Reversal of clonidine induced miosis by the alpha 2‐adrenoreceptor antagonist RX 781094.

Clifford, J. M.; Day,; Orwin, JM

doi:10.1111/j.1365-2125.1982.tb04941.x

Cited by 35 publications

(17 citation statements)

References 4 publications

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“…However, a miotic effect of clonidine has been described when pupil diameter is measured in an illuminated environment (Clifford et al 1982(Clifford et al , 1989Fanciullacci et al 1988;Bitsios et al 1996Bitsios et al , 1998. On the other hand, yohimbine increased resting pupil diameter, both in the present study and the earlier experiment of Morley et al (1991).…”

Section: Discussioncontrasting

confidence: 47%

Comparison of the effects of clonidine and yohimbine on spontaneous pupillary fluctuations in healthy human volunteers

2000

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Section: Discussioncontrasting

confidence: 47%

Comparison of the effects of clonidine and yohimbine on spontaneous pupillary fluctuations in healthy human volunteers

2000

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“…Although a quantitative relationship between the level of illumination and the size of the miotic response to clonidine has not been demonstrated previously, the present results are in good qualitative agreement with previous reports in the literature. Firstly, the effect of clonidine on the pupil in the dark has been reported to be either nonobservable [6], or very small [4], and most reports of a miotic effect of clonidine are based on experiments conducted in an illuminated room [1–3]. Secondly, it has been reported that the size of the miotic response to clonidine in the same group of subjects is larger when the measurement is carried out under illumination rather than in the dark [4].…”

Section: Discussionmentioning

confidence: 99%

“…In humans the systemic administration of the α 2 ‐adrenoceptor agonist clonidine evokes a miotic response [1–5], whilst administration of the α 2 ‐adrenoceptor antagonist yohimbine evokes mydriasis [6]. Furthermore, the clonidine‐evoked miosis is susceptible to antagonism by α 2 ‐adrenoceptor antagonists [1, 3]. In a recent study Bitsios et al.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the effects of clonidine and yohimbine on pupillary diameter at different illumination levels

Phillips¹,

Szabadi²,

Bradshaw³

2000

Brit J Clinical Pharma

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Aims To evaluate the pupillary effects of single doses of the a 2 -adrenoceptor agonist clonidine and the a 2 -adrenoceptor antagonist yohimbine under several illumination conditions. Methods Sixteen healthy male volunteers received clonidine 0.2 mg, yohimbine 22 mg, clonidine 0.2 mg+ yohimbine 22 mg in a double-blind placebo-controlled, cross-over study. 2 h post drug ingestion pupil diameter was recorded in darkness, and at luminance levels of 6 Cd m x2 , 91 Cd m x2 and 360 Cd m x2 . The effects of the active treatments on pupil diameter were also expressed as the differences from the placebo condition (`placebo-corrected' data; mean [95% CI]). Results Clonidine had little effect on pupil diameter in darkness; however, it caused a signi®cant, light-dependent, miosis when the eye was illuminated. On the other hand yohimbine increased pupil size; this increase was signi®cant at 91 and 360 Cd m x2 . There were no signi®cant differences between the effects of the combined treatment (clonidine 0.2 mg+ yohimbine 22 mg) and the effect of placebo. Conclusions The pupillary effects of clonidine and yohimbine are likely to re¯ect the interaction of these drugs with inhibitory a 2 -adrenoceptors located on central noradrenergic neurones, which in turn would lead to a decrease and an increase, respectively, in sympathetic out¯ow to the iris. The light dependence of the pupillary effects of these drugs, however, suggests that the parasympathetic light re¯ex pathway is also involved, which is known to be under inhibitory control from the central noradrenergic neurones. Modulation of parasympathetic out¯ow seems to play an important role since both drugs had relatively little effect on pupil diameter in darkness when sympathetic activity predominates.

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“…In human, there is reduction in gastrointestinal motility, sedation, inhibition of the micturition reflex, and miosis (Clifford et al, 1982). In rodent, some of them are the same reaction, but some are different from human.…”

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confidence: 99%

Chronopharmacology of Analgesic Effect and Its Tolerance Induced by Morphine in Mice

Yoshida

Ohdo²,

Takane

et al. 2003

J Pharmacol Exp Ther

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The influence of morphine dosing time on analgesic effect after acute or chronic treatment, recovery of analgesic effect after once developed tolerance, and their pharmacological mechanisms were investigated in ICR male mice under a 12-h light/ dark cycle (light on from 7:00 AM to 7:00 PM). There was a significant 24-h rhythm in the latency of thermal response at 30 min after morphine injection. The analgesic effect was significantly greater at the dark phase than at the light phase. The rhythmic pattern resembled overall the rhythm occurring in the latency of thermal response under nondrugged state. The absolute value of morphine analgesic effect (the real time spent on the hot-plate) on days 1 and 2 after morphine daily injection was significantly larger after morphine injection at 9:00 PM than after saline injection at 9:00 PM or after morphine injection at 9:00 AM. The recovery from tolerance of analgesic effect was significantly faster at the dark phase than at the light phase. The time-dependent difference in the analgesic effect after chronic treatment or recovery from tolerance is closely related to that in the expression of -opioid receptor. The present study suggests that 24-h rhythm of morphine analgesic effect is consistent with 24-h rhythm of -opioid receptor expression.A large number of physiological rhythms are controlled by the central nervous system, hormone secretion, and so on (Thomson et al., 1980;Naber et al., 1981). Also, many drugs vary in potency and/or toxicity according to the time in the 24-h cycle when they have been administered (Walker and

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Reversal of clonidine induced miosis by the alpha 2‐adrenoreceptor antagonist RX 781094.

Cited by 35 publications

References 4 publications

Comparison of the effects of clonidine and yohimbine on spontaneous pupillary fluctuations in healthy human volunteers

Comparison of the effects of clonidine and yohimbine on spontaneous pupillary fluctuations in healthy human volunteers

Comparison of the effects of clonidine and yohimbine on pupillary diameter at different illumination levels

Chronopharmacology of Analgesic Effect and Its Tolerance Induced by Morphine in Mice

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