Intravitreal human chorionic gonadotropin decreases intraocular pressure in rabbits: mechanism of action

The eye in pregnancy: ophthalmologic and neuro-ophthalmologic changes

A variety of changes in the eye can occur during pregnancy. These can be physiological, pathologic related to the pregnancy, or pathologic unrelated to the pregnancy. Pregnancy also can affect preexisting conditions. Pregnant women often discuss changes in their health first with their obstetrician; therefore, knowledge of common ophthalmic complaints during pregnancy is of particular concern for the practicing obstetrician. We reviewed the literature for ophthalmic and neuro-ophthalmic conditions that occur during pregnancy or in the postpartum period. Results are presented anatomically, first discussing general ophthalmologic conditions, then neuro-ophthalmic conditions follow. Effects of ocular medications on the fetus are reviewed.

Chorionic gonadotropin and its receptor are both expressed in human retina, possible implications in normal and pathological conditions

Extra-gonadal role of gonadotropins has been re-evaluated over the last 20 years. In addition to pituitary secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH), the CNS has been clearly identified as a source of hCG acting locally to influence behaviour. Here we demonstrated that human retina is producing this gonadotropin that acts as a neuroactive molecule. Müller glial and retinal pigmented epithelial (RPE) cells are producing hCG that may affects neighbour cells expressing its receptor, namely cone photoreceptors. It was previously described that amacrine and retinal ganglion (RGC) cells are targets of the gonadotropin releasing hormone that control the secretion of all gonadotropins. Therefore our findings suggest that a complex neuroendocrine circuit exists in the retina, involving hCG secreting cells (glial and RPE), hCG targets (photoreceptors) and hCG-release controlling cells (amacrine and RGC). The exact physiological functions of this circuit have still to be identified, but the proliferation of photoreceptor-derived tumor induced by hCG demonstrated the need to control this neuroendocrine loop.

Intramuscular injection of chlorpromazine decreases intraocular pressure by lowering systemic blood pressure

Intramuscular injection of chlorpromazine in rabbits caused a significant decrease in intraocular pressure (IOP). The dose-response curve was generated. The threshold dose was 0.1 mg/kg (approximately 0.35 mg per rabbit) and 10 mg/kg chlorpromazine produced the maximal response which lasted for several hours. This decrease in IOP was not due to the release of pituitary prolactin by a central dopaminergic-2 antagonistic activity of chlorpromazine. Intracerebroventricular (i.c.v.) injection of chlorpromazine also caused a decrease in IOP. The threshold dose was 0.33 mg per rabbit. This high i.c.v. threshold dose indicates that no direct central mechanism is responsible for the decrease of IOP after an i.m. injection of chlorpromazine. Intravitreal injection of 0.35 mg chlorpromazine caused significant miosis without any change in IOP. It appears that direct mechanisms of chlorpromazine in ocular tissues do not decrease IOP. After an i.m. injection of 0.1 or 10 mg/kg chlorpromazine, systemic blood pressure (BP) was lowered in a similar pattern as the decrease in IOP. Neither IOP nor BP was affected by an i.m. injection of a subthreshold chlorpromazine dose of 0.01 mg/kg. These observations suggest that the decrease in IOP after an i.m. injection of chlorpromazine is mainly due to the decrease of BP.