Effects of chlordiazepoxide on footshock- and corticotropin-releasing factor-induced increases in cortical and hypothalamic norepinephrine secretion in rats.

Noradrenergic and corticotropin-releasing factor (CRF) neuronal systems within the brain have been implicated in stress and anxiety. Synaptic release of cerebral norepinephrine (NE) is increased during stress, and following intracerebral CRF administration. Benzodiazepines are commonly used anxiolytic drugs but information on their effects on the stress- and CRF-related release of NE is limited. We have used in vivo microdialysis to test the effects of the benzodiazepine, chlordiazepoxide (CDP) on the noradrenergic responses to footshock and intracerebroventricular CRF in the medial hypothalamus and the medial prefrontal cortex (PFM) of freely moving rats. Footshock (60 x 0.1-0.2 mA shocks in 20 min) significantly increased microdialysate concentrations of NE in the first sample collected after initiating the footshock. In the hypothalamus, microdialysate NE was augmented 64% above baseline. A second footshock session (100 min after the first footshock) increased microdialysate NE to 313% of the baseline. Thus the noradrenergic responses to footshock were enhanced by preceding footshocks. CRF (100 ng) administered into the locus coeruleus (LC) almost tripled microdialysate concentrations of NE in the PFM. CDP (5mg/kg, i.p.) had no statistically significant effects on the basal dialysate concentrations of NE, but it significantly attenuated both footshock- and CRF-induced increases in dialysate NE. CDP may exert a direct inhibitory effect on the noradrenergic neurons, alter the input to LC noradrenergic neurons, or alter the ability of CRF to activate the LC noradrenergic system.

Corneal protection by the ocular mucin secretagogue 15(S)-HETE in a rabbit model of desiccation-induced corneal defect.

The mucin secretagogue 15(S)-HETE was found to stimulate glycoprotein secretion in human ocular tissue at submicromolar concentrations in the present studies. Therefore, the ability of topically applied 15(S)-HETE to preserve corneal integrity was investigated in a rabbit model of desiccation-induced corneal defect. Desiccation-induced corneal injury was elicited in anesthetized rabbits by maintaining one eye open with a speculum. Corneal staining and corneal thickness changes were determined immediately following desiccation. 15(S)-HETE dose-dependently reduced corneal damage (ED50 = 120 nM) during a two-hour desiccation. Corneal staining was unchanged relative to control using a 1 microM dose of 15(S)-HETE. Through four hours of desiccation, 15(S)-HETE (500 nM) decreased corneal staining by 71% and completely prevented corneal thinning. 15(S)-HETE (1 microM) was significantly more efficacious than an artificial tear product over the 4-hour desiccation period. There was no evidence of tachyphylaxis following repeated topical ocular dosing of 15(S)-HETE. These studies demonstrate that 15(S)-HETE stimulates ocular mucin secretion in vitro and effectively protects the cornea in a rabbit model of desiccation-induced injury. The results suggest that the ocular mucin secretagogue 15(S)-HETE may have therapeutic utility in dry eye patients, alleviating corneal injury and restoring corneal integrity.