Evaluation of Total Brain Acetylcholine in rats treated with inhaled Tetrahydrocannabinol. (A Bioassay Study)

Abstract

A Bioassay study using rabbit ileum was used to evaluate changes in Total Brain Acetylcholine of wistar rats treated for 4, 8 and 12 weeks with inhaled tetrahydrocanabinol smoke; a widely abused substance worldwide. Puffing of cannabis smoke was performed with the use of a Hamilton syringe delivering 100-ml puffs at 20-sec intervals into the nose -only manifold for a total of 5 minutes. Smoke was first pumped into a 500ml dilution chamber with the aid of a vacuum pump. The smoke was then displaced from the dilution chamber through the nose-only manifold at 300 ml/min; that is the rats received Inhaled THC at 5ml/sec for 5 minutes. After treatment the rat Brains were accessed for Total Brain Acetylcholine (TBA) levels. To achieve this; an increasing amounts of homogenized Brain extracts from the rats in each group and Laboratory acetylcholine were used and their ability to contract the rabbit ileum when introduced into an organ bath was recorded as height of contraction which was then used to calculate actual TBA concentration. This was first done for all groups to first determine an effective dose to be used. For the actual Bioassay study the chosen effective dose of 0.5ml of Brain preparation from Control group, 4, 8, 12 weeks treated groups and standard Laboratory Acetylcholine were used to determine the concentrations of Total Brain Acetylcholine present in the Brain extracts. Atropine was also introduced to ascertain the presence of Ach in the Brain extracts. The experiments showed significant increase in TBA in the treated rats showing an accumulation of Ach in the Brain due to THC inhalation. This is part of a series of studies to establish the influence of THC on the neurotransmitter acetylcholine and cells of the Brain stem for its possible importance in neurotransmitter deficiency and related neurodegenerative diseases.

Keywords: Total Brain Acetylcholine (TBA), Tetrahydrocannabinol (THC), Inhalation treatment, Bioassay,  Rabbit ileum,  Height of Contraction, Nose-Only smoke model.