[Asymmetric distribution of peptide regulators of muscle tonus and substance P in the spinal cord of rats with unilateral hyperactivity of the lumbar enlargement neurons].

The injection of tetanus toxin in m. gastrocnemius of the left or right hind limb of rats evokes ipsilateral hyperactivity of lumbar neurons in the spinal cord. In this case the lumbar enlargement extract after its intracisternal injection to healthy animals increases the duration of hind limb passive extension on the side where the donor neurons are hyperactive. The extract of the spinal cord of healthy rats was ineffective. Proteolysis of the extract with pronase or co-injection of opiate antagonist--naloxone--completely eliminated the lateralized changes in the muscular tone of the recipient. Substances that cause the unilateral changes in the muscular tone of the recipient are believed to be peptides. They are assumed to be involved in the functioning of endogenous opioid system. The level of substance P in the donor spinal cord was elevated bilaterally, but was higher in the hyperactive half of the spinal cord.