The gastrointestinal pharmacology of cannabinoids: an update.

Recent work in the field of gastrointestinal pharmacology of cannabinoids has focused on enteric endocannabinoid and endovanilloid systems and their modulation in pathophysiological conditions. CB(1) receptor immunoreactivity was detected on enteric cholinergic neurones and vasoactive intestinal peptide-containing submucosal ganglion cells, on discrete nuclei of the dorsovagal complex (involved in emesis) and on central and peripheral vagal terminals, thus controlling gastroesophageal reflux and gastrointestinal motility. CB(1) receptor activation by endocannabinoids inhibited induced fluid secretion and inflammation in animal models and reduced proliferation of cultured colorectal cancer cells.

Cannabinoids on the brain.

Cannabis has a long history of consumption both for recreational and medicinal uses. Recently there have been significant advances in our understanding of how cannabis and related compounds (cannabinoids) affect the brain and this review addresses the current state of knowledge of these effects. Cannabinoids act primarily via two types of receptor, CB1 and CB2, with CB1 receptors mediating most of the central actions of cannabinoids.

Cellular distribution of vanilloid VR1 receptor immunoreactivity in the guinea-pig myenteric plexus.

Recent investigations suggest that vanilloid receptor-1 (VR1) immunoreactivity occurs in the intestine. We have determined and quantified this immunoreactivity in the myenteric plexus with respect to cholinergic and neurofilament protein-positive neurones. Guinea-pig and rat preparations were dual-labelled with specific antibodies raised in rabbit or goat against vanilloid receptor-1 and against other neurochemical markers.

Localisation of cannabinoid CB(1) receptor immunoreactivity in the guinea pig and rat myenteric plexus.

Activation of cannabinoid CB(1) receptors inhibits gastrointestinal motility, propulsion, and transit, whereas selective antagonism of these receptors has the opposite effects, suggesting the presence of endocannabinoid tone. Supporting evidence for presynaptic CB(1) receptors on myenteric neurons has been found in vitro. In this study, selective CB(1) receptor antibodies and neuronal markers were used to identify and characterise myenteric neurons expressing cannabinoid receptors.

Vanilloid receptor type 1-immunoreactivity is expressed by intrinsic afferent neurones in the guinea-pig myenteric plexus.

The enteric sensory nervous system consists of extrinsic and intrinsic components. The cellular distribution of vanilloid receptor type 1 (VR1) and its relation to the intrinsic sensory neurones were studied in myenteric plexus-longitudinal muscle preparations of rat ileum and guinea-pig ileum and colon. VR1-immunoreactivity was localized on fine fibres and expressed by ganglionic cells.