Mydriasis In Mice Research Articles

Role of α₁-adrenoceptor subtypes in pupil dilation studied with gene-targeted mice.

The α₁A-adrenoceptor (α₁A-AR) subtype was suggested to mediate contraction and trophic effects in the iris dilator muscle, and thus its pharmacological blockade may be involved in intraoperative floppy iris syndrome. We tested the hypothesis that the α₁A-AR mediates pupil dilation and trophic effects in the mouse iris. The α₁-AR subtype mRNA expression was quantified in iris tissue by real-time PCR. To assess the role of individual α₁-ARs for mediating pupil dilation, the α₁-AR agonist phenylephrine was topically applied to the ocular surface of mice deficient in one of the three α₁-AR subtypes (α₁A-AR(-/-), α₁B-AR(-/-), α₁D-AR(-/-), respectively) and wild-type controls. Changes in pupil diameter were measured under a microscope in restrained mice. Moreover, iris and iris muscle thickness were determined in cryosections. Messenger RNA for all three α₁-AR subtypes was detected the iris of wild-type mice with a rank order of abundance of α₁A ≥ α₁B > > α₁D. The lack of a single α₁-AR gene did not affect mRNA expression of the remaining two receptor subtypes. Phenylephrine induced pupil dilation in wild-type mice that was reduced in extent and duration in α₁A-AR(-/-) and, less so, in α₁B-AR(-/-) but not in α₁D-AR(-/-) mice. The lack of a single α₁-AR subtype had no effect on iris or iris muscle thickness. The α₁-AR-induced mydriasis in mice is mediated mainly by the α₁A-AR, with a smaller contribution of the α₁B-AR, matching the relative abundance of these subtypes at the mRNA level. The lack of a single α₁-AR subtype does not appear to cause atrophy in the mouse iris.

Pharmacology of (+)-, (+)-and (-)-2:2-diphenyl-3-methyl-4-morpholino-butyrylpyrrolidine.

Abstract (±)-2:2-Diphenyl-3-methyl-4-morpholino-butyrylpyrrolidine (R610) is a more active analgesic agent in mice, rats and guinea pigs than morphine. The analgesic activity is due to the (+)-isomer (R875). The (–)-isomer (R898) is nearly inactive. R610 lowers the body temperature to below control levels in immobilised rats, inhibits the respiration in unnarcotised rats, lowers the blood pressure in unnarcotised rats with experimental renal hypertension, and causes mydriasis in mice. It also augments the action of barbiturates in mice. In all these respects the (+)-isomer is the active compound of the racemic mixture. The (–)-isomer is almost as toxic as the (+)-isomer, which has a broader therapeutic margin than the (±)-form. The dosage-toxicity relation of highly active analgesic agents in mice and rats is irregular especially in the lower dosage range.

Neuromuscular blocking and antimuscarinic activity of a series of bis-atropinium and N-n-alkyl atropinium compounds.

Abstract Measurements of neuromuscular blocking and antimuscarinic activity have been made in a series of bis-atropinium (BA) and N-n-alkyl atropinium (N-AA) compounds. That the second atropinium group contributed to the neuromuscular blocking activity of BA compounds was shown by the relative lack of such activity in the N-AA series of compounds. Peak neuromuscular blocking activity occurred when two atropinium groups were separated by a chain of either 10 or 11 methylene groups. Members of both series of compounds displayed antimuscarinic properties but estimates of activity differed according to whether they were obtained by determination of affinity constants on guinea-pig isolated ileum or production of mydriasis in mice. From measurements of affinity constant on the guinea-pig ileum it is concluded that BA compounds interact with only one muscarinic receptor. However, the high activity of the deca- and undecamethylene BA compounds in producing mydriasis suggest that these compounds possibly interact with two receptors at once.

Anticholinergic activity of antipsychotic drugs in relation to their extrapyramidal effects.

Antipsychotic drugs were evaluated with two indices of anticholinergic activity, mydriasis in mice in vivo and antagonism of carbamylcholine-induced contractions of guinea-pig tracheal strips in vitro. The drugs from most to least potent as oral mydriatic agents were mepazine, clozapine, thioridazine, promazine and chlorpromazine. Trifluoperazine, pimozide and haloperidol were inactive. These results were consistent with the hypothesis that anticholinergic activity of antipsychotic drugs is inversely related to their propensity to produce extrapyramidal effects in man. In vitro results appeared to predict the incidence of extraphyramidal effects less accurately than in vivo results.

