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Correlation of isonicotinic acid hydrazide infiltration across the blood-brain barrier to postnatal development in
Insights
Postnatal development alters the blood-brain barrier in rats, affecting isonicotinic acid hydrazide (INH) brain penetration. Young rats show higher INH central nervous system (CNS) levels compared to adults.
Area of Science:
- Pharmacology
- Neuroscience
- Developmental Biology
Background:
- The blood-brain barrier (BBB) is crucial for regulating the central nervous system (CNS) environment.
- Understanding how the BBB matures during postnatal development is essential for predicting drug efficacy and toxicity.
Purpose of the Study:
- To investigate the impact of postnatal development on the concentration of isonicotinic acid hydrazide (INH) in rat blood and brain.
- To determine if the BBB's permeability to INH changes with age.
Main Methods:
- Isonicotinic acid hydrazide (INH) was administered intravenously to rats at three age groups: 21 days, 42 days, and 3 months.
- Two dosing strategies were employed: a fixed dose (100 mg/kg) and a dose adjusted for extracellular fluid volume.
- INH concentrations in blood and brain were measured and compared across age groups.
Main Results:
- With a fixed dose, lower INH blood levels were observed in 21-day-old rats compared to older groups, with no significant brain level differences.
- When dosed relative to extracellular fluid, blood INH levels were similar across ages, but brain INH levels were significantly higher in 21- and 42-day-old rats than in adult rats.
- No significant age-related differences in blood volume relative to body or brain weight were found.
Conclusions:
- The blood-brain barrier (BBB) permeability to isonicotinic acid hydrazide (INH) undergoes significant alterations during postnatal development in rats.
- Younger rats (21 and 42 days old) exhibit increased INH infiltration into the CNS compared to adult rats.
- These findings highlight age-dependent changes in BBB function and their implications for neuropharmacology.
Abstract:
Changes in the isonicotinic acid hydrazide (INH) concentration in rat blood and brain were studied in correlation to postnatal development in groups of animals aged 21 and 42 days and 3 months. In the first part of the experiments, INH was administered intravenously to all the age groups in a dose of 100 mg/kg. In the second part, the dose was related to extracellular fluid volume, so that the 3-week-old rats were given 154 mg/kg, the 6-week-old animals 129 mg/kg and the 3-month-old animals 100 mg/kg. After a dose of 100 mg/kg, INH levels in the blood of 21-day-old rats were significantly lower than in 42-day-old and adult animals. The brain INH levels did not differ significantly. On relating the dose to the amount of extracellular fluid, there were no significant differences in the blood INH levels, but the levels in the brain of 21- and 42-day-old rats were significantly higher than in 3-month-old animals. Blood volume related to body weight and brain weight did not differ in the various age groups. The authors conclude that the blood-brain barrier for isonicotinic acid hydrazide alters in rats during postnatal development. In young animals (21- and 42-day-old), more INH infiltrates into the CNS than in adult animals.