• Journal of Veterinary Clinics
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• v.6 no.1
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• pp.165-171
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• 1989

Antagonistic effects of yohimbine on xylazine and ketamine anesthesia in goats were studied. Xylazine or ketamine anesthesia alone was not antagonized by yohimbine, but the time for consciousness and recovery in xylazine and ketamine anesthetized goats were remarkably shortened by yohimbine. Reversal effect of yohimbine on the heart rate and body temperature which decreased following xylazine and ketamine was not observed and respiratory rate which increased after xylazine and ketamine was sligtly reduced by yohimbine.

• Journal of Veterinary Clinics
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• v.5 no.2
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• pp.61-71
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• 1988

This study was performed to compare the antagonistic effects of intravenous(0.125mg / kg) and subcutaneous(0.25mg /kg) administration of yohimbine on xylazine-induced immobilized(4.5mg/ kg) dog and to investigate the effectiveness of yohimbine compound(0.25mg / kg) in clinical practice. Mean arousal time(MAT), mean walk time(MWT), and time to return to normal electroencephalograms were remarkably decreased in all yohimbine-treated groups compared with the control. In electroencephalograms(A-B$\sub$I/ lead), there were no significant alteration, except RR interval. RR interval was decreased in all yohimbine-treated groups compared with the control. Second-degree heart blocks(41.7%) shown after xylazine administration disappeared within 2 min after yohimbine administration. The frequency of electroencephalograms(RO-RF trace) was recovered faster to normal in yohimbine-treated groups than that of the control. In histopathological changes of ICR mice given yohimbine compound subcutaneously, edema with inflammatory cells of hypodermis was slightly shown on the 1st day, but this findings were not observed on the 5th day. It was considered that no difference in the antagonistic effects of intravenous and subcutaneous administration of yohimbine on xylazine- induced immobilized dog were observed and yohimbine compound was usable in clinical practice for antagonistic agent to the xylazine.

• Korean Journal of Veterinary Research
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• v.28 no.1
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• pp.37-47
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• 1988

Xylazine hydrochloride is a widely used analgesic, sedative and muscle relaxant agent in veterinary clinic. Yohimbine hydrochloride and 4-aminopyridine are known as antagonists of xylazine hydrochloride. This paper was investigated to know that the effect of xylazine hydrochloride, yohimbine hydrochloride and 4-aminopyridine, and that whether or not antagonism of yohimbine hydrochloride and 4-aminopyridine to xylazine hydrochloride-induced effect on gizzard motility in chicken. The results were as follows. 1. After xylazine hydrochloride administration, the gizzard motility in chicken was instantly inhibited in relaxation state, and this state was prolonged in proportion to increase of dose. 2. After yohimbine hydrochloride administration, the gizzard motility in chicken showed increase of contractile frequency. 3. After 4-aminopyridine administration, the gizzard motility in chicken was gradually recovered next to decrease of contractile amplitude and frequency. 4. After the combination of yohimbine hydrochloride and 4-aminopyridine administration, the gizzard motility in chicken showed increase of amplitude and radical increase of frequency. 5. After xylazine hydrochloride administration, the relaxation time was shortened by yohimbine hydrochloride, 4-aminopyridine and the combination of yohimbine hydrochloride and 4-aminopyridine. In conclusion, the gizzard motility in chicken was inhibited by xylazine hydrochloride, and this effect was antagonized by the combination of yohimbine hydrochloride and 4-aminopyridine.

• Journal of Veterinary Clinics
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• v.16 no.1
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• pp.65-68
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• 1999

This study was carried to get detailed information about the analeptic effect of yohimbine on succinylcholine muscle relaxant. Succinylcholine was administered intra- venously at a dose rate of 0.05 mg per kg of body weight and then ten minutes after the succinylcholine injection, yohimbine was administered intravenously at a dose rate of 0.1 mg per kg of body weight. The results obtained were as follows. 1. Induction time of muscle relaxation was fast and favourable as 38 seconds. 2. Mean arousal time and mean walk time were significantly shortened by yohimbine administration in the dogs immobilized with succinylcholine (p＜0.01). 3. Heart rate was slightly increased after succinylcholine administration, and increased significantly after yohimbine administration compared to the control group (p＜0.05). 4. Glucose concentration was slightly increased after succinylcholine administration, and decreased after yohimbine administration compared to the control group.