Pharmacological studies of 8-OH-DPAT-induced pupillary dilation in anesthetized rats

Serotonin (5-HT) 1A receptor agonists have been reported to produce mydriasis in mice, and miosis in rabbits and humans. However, the underlying mechanisms for this action are unclear. This study was undertaken in an attempt to explore the mechanism by which 5-HT 1A receptors are involved in the modulation of pupillary size in pentobarbital-anesthetized rats. Intravenous administration of the 5-HT 1A receptor agonist, (2 R)-(+)-8-hydroxy-2-(di- n-propylamino)tetralin hydrobromide (8-OH-DPAT; 0.003–3 mg/kg), elicited dose-dependent pupillary dilation, which was not affected by section of the preganglionic cervical sympathetic nerve. 8-OH-DPAT-elicited mydriatic responses were attenuated by the selective 5-HT 1A receptor antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]- N-2-pyridinylcyclohexanecarboxamide maleate (WAY 100635; 0.3–1 mg/kg, i.v.), as well as by the selective α 2-adrenoceptor antagonist, (8 aR,12 aS,13 aS)-5,8,8 a,9,10,11,12,12 a,13,13 a-dechydro-3-methoxy-12-(ethylsulfonyl)-6 H-isoquino[2,1- g][1,6]naphthyridine hydrochloride (RS 79948; 0.3 mg/kg, i.v.), but not by the selective α 1-adrenoceptor antagonist, prazosin (0.3 mg/kg, i.v.). Mydriatic responses elicited by the α 2-adrenoceptor agonist, guanabenz (0.003–0.3 mg/kg, i.v.), were not antagonized by WAY 100635 (0.3–1 mg/kg, i.v.). To determine whether central nervous system (CNS) 5-HT 1A receptors, like α 2-adrenoceptors, are involved in reflex mydriasis, voltage response curves of pupillary dilation were constructed by stimulation of the sciatic nerve in anesthetized rats. WAY 100635 (1 mg/kg, i.v.) did not antagonize the evoked reflex mydriasis, which, however, was blocked by RS 79948 (0.3 mg/kg, i.v.). Taken together, these results suggest that 8-OH-DPAT produces pupillary dilation in anesthetized rats by stimulating CNS 5-HT 1A receptors, which in turn trigger the release of norepinephrine, presumably from the locus coeruleus. The latter reduces parasympathetic neuronal tone to the iris sphincter muscle by stimulation of postsynaptic α 2-adrenoceptors within the Edinger-Westphal nucleus. Unlike α 2-adrenoceptors, 5-HT 1A receptors in the CNS do not mediate reflex mydriasis evoked by sciatic nerve stimulation.

Clonidine-induced hypoactivity and mydriasis in mice are respectively mediated via pre- and postsynaptic α2-adrenoceptors in the brain

Since brain α 2-adrenoceptors occur both pre- and postsynaptically, experiments were carried out to determine the synaptic locations of those receptors mediating clonidine-induced hypoactivity and mydriasis. Intraperitoneal (i.p.) injection of clonidine (1–3000 μg/kg) to mice dose dependently induced these two responses and also decreased brain concentrations of 3-methoxy-4-hydroxyphenylglycol (MHPG). The ED 50 values were: 120 μg/kg for hypoactivity (95% confidence limits 103–140 μg/kg), 54 μg/kg for mydriasis (95% confidence limits 40–74 μg/kg) and 18 μg/kg for MHPG reduction (95% confidence limits 8–36 μg/kg) suggesting that these responses could all be presynaptically mediated. However, methamphetamine which increases noradrenaline turnover was found to dose depedently produce mydriasis, but not hypoactivity, after peripheral (0.1–5 mg/kg i.p.) or central (0.5–10 gmg i.c.v.) injection. The mydriasis produced by methamphetamine (0.5 mg/kg i.p.) was abolished by i.c.v. injection of 1 μg idazoxan or yohimbine, but not 2.5 μg prazosin or pindolol, showing this effect was mediated by central α 2-adrenoceptors. Methamphetamine (1–10 μg i.c.v.) potentiated the mydriasis induced by clonidine (50 μg/kg i.p.) suggesting this was a postsynaptic α 2-adrenoceptor response. By contrast, methamphetamine (1–10 μg i.c.v.) dose dependently reversed clonidine (100 μg/kg i.p.) hypoactivity indicating this response was mediated by presynaptic α 2-adrenoceptors. These hypotheses were confirmed by destruction of noradrenergic neurones using DSP-4 (100 mg/kg i.p. × 2). This treatment prevented the mydriasis response to methamphetamine (0.5 mg/kg i.p.), but not clonidine (100 μg.kg i.p.) and markedly attenuated clonidine (100 μg/kg i.p.) hypoactivity.

