Difluoromethylornithine (DFMO) reduces deficits in isolation-induced ultrasonic vocalizations and balance following neonatal ethanol exposure in rats

Abstract

Neonatal ethanol (EtOH) exposure is associated with central nervous system dysfunction and neurotoxicity in rats. Increases in polyamine levels have been implicated as one underlying mechanism for some of EtOH's effects on the developing brain. In this study we addressed whether the inhibition of polyamine biosynthesis by alpha-difluoromethylornithine (DFMO) could reduce behavioral deficits induced by early EtOH exposure. Male and female rat pups received ethanol (6 g/kg/day EtOH i.g.), or isocaloric maltose (control) from postnatal days (PND) 1-8. On PND 8, animals were injected with either saline or DFMO (500 mg/kg, s.c.) immediately following the final neonatal treatment. Subjects were tested for isolation-induced ultrasonic vocalizations (USV) on PND 16; spontaneous activity in an open field apparatus on PND 20 and 21; and balance on PND 31. Animals exposed to EtOH neonatally displayed an increased latency to the first USV and reduced frequencies of USV, hyperactivity and preference for the center of the open field and poorer balance relative to controls. DFMO minimized these deficits in latency to the first USV and balance. These data provide further support that polyamines play a role in some of the functional deficits associated with EtOH exposure during early development and that reducing polyamine activity can improve outcome.

Figure 1

DFMO minimized the increase in latency to the first vocalization as a result of neonatal ethanol (EtOH) exposure when offspring were tested at PND 16 (A), but had no effect on the EtOH -related decrease in the number of USVs (B). Data presented are mean (collapsed across sex) + SEM. The control group represents the pooled nontreated and intubated controls since these groups did not differ from each other and this pooled control was used in the 2 × 2 factorial design. The n’s per treatment condition are presented in the parentheses above each bar. * differs from all other treatment groups; # differs from controls (p’s< 0.05).

Figure 2

Neonatal EtOH increased the total distance traveled in the open field on PND 20-21. Data presented are mean (collapsed across sex) ± SEM. The control group represents the pooled nontreated and intubated controls since these groups did not differ from each other and this pooled control was used in the 2 × 2 factorial design. The n’s per treatment condition are presented in the parentheses alongside the figure legends. * differs from EtOH subjects (p< 0.05).

Figure 3

Neonatal EtOH exposure increased the percent of distance traveled (A) and time spent (B) in the center 50% of the open field on PND 20-21. Data presented are mean ± SEM. The control group represents the pooled nontreated and intubated controls since these groups did not differ from each other and this control was used in the 2 × 2 factorial design. The n’s per treatment condition are presented in the parentheses alongside the figure legends in Figure 2.

Figure 4

DFMO on PND 8 reduced the deleterious effect of neonatal EtOH exposure on the total distance achieved in the balance test at PND 31. Data presented are mean (collapsed across sex) ± SEM. The control group represents the pooled nontreated and intubated controls since these groups did not differ from each other and this pooled control was used in the 2 × 2 factorial design. The n’s per treatment condition are presented in the parentheses alongside the figure legends. * differs from all other treatment groups.

Figure 5

Neonatal EtOH administration was associated with reduced body weights relative to controls beginning on PND 2 and continuing through PND 8. Data presented are mean (collapsed across sex) ± SEM. The control group represents the pooled nontreated and intubated controls since these groups did not differ from each other and this pooled control was used in the 2 × 2 factorial design. The n’s per treatment condition are presented in the parentheses alongside the figure legends. The EtOH group differed from controls from PND 2 through PND 8 (p’s <0.05).

Figure 6

Blood EtOH levels did not differ between DFMO-treated and saline control rats following EtOH intubation. EtOH (3 g/kg) was administered twice daily from PND 1-8. Blood levels were assayed on PND 8.