Synthesis, ocular effects, and nitric oxide donation of imidazole amidoximes.

Novel 1-R-imidazole-5-amidoximes and 1-R-5-cyano-imidazole-4-amidoximes (R: H, Me, Bn) were prepared from their corresponding nitriles and were tested for their efficacy to lower intraocular pressure (IOP) in rabbits. The ability of these compounds to donate nitric oxide (NO) was studied by observing the stimulation of formation of cyclic guanosine-3',5'-monophosphate (cGMP) in the incubation of porcine iris-ciliary body. In the incubation experiments, 1-methylimidazole-5-amidoxime and 1(H)-imidazole-4(5)-amidoxime stimulated formation of cGMP indicating NO donating ability of these compounds. 1-Methylimidazole-5-amidoxime lowered IOP significantly after intravitreal injection.

Destruction of the epithelial anchoring system in lichen planus.

To find out whether the epithelial anchoring system shows any alterations in lichen planus, we examined the distribution of type VII collagen, alpha 6 beta 4 integrin, and kalinin in lesions of lichen planus. These molecules were chosen because they are structural components of anchoring fibrils, hemidesmosome-associated complexes, and anchoring filaments. The localization of type VII collagen in lichen planus was strikingly different from that in nonaffected mucosa or dermis or in other mucocutaneous lesions. In the normal mucosa, type VII collagen was localized only at the basement membrane zone. In lichen planus, type VII collagen was present not only in the basement membrane area but also in streaked patterns deep in the connective tissue. The hemidesmosome-associated complex, alpha 6 beta 4 integrin, was localized at the basal aspect of basal epithelial cells of nonaffected sites, but was diffuse and discontinuous in lichen planus lesions. Most of the basal keratinocytes, however, stained for this integrin. Kalinin staining was discontinuous in lichen planus lesions. Often, finger-like projections of kalinin staining were found protruding into the connective tissue stroma. Kalinin was localized at the basement membrane zone of the nonaffected tissue and other mucocutaneous lesions. These results indicate that in cutaneous and mucosal lichen planus, the epithelial anchoring system is disturbed.

Immunohistochemical localization of proteoglycans in human periodontium.

Proteoglycans (PGs) are extracellular and cell surface-associated macromolecules that regulate cell adhesion, cell growth, matrix formation, and bind growth factors. In this work we studied the distribution of core proteins of four PGs (decorin, biglycan, a large molecular weight PG, and CD44) in human gingiva and periodontal ligament by immunohistochemical staining of frozen tissue sections with specific antibodies. Decorin, a major PG of this tissue, was localized on collagen fiber bundles in the gingival and periodontal connective tissues. Staining for decorin was most intense at the subepithelial region. Biglycan was a minor PG component of the human periodontium, showing some accumulation in connective tissue under the oral epithelium. At the immunohistochemical level, biglycan appeared to form fine filament-like structures on extracellular matrix fibers. Localization of large molecular weight PG differed from that of decorin and biglycan. It was concentrated in deep connective tissue areas of the gingiva and in the periodontal ligament, and was only weakly present at the subepithelial region. CD44 was mainly concentrated in cell-cell contact areas of basal and spinous layers of oral epithelium. In the connective tissue of gingiva and periodontal ligament, CD44 was localized on fibroblast cell surfaces. Connective tissue area under the junctional epithelium contained relatively small amounts of PGs. The results indicate that different parts of human periodontium contain a typical variety of PGs, suggesting a specific function for each PG species in the location at which they accumulate.

Expression of proteoglycans and hyaluronan during wound healing.

We investigated the expression of proteoglycans (PGs) and hyaluronan (HA) during healing of human mucosal wounds. Biopsy specimens of experimental wounds were taken 1, 3, and 7 days after wounding. Frozen sections were used for immunolocalization of CD44, syndecan-1, basement membrane-associated heparan sulfate proteoglycan (BM-HSPG), decorin, and biglycan. HA was localized in paraffin sections with a specific HA-binding probe. Epithelium showed first signs of migration on Day 1, more progressive migration on Day 3, and epithelial sheets confronted on Day 7. CD44 surrounded migrating keratinocytes at all stages of wound healing. In epithelium, CD44 and HA remarkably localized to the same region. Expression of syndecan-1 was switched from the suprabasal cell layer of unwounded epithelium to the basal cell layer of the migrating wound epithelium. BM-HSPG was absent under migrating keratinocytes. It started to reappear at the basement membrane zone on Day 7. The area under the wound epithelium containing newly synthesized collagen fibers first became positive for decorin on Day 7, whereas staining of biglycan was negative. Granulation tissue was also strongly positive for CD44 and hyaluronan. Our results indicate that migrating keratinocytes express both CD44 and syndecan-1 but not BM-HSPG. During differentiation of keratinocytes, expression of CD44 preceded that of syndecan-1. The results suggest that different HSPGs have multiple functions in keratinocyte migration and differentiation during reepithelialization.

