[New experimental model of central regulation of intraocular pressure]

We investigated the effect on the intraocular pressure (IOP) of microiontophoretic injection of oxytocin (OXT) into the cat hypothalamus, to elucidate the mechanisms of IOP regulation by the central nervous system (CNS). Under sodium pentobarbital anesthesia, the cat was fixed in a stereotaxic apparatus, immobilized, and ventilated artificially through a tracheal cannula. The IOP and blood pressure were continuously recorded with an electromanometer. A 3- to 5-barreled glass microelectrode was used; OXT and saline as a control were injected iontophoretically into the hypothalamus according to the stereotaxic coordinates. On completion of the experiment, the animal was deeply anesthetized and perfused transcardially. Frozen sections were cut and stained with neutral red, and the tracks of the electrodes were reconstructed. The IOP was elevated gradually without change in blood pressure, when OXT was injected into the supraoptic nucleus. The latency and the amplitude of this response were 171 +/- 25 sec and 0.99 +/- 0.46 mmHg (average +/- SD; n = 4), respectively. The IOP showed no change after saline application to the same site. We concluded that OXT-sensitive cells in the cat hypothalamus may play a role in regulating IOP. This model may be useful to study the mechanisms of IOP regulation by the CNS.