Cholinomimetic activities of minaprine.

The cholinomimetic activities of the antidepressant drug minaprine have been investigated, in vitro and in vivo, in rodents. Minaprine, and its metabolite SR 95070B [3-(2-morpholinoethylamino)-4-methyl-6-(2-hydroxyphenyl) pyridazine hydrochloride] selectively displaced [3H]-pirenzepine from its cortical and hippocampal binding sites, and only weakly inhibited the binding of [3H]-N-methylscopolamine in either the rat cerebellum, heart and salivary glands, or the guinea-pig ileum. In mice, none of these drugs induced the typical cholinergic side-effects up to lethal doses. Minaprine and SR 95070B antagonized rotations induced by an intrastriatal injection of pirenzepine in mice, after intraperitoneal and/or oral administration. Minaprine also antagonized atropine-induced mydriasis in mice. Both minaprine and SR 95070B potentiated the tremorigenic effect of oxotremorine without inducing tremor when injected alone. Finally, minaprine and SR 95070B, after parenteral and/or oral injection, antagonized the scopolamine-induced deficit in passive avoidance learning, and enhanced short-term retention in the social memory test, in rats. The muscarinic agonists arecoline, oxotremorine and RS 86 [2-ethyl-8-methyl-2,8 diazaspiro-4,5 decan-1,3 dion hydrobromide], as well as the acetylcholine esterase inhibitors physostigmine and tacrine were active in most of these models. These results indicate that minaprine, and its metabolite SR 95070B, have cholinomimetic activities which could be, at least in part, mediated by their selective affinity for M1 muscarinic receptors. Thus minaprine could represent a potential useful drug for the treatment of senile dementias and cognitive impairments occurring in elderly people.

Hyperglycemia Does Not Modify the Pupillary Effects of [unk] and k Opiate Agonists in Mice

The effects of mu and kappa opiate agonists were assessed on the pupillary size in normoglycemic and hyperglycemic conditions in mice. The mu agonists used were, morphine (10, 30 and 100 mg/kg), fentanyl (50, 100 and 150 micrograms/kg) and sufentanil (5, 10 and 20 micrograms/kg). The highly selective kappa opiate agonists used were, U-50488H and U-69593 (30 mg/kg). Chronic hyperglycemia was induced by streptozotocin injection (200 mg/kg i.p) 7-8 days before the experiment. Acute hyperglycemia was induced by intraperitoneal glucose (5 g/kg i.p) injection at the time of subcutaneous injection of opiates. In the normoglycemic mice, the mu agonists produced significant mydriasis (P less than 0.05), while kappa agonists had no effect on the pupil. However, both acute and chronic hyperglycemic condition did not affect the mydriatic ratio of the mu opiate agonists. These results indicate that mu opiate receptors induce mydriasis in mice and suggest that the hyperglycemia is not the mechanism involved in the opiate induced mydriasis in mice. With the dose of kappa agonists used, the involvement of kappa receptors in the pupillary effects in mice were not clear. These results support the hypothesis that hyperglycemia is not the primary mechanism for the altered sensitivity of opiates in the animal models of diabetes.

Opioid mydriasis: cross-tolerance between morphine and enkephalins.

The occurrence of cross-tolerance between morphine and met-enkephalin, and between morphine and DADL (D-Ala-D-Leu-enkephalin) in causing mydriasis in mice was studied. Morphine-tolerant mice treated with met-enkephalin or DADL intracerebroventricularly (ICV) showed marked reduction of the pupillary effect of the endopioids. Maximal mydriasis in tolerant animals was only about 30% for met-enkephalin and 50% for DADL, compared to levels in nontolerant animals. These results are among the first to demonstrate cross-tolerance between morphine and enkephalins in intact animals and may suggest involvement of multiple opiate receptor systems in producing mydriasis.

Pilocarpine mydriasis in mice.

In several rodent species pilocarpine and oxotremorine produce mydriasis, rather than the miosis which is characteristic of most other species. We have established that pilocarpine is a mydriatic drug in mice, a species in which the action has previously not been described, and that this effect occurs after local ocular, intraperitoneal (IP) or intracerebroventricular (ICV) application. Arecoline produces miosis or mydriasis (depending on dose) following direct ocular application but mild mydriasis after IP or ICV injection. Atropine also produces mydriasis in mice, and the effect of pilocarpine is additive with that produced by atropine and is not antagonized by antihistamines. Direct ICV pilocarpine injection produces mydriasis at doses equivalent to those used systemically. Pilocarpine mydriasis probably results from inhibition of parasympathetic activity.

Isolation of a new toxin, prosurugatoxin, from the toxic Japanese ivory shell, Babylonia japonica.

A new toxin, named prosurugatoxin because it formed surugatoxin on decomposition, was isolated from the toxicated Japanese ivory shell (Babylonia japonica). Prosurugatoxin evoked mydriasis in mice at a minimum effective intraperitoneal dose of 15 ng/g body weight, and inhibited the contractile response of isolated guinea pig ileum induced by 3×10-5g/ml of nicotine at a concentration of 5×10-9g/ml. In this mollusc the prosurugatoxin content was about 5 times that of neosurugatoxin. Prosurugatoxin was deduced on the basis of physical and chemical data to be des-xylopyranosyl-neosurugatoxin.

Some pharmacological effects of tizanidine on smooth muscle organs and α 2-adrenoceptor

1. 1.|Microsomal and crude synaptosomal fractions were prepared from the longitudinal muscle of guinea-pig ileum. 2. 2.|A specific binding of [ 3H]yohimbine (10 nM) to α 2-adrenoceptor in the crude synaptosomal fraction was inhibited by tizanidine and clonidine. Tizanidine is about one-third as potent as clonidine. 3. 3.|A specific binding of [ 3H]QNB (0.3 nM) to muscarine receptor in the microsomal fraction was inhibited by atropine (10 −8−10 −7M) but not by tizanidine (up to 10 −4M). 4. 4.|Tizanidine inhibited spontaneous movements of guinea pig ileum and rat stomach ( in situ) and intestinal transit in mice, and induced mydriasis in mice. 5. 5.|These effects induced by tizanidine might be due to activation of α 2-adrenoceptor but not to atropine like action.

Central and peripheral components of morphine mydriasis in mice

Mice treated with morphine (intracerebroventricularly, retrobulbarly or intraperitoneally) demonstrated dose related bilateral mydriasis. Intracerebroventricular (ICV) injection was much more potent than either retrobulbar (RB) or intraperitoneal (IP) injections. Morphine applied topically onto one eye resulted in bilateral mydriasis which was more marked in the treated eye. The mydriatic effect was antagonized by naloxone administered either IP or ICV or given on one eye. Here again, ICV naloxone was most effective. Naloxone eye drops diminished the mydriasis produced by systemic morphine bilaterally but more in the treated eye. These results suggest that in mice the mydriasis produced by morphine is mainly of central origin, but a local ocular effect also occurs.

Antagonism of opiate mydriasis in mice.

1 Morphine-induced mydriasis in mice is antagonized by nalorphine, levallorphan and naloxone in a dose-dependent manner. 2 The relative potency of the three agents is 10:56: 134 respectively, thus being in accordance with other tests of narcotic antagonism. Naloxone has the shortest duration of action. 3 When injected into naive animals, nalorphine (but not levallorphan or naloxone) produces a slight mydriasis. 4 Measurement of the diameter of the pupil in mice seems to be a precise, simple and rapid test for studying narcotic antagonist as well as agonist action and has several advantages over standard methods used for this purpose.