Effects of calcitonin gene-related peptide in the eye. A study in rabbits and cats.

Calcitonin gene-related peptide (CGRP) has recently been demonstrated in sensory neurons of the eye. The purpose of the present study was to determine the effects of exogenous CGRP in the rabbit and cat eye. CGRP was injected intracamerally and the intraocular pressure was measured in cannulated eyes. The pupil diameter and the aqueous humor protein concentration were also measured. Indomethacin was used to prevent prostaglandin synthesis and tetrodotoxin (TTX) to block nerve conductance. In the rabbit eye, CGRP caused iridial hyperemia, a breakdown of the blood-aqueous barrier and increased intraocular pressure. These responses were dose-related. The increase in IOP as well as the breakdown of the blood-aqueous barrier could not be blocked with TTX or indomethacin. In cats CGRP caused a decrease in IOP and had only slight effect on the aqueous humor protein concentration. Neither in rabbits nor in cats had CGRP any detectable effect on the pupil size. Intracameral injection of 0.1 microgram (7.4 x 10(-11) moles) substance P together with 0.1 microgram (2.6 x 10(-11) moles) CGRP in rabbits caused maximal miosis but did not potentiate the intraocular effects of CGRP only. These results indicate that CGRP has marked vascular effects in the rabbit eye, causing a breakdown of the blood-aqueous barrier and increased IOP. The mechanism of this phenomenon does not involve prostaglandins neither nerve conduction, implying most likely a direct effect on the vascular smooth muscle. The mechanism of the decrease of IOP in cats remains unknown.

Effect of photorefractive keratectomy on the accuracy of pneumatonometer readings in rabbits.

PURPOSE: To determine whether measurement of intraocular pressure (IOP) using a pneumatonometer is reliable after myopic 5 or 15 D excimer laser photoablation in rabbits. METHODS: Ten rabbits underwent 5 D myopic photorefractive keratectomy (PRK) of the left eye. Another seven rabbits underwent 15 D PRK: The right eye served as a control. The diameter of each PRK was 5 mm. Rabbits were examined 2.5 to 3 months later under general anesthesia. Eyes were cannulated, and the IOP was maintained at 5 to 40 mm Hg and measured using an intracameral manometer and a pneumatonometer at each pressure level; approximately 50 pressure points were formed. Readings of the two techniques were compared. RESULTS: Linear regression analysis comparing manometric and pneumatonometric readings revealed the following data in eyes with 5 D corrections (n = 10): correlation coefficient (r) = 0.926, slope = 1.058, and intercept = -3.133. The values of the unoperated control eyes were: r = 0.900, slope = 0.962, and intercept = -1.010. The following results were obtained in eyes with 15 D photoablation (n = 7): r = 0.876, slope 1.133, and intercept -3.147. Values for the control eye were: r = 0.885, slope = 1.175, and intercept = -3.497. When the manometer and pneumatonometer readings of all animals were compared, the adjusted squared correlation coefficient was 79%. When the variabilities associated with the animals and the PRK procedure (pooled 5 and 15 D corrections) were taken into account, adjusted squared correlation coefficient increased from 8% to 87%. CONCLUSIONS: Photorefractive keratectomy as high as 15 D/5 mm had only a minor effect on pneumatonometer readings in rabbits, indicating that the elastic properties of the cornea related to the accuracy of pneumatonometry were not significantly altered. Postoperative IOP monitoring with tonometers, based on flattening of the cornea under pressure, is accurate after PRK.

Inhibitory effect of methysergide on calcitonin gene-related peptide-induced vasodilatation and ocular irritative changes in the rabbit.

