Electrical stimulation of the preganglionic cervical sympathetic nerve produced frequency-related contraction of the nictitating membrane (NM) and dilation of the pupil in anesthetized cats. Observations of the effects of alpha-adrenoceptor blockade on these effectors were made simultaneously from the same preparations. All of the alpha1 -adrenoceptor antagonists tested produced a doserelated blockade of the NM with the relative potencies being prazosin > WB-4101 > phentolamine > ...

Inhibition of parasympathetic neural tone to the iris was produced by electrical stimulation of the afferent sciatic nerve, medullary reticular formation, and posterior hypothalamus in anesthetized cats in which only the parasympathetic nerves to the eye were intact. Stimulation of all 3 sites of activation produced a graded pupillary dilation and reduction of tonic nerve activity in the short ciliary nerves. Intravenous administration of the alpha-2-adrenoceptor antagonist, yohimbine ...

The specificity of ethyl 8-fluro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo (1,5-a) (1,4) benzodiazepine-3-carboxylate (RO 15-1788) in reversing the effectiveness of diazepam and des-methylclobazam, but not of pentobarbital, in antagonizing discriminative stimuli produced by pentylenetetrazol is described. Male hooded rats were trained to discriminate pentylenetetrazol-induced interoceptive discriminative-stimuli (IDS) in a two-lever choice paradigm on an FR10 schedule of food reinforcement. ...

The relationship between intraocular pressure (IOP) and arterial blood pressure (BP) was analyzed in response to two pressor agents (norepinephrine and angiotensin II) and two depressor agents (methacholine and isoproterenol) in pentobarbital anesthetized cats. Both IOP and BP were measured manometrically in the same animals. Intravenous norepinephrine and angiotensin II produced dose-dependent increases, whereas intravenous methacholine and isoproterenol produced dose-dependent ...

Pupillary dilation and nictitating membrane (NM) contraction were elicited by pharmacological activation of alpha-adrenoceptors in vivo in anesthetized cats. A constant intravenous infusion of the alpha 1-adrenoceptor selective agonist phenylephrine (150 micrograms/min) was administered to produce a near maximal activation of both organs. Steady-state responses were attained about 15 minutes after starting the phenylephrine infusion. Administration of the alpha 1-adrenoceptor selective ...

Summaryalpha-methyl-Dopa (10–100 mg/kg, i.v.) produced a dose-dependent mydriasis in cats anaesthetized with pentobarbital (30 mg/kg, i.p.). The onset was gradual, reaching a maximum plateau in 2–2.5 h. Intracerebroventricular administration of 1 or 3 mg of alpha-methyl Dopa (MD) also produced pupillary dilation with a similar time course. These dosages were without effect when given intravenously. Pretreatment with the alpha2-adrenoceptor antagonist, yohimbine (0.5 mg/kg, i.v.), blocked ...

Pupillary responses to clonidine (3--100 micrograms/kg, i.v.) and epinephrine (1--30 micrograms/kg, i.v.) were observed in anesthetized rats. Clonidine caused a dose-dependent mydriasis which was effectively antagonized by pretreatment with yohimbine (1.5 mg/kg, i.v.). Pretreatment with phentolamine (5 mg/kg, i.v.) was less effective in antagonizing this clonidine-induced mydriasis. Phenoxybenzamine (2 mg/kg, i.v.) was almost without effect. In contrast, both phentolamine and ...

Graded pupillary dilations and nictitating membrane (NM) contractions were elicited in anesthetized cats by electrical stimulation of the preganglionic sympathetic nerve or by i.a. administration of norepinephrine (NE) or phenylephrine into the carotid artery. Pupil and NM responses were measured simultaneously from the same side. Alpha-adrenoceptor antagonists were administered intravenously. All of the alpha 1-adrenoceptor blockers tested produced a dose-related reduction of NM ...

Intra-arterial administration of (+)- and (−)isomers of adrenaline and noradrenaline produced doserelated contraction of the nictitating membrane (NM) and dilation of the pupil in anesthetized cats. The relative potencies were (−)-adrenaline > (+)-adrenaline = (−)-noradrenaline > (+)-noradrenaline. Observations of the effects of α-adrenoceptor antagonists on (−)-noradrenaline activation of these two effectors were made simultaneously. All of the α1-adrenoceptor antagonists tested ...

Electrical or chemical activation of the oculomotor nucleus (ONC) was performed in pentobarbital anesthetized cats to determine the role of parasympathetic nervous input to the eye in modulating intraocular pressure (IOP). In all animals, the vagosympathetic nerve trunks were sectioned bilaterally at the mid-cervical level. Intracranial stimulation of the ONC produced miosis and a bilateral sustained rise in IOP with little or no cardiovascular response. During stimulation, IOP increased ...

Argon laser energy was applied to the trabecular meshwork of pigmented rabbits in an attempt to develop an animal model of 'glaucoma'. Laser energy was varied to determine the optimal level needed to produce sustained ocular hypertension. An initial response of ocular hypertension followed by hypotension was observed in all of the animals tested. Approximately half of the laser-treated rabbits developed a secondary buphthalmus and sustained ocular hypertension. In these animals outflow ...

The short-term effect of argon laser trabeculoplasty (ALT) was studied in a nonhuman primate model. The ALT treatment produced a consistent intraocular pressure elevation in the treated eye for eight hours. A statistically significant indomethacin-resistant increase in aqueous humor protein concentration was also observed. Morphologic observations using light microscopy and scanning and transmission electron microscopy revealed evidence of a fibrinous material covering the trabecular ...

Because of the need to develop ocular hypotensive agents with low incidence of side effects, the dextrorotatory enantiomers of adrenergic agents have prompted some attention. In the present study, the relative potency and efficacy of various adrenergic stereoisomers with respect to their ocular hypotensive and mydriatic effects have been determined after topical administration to conscious rabbits. The relative order of potency was found to be, iris: 1-epinephrine much greater than ...

In pentobarbital anaesthetized cats, intravenous administration of 30 mg/kg, alpha-methyl-DOPA produced mydriasis that reached a maximum plateau in 2–2.5 h. The oculomotor nucleus was perfused with saline using a pushpull cannula system chronically implanted over the nucleus. Perfusate samples were collected and subsequently analyzed by liquid chromatography with electrochemical detection (LC-EC). Alpha-methyl-DOPA administration resulted in a gradual build up of ...