NEUROCHEMICAL CODING IN THE MYENTERIC PLEXUS OF THE UPPER GASTROINTESTINAL-TRACT OF HIBERNATING HAMSTERS

As part of our investigation of the plasticity of autonomic nerves in physiological and pathological conditions, we have examined the effect of hibernation on the neurochemical content of myenteric nerves and n erve cell bodies of the upper gastrointestinal tract of the non-season al hibernator, the golden hamster. Age marched hamsters kept at room t emperature and those kept at 5 degrees C but which failed to hibernate , were used as controls. Possible changes in nerve fibres and nerve ce ll bodies containing the general neuronal marker, protein gene product 9.5, the peptides, vasoactive intestinal polypeptide, substance P (SP ) and calcitonin gene-related peptide (CGRP), the catecholamine synthe sizing enzyme tyrosine hydroxyl ase and the enzyme responsible for syn thesizing nitric oxide, nitric oxide synthase, were examined in the oe sophagus, proventriculus and proximal and distal stomach of the golden hamsters using immunohistochemical techniques. The results of the pre sent study revealed a significant increase in the number of nerve cell bodies and density of nerve fibres containing SP-immunoreactivity and increased number of CGRP-immunoreactive cell bodies but not the other markers examined in the proximal stomach and proventriculus. In contr ast, there was no change in the distribution of any of the neuroactive substances examined in the myenteric plexus of the oesophagus and dis tal stomach. It is suggested that the change in the environment of the hibernating hamsters perturbs the normal digestive physiology in the proximal stomach and proventriculus that is reflected by the selective changes in SP- and CGRP-containing enteric nerves; these changes may be part of protective reflex mechanisms to the environmental changes r esulting from hibernation, where upgrading of nerve cell bodies expres sing CGRP and SP has occurred. (C) 1997 ISDN.