1. Calcitonin gene-related peptide (CGRP) is involved in ocular neurogenic inflammation in the rabbit, causing vasodilatation in the anterior uvea, breakdown of the blood-aqueous barrier, increase in the intraocular pressure (IOP) and rise in the adenosine 3':5'-cyclic monophosphate (cyclic AMP) content in the aqueous humour. So far there is no means of preventing these CGRP-induced ocular effects. 2. In the present study, the effect of intravenous methysergide (1-10 mg kg-1, b.w.) on CGRP-induced changes in the IOP, blood-aqueous barrier and cyclic AMP content in the aqueous humour was studied in vivo. The effect of methysergide on CGRP-induced vasodilatation both in vivo and in vitro was also investigated. 3. Methysergide decreased intraocular pressure but had only a transient effect on blood pressure. Methysergide decreased the regional blood flow in ocular tissues by 53-65%, but did not have such a vasoconstrictor effect in most extra-ocular tissues studied. 4. Methysergide inhibited CGRP-induced vasodilatation, increase in the IOP, breakdown of the blood-aqueous barrier and increase in the cyclic AMP content in the aqueous humour in vivo. 5. In vitro, methysergide alone did not have effects on the vascular tone in isolated ophthalmic artery of rabbit. However, it potentiated noradrenaline (NA)-induced contraction. There were no differences in the IC50 values for CGRP on the NA-induced contraction in the presence and absence of methysergide, indicating that methysergide has no direct effect on the vasorelaxant effect of CGRP in vitro. 6. The present study demonstrates that in the rabbit eye methysergide inhibits CGRP-induced changes.One inhibitory mechanism of methysergide may be to enhance the effect of a vasoconstrictor (NA) to antagonize the vasodilator effect of CGRP. The present findings suggest that a methysergide-sensitive mechanism may be used to limit some pathophysiological conditions in the eye that involve neurogenic inflammation and the release of CGRP.

Calcitonin gene-related peptide in the eye: release by sensory nerve stimulation and effects associated with neurogenic inflammation.

Calcitonin gene-related peptide (CGRP) in the anterior uvea coexists with tachykinins (substance P and neurokinin A) in sensory nerve fibers deriving from the trigeminal ganglion. Mechanical or electrical stimulation of the intracranial part of the trigeminal nerve/ganglion in rabbits produced a marked hyperemia in the anterior segment of the eye, increased intraocular pressure, breakdown of the blood-aqueous barrier and miosis. Simultaneously, CGRP-like immunoreactivity was released into the aqueous humor. This suggests that the highly vasoactive CGRP can be released from sensory nerve fibers to participate in vascular responses. Unlike the tachykinins, CGRP per se was without effect on the pupillary diameter while disrupting the blood-aqueous barrier (resulting in aqueous flare) upon intravitreal injection. In addition, CGRP enhanced the aqueous flare evoked by a minimal eye trauma (infrared irradiation of the iris). The miosis evoked by the intravitreal injection of substance P was more pronounced when CGRP was injected simultaneously, and finally, substance P induced aqueous flare much more effectively when given together with a threshold dose of CGRP.

Expression of heparan sulphate and small dermatan/chondroitin sulphate proteoglycans in chronically inflamed human periodontium.

Proteoglycans (PGs) function in regulating aspects of cell behavior, such as proliferation, adhesion, and migration. In this report, we investigated the localization of three heparan sulphate PGs (basement membrane [BM] heparan sulphate PG, CD44, and syndecan-1) and two small dermatan/chondroitin sulphate PGs (decorin and biglycan) in chronically inflamed human periodontium. Frozen sections were analyzed by immunofluorescence microscopy. In inflamed tissue, BM heparan sulphate PG showed reduced immunostaining in subepithelial and subendothelial basement membrane. Loss of CD44 and syndecan-1 was common in epithelial cells of inflamed periodontal tissue. Suprabasal keratinocytes of epithelium expressed involucrin, a cornified envelope protein and marker for epithelial differentiation, while the expression of syndecan-1 was weak or absent. In contrast, expression of the mesenchymal variant of CD44 and syndecan-1 was strong in infiltrating lymphocytes. Small dermatan/chondroitin sulphate PGs, decorin and biglycan, were also present in markedly reduced amounts in the periodontal connective tissue in chronic inflammation. In addition, decorin localized in the connective tissue along short rod-like structures. The results suggest that proteoglycan-dependent intercellular adhesion of keratinocytes is decreased and that adhesion of lymphocytes to matrix molecules via cell surface PGs increased in chronic inflammation. Disappearance of adhesion-modulating small dermatan/chondroitin sulphate PGs may further regulate cell migration in inflamed periodontium.

