Increased sensitivity to cocaine by cholinergic cell ablation in nucleus accumbens.

Chronic exposure to cocaine causes long-lasting behavioral changes associated with cocaine reinforcement and addiction. An important neural substrate for cocaine addiction is the nucleus accumbens (NAc), which receives dopaminergic input from the ventral tegmental area. Although the neural circuit of the NAc is controlled by several other neurotransmitters, their involvement in cocaine addiction remains elusive. In this investigation, we ablated cholinergic interneurons from the adult NAc with immunotoxin-mediated cell targeting and examined the role of acetylcholine transmitter in adaptive behavioral changes associated with cocaine reinforcement and addiction. Acute exposure to cocaine induced abnormal rotation in unilaterally cholinergic cell-eliminated mice. This abnormal turning was enhanced by repeated exposure of cocaine. In bilaterally cholinergic cell-eliminated mice, chronic cocaine administration induced a prominent and progressive increase in locomotor activity. Moreover, these mice showed robust conditioned place preference with a lower dose of cocaine, compared with wild-type littermates. This investigation demonstrates that acetylcholine in the NAc plays a key role in both acute and chronic actions of cocaine.

Postural modulation of soleus H-reflex under simulated hypogravity by head-out water immersion in humans.

To test our hypothesis that somatosensory inputs would influence postural modulation of soleus H-reflex, eleven subjects were investigated under the head-out water immersion (HOWI) conditions. Subjects were supine or standing on a tilting bed in each condition. They were instructed to maintain an upright posture with both legs. The water was filled to the subject's neck level in a test tank to reduce 95% of the gravitational effect by buoyancy. Surface electromyography of the soleus and tibialis anterior was measured. The soleus H-reflex was elicited at a stimulation intensity of 1.05 times the motor threshold. The recruitment profile of the motor response was unchanged between the conditions. The background activities of the soleus and tibialis anterior were not detected in any condition. The peak-to-peak amplitude of the H-reflex was significantly different between the conditions while the stimulation intensity (small M size) was not different. The soleus H-reflex during standing was significantly decreased compared with being supine in the control condition, whereas it did not in the HOWI condition. It was concluded that somatosensory inputs due to gravity exert an influence on postural modulation of the soleus H-reflex to maintain static posture in humans.

[Development of a functional fitness test for the elderly].

A test of functional fitness defined as physical capacity to independently perform daily functional activities was developed for aged persons. The functional fitness test was composed of four physical capacity evaluation tasks representing physical abilities necessary to perform main activities of daily living; viz. sitting and standing up test, zig-zag walking test, hand working test with pegboard for dexterity evaluation, and rope working test for self-care evaluation. The reliability and feasibility of the test were examined with 765 aged persons living in the community. The distribution of measurement values in each item showed neither extreme skewness nor kurtosis. Retest reliabilities for each task were 0.857 to 0.942, but the second trial showed significantly reduced (p < 0.001) values than the first trial in test-retest. Significant relationships (r = 0.503 to 0.627) between measurement values in each items and chronological age were found in both male and female. Functional fitness test and physical fitness test scores were correlated 0.740. These results showed that the functional fitness test developed in the present study has a high reliability and feasibility to evaluate functional capacity of daily living in aged persons.