Substance P in nociceptive sensory neurons. [Review] [44 refs]
Ciba Foundation Symposium. (91):225-48, 1982.
Abstract:
Substance P is contained within a subpopulation of nociceptive primary sensory neurons that project to the superficial dorsal horn of the spinal cord. Stimulation of the peripheral processes of primary afferent fibres at intensities that activate A delta and C fibres elicits a pronounced release of substance P from the cat spinal cord in vivo.
Experiments with the neurotoxins capsaicin and 5,6 dihydroxy-tryptamine have shown that substance P release from the spinal cord in vivo derives largely from afferent fibres. Intrathecal perfusion of the cat spinal cord with morphine abolishes the nerve-evoked release of substance P while capsaicin produces a dramatic increase in peptide release. Prolonged treatment of rats with capsaicin depletes substance P from the dorsal horn and results in reduced sensitivity to noxious peripheral stimuli. The duration of the somatic action potential recorded from cultured sensory neurons is known to be decreased by enkephalin and is prolonged by capsaicin. The acute effects of both morphine and capsaicin on substance P may be mediated by an interaction with voltage-sensitive ion channels on the sensory neuron. These observations suggest that nociceptive input to the dorsal horn can be regulated by drugs that interact directly with substance P-containing sensory terminals.
[References: 44]
Department of Anesthesia, University Hospital Ghent, Belgium.
Dual channel electrostimulation in pain.
Acta Neurologica Belgica. 98(2):195-8, 1998 Jun.
Abstract:
Spinal cord stimulation is an accepted treatment for neuropathic pain. Technical advances in electrode design and better patient selection have led to better and sustained pain control by these devices. Multilead electrical stimulation is the latest innovation in implantable electrostimulation (Mattrix, Medtronic Minneapolis, USA). Two combined multipolar leads connected to a radiofrequency-coupled system can deliver electrical pulses of various amplitudes and pulse widths at different dermatome levels. Single stimulation is applied with different electrode configurations using both electrodes with identical stimulation parameters. In dual stimulation, the amplitude and the pulse width can vary between the electrode configurations. Dual channel stimulation helps steering stimulation paresthesias. Three patients illustrate the technical advantages of dual channel electrostimