution Each animal was anesthetized with pentobarbital sodium (6 mg/lOO g, i.p.) and placed in a Kopf stereotaxic apparatus. For the direct injection of kainic acid or control vehicle into the striatum (caudate-putamen complex), stainless steel cannulae, consisting of a guide tube with a snug fitting trocar, and a cannula insert, was introduced into the tube at the time of injection (Lin, Chandra, Tsay and Chern, 1982; Lin, Wu, Chandra and Tsay, 1981). The cannula guide tube with trocars was implanted using the stereotaxic atlas and co-ordinates of Kiinig and Klippel (1963). The following co-ordinates were used: A, 7.9-9.1 mm; L, 1.7-2.3 mm; and H, 1.4-0.6 mm. After appropriately-located craniotomy holes had been trephined, two self-tapping screws were attached to the calvarium of the parietal bones and the cannulae guide tubes were inserted to the desired depth through the craniotomy holes. They were anchored with fast-drying acrylic dental cement to the cranial surface that had been scraped clean of periosteum. The reflected skin was replaced around the acrylic mould containing the guide tubes and was sutured with chromic gut. At the time of injection. the cannula inserted was connected to a 10 p I Hamilton microsyringe by PE-10 polyethylene tubing, and the 1231
J. J. Wu et ui.
1232
0.9 % saline
90
min
after
kalnic
acid
600
Heart rate beats/min
400
-_
7-
200
Arterial blood pressure mmHg
OL
t-l adrenaline
25pg/
kg, i.v.
adrenaline
2.5 pg/
kg, Iv.
Fig. 1. The cardiovascular responses induced by intravenous administration (iv.) of adrenaline in urethane-anesthetized rats both before and after an intra-striatal injection of 2 pg of kainic acid.
syringe and tubing were filled with silicone fluid to act as a piston. A volume of 0.5 ~1 was infused into the striatum over a period of I min. In preparing spinal animals, the cervical vertebrae was exposed and complete transection was made with a spatula at the seventh cervical segment of the spinal cord (C7). Bilateral vagotomy were made at the neck region (Chai and Lin, 1977).
by irradiation with infra-red light. The trachea was cannulated and the femoral artery catheterized. The femoral arterial pressure was monitored with a Stathan P23AC transducer, and heart rate was monitored with a Grass 7C tachometer triggered by arterial pulses. The right femoral vein was cannulated for intravenous injection. All recordings were made on a four-channel Grass 7C polygraph.
Drug solution
Histological
All drug solutions were prepared in pyrogen-free glassware baked for 5 hr at 180°C before use. The drug kainic acid (Sigma Chemical Co., St Louis, Missouri) was freshly made up as a stock solution by dissolving certain amount in 0.9D/ saline. Adrenaline (epinephrine. USP) (Retired Servicemen’s Pharmaceutical Plant of Taiwan) was administered intravenously by way of the femoral vein. In the present study, the reflex bradycardia was induced by intravenous infusion of adrenaline in rats (Lin and Chern, 1979).
After the experiments were completed, the animals were killed with an overdose of sodium pentobarbital and the cerebral circulation was perfused with 0.9”,, saline, followed by 10% (v/v) formalin solution. Later, sections of the fixed brain were cut at a 40 itrn section and stained with thionin so that the stereotaxic co-ordinates of the cannulae were verified.
Physiological
Table 1 shows (2 pg in 0.5 ~1) caused a rise in arterial pressure
mensurements
The animals were anesthetized with urethane (1.2 g/kg, i.p.). Rectal temperature was maintained at 37 k 0S”C throughout the course of the experiments Table
I.