Localization of calcitonin gene-related peptide binding sites in the eye of different species.

The localization of calcitonin gene-related peptide (CGRP) binding sites in the eye of monkey, pig, cat and guinea pig was studied by autoradiography. Specific binding of CGRP was found in ciliary muscle, ciliary processes and limbal conjunctiva in all tested species. Furthermore, specific binding sites of CGRP was found in the choroidea of monkey, pig and guinea pig, in the iris of pig, cat and guinea pig, in the retina of pig and in the anterior chamber angle of cat. The number of specific binding sites varied depending on the tissue and species. The present study shows that there are specific binding sites of CGRP in the eye of monkey, pig, cat and guinea pig. CGRP binding sites found in vascular system of ciliary body, choroidea and iris further demonstrates the role of CGRP as a vasoregulatory peptide. Binding sites in the ciliary muscle, in the limbal conjunctiva and in the chamber angle area may indicate a role in the regulation of ciliary muscle tone, epithelial cell regeneration and aqueous humour outflow.

Ocular irritative response to YAG laser capsulotomy in rabbits: release of calcitonin gene-related peptide and effects of methysergide.

The Neodymium (Nd):YAG laser is commonly used in ophthalmology mainly for the posterior capsulotomy in patients with secondary cataract after extracapsular cataract extraction. A frequent side-effect following different kinds of YAG laser treatments is an acute increase in the intraocular pressure (IOP). The present study addresses the role of calcitonin gene-related peptide (CGRP) in the ocular irritative response following YAG laser anterior capsulotomy in rabbits. The YAG laser anterior capsulotomy caused an irritative response in the eye, which consisted of an increase in the IOP, miosis and breakdown of the blood-aqueous barrier. Following YAG laser capsulotomy, CGRP-immunoreactivity was found in the aqueous humour in different molecular weight forms as revealed by gel-permeation chromatography. One of the peaks coeluted with synthetic human CGRP. Methysergide attenuated the increase in the IOP and disruption of the blood-aqueous barrier, but not the miosis, following YAG laser anterior capsulotomy. The present study demonstrates the release of CGRP into the aqueous humour following YAG laser capsulotomy, and suggests that CGRP is partly causing the increase in IOP and disruption of the blood-aqueous barrier in this irritative response.

Prevention of high risk corneal graft rejection using cyclosporine A (CsA) incorporated into a collagen matrix.

The aim of this work was to compare the efficacy of cyclosporine (CsA) collagen shields and fragments in suppressing experimental allograft rejection in an animal model for high risk keratoplasty. Altogether 23 experimental animals were treated either with plain collagen shields, oral cyclosporine, collagen CsA shields, or with CsA collagen fragments after corneal transplantation (PKP) in previously vascularized corneas. The study medications were started immediately following PKP. For these animals slit lamp examinations were performed twice a week for the duration of the experiment and the signs of corneal rejection were observed. The animals were followed until an irreversible rejection or until the end of the experiment (14-149 days). The inflammation of the graft was also evaluated histologically when animals were sacrificed. The grafts treated with plain collagen shields all were rejected within 36 days, and the mean graft survival time for these corneas was 25 days. Five transplants that were treated with oral CsA had better survival, and two of five grafts stayed clear until postoperative day 119, when the treatment was stopped. The best graft survival was seen in grafts treated with CsA collagen fragments and all these stayed clear up to 77 days postoperatively. The treatment of the grafts with CsA collagen shields was almost as effective as with CsA fragments, and first signs of rejection appeared as late as nine weeks postoperatively in two of seven grafts. The other of these rejected corneas were later treated with CsA collagen fragments and showed a dramatic improvement in transparency of the cornea and disappearance of inflammation of the graft. The discontinuation of study medication caused an irreversible rejection to appear in a previously clear graft that had been treated successfully with any study medication. We conclude that topical CsA in shields or in fragments will provide a significant advance over systemic CsA alone, and that CsA fragments appear to be as effective as shields in preventing corneal allograft rejection.

Effect of captopril on ocular irritative response to topical neutral formaldehyde and YAG-laser capsulotomy in the rabbit.