• The Korean Journal of Pharmacology
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• v.29 no.1
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• pp.23-32
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• 1993

Recent studies have shown that a GABAergic mechanism in the brain modulates arterial blood pressure (BP) through alterations of sympathetic activity in the brain. The purpose of the present study was to determine if this modulation is involved in the pressor response to raised intracranial pressure (ICP). The pressor response to raised ICP was abolished by pretreatment of anesthetized rabbits with intracerebroventricular (icv) muscimol (a GABA agonist) as well as with icv clonidine $(an\;{\alpha}_2-agonist)$. Raising ICP in the hypertensive state after icv yohimbine $(an\;{\alpha}_2-antagonist)$ did not cause an additional increase in the BP, whereas raising ICP in the hypertensive state following icv bicuculline (a GABA antagonist) produced a further increase. Bicuculline produced an increase of the BP which had been lowered by muscimol or by clonidine, whereas it failed to increase the hypertensive state induced by either previous yohimbine or raised ICP. Yohimbine reversed the BP which had been made low by clonidine but was incapable of raising the hypotensive state after muscimol. Yohimbine failed to increase the heightened BP due to raised ICP, whereas bicuculline-induced pressor state was further elevated by yohimbine. Muscimol, besides the bicuculline-antagonizing property, inhibited the pressor response to yohimbine, suggesting participation of a GABAergic mechanism in the pressor action of yohimbine. From these results it was inferred that there were three ways in which BP could be increased via raised ICP: inactivation of the inhibitory sympathetic activity through (1) ${\alpha}_{2}-adrenoceptors$, (2) bicuculline-sensitive GABA receptors, (3) yohimbine-sensitive, clonidine-acting GABAergic sites.

• Journal of Veterinary Clinics
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• v.10 no.1
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• pp.37-46
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• 1993

This study was carried out to evaluate the effects of yohimbine on medetomidine sedation. Twenty dogs were sedated with medetomidine(0.04mg/kg, IM). Twen쇼 minutes after the injection, ten dogs were injected with saline(0.1mg/, IV)for the control group and the others were injected wi yohimbine(0.1mg/kg, IV)for the experimental group. Onset, recovery time, respiratory rate, body temperature, blood chemistry, electrocardiogram(ECG) finding were recorded. The results obtained were summarized as follows; 1. Onset of the sedation was fast and favorable. 2. Recovery time was shorted significantly by yohimbine treatment(p<0.01). 3. Respiratory rates were decreased significantly, but increased to normal level after the yohimblne treatment(p<0.01). 4. Heart rates were decreased significantly; but increased to normal level after the yohimbine treatment(p<0.01). 5. Body temperatures of dogs in the experimental group revealed higher level than those of control group(p<0.01). 6. Arrythmias were observed in both groups but relieved to normal after the yohimbine treatment. 7. Blood chemistry values were not changed significantly by medetomidine and yohimbine treatment. 8. These results showed that yohimbine is an excellent antagonist of medetomidine.

• Journal of Veterinary Clinics
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• v.28 no.3
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• pp.291-296
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• 2011

