Teratologic evaluation of synthetic delta 9-tetrahydrocannabinol in rabbits

Propylene glycol and Kolliphor as solvents for systemic delivery of cannabinoids via intraperitoneal and subcutaneous routes in preclinical studies: a comparative technical note

BACKGROUND

Substance administration to laboratory animals necessitates careful consideration and planning in order to enhance agent distribution while reducing any harmful effects from the technique. There are numerous methods for administering cannabinoids; however, several parameters must be considered, including delivery frequency, volume of administration, vehicle, and the level of competence required for staff to use these routes properly. There is a scarcity of information about the appropriate delivery method for cannabinoids in animal research, particularly those that need the least amount of animal manipulation during the course of the investigation. This study aims to assess the feasibility and potential side effects of intraperitoneal and subcutaneous injection of CBD and THC using propylene glycol or Kolliphor in animal models. By evaluating the ease of use and histopathological side effects of these solvents, this study intends to help researchers better understand an accessible long-term delivery route of administration in animal experiments while minimizing the potential confounding effects of the delivery method on the animal.

METHODS

Intraperitoneal and subcutaneous methods of systemic cannabis administration were tested in rat models. Subcutaneous delivery via needle injection and continuous osmotic pump release were evaluated using propylene glycol or Kolliphor solvents. In addition, the use of a needle injection and a propylene glycol solvent for intraperitoneal (IP) administration was investigated. Skin histopathological changes were evaluated following a trial of subcutaneous injections of cannabinoids utilizing propylene glycol solvent.

DISCUSSION

Although IP delivery of cannabinoids with propylene glycol as solvent is a viable method and is preferable to oral treatment in order to reduce gastrointestinal tract degradation, it has substantial feasibility limitations. We conclude that subcutaneous delivery utilizing osmotic pumps with Kolliphor as a solvent provides viable and consistent route of administration for long-term systemic cannabinoid delivery in the preclinical context.

Effects of Prenatal Cannabinoids Exposure upon Placenta and Development of Respiratory Neural Circuits

Cannabis use has risen dangerously during pregnancy in the face of incipient therapeutic use and a growing perception of safety. The main psychoactive compound of the Cannabis sativa plant is the phytocannabinoid delta-9-tetrahydrocannabinol (A-9 THC), and its status as a teratogen is controversial. THC and its endogenous analogues, anandamide (AEA) and 2-AG, exert their actions through specific receptors (eCBr) that activate intracellular signaling pathways. CB1r and CB2r, also called classic cannabinoid receptors, together with their endogenous ligands and the enzymes that synthesize and degrade them, constitute the endocannabinoid system. This system is distributed ubiquitously in various central and peripheral tissues. Although the endocannabinoid system's most studied role is controlling the release of neurotransmitters in the central nervous system, the study of long-term exposure to cannabinoids on fetal development is not well known and is vital for understanding environmental or pathological embryo-fetal or postnatal conditions. Prenatal exposure to cannabinoids in animal models has induced changes in placental and embryo-fetal organs. Particularly, cannabinoids could influence both neural and nonneural tissues and induce embryo-fetal pathological conditions in critical processes such as neural respiratory control. This review aims at the acute and chronic effects of prenatal exposure to cannabinoids on placental function and the embryo-fetal neurodevelopment of the respiratory pattern. The information provided here will serve as a theoretical framework to critically evaluate the teratogen effects of the consumption of cannabis during pregnancy.

[Alcohol, tobacco and cannabis: Review of teratogenicity studies in animals]

Despite an intensive national campaign of information, the drugs most frequently consumed by young adults undoubtedly continue to be alcohol, tobacco and cannabis. If the impact of these drugs on the health of the consumers can be evaluated in conjunction with the clinical and epidemiologic data, the consequences on the embryo due to their consumption by the pregnant women can be appreciated thanks to the abundant literature describing their effects in the gravid animal. Taking into account the abundant literature available in multiple animal species, the zero drug recommendation should be widely diffused to pregnant women.

Maternal toxicity: a possible etiological factor in embryo-fetal deaths and fetal malformations of rodent-rabbit species

Data from animal teratology studies were surveyed to determine whether embryo-fetal mortality and fetal malformations result from a primary action of the agent on the conceptus or if they are secondary to maternal toxicity--a consequence of administration with high dose levels of test chemicals. A fairly strong association between embryo-fetal mortality and maternal toxicity was revealed by analysis of data from hamsters, mice, rats, and rabbits in 234 studies of chemical and physical agents, of which 83 were conducted at both maternotoxic and nonmaternotoxic doses, 94 only at maternotoxic doses, and 49 at nonmaternotoxic doses. In the above studies, only nine chemicals (four each in hamsters and rabbits and one in rats) were reported to induce embryo-fetal deaths at apparently nonmaternotoxic doses. These findings tend to suggest a contributory role for maternal toxicity in the induction of embryo-fetal deaths. The previously reported hypothesis that certain fetal defects in mice may perhaps be caused by maternal toxicity was also found to be true in a review of data on hamsters, rats, and rabbits. Salient maternal toxicity-associated fetal malformations were exencephaly, encephalocele, micro- or anophalmia, and fused ribs in hamsters and defective (fused, missing, or extra) ribs, vertebrae, and sternebrae, ex-, an-, or microphthalmia, and cleft palate in rats and rabbits. These malformations occurred at low frequencies, generally with no readily apparent dose-response relationship. Presumptive evidence indicates that embryo-fetal deaths, and the above-mentioned fetal malformations in experimental animals, which in published literature are presently attributed to chemical induction for a large number of chemicals, may be a consequence of maternal toxicity per se.

Effects of multiple, chronic and early hashish exposure on mating behavior, nest-building and gestation in mice

1. The effects of hashish extract on social behavior were investigated in pairs of mice living together from mating to parturition. The drug was administered orally to both animals at a dose of 20 mg delta 9-tetrahydrocannabinol/kg three times a week, either (I) during the 3 weeks from mating to parturition, (II) during the 12 weeks from weaning to mating and parturition, or (III) only during the 3 weeks after weaning. 2. In the mating tests, an acute administration (I) caused a general sedation. Chronically treated animals (II) showed decreased sexual behavior and lower social investigations despite significantly more non-social activities. Early drug treatment (III) had no effect on mating behavior. In all three series of experiments the females had conceived by the next morning. 3. The nest-building behavior during pregnancy was suppressed after multiple (I) and chronic (II) drug administration. In early drug-treated animals (III) the transport of nesting material was only slowed down. Non-social activities were normal or increased in all three series. 4. Parturition was significantly delayed by one day after multiple (I) and chronic (II) drug administration. The birth weight was not affected, but the litter size was decreased after chronic drug treatment. Early drug administration (III) had no effects on these parameters. 5. In conclusion, whereas tolerance to the sedative effects of hashish developed very rapidly, the drug influences on social behavior were stable. Therefore, discussions on legalization of cannabis should pay attention to the drug effects on social behavior.

Effects of marihuana on pregnant rats and their offspring

Pregnant rats were intubated with marihuana extract (10, 150 mg/kg) from gestation day 3 to parturition. Control animals were pair-fed. At parturition pups were culled and assigned to nondrug-treated dams. A positive control group consisting of animals prenatally exposed to alcohol (6 g/kg/day) was included for comparison of birth weight data. Marihuana reduced food and water consumption and maternal weight gain. Pup weight at birth was reduced by about 10% relative to pair-fed controls in animals exposed to the high doses of marihuana, and by approximately 15% in pups exposed to alcohol relative to their pair-fed controls. Litter size and pup mortality at birth were not affected significantly. Postnatal mortality was increased and neonatal weight was decreased at 21 days in marihuana-treated offspring. At 11 weeks of age body weights of drug-treated females but not males, were still significantly less than that of pair-fed controls.