Angiotensin converting enzyme (ACE) -inhibitors inhibit degradation of inflammatory mediators substance P (SP) and bradykinin, which may further stimulate the synthesis of prostaglandins. The resulting increase in inflammatory mediators in tissues is suggested to be the reason for the dry cough, involving sensory C-fiber activation, among patients receiving ACE-inhibitor therapy. In the present study, the effect of an ACE-inhibitor, captopril, on ocular irritative responses was studied in the rabbit. Intravenous captopril decreased markedly the blood pressure and the intraocular pressure (IOP) modestly. Topical neutral formaldehyde elicits an irritative response in the eye mediated through sensory neuropeptides SP and calcitonin gene-related peptide (CGRP). Following topical neutral formaldehyde, the increase in IOP and breakdown of the blood-aqueous barrier were inhibited by captopril, while miosis was not affected. Cyclic AMP (cAMP) content in the aqueous humour was increased by captopril, and this increase was inhibited by indomethacin. Following YAG-laser anterior capsulotomy, captopril inhibited the increase in IOP, breakdown of the blood-aqueous barrier and miosis. The present study demonstrates that use of short-term administration of captopril prior to sensory nerve stimulation or YAG laser anterior capsulotomy does not enhance the ocular responses to these stimuli in the rabbit. In the present study, captopril inhibited these responses, at least partly by decreasing the blood pressure.

Binding of CGRP analogs and their effect on adenylate cyclase activity in porcine iris-ciliary body.

The structure-activity relationship of the calcitonin gene-related peptide (CGRP) in the porcine iris-ciliary body was studied using different CGRP analogs. The receptor binding affinity is located mainly in the carboxyterminal end of the CGRP peptide while the ability to stimulate adenylate cyclase (AC) enzyme is mainly in the aminoterminal end of the peptide. The binding of CGRP analogs was also found to be temperature-dependent. Changes in the alpha-helical region or in the beta-turn, as well as replacements of threonine-4, asparagine-25 or asparagine-26, reduce the binding affinity already at +4 degrees C. Truncated aminoterminus, changes in the loop region between cysteines 2 and 7, and especially in threonine 6, have for their part an important role in maintaining AC-stimulating activity.

Is there a relationship between blood pressure and intraocular pressure? An experimental study in hypertensive rats.

PURPOSE: Evaluation of relation between blood pressure (BP) and intraocular pressure (IOP) in two hypertensive rat strains: spontaneously hypertensive rats (SHR) and double transgenic (dTGR) (harboring human renin and angiotensinogen genes) rats, and in their normotensive control Wistar Kyoto and Sprague Dawley rats, respectively. METHODS: Each rat strain was divided into medicated and non-medicated groups. Medicated rats were treated orally with an angiotensin II receptor type 1 blocker. IOP was measured using a specific rebound tonometer and BP by a tail-cuff method. Both parameters were determined in conscious animals every second week. For comparison, at the end of the study, IOP was measured in conscious and anesthetized rats. RESULTS: The baseline IOP was higher in hypertensive rats vs their normotensive controls. Eight weeks of treatment with an angiotensin type 1 receptor blocker did not prevent a slight increase in IOP, although it abolished the development of hypertension in SHR. The markedly elevated IOP was reduced in medicated and non-medicated dTGR animals during the short follow-up period. General anesthesia reduced IOP significantly. CONCLUSION: The results suggest a positive relation between BP and IOP in hypertensive rats.

Effects of calcitonin gene-related peptide and substance P on regional blood flow in the cat eye.

The effects of calcitonin gene-related peptide (CGRP) and substance P (SP) on the regional blood flow of the eye were studied in cats. The animals were anaesthetized and the eyes were cannulated for intracameral administration of the test substances and intraocular pressure measurement. Regional blood flow was determined using the radioactively labelled microsphere method. Intracameral injection of 1.3 x 10(-9) mol of CGRP increased markedly the blood flow of the iris, the ciliary body, and the sclera. There was no clear-cut effect in the choroid or in the retina. Intracameral administration of 1.3 x 10(-9) mol of SP had no clear-cut effect on the blood flow of any of the ocular tissues studied. In addition, CGRP reduced the intraocular pressure statistically significantly, whereas SP had no effect. The results of the present study indicate that CGRP is a potent vasodilator in the anterior uvea of the cat eye when administered from the adventitial side, whereas SP seems to have little or no effect.

Characterization of the mechanism of acute ocular irritation to YAG laser capsulotomy in rabbits: effects of substance P antagonists, Met-enkephalin, tetracaine and tetrodotoxin.

This study was undertaken to characterize the mechanism of ocular irritation to YAG laser capsulotomy in rabbits. The blocking agents were administered intravitreally. (D-Arg1,D-Pro2,D-Trp7,9)-SP, a substance P antagonist, tended to reduce miosis but had no effect on intraocular pressure (IOP). It had less effect on miosis than (D-Arg1,D-Pro2,D-Trp7,9,Leu11)-SP another SP antagonist. Met-enkephalin and tetracaine had no effect on miosis or the increase in IOP after YAG laser capsulotomy, whereas tetrodotoxin reduced miosis, but had no clear-cut effect on IOP, or the increase in aqueous humor protein concentration. This indicates an involvement of sensory neurons with release of SP or a closely related peptide in the miotic component part while the increase in IOP and the barrier breakdown probably are dependent mainly on a release of prostaglandins.

A study of the mechanism of ocular irritation following YAG laser capsulotomy in rabbits.

The irritative response to Nd:YAG laser capsulotomy was studied in unanaesthetized rabbits. Posterior lens capsulotomy with a total energy of 100 mJ had no effect on the pupil size but increased the intraocular pressure by 5-10 mmHg and caused a breakdown of the blood-aqueous barrier. Anterior lens capsulotomy with a total energy of 20, 60 or 100 mJ caused constriction of the pupil, and an increase in intraocular pressure in a dose-dependent manner, and a breakdown of the blood-aqueous barrier. Indomethacin attenuated all the component parts of the irritative response and (D-arg1, D-pro2, D-trp7,9, leu11)-SP attenuated the miotic response. A combination of indomethacin and the substance P antagonist almost completely abolished the irritative response. This indicates that the acute YAG-laser-induced irritation in the rabbit eye is dependent both on a release of prostaglandins and on substance P, the former probably releasing the latter from sensory nerves.

Effect of intracameral and intravitreal injection of calcitonin gene-related peptide on the intraocular pressure and outflow facility of aqueous humor in the rabbit.

After intracameral injection calcitonin gene-related peptide has been demonstrated to break the blood aqueous barrier and increase intraocular pressure in rabbits. However in cats, calcitonin gene-related peptide decreases intraocular pressure by increasing the outflow facility of aqueous humor. In the present study, the effect of intracameral injection of calcitonin gene-related peptide on the outflow facility in rabbits has been investigated and the intraocular pressure and outflow facility were measured following intravitreal administration of calcitonin gene-related peptide. The results demonstrate that in spite of the apparent pseudofacility component caused by a breakdown of the blood aqueous barrier also the true trabecular outflow is probably increased in the rabbit eye after intracameral injection of calcitonin gene-related peptide. The intravitreal administration of calcitonin gene-related peptide leaves the blood aqueous barrier intact and causes an increase in the outflow facility of aqueous humor with a concomitant long-lasting decrease in intraocular pressure.

Effects of somatostatin, a somatostatin analog, neurotensin and met-enkephalin in the eye with special reference to the irritative response.

The effects of somatostatin, cyclo(D-Trp-Lys-Thr-Phe-Pro-Phe) acetate, a somatostatin analog, neurotensin, and met-enkephalin were studied in the rabbit eye by measuring the intraocular pressure (IOP), aqueous humor protein concentration, ocular blood flow and the pupil diameter. Somatostatin or the analog injected intracamerally (10 micrograms/eye) and infused intra-arterially (0.6-4 micrograms/min) had no significant effect on the parameters studied in normal eyes. However, somatostatin and, particularly, the analog attenuated the miotic response to a standard nociceptive stimulus consisting of topical application of 1% neutral formaldehyde. The other component parts of the irritative response were not attenuated. Intracameral injection of 1-2 micrograms neurotensin caused vasodilation in the anterior segment of the eye, a slight increase in aqueous humor protein concentration, and some decrease in IOP. Intracameral injection of 1-50 micrograms met-enkephalin had no effect on the blood-aqueous barrier, IOP or the pupil diameter. Neither did this dose of met-enkephalin attenuate the miotic response to exogenous substance P. It seems likely that somatostatin and the somatostatin analog attenuate the miotic response to nociceptive stimuli by preventing the release of a substance, presumably substance P, from sensory nerves.