Evaluation of colonic myoelectrical activity in health and functional disorders.

Electrical activity of the colon was investigated in six healthy volunteers and 22 patients presenting functional colonic disorders associated with pain, constipation, or diarrhoea. Myoelectrical activity during 10 hours, including two daily meals, was recorded from eight groups of nickel-chrome electrodes using a 1.5 m length probe introduced by the rectal route. Electromyograms of volunteers consisted of slow waves at two distinct rhythms, approximately 3 and 10 cycles per minute, during 16 to 28% of the recording time respectively for each site. Action potentials were also recorded as 11 to 80 short spike bursts (SSB) per hour lasting 1.5 to 3.5 s at any site and 20-26 long spike bursts (LSB) per hour, lasting 17 to 21 s, occurring in series of four to eight propagated bursts. Additional high-velocity propagated bursts were recorded during the three hour postprandial period. Three typical changes in spike activity patterns were detected: an increase by 170-420% of the number of SSB associated to a high spiking activity was recorded in 13 patients (group I), the absence of SSB, a low spiking activity level and only 3 to 8 LSB per hour (group II), in six patients; and the postprandial response was absent (group III) in three other investigated patients. Evidence for three groups of motor disturbances and their possible relation to clinical manifestations of functional disorders is presented.     

Behavioral consequences of dopamine deficiency in the Drosophila central nervous system

The neuromodulatory function of dopamine (DA) is an inherent feature of nervous systems of all animals. To learn more about the function of neural DA in Drosophila, we generated mutant flies that lack tyrosine hydroxylase, and thus DA biosynthesis, selectively in the nervous system. We found that DA is absent or below detection limits in the adult brain of these flies. Despite this, they have a lifespan similar to WT flies. These mutants show reduced activity, extended sleep time, locomotor deficits that increase with age, and they are hypophagic. Whereas odor and electrical shock avoidance are not affected, aversive olfactory learning is abolished. Instead, DA-deficient flies have an apparently "masochistic" tendency to prefer the shock-associated odor 2 h after conditioning. Similarly, sugar preference is absent, whereas sugar stimulation of foreleg taste neurons induces normal proboscis extension. Feeding the DA precursor L-DOPA to adults substantially rescues the learning deficit as well as other impaired behaviors that were tested. DA-deficient flies are also defective in positive phototaxis, without alteration in visual perception and optomotor response. Surprisingly, visual tracking is largely maintained, and these mutants still possess an efficient spatial orientation memory. Our findings show that flies can perform complex brain functions in the absence of neural DA, whereas specific behaviors involving, in particular, arousal and choice require normal levels of this neuromodulator.