Neurohumoral substances and their receptors play a major part in the complex regulation of gastrointestinal motility and have therefore been the predominant targets for drug development. The numerous receptors involved in motility are located mainly on smooth muscle cells and neuronal structures in the extrinsic and intrinsic parts of the enteric nervous system. Within this system, receptor agonists and antagonists interacts directly to modify excitatory or inhibitory signals. In view of this complexity it is not surprising that our knowledge about the mechanisms of actions of the various neurohormones and drugs affecting gut motility has been rather fragmented and incomplete. However, recently substantial progress has been achieved, and drug therapy for gut dysmotility is emerging, based primarily on neurohumoral receptors. This paper presents a selective review of the neurohumoral regulatory mechanisms of gastrointestinal motility. In this context, the physiology and pharmacology of the smooth muscle cells, gastrointestinal motility and dysmotility, the enteric nervous system, gastrointestinal reflexes, and serotonin is presented. Further investigation and understanding of the transmitters and receptors involved in especially the reflex activation of peristalsis is crucial for the development of novel therapies for motility disorders., M. B. Hansen., and Obsahuje bibliografii
Species of the cnidarian genus Henneguya Thélohan, 1892 (Myxosporea: Myxobolidae) are histozoic parasites commonly found in freshwater and, more rarely, in marine fish. The development of these parasites in fish tissues includes the formation of plasmodia within which occurs the sporogony originating spores with two caudal processes, which are usually randomly distributed within the plasmodia. In this report the authors present some cases of non-random distribution of the spores of six species of Henneguya within their plasmodia. Two different patterns of non-random distribution were found based on a literature survey. These patterns and their origin are discussed. Apparently this non-random distribution of the spores is due to both internal and external factors.
The role of afferent sensory neurones in gastric mucosal protection is discussed. The principal effects of substance P and capsaicin on gastric motility and mucosal blood flow are taken in correlation with gastric mucosal injury. It seems likely that the protective effect of sensory neuropeptides is dependent on gastric mucosal blood flow and is mediated through the nitric oxide-generating system and partly the prostaglandins. The interaction between these two systems and the primordial effect of one of them on gastric mucosal blood flow and mucosal integrity after neuropeptide release is still not clear.