Entry of the antipsychotic drug, olanzapine, into the developing rat brain in mono- and combination therapies

ABC Efflux Transporters and Solute Carriers in the Early Developing Brain of a Marsupial Monodelphis domestica (South American Gray Short-Tailed Opossum)

This study used a marsupial Monodelphis domestica, which is born very immature and most of its development is postnatal without placental protection. RNA-sequencing (RNA-Seq) was used to identify the expression of influx and efflux transporters (ATP-binding cassettes [ABCs] and solute carriers [SLCs]) and metabolizing enzymes in brains of newborn to juvenile Monodelphis. Results were compared to published data in the developing eutherian rat. To test the functionality of these transporters at similar ages, the entry of paracetamol (acetaminophen) into the brain and cerebrospinal fluid (CSF) was measured using liquid scintillation counting following a single administration of the drug along with its radiolabelled tracer [3H]. Drug permeability studies found that in Monodelphis, brain entry of paracetamol was already restricted at P5; it decreased further in the first week of life and then remained stable until the oldest age group tested (P110). Transcriptomic analysis of Monodelphis brain showed that expression of transporters and their metabolizing enzymes in early postnatal (P) pups (P0, P5, and P8) was relatively similar, but by P109, many more transcripts were identified. When transcriptomes of newborn Monodelphis brain and E19 rat brain and placenta were compared, several transporters present in the rat placenta were also found in the newborn Monodelphis brain. These were absent from E19 rat brain but were present in the adult rat brain. These data indicate that despite its extreme immaturity, the newborn Monodelphis brain may compensate for the lack of placental protection during early brain development by upregulating protective mechanisms, which in eutherian animals are instead present in the placenta.

Entry of cannabidiol into the fetal, postnatal and adult rat brain

Cannabidiol is a major component of cannabis but without known psychoactive properties. A wide range of properties have been attributed to it, such as anti-inflammatory, analgesic, anti-cancer, anti-seizure and anxiolytic. However, being a fairly new compound in its purified form, little is known about cannabidiol brain entry, especially during development. Sprague Dawley rats at four developmental ages: embryonic day E19, postnatal day P4 and P12 and non-pregnant adult females were administered intraperitoneal cannabidiol at 10 mg/kg with [3H] labelled cannabidiol. To investigate the extent of placental transfer, the drug was injected intravenously into E19 pregnant dams. Levels of [3H]-cannabidiol in blood plasma, cerebrospinal fluid and brain were estimated by liquid scintillation counting. Plasma protein binding of cannabidiol was identified by polyacrylamide gel electrophoresis and its bound and unbound fractions measured by ultrafiltration. Using available RNA-sequencing datasets of E19 rat brain, choroid plexus and placenta, as well as P5 and adult brain and choroid plexus, expression of 13 main cannabidiol receptors was analysed. Results showed that cannabidiol rapidly entered both the developing and adult brains. Entry into CSF was more limited. Its transfer across the placenta was substantially restricted as only about 50% of maternal blood plasma cannabidiol concentration was detected in fetal plasma. Albumin was the main, but not exclusive, cannabidiol binding protein at all ages. Several transcripts for cannabidiol receptors were expressed in age- and tissue-specific manner indicating that cannabidiol may have different functional effects in the fetal compared to adult brain.

Effects of paracetamol/acetaminophen on the expression of solute carriers (SLCs) in late-gestation fetal rat brain, choroid plexus and the placenta

Solute carriers (SLCs) regulate transfer of a wide range of molecules across cell membranes using facilitative or secondary active transport. In pregnancy, these transporters, expressed at the placental barrier, are important for delivery of nutrients to the fetus, whilst also limiting entry of potentially harmful substances, such as drugs. In the present study, RNA-sequencing analysis was used to investigate expression of SLCs in the fetal (embryonic day 19) rat brain, choroid plexus and placenta in untreated control animals and following maternal paracetamol treatment. In the treated group, paracetamol (15 mg/kg) was administered to dams twice daily for 5 days (from embryonic day 15 to 19). In untreated animals, overall expression of SLCs was highest in the placenta. In the paracetamol treatment group, expression of several SLCs was significantly different compared with control animals, with ion, amino acid, neurotransmitter and sugar transporters most affected. The number of SLC transcripts that changed significantly following treatment was the highest in the choroid plexus and lowest in the brain. All SLC transcripts that changed in the placenta following paracetamol treatment were downregulated. These results suggest that administration of paracetamol during pregnancy could potentially disrupt fetal nutrient homeostasis and affect brain development, resulting in major consequences for the neonate and extending into childhood.