The aims of the present study were to investigate the anesthetic and hemodynamic effects of medetomidine-ketamine combination and to compare antagonistic effects of atipamezole and yohimbine on the recovery of pig from anesthesia induced by medetomidine-ketamine combination. Landrace and Yorkshire cross-bred pigs were evaluated in the present study. Pigs (n = 8) received three different treatments (one treatment per 14 days in a random order). All pigs were injected intramuscularly with medetomidine, and ketamine in a single syringe. Intravenous injections of atipamezole (MKA), yohimbine (MKY), or a control saline solution (MK) were administered 20 minutes after the medetomidine-ketamine combination injection. The intravenous antagonist injections quickly reversed the medetomidine-ketamine induced sedation in the pigs, resulting in a significantly shorter duration of anesthesia in the MKA and MKY groups compared to the MK group. Mean arterial pressure (MAP) levels were significantly lower in the MKA and MKY groups compared to the MK group. Scores for posture and responses to noxious stimuli after atipamezole and yohimbine administration were significantly lower in the MKA and MKY groups than in the MK. In conclusion, the sedative effects and increases in blood pressure induced by a medetomidine-ketamine combination were quickly and smoothly reversed by atipamezole or yohimbine.

• Biomolecules & Therapeutics
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• v.1 no.2
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• pp.151-159
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• 1993

Effect of yohimbine, a specific antagonist for presynaptic adrenoceptor, on the renal action of clonidine, a specific presynaptic adrenoceptor agonist, was investigated in dog. Clonidine, when given intravenously, produced diuretic action accompanied with augmentation of osmolar and free water clearance (Cosm and 4C_{H_2O}$), and elicited the increase of amounts of sodium and potassium excreted in urine ($E_{Na}\; and\; E_k$). These actions of clonidine were inhibited by yohimbine either injected intravenously or infused into a renal artery. Clonidine, when infused into a renal artery, produced antidiuretic action accompanied with decreased of glomerular filtration rate (GFR) and renal plasma flow (RPF), and exhibited the reduced amounts of sodium and potassium in urine. These actions of clonidine injected into a renal artery were blocked by yohimbine administered either into vein or into a renal artery. Above results suggest that yohimbine block the renal action of clonidine only in central system, do not in kidney.

• Korean Journal of Veterinary Research
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• v.30 no.1
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• pp.113-121
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• 1990

The present study was undertaken to determine the effect of xylazine-pentobarbital anesthesia on the gastroduodenal transit time of barium sulfate and whether this condition can be antagonized by yohimbine, 4-aminopyridine and yohimbine+4-aminopyridine in dogs. Xylazine-pentobarbital anesthesia prolonged the gastroduodenal transit time to $121.50{\pm}21.25$ minutes compared with $5.25{\pm}0.90$ minutes of control. Yohimbine and yohimbine+4-aminopyridine reversed $121.50{\pm}21.25$ minutes of transit time of anesthetized dog to $25.25{\pm}6.83$ and $63.25{\pm}15.69$ minutes, respectively. 4-aminopyridine alone, $115.75{\pm}$18.35 minutes, was not effective in reversing the xylazine-pentobarbital-induced prolongation of gastroduodenal transit time. Yohimbine was the most effective for reversal of xylazine-pentobarbital-induced prolongation of gastroduodenal transit time in dogs.

• Journal of Veterinary Clinics
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• v.6 no.1
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• pp.199-208
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• 1989

This study was carried out to Investigate the effects of detomidine and xylazine on physical sign, electrocardiogram, blood pressure, acid-base status and the antagonistic effect of yohimbine on detomidine in goats. Yohimbine was administered 10 minutes after detomidine injection. Maintenance time of sedation was remarkably decreased in yohimbine-treated group(59.5${\pm}$3.8min). compared with detomidine-treated group(99.8 ${\pm}$ 14.7min). Body temperature was slightly decreased, heart rate was markedly decreased in all experimental groups and respiratory rate increased in detomidine-treated group and decreased in zylazine-treated group. However they were recovered rapidly after yohimbine administration In electrocardiogram, there were no significant changes except T waves and RR intervals. T waves showed negative form and RR intervals were increased but they were recovered rapidly in yohimbine-treated group compared with detomidine-treated group. Blood pressure was decreased after detomidine administration but recovered faster in yohimbine-treated group than in detomidine alone group. Blood pH was increased in detomidine-treated and yohimbine-treated groups but unchanged in xylazine-treatd group. It is considered that the effects of detomidine are similar to those of xylaxine and yohimbine is effective antagonist to detomidine in goats.