Humoral endorphin: A new endogenous factor with opiate-like activity

Humoral (H) endorphin, a novel endogenous opioid ligand detected in brain, blood and cerebrospinal fluid was tested in a series of opiate sensitive assays. H-endorphin displaced radiolabeled enkephalin from its specific bindings sites and inhibited the electrically evoked contraction of the guinea pig ileum and mouse vas deferens. When injected to unanesthesized animals, humoral endorphin induced analgesia in rats and mydriasis in mice. The activity of H-endorphin both in vitro and in vivo attests to its opioid nature. However, while its antinociceptive effect was blocked by naloxone, mydriasis induced by H-endorphin was resistant to the effect of the opiate antagonist. Similarly, intermediate concentrations of naloxone inhibited the effect of H-endorphin on the guinea pig ileum while its effect on the mouse vas deferens was completely refractory to naloxone. The physiological function of humoral endorphin in various naturally occuring states that show similar paradoxical interactions with naloxone is discussed.

Enkephalin mydriasis in mice

Morphine is known to produce mydriasis in mice. We have found that enkephalins caused a similar effect. Morphine was twice as active as D-Ala-D-Leu-enkephalin (BW-180C), 5 times as active as Met-enkephalin and 7 times as active as Leu-enkephalin. The time course of the effect was shortest for the enkephalins ( t 1 2 = 8–12 min ), intermediate for BW-180C (60 min) and longest for morphine (80 min). Naloxone antagonised the effect of all agents to a similar extent. The question whether enkephalins are involved in the physiological regulation of pupillary diameter was investigated by administering either naloxone or D-phenylalanine to mice. None of these agents changed pupillary size, thus making such an involvement unlikely.

Monoamine oxidase inhibition by substituted benzylideneamino guanidines and their CNS activities.

The present study reports the synthesis and characterization of eight new substituted benzylideneamino guanidines. All compounds inhibited the monoamine oxidase (MAO) activity of rat brain mitochondria in vitro. The I50 values were determined and were found to be in the range of 10(-4) to 10(-5) mol/l. Preincubation, dialysis and kinetic studies carried out with isolated brain mitochondria by conventional Dixon plot revealed reversible and noncompetitive type of MAO inhibition. These compounds were also screened for anticonvulsant and antidepressant activities. In the present series of compounds only one compound -- 1-amino-3-(4-chloromethylbenzylidene-amino)guanidine hydroiodide -- was found to afford 20% protection against pentetrazol-induced seizures in mice. 1-Amino-3-(3,4-dichlorobenzylideneamino)guanidine hydroiodide which produced maximum inhibition of MAO activity, also produced reversal of reserpine-induced sedation and miosis into excitation and mydriasis in mice.

Central and peripheral actions of anticholinergic drugs when administered with triflupromazine

Triflupromazine was found to potentiate the actions of six anticholinergic drugs in producing elevation of EEG arousal thresholds, and dissociation between EEG and behavioural arousal thresholds, in cat encéphale isolé preparations. The effects of triflupromazine on the anticholinergic activity of the six drugs were studied using as tests antagonism of oxotremorine-induced salivation and tremors and production of mydriasis in mice. It is concluded that the potentiating effect of triflupromazine on the EEG cannot be explained on the basis of an addition of anticholinergic activities and that other, as yet not understood, synergistic mechanisms are involved.

バイの毒の精製

1. The ivory shell toxin was purified by using gel filtration with Sephadex G-25 and silica gel column chromatography. The purified specimen evoked a minimum mydriasis in mice at a dose of about 0.02 μg/g body weight. 2. The purified toxin was only positive in the ferric chloride reaction, although many qualitative tests were carried out. It was thought to be a polyfunctional, highly oxygenated, complex bromo compound having a relatively low molecular weight. 3. The purified toxin evoked the similar symptoms in a cat as did the raw mid-gut gland.

The peripheral and central actions of some anticholinergic substances.

The peripheral and central anticholinergic potencies of six glycollic acid esters were measured and compared with similar results for atropine and hyoscine. There was no correlation between estimates of in vivo peripheral anticholinergic activity as measured by production of mydriasis in mice and by antagonism of oxotremorine-induced salivation in mice. The reason for this lack of correlation is not apparent. A significant correlation was demonstrated between estimates of central activity obtained by measuring antagonism of oxotremorine-induced tremors in mice and elevation of the EEG arousal threshold in cat encéphale isolé preparations. It is concluded that blockade of central cholinergic synapses was responsible for both effects and there is some discussion of the significance of the system involved in EEG arousal. The relationship between chemical structure of the drugs and their pharmacological activity is also discussed.