Intragastric Intubation: Important Aspects of the Model for Administration of Ethanol to Rat Pups During the Postnatal Period

Abstract

One technique for the controlled delivery of ethanol to neonatal rat pups is intragastric intubation. Often, the vehicle used for delivery of ethanol is composed of a nutrient mixture to compensate for decreased suckling or other possible nutritional compromise. This study analyzed the selection of nutrient vehicle, the combination of experimental treatment groups within a litter, and the overall litter size on the growth rate of ethanol-intubated and intubated-control pups, compared with mother-raised control pups. Sprague-Dawley rat pups were raised in litters of 8 or 10, and administered ethanol by intragastric intubation with 20% (v/v) Sustacal or 80% (v/v) Intralipid-II nutrient vehicle. Pups were treated between postnatal days 2 and 10, and body weight was analyzed on day 10. Pups were assigned to a treatment group as either intubated ethanol, intubated control, or nonintubated mother-raised controls. Experimental comparison by statistical analyses was performed to identify the optimal treatment design (mixed treatment groups in a single litter or a single treatment group per litter), the optimal vehicle (Sustacal or Intralipid-II), and the optimal number of pups per litter (8 vs. 10). The analyses demonstrate that the mixing of intubated control, intubated ethanol, and nonintubated mother-raised control treatment groups within a single litter introduced an uncontrolled variable that confounded measurement of ethanol-specific alterations. The sensitivity of treatment groups to inclusion in mixed litters was dependent on the nutrient vehicle and thus nutritional adequacy. Our results suggest that an optimal design was achieved with eight pups per litter. Furthermore, ethanol intubated and intubated control pups grow at a rate identical to parallel litters of eight mother-raised control pups when Intralipid-II is used as nutrient vehicle, and a single treatment group is present in a litter. Optimization of these experimental parameters has provided an excellent neonatal rat model for analysis of specific ethanol effects on brain development during the third trimester.

Intrauterine ethanol exposure results in hypothalamic oxidative stress and neuroendocrine alterations in adult rat offspring

“…Because of reports of detrimental effects of the gavage procedure during pregnancy or early development on offspring brain function (60,62), a group of normal age-matched male rats were used as nongavaged controls. We found no effect of gavage on the parameters studied, in agreement with most (38,41,61,62), but not all (60,62), previous reports. Torres and Zimmerberg (60) reported that gavage treatment of rat dams during pregnancy affected neuromotor development in the offspring.…”

“…In other studies by the same authors, gavage treatment of rat pups had no effect on hippocampal oxidative stress (41) or cerebellar function (61). Others found no effect of gavage on pups weight gain (38). The reasons for these discrepancies remain unclear, but may be related to the gavage vehicle, dose, volume, and duration or to the overall experience with the procedure (8,45,62).…”

Eyeblink Classical Conditioning and Interpositus Nucleus Activity Are Disrupted in Adult Rats Exposed to Ethanol as Neonates

“…The use of a neonatal rat model of binge alcohol exposure during the period of brain development comparable to that of the human third trimester has been critical to this research. This model involves exposing neonatal rats to high doses of alcohol over a short period of time via either a chronic (Diaz and Samson 1980;West 1993) or an acute (Sonderegger et al 1982;Light et al 1998) intragastric infusion procedure. Either of these procedures allows control of the dose, pattern, and resulting profile of blood alcohol concentrations produced (BACs) while administering alcohol during a stage of brain development that is vulnerable to environmental insults (Goodlett and Johnson 1999).…”

Ethanol exposure of neonatal rats does not increase biomarkers of oxidative stress in isolated cerebellar granule neurons

“…Ethanol treated animals were administered a 15% w/v solution of ethanol (6 g/kg) in Intralipid-20%® (Fresenius Kabi Clayton, L.P.) vehicle by intragastric gavage Light et al, 2002b;Light et al, 1998;Pierce et al, 1993;Pierce et al, 1999). The blood ethanol concentration was 355-385 mg/dl (n=6; Diagnostic Chemicals Limited kit) 1 hr posttreatment.…”

“…The pathology of Fetal Alcohol Syndrome includes significant malformation and dysfunction in the brain including learning, behavioral, social, and psychiatric disorders that persist into adulthood (Sowell et al, 2002;Warren and Bast, 1988). Animal models (Bonthius and West, 1991;Driscoll et al, 1990;Green et al, 2002;Kane et al, 1997;Klintsova et al, 2002;Light et al, 2002b;Light et al, 1998) demonstrate that ethanol exposure during brain development causes significant neuronal loss (Hamre and West, 1993;Maier et al, 1999;Pierce et al, 1989;Pierce et al, 1997;Pierce et al, 1993;Pierce and West, 1987;Pierce et al, 1999). The neonatal rodent model of maternal drinking in the third trimester demonstrates striking Purkinje cell and granule neuron loss in the cerebellum (Goodlett et al, 1990;Light et al, 2002a;Pierce et al, 1999).…”