Preproenkephalin targeted antisenses cross the blood-brain barrier to reduce brain methionine enkephalin levels and increase voluntary ethanol drinking.

Antisense potentially can manipulate target gene expression in the brain if it can cross the blood-brain barrier (BBB). We designed three (10mer, 17mer, and 19mer) phosphorothioated antisenses (PS-ODNs) directed against the precursor molecule of methionine enkephalin (Met-Enk), an opiate peptide which suppresses voluntary ethanol drinking. We measured the ability of the antisenses to cross the BBB, accumulate in the brain and CSF, decrease levels of Met-Enk in brain and blood, and affect voluntary ethanol drinking. Each antisense readily crossed the BBB, with 0.07-0.16% of the i.v. dose accumulating per gram of brain. Capillary depletion and CSF sampling each confirmed that the antisenses entered the CNS. Gel electrophoresis of radioactivity recovered from brain and serum showed intact antisense and a higher molecular weight form likely representing antisense bound to protein, but no degradation products. Each antisense molecule and a cocktail of all three reduced Met-Enk levels in brain and serum. Met-Enk levels in the brain were reduced more rapidly and for a longer duration than Met-Enk levels in the serum, indicating a degree of selective targeting to the CNS. Additionally, administration of the cocktail was more effective in reducing Met-Enk levels than any of the individual antisenses. Each antisense increased voluntary ethanol drinking by about 20% and the cocktail increased it by about 80%. Taken together, these results used pharmacokinetic, immunochemical, and behavioral methods to show that PS-ODN antisenses that readily cross the BBB can decrease brain levels of Met-Enk and increase voluntary ethanol drinking.

Inhibition of luteinizing hormone secretion by localized administration of estrogen, but not dihydrotestosterone, is enhanced in the ventromedial hypothalamus during feed restriction in the young wether.

The ability of steroids to inhibit LH secretion is enhanced during undernutrition. To identify potential hypothalamic sites at which this enhancement may occur, we examined LH secretion in feed-restricted or fed young wethers treated with locally administered metabolites of testosterone. In experiment 1, microimplants containing crystalline estradiol-17beta (E) or cholesterol were administered via chronic guide tubes directed to the preoptic area (POA) or ventromedial hypothalamus (VMH) in fed or feed-restricted wethers. E treatment in the VMH decreased LH pulse frequency, pulse amplitude, and mean LH concentration in feed-restricted, but not fed, wethers. E may act in the POA to suppress LH under feed restriction, but definite conclusions cannot be drawn because of steroid-independent effects of feed restriction on LH pulse frequency. In experiment 2, the effect of dihydrotestosterone (DHT) in the VMH was determined. DHT administration to the VMH did not alter LH secretion in either feed-restricted or fed wethers. Thus the VMH is one site wherein E negative feedback is enhanced during feed restriction in the wether. In contrast, we found no evidence for enhanced responsiveness to androgen negative feedback within the VMH of feed-restricted wethers. We suggest that increased sensitivity within the VMH to E, but not to DHT, is important for suppressing LH secretion in undernourished male sheep.