Effects
of intra-striatal
Treatments Mean arterial pressure I. Saline 0.996 2. Kainic acid I pg 3. Kainic acid 2bg Heart rate (beatslmin) I. Saline 0.9>,, 2. Kainic acid I pg 3. Kainic acid 2pg
oer@cation
RESULTS
l@cts of‘intra-striatal injection of kainic acid on the basal leaels of heart rate and urteriul pressure
administration
of saline vehicle or urethane-anesthetized rats
kainic
that a direct injection of kainic acid into the caudate-putamen complex both the heart rate and the mean in urethane-anesthetized animals.
acid
on
cardiovascular
responses
m
Time of reCW0-y (“II”)
Maximal
n
Control values
values
Difference
Time to maximal rise C”““)
X 4 R
104 * 15.8 IO1 i 16.7 102 2 17.8
104 f 14.9 IO1 t 17.2 178&179
0 0 16 f 6.96’
0 0 32.8 + I .74*
0 0 ho*5
8 4 8
399 * 13.5 404 f 16.9 402 + 12.2
399 + 15.5 404 f 17.8 592 + 12.9
0 0 190 f 20.8’
0 0 54.6 k 2.37”
0 0 X9 k 6.3l*
(mmHg)
‘Difference is statistically significant from corresponding as mean +SE: n = numbers of animals tested
control values. P c 0.05 (Student’s
14*
r-test). The values are expressed
Striatal lesions on cardiovascular functions Table
2. Effects
of bilateral
vagotomy
and spinal transection on the cardiovascular kainic acid in urethane-anesthetized Mean arterial
Treatments
n
Sham operation 2. Bilateral vagotomy 3. Spinal transection
8 8 8
I.
Control 103 f 15.8 128 i_ 12.1 80 k 7.5
*Significantly different from corresponding n = numbers of animals tested.
control
pressure
responses rats
178 i 13.7 I81 * 11.3 160 f 14.2
75 i 5.12 53 f 3.25’ 80 + 7.91
Table 3 summarizes the vasopressor and bradycardic responses to intravenous infusion of adrenaline in urethane-anesthetized animals before and after an intra-striatal injection of 2 pg of kainic acid. Over the dose range (1.2-5.0 pg/kg, i.v.) of adrenaline, a dose-dependent response was obtained. Before the injection of kainic acid, the administration of adrenaline (e.g. 2.5 pgg/kg, i.v.) induced an average increase in mean arterial pressure of 75 f 12.1 mmHg and an average decrease in heart rate of 90 ) 8.9 beats/min. Ninety minutes after the injection of kainic acid, the basal levels of both mean arterial pressure and heart rate had already recovered, the animals were subjected to injection of adrenaline. It was found that the bradycardic effects induced by adrenaline were greatly reduced by pretreatment of animals with intra-striatal administration of kainic acid. However, the vasopressor effects induced by adrenaline were not significantly affected by pretreatment with intra-striatal administration of kainic acid. Either intrastriatal administration of control vehicle solution or intravenous administration of kainic acid (2~0 had no significant effects on the cardiovascular responses induced by intravenous infusion of adrenaline. DISCUSSION It has been well established that dopamine is a transmitter in neurones arising in the pars compacta of substantia nigra and projecting to the striatum
of 2 fig of
After kainic
P c 0.05 (Student’s
Eflects of intra-striatal injection of kainic acid on the reflex bradycardia induced by adrenaline
injection
Heart rate (beats:min)
Difference
After an intra-striatal injection of 2 pg of kainic acid, the heart rate rose almost immediately and reached the maximum level (e.g. 190 beats/min) at about 50min. The trachycardia responses recovered at 90 min after the injection of kainic acid. On the other hand, the mean arterial pressure also rose immediately and reached the maximum level (e.g. 76 mmHg) at about 30 min. The pressor responses recovered at 60 min after the injection of kainic acid. Table 2 shows that the tachycardia induced by intra-striatal injection of kainic acid was antagonized by either prior spinal transection (at C7) or bilateral vagotomy of the animals. However, the hypertension induced by kainic acid was antagonized by prior bilateral vagotomy, but not spinal transection in urethane-anesthetized animals.
induced by intra-striatal
(mmHg)
After kainic acid
values,
1233
l-test).
Control 401 f 14.5 485 + 17.9 350 rt 15.4 The values
acid
DilTerence
588 f 14.6 524 * 14.5 382 f I I .7
187 i 17.6 39 + 7.12’ 32 k 2.51*
are expressed
as the means
+SE;
(caudate nucleus plus putamen or caudate-putamen complex) (Anden, Carlsson, Dahlstrom, Fuxe, Hillarp and Larsson, 1964; Anden, Dahlstrom, Fuxe and Larsson, 1965; Dahlstrom and Fuxe, 1964; Faull and Laverty, 1969; Gumulka, Ramirez-Del Angel, Samanin and Valzelli, 1970; Hornykiewicz, 1966; Poirier and Sourkes, 1965). In addition, there is a glutamic acid-containing corticostriatal connection (Divac, Fonnum and Storm-Mathiesen, 1977; McGeer, McGeer, Scherer and Singh, 1977; Spencer, 1976) and a cholinergic thalmostriatal projection (Simke and Saelens, 1977). On the other hand, it is believed that y-aminobutyric acid (GABA) is the transmitter for the strionigral and striopallidal efferent systems (Kim, Bak, Hassler and Okada, 1971; Okada and Hassler, 1973; Feltz, 1971; Obata and Yoshida. 1973). Moreover, a possible correlation between nigrostriatal dopaminergic, striatal cholinergic and strionigral GABAergic reverberating neurone circuit has been described (Di Chiara, Corsini, Mereu, Tissari and Gessa, 1978). In fact, the role played by the nigrostriatal dopaminergic pathway, one of the three main dopamine pathways in the brain, in the central control of the arterial baroreflex had been assessed in rats (Lin, Tsay and Chen, 1982; Chen, and Lin, 1980). It was demonstrated that inhibiting the nigrostriatal dopamine pathway with the electrolytic lesions in the substantia nigra, depressed reflex bradycardia. In contrast, activating the nigrostriatal dopamine pathway with electrical stimulation in the substantia nigra, facilitated reflex bradycardia in rats. Furthermore, local administration of apomorphine (a dopamine receptor agonist) into the caudate-putamen complex facilitated reflex bradycardia, while local administration of dopaminergic receptor antagonists such as haloperidol and pimozide into the same site depressed reflex bradycardia in the rat. Moreover, the facilitation in the reflex bradycardia induced by local administration of apomorphine into the caudateputamen complex could be readily abolished by pretreatment of animals with administration of either haloperidol or pimozide in the striatum. Thus. it appears that a dopaminergic synapse exists in the caudate-putamen complex which mediates reflex bradycardia in the rat. The present results also showed that lesion of striatal neurones (Enna et a/., 1977; Lloyd, 1980; Bird and Iversen, 1974; Coyle and Schwartz, 1976; Fibiger, 1978; McGeer and McGeer, 1976) with intrastriatal administration of kainic acid
1234
J. J. WU et al.
depressed reflex bradycardia in the rat. These observations prompted the idea that intra-striatal administration of kainic acid would destroy the dopaminergic receptors which are located on these neurones within the striatum and depress reflex bradycardia, mediated through baroreceptor reflexes in response to an acute increase in arterial pressure. In addition, the present results showed that lesion of striatal neurones with kainic acid caused both tachycardia and hypertension in urethaneanesthetized animals. The tachycardia induced by intra-striatal administration of kainic acid was antagonized by either prior spinal transection (at C7) or bilateral vagotomy of the animals. This indicates that the induced tachycardia is brought about by both an increase in sympathetic efferent activity and a decrease in vagal efferent activity. On the other hand. the hypertension induced by intra-striatal administration of kainic acid was antagonized by prior bilateral vagotomy, but not spinal transection, This strongly suggests that, in addition to a decrease in vagal efferent activity, certain unknown neurochemical factors (e.g. vasopressin), released from the brain following the intra-striatal administration of kainic acid, may also be responsible for the development of hypertension in the animal. Of course. this hypothesis needs further verification. In summary, the present results show that intrastriatal administration of kainic acid caused tachycardia, hypertension and suppressed reflex bradycardia. The induced tachycardia may be due to both increased sympathetic efferent activity and decreased vagal tone, whereas the induced hypertension may be due to decreased vagal tone and enhanced release ol certain unknown neurohumoral factors from the brain. The data indicate that strtatal neurones are involved in central control of cardiovascular functions. Acknowledgements-The work reported here was supported by a grant from the National Science Council of the Republic of China. The authors wish to thank Miss Ba-Ling Tsay for her excellent technical assistance. We are grateful to Professor J. S. Kuo for his comments during the preparation of this paper.
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