Short-term swimming exercise attenuates the sensitization of dorsal horn neurons in rats with NGF-induced low back pain.

BACKGROUND: Physical exercise has been shown to be an effective therapy for non-specific low back pain. The study investigated if swimming exercise is a means to reduce the spinal sensitization in an animal model of non-specific low back pain. METHODS: In deeply anesthetized rats, dorsal horn neurons were recorded in spinal segment L2. To induce sensitization of dorsal horn neurons, two injections of nerve growth factor were made into the lumbar multifidus muscle at an interval of 5 days. Swimming exercise for 30 min was performed on the 5 days between both NGF injections. A control group received the NGF injections without exercise treatment. RESULTS: Swimming exercise caused a significant decrease in the NGF-induced hyperexcitability of dorsal horn neurons. Compared to control, the proportion of neurons with input from deep somatic tissues and of convergent neurons with input from at least two types of different tissues decreased significantly (50% vs. 25% and 37% vs. 15%; both p < 0.05). Swimming exercise also reduced the NGF-induced increase in neuronal resting activity. Both the proportion of active neurons and the mean discharge frequency of all neurons decreased significantly (60%, 76.3 ± 23.1 imp/min; vs. 25%, 51.7 ± 35.1 imp/min; both p < 0.01). CONCLUSIONS: In our animal model of low back pain, short-term swimming exercise effectively reduced the latent sensitization of spinal dorsal horn neurons. Swimming exercise decreased the hyperexcitability of the neurons to low back input and lowered the resting activity of sensitized neurons. SIGNIFICANCE: Physical exercise is a common treatment for low back pain. The possible mechanisms underlying the effects of exercise are probably multifold. This work shows that swimming exercise prevents sensitization of dorsal horn neurons, which may be one mechanism for the positive effects of exercise.

Ankle clonus and thiocyanate, linamarin, and inorganic sulphate excretion in school children in communities with Konzo, Mozambique.

We examined 397 school children for ankle clonus in five communities in three districts affected by konzo, spastic paraparesis associated with cassava consumption. From a subsample of 131 children, we analysed urine specimens for urinary thiocyanate, linamarin, and inorganic sulphate. The proportion of children with clonus varied between sites, ranging from 4 to 22 per cent. Geometric mean thiocyanate, linamarin, and inorganic sulphate concentrations were 163 and 60 mumol/l and 4.4 mmol/l, respectively. Children with ankle clonus had higher urinary thiocyanate concentrations. We recommend prevention to reduce cyanide exposure and further monitoring of cyanide exposure and neurological damage in these communities.

Konzo associated with war in Mozambique.

We report an epidemic of konzo, symmetric spastic paraparesis associated with cassava consumption and cyanide exposure: 384 patients were treated in rehabilitation centres; the prevalence rate in a badly affected area was 30/1000. Most patients were children over 3 and women. Owing to war, communities turned to bitter cassava as their staple and took shortcuts in its processing. When the war ended, they continued to depend on inadequately processed bitter cassava. The epidemic lasted 2 years (the last year of war and the first of peace) with peaks each year during the cassava harvest. Although most cases were reported from rural inland areas, patients also came from small towns and the coast. School children had raised urinary thiocyanate and linamarin and low inorganic sulphate concentrations. Urinary thiocyanate values were lower than those previously reported in konzo epidemics, probably because we collected specimens before the cassava harvest and epidemic peak. The necessary conditions for konzo were present: intensive cultivation of bitter casava, insufficient processing, a probable high cyanide intake, and a low intake of protein-rich foods.