Behavioral and developmental changes associated with prenatal opiate receptor blockade.

Pregnant Long-Evans hooded rats were dosed with 1, 5, or 10 mg/kg per day naloxone from gestational day 7 (GD7) through GD20. The control groups included both uninjected animals and injected animals pairfed to the 10-mg dose animals. At birth, all litters were culled to four males and four females, and fostered to undosed surrogate dams. Prenatal naloxone exposure produced changes in body weight development, pain sensitivity, and motor behavior in the offspring. Five and 10 mg/kg naloxone increased adult body weights in females only, as did the pairfeeding condition. The 10 mg/kg naloxone altered pain sensitivity (in males only) as measured by the tail flick test. Animals in the 1 mg/kg dose condition habituated more rapidly than uninjected (UN) subjects in the open field, and showed less activity than UNs as they matured. Bar pressing rates were reduced in the 10 mg/kg dose males in a visual discrimination task, while 10 mg/kg males and females showed reduced bar pressing rates on differential reinforcement of low rates of responding (DRL). These findings confirm that prenatal exposure to naloxone alters some aspects of neurobehavioral development in the rat, and are consistent with the hypothesis that 1 mg/kg prenatally may increase opiate function in offspring, while 10 mg/kg prenatally may decrease opiate functioning in the offspring.

Behavioral and neuroanatomical sequelae of prenatal naloxone administration in the rat.

Pregnant Long-Evans hooded rats were dosed subcutaneously with 1 or 5 mg/kg/day naloxone hydrochloride, or an equal volume of vehicle, from gestational Day 4 (GD4) through GD19. Offspring were assessed for development of righting reflex, negative geotaxis, and open field activity, and for acquisition of a Warden maze; offspring sacrificed at postnatal Day (PND) 21 were assessed for several parameters of cerebellar, hippocampal, and motor cortical morphology. Five mg/kg/day naloxone accelerated development of negative geotaxis and righting reflex, while 1 mg/kg/day naloxone tended to slow development. Low dose females had significantly more errors than controls on the first day of maze learning. The high dose group had a significantly higher concentration of granule cells in the curvature of the dentate gyrus than controls; other neuroanatomical measures were unaffected by dosing. These findings confirm and extend previous work indicating that prenatal exposure to naloxone may alter neurobehavioral development in the rat.

In vitro cell changes in laser-exposed tissue.

Tissue cultures of WI 38 human embryonic lung were exposed to CO2 laser irradiation while others were maintained unexposed as controls. In the test cultures the target area demonstrated cell dehydration and distortion, consisting of nuclear and cellular elongation and cytoplasmic fragmentation. Regeneration of the cultures was gradual and incomplete.