Distribution of peptidergic nerve fibres in the guinea pig trabecular meshwork

Seasonal Differences in Expression of Neuropeptide Y (NPY) in Visual Centers of Spotted Munia (Lonchura punctulata)

The visual perception of birds is an incredibly exciting subject of research. Birds have significantly higher visual acuity than most other animals, which helps them stay safe in flight and detect their prey. Understanding how the eyes send information to the brain for additional processing is crucial. The brain has sections (nuclei) that accept input from the retina. The key areas where information is processed are the hyperpallium apicale (HA), hippocampus (HP), optic tectum (TeO), nucleus rotundus (RoT), and the geniculatus lateralis ventralis (Glv); among these, the RoT is one of the most investigated nuclei for vision. This study looked at how the visual centers of non-photoperiodic songbirds (Spotted Munia) adapt in different life history stages by looking at NPY expression. We immunohistochemically quantified NPY expression in four different seasons, including pre-breeding (June), breeding (September), post-breeding (December), and regressed (March) in the brain of Spotted Munia. We evaluated changes in the expression levels of the peptide throughout the year, by determining the expression at four different periods throughout the year. Peptide expression levels were projected to fluctuate within photoperiod-induced seasons. It was discovered that the parts of the brain related to vision (RoT, HA, and HP) have a higher number of immunoreactive cells during their mating season, i.e., during the summer. The appearance of NPY, a non-photic marker, in brain areas linked with light perception, was fascinating. Indirectly, NPY aids avian reproduction in a variety of ways. These findings demonstrate the importance of these nuclei in the process of reproduction, as well as the involvement of NPY in the visual brain areas of Spotted Munia.

Effectiveness of 0.1% topical salicylic acid on blepharoconjunctivitis affecting glaucoma patients treated with topical prostaglandin analogues: a prospective randomized trial

AIM

To evaluate the efficacy of 0.1% topical salicylic acid (TSA) to treat iatrogenic chronic blepharoconjunctivitis in patients with primary open angle glaucoma (POAG), treated with topical prostaglandin analogues (TPAs).

METHODS

Totally 60 patients were randomly distributed into 3 equal size groups, two of which treated with 0.1% TSA (OMKASA^®) and 0.1% topical clobetasone butyrate (TCB; VISUCLOBEN^®) respectively, and one consisting of untreated controls. The parameters taken into account at baseline (T0) and after 30d (T1) of therapy were: conjunctival hyperemia, lacrimal function tests [Schirmer I test and break up time (BUT)] and intraocular pressure (IOP).

RESULTS

Conjunctival hyperemia showed a substantial improvement in both treated groups (P<0.001) but not among controls. Similarly, lacrimal function tests displayed an improvement of Schirmer I test in both treated groups (P<0.05) and an extension of BUT only in the group treated with 0.1% TSA (P<0.05). The IOP increase was statistically significant only in those patients treated with 0.1% TCB (P<0.001).

CONCLUSION

The 0.1% TSA has proved to be an effective anti-inflammatory treatment of blepharoconjunctivitis affecting glaucoma patients on therapy with TPAs, leading to a sizeable decrease of inflammation as well as both quantitative and qualitative improvement of tear film. Furthermore, differently from 0.1% TCB, it does not induce any significant IOP increase.

Microvessels of the human optic nerve head: ultrastructural and radioreceptorial changes in eyes with increased IOP

BACKGROUND

Ultrastructural, morphological modifications in the microvessels of the optic nerve head were studied in human eyes with normal intraocular pressure (IOP), with slightly increased IOP, and with strongly increased IOP. Moreover, the distribution of beta-adrenergic receptors was analyzed in the same samples.

METHODS

Six enucleated human eyes were studied. Small pieces of the optic nerve head and of iridocorneal angle (including trabecular meshwork) were dissected immediately after autopsy. The sections were studied with transmission electron microscopy and autoradiography. Radiolabelled pindolol was used to locate beta-adrenergic receptors topographically on fresh sections of human eye.

RESULTS

Transmission electron microscopy demonstrated that elevated IOP induces ultrastructural modifications of the microvessels of the optic nerve head. Autoradiographic experiments showed the presence and distribution of beta-adrenergic receptors in the optic nerve head of eyes with both normal and increased IOP.

INTERPRETATION

Increased IOP initially compresses the microvessels of the optic nerve head. The number of beta-adrenergic receptors increased markedly in the eyes with raised IOP. Further studies are needed to clarify the physiological and pathological roles of these receptors.

Re-evaluation and quantification of the different sources of nerve fibres supplying the rat eye

The denervation and/or the removal of peripheral nerve ganglia are useful surgical techniques for studying the source and distribution of peripheral nerves in all organs, including the eye. The amount and distribution of the remaining nerve fibres supplying the eye (after sectioning of various types of nervous fibres and/or removal of nerve ganglia) were evaluated in the rat. Male Sprague-Dawley rats were anaesthetized and one or more of the following nervous tissues were removed: superior cervical ganglion, main ciliary ganglion, pterygopalatine ganglion, trigeminal ganglion and the ophthalmic-maxillary nerve. In some animals, chemical sympathectomy was performed by administration of 6-OH dopamine. The eyes were cut in serial sections, but only three regions (cornea, iris and choroid) were harvested and submitted for various nerve fibre staining techniques. The results were quantified and statistically analysed. Superior cervical ganglionectomy and/or chemical sympathectomy induced the destruction of almost all the catecholaminergic nerve fibres in the three examined regions of the rat eye. Removal of the ciliary ganglion (partial parasympathectomy) caused the destruction of about 60% of the cholinergic nerve fibres of the same regions of the rat eye, while subtotal parasympathectomy destroyed about 80% of the cholinergic nerve fibres. Surgical transsection of the ophthalmo-maxillary nerve or the removal of the trigeminal ganglion led to a degeneration of almost all sensitive nerve fibres of the three examined regions of the rat eye. The denervation experiments confirmed the presence of the different types of nerve fibres (sympathetic, parasympathetic and sensitive) in the three studied structures of the rat eye.