ALTERATION OF THE PROPERTIES OF GASTRIC SMOOTH-MUSCLE IN THE GENETICALLY HYPERGLYCEMIC OLETF RAT

Membrane responses were recorded from isolated gastric smooth muscle o f Otsuka Long-Evans Tokushima Fatty (OLETF) and Long-Evans Tokushima O tsuka (LETO) rats, using microelectrode techniques. At the age of 68-7 6 weeks, the blood sugar level was 181 mg/dl in LETO rats and 350 mg/d l in OLETF rats. In both rats, the membrane potential was stable in fu ndus muscle and spontaneously active with generation of slow waves in antrum muscle. The resting membrane potential was about -46 mV in fund us and -55 mV in antrum muscles of LETO rats, and the values were 3-7 mV lower in OLETF rats. The slow waves were generated regularly in LET O rats. while they were irregular and of small amplitude in OLETF rats . Transmural nerve stimulation evoked a cholinergic excitatory junctio n potential and following inhibitory junction potential in LETO rats, and only an inhibitory junction potential of smaller size was generate d in most of OLETF rats. The acetylcholine-induced depolarization was greater in OLETF than in LETO rats. The level of hyperpolarization pro duced by noradrenaline was similar between OLETF and LETO rats. Thus, the reduction of the resting membrane potential, weakening of spontane ous activity, impairment of cholinergic transmission and cholinergic s upersensitivity were associated with hyperglycemia. These alterations were considered due to the development of diabetes mellitus. (C) 1998 Elsevier Science B.V. All rights reserved.