• The Korean Journal of Physiology
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• 제25권2호
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• pp.201-209
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• 1991

The rostral ventrolateral medulla (RVLM) has been established recently as a sympathoexcitatory area. The present study was conducted to investigate whether the somatosympathetic pressor and/or depressor responses are mediated through RVLM in cats anesthetized with ${\alpha}-chloralose$. An occipital craniectomy was performed and ventrolateral medulla were stimulated either electrically or chemically to evoke changes in arterial blood pressure. And then the effect of lesions in the ventrolateral medulla on the changes in blood pressure elicited by the peripheral nerve stimulation was observed. Followings are the results obtained: 1) Pressor areas were found in the ventrolateral medulla, lateral reticular nucleus and rostral dorsal area. 2) Depressor areas were found mainly in the ventrolateral medulla rostral to the pressor areas. 3) Some areas showed biphasic responses: a depressor response to lower frequency and a pressor response to higher frequency stimulation. 4) After electrical lesion in pressor area in RVLM, the somatosympathetic pressor response was abolished or depressed markedly. The somatosympathetic depressor response, however, remained after the lesion. 5) Electrical lesion in the depressor area abolished somatosympathetic depressor response. From the above results it is concluded that somatosympathetic pressor response is mediated through RVLM, while somatosympathetic depressor response is not mediated through RVLM.

• The Korean Journal of Physiology
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• 제22권2호
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• pp.231-243
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• 1988

This study was performed to investigate the mechanism of changes in arterial blood pressure, as a typical example of somatosympathetic reflex, induced by activation of muscular afferent nerves. Cats were anesthetized with ${\alpha}-chloraloae$ (60 mg/kg, i.p.). Afferent fibers in muscle nerve were activated by various method muscle contraction, electrical stimulation of muscle nerves, intraarterial injection of some algesic substances and noxious mechanical stimulation etc-and the evoked changes in arterial blood pressure were monitored. The effects of intravenous or direct spinal administration of morphine on the changes in arterial blood pressure induced by activation of the muscle afferent fibers were observed and also the effects of spinal lesions made in the $L1{\sim}L3$ spinal cord on them were studied to identify the ascending spinal pathways of the somatosympathetic reflexes. Followings are the results obtained. 1) The stimulation of medial gastrocnemius nerve under non-paralyzed condition with C-strength, low frequency (lower than 20 Hz) stimuli elicited a depressor response and a pressor response was elicited with C-strength, high frequency stimuli, of which the maximal response was observed at 100 Hz stimulation. 2) When the animal was paralyzed, depressor response to stimulation of the medial gastrocnemius nerve was observed with C-strength, $0.5{\sim}5Hz$ stimuli although the amplitude of the depressor response was decreased. The maximal pressor response was observed during stimulation with C-strength, $20{\sim}100Hz$ stimuli. 3) Intraarterial injection of some algesic substances induced marked pressor responses while noxious mechanical stimulation of the medial gastrocnemius muscle was not enough to elicit any significant changes (larger than 10 mmHg) in arterial blood pressure. 4) Systemically administered morphine (2 mg/kg) lowered the arterial blood pressure immediately and persistently and it was reversed by administration of naloxone. Direct spinally administered morphine did not elicit any changes. 5) The pressor response elicited by the activation of muscle afferent nerves was strengthened by systemic morphine administration while the depressor response tended to decrease. 6) Morphine administered on the spinal cord directly, decreased pressor response but did not change depressor response. From the above results it is concluded that there are separate groups of afferent nerves in the medial gastrocnemius nerve, which elicit pressor and depressor responses and the spinal ascending pathways of them are also separated from each other.

• Journal of Chest Surgery
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• 제23권5호
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• pp.833-843
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• 1990

Vasomotor areas were identified by stimulating various sites of the medulla electrically in adult cats anesthetized with a-chloralose and their correlation with somatosympathetic pressor or depressor responses was investigated. Followings are the results obtained: 1. Pressor areas were found in the rostral ventrolateral, the caudal ventrolateral and the rostral dorsolateral medulla. 2. Separate depressor areas were found dorsal and ventral to the rostral ventrolateral pressor area. 3. Some areas showed biphasic responses: depressor responses to low frequency[1 \ulcorner2 Hz] and pressor responses to high frequency[20 \ulcorner100 Hz] stimulation 4. Lesions on the rostral ventrolateral pressor areas abolished the somatosympathetic pressor responses to the stimulation of peripheral afferent nerves, while the depressor responses remained. Lesions on the caudal ventrolateral pressor area affected neither the pressor nor depressor responses to the peripheral nerve stimulation. 5. Lesions on the depressor areas resulted in decreased depressor responses to the peripheral nerve stimulation, but to a lesser degree than that resulted from lesions on the pressor areas. 6. A microinjection of glutamate solution to the pressor area resulted in a prolonged pressor response, while glutamate injection to the depressor areas did not elicit depressor responses. From the above results, it is concluded that there are separate pressor and depressor areas in the rostral medulla of cats and each area plays a role in somatosympathetic pressor and depressor responses, respectively.

• Journal of Pharmaceutical Investigation
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• 제6권2호
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• pp.101-110
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• 1976

1. In the rabbit and the dog, the blood pressure response to water extract and methanol extract obtained from Atractylodes rhizoma alb'a was investigated. 2. Water extract and methanol extract, when administered into the rabbit and the dog by the route of vein, produced fall of the blood pressure. 3. The depressor response of the rabbit to water extract and methanol extract was not affected by $Avicel{\circledR}$, propranolol and atropine. 4. The depressor response by water extract and methanol extract in the rabbit was not affected by guanethidine, but water extract and methanol extract produced elevation of blood pressure in this rabbit. 5. Pretreatment of rabbit with chlorisendamine or phenoxybenzamine weakened the depressor response to water extract and methanol extract, and the both extracts produced secondary elevation of blood pressure in this rabbit. 6. The pressor response of the chlorisondamine-treated rabbit to water extract and methanol extract was not affected by atropine. 7. Water extract decreased the pressor action of tyramine and depressor action of pilocarpine and isoproterenol, but did not affect the blood pressure response of nor einephrine, angiotensin and dimethylpehnyl piperazinium iodide(DMPP).

• 대한한의학회지
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• 제16권2호
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• pp.433-446
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• 1995

The present study was carried out to investigate the effect of water extract and 70% ethanol extract from Gastrodiae Rhizoma on cardiovascular activities and plasma levels of catecholamines in unanaesthetized spontaneously hypertensive rats. The depressor response in SHR was observed during three to six hour period after an oral administration of water extract from Gastrodiae Rhizoma(GR). There was a statistically significant correlation between the magnitude of the depressor response induced by an oral administration of water extract from GR and the initial control blood pressure level. The increase in blood pressure induced by norepinephrine was less in Wistar rat treated with GR water extract than those without GR extract. No significant change in heart rate was observed in SHR receiving either water extract or ethanol extract from GR. Associated with the depressor response, there was a concomitant reduction in plasma levels of norepinephrine in SHR at 4 hour after an oral administration of water extract from GR. Plasma levels of norepinephrine and epinephrine were decreased slightly at 2 hour after an oral administration of ethanol extract from GR. These results suggest that the depressor effect of water extract from GR may be due, in part, to a decreased sympathoadrenal activity.

• 약학회지
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• 제20권1호
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• pp.83-91
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• 1976

Effects of Alismatis water extract (AE) on the blood pressure were investigated in the rabbit and the dog. AE, when administered into the vein of rabbit and dog, into the lateral ventricle of rbbit, produced fall of blood pressure. The depressor response of the rabbits to intravenous AE was abolished by treatment with atropine, but not with chlorisondamine weakened the depressor effect of AE. Intravenous AE in this rabbit produced secondary elevation of the blood pressure. AE potentiated the pressor response of the rabbit to norepinephrine and tyramine, but nor to angiotensin, acetylcholine, and DMPP.

• The Korean Journal of Physiology
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• 제27권2호
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• pp.185-197
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• 1993

The rostral ventrolateral medulla (RVLM) includes vasopressor neurons, which transmit activation signals to the intermediolateral nucleus (IML) of the spinal cord, where the preganglionic sympathetic nucleus is located, to raise arterial blood pressure (BP). However, controversy exists as to the possible depressor area in the RVLM and the pathway involved. The present study persued evidence far the location of depressor neurons and the pathway by simultaneously observing changes in BP and the firing rate (FR) of cardiovascular neurons (CVNs) in the RVLM during the somatosympathetic reflex (SSR) elicited by peripheral nerve stimulation, since CVNs are known to contribute to the generation of the sympathetic nerve discharge. In 42 cats, anaesthetized with $\alpha-chloralose$, single unit recording was performed, using carbon filament electrodes inserted into the RVLM, enabling estimation of the post R wave unit histogram (PR-UNlT) and the spike triggered average of sympathetic nerve discharge (STA-SND), allowing identification of CVNs. Antidromic stimulation of spinal $T_2$ segment was followed to determine whether the identified CVN projects axonal endings to the spinal cord (reticulospinal neuron). The sciatic nerve was electrically stimulated at $A\delta-intensity$ (1 mA, 0.1 ms), 1 Hz and C-intensity (10 mA, 0.5 ms), 20 Hz to elicit the depressor, and pressor responses of the SSR, respectively. Simultaneous measurement of CVN firing rate was made. Experimental results are summarized as follows. 1) 20 out of 98 CVNs had axonal projections to the spinal cord and 17 out of 98 CVNs showed FR changes during SSR. 2) Response patterns of FR and BP during SSR were classified into 8 types. 3) These 8 different response patterns could be further classified into those from pressor and depressor neurons. These results demonstrate that some CVNs were identifiable as reticulospinal neurons responding to anti-dromic stimulation and that CVNs operating as depressor neurons as well as pressor neurons exist in the RVLM, both of which are involved with SSR mediation. Therefore, evidence was found that an independent depressor pathway might be involved in the mediation of SSR.

• The Korean Journal of Physiology
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• 제18권2호
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• pp.171-180
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• 1984

The death of cattle from acute bracken poisoning has been recognized for many years. Acute bracken poisoning is characterized by mucoidal nasal and anal hemorrhage, severe anorexia. pyrexia, gastric ulcer and myocardial damage. In 1958 Evans first suggested that clinical picture of bracken poisoning was very much similar to that of radiation injuries such as aplastic anemia, leucopenia, thrombocytopenia and increased capillary fragility. Bracken has been clearly demonstrated to contain a carcinogen as well as thiaminase. However, the nature of carcinogen in bracken has not definetely elucidated. Also it was warned by several workers that bracken could be a causative factor for stomach cancer in Korean and Japanese. It appears that little is known on the e(feet of bracken on the function of cardiovascular system. Therefore the present study was designed to explore effects of ethanol extract of raw and toiled bracken (RBEE:BBEE) on blood pressure in cats. Also studied was the mechanism underlying changed in blood pressure of cats by bracken. The result obtained were as follows; 1) Mean arterial blood pressure was invariably decreased following administration of either RBEE or BBEE. Tn general depressor responses to RBEE persisted longer than that to BBEE. Generally, depressor responses were proportional to debases of RBEE and BBEE administered. 2) After administration of 60 mg/kg RBEB and BBEE, blood Pressure decreased by $62.1{\pm}1.7mmHg$ and $68.0{\pm}3.0mmHg$, respectively. No change was observed between depressor responses to RBEE and that to BBEE. 3) Depressor responses to BBEE and RBEE were not affected by vagotomy, propranolol and regitine. 4) In atropinized animal depressor responses to BBEE and RBEE were reduced by 30-40% showing part of depressor response was resulted from cholinergic effect of bracken.

• 약학회지
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• 제23권2호
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• pp.69-80
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• 1979

Effects of Astragali Radix Water Extract (ARWE) on the blood pressure were investigated in the whole rabbit and the spinalized rabbit. ARWE, when administered into the ear-vein or lateral ventricle, produced a fall in the blood pressure in the whole rabbit, but intravenous ARWE in the spinalized rabbit did not elicite the hypotensive action. Pretreatments with chlorisondamine, guanethidine, phentolamine and cyproheptadine in the whole rabbit weakened the depressor action of ARWE. The hypotensive action of the whole rabbit to ARWE was not influenced by the pretreatment of the animals with diphennylhydramine, propranolol, and vagotomization, whereas inhibited by atropine. ARWE did not affect the pressor response by angiotensin. However, it enhanced the hypertensive action by norepineprine and reduced the elevation in the blood pressure by carotid occlusion in the whole rabbit. These experimental observations suggest that ARWE may cause the depressor response via mechanisms of the central sympathetic blocking action, cholinergic action by peripheral origin and serotonin-like action.

• Biomolecules & Therapeutics
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• 제14권2호
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• pp.119-124
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• 2006

This study was performed to investigate the influence of the spinal adenosine $A_1$ receptors on the central regulation of blood pressure (BP) and heart rate (HR), and to define whether its mechanism is mediated by cyclic AMP (cAMP), cyclic GMP (cGMP) or potassium channel. Intrathecal (i.t.) administration of drugs at the thoracic level were performed in anesthetized, artificially ventilated male Sprague-Dawley rats. I.t. injection of adenosine $A_1$ receptor agonist, $N^6$-cyclohexyladenosine (CHA; 1, 5 and 10 nmol) produced dose dependent decrease of BP and HR and it was attenuated by pretreatment of 50 nmol of 8-cyclopentyl-1,3-dimethylxanthine, a specific adenosine $A_1$ receptor antagonist. Pretreatment with a cAMP analogue, 8-bromo-cAMP, also attenuated the depressor and bradycardiac effects of CHA (10 nmol), but not with cGMP analogue, 8-bromo-cGMP. Pretreatment with a ATP-sensitive potassium channel blocker, glipizide (20 nmol) also attenuated the depressor and bradycardiac effects of CHA (10 nmol). These results suggest that adenosine $A_1$ receptor in the spinal cord plays an inhibitory role in the central cardiovascular regulation and that this depressor and bradycardiac actions are mediated by cAMP and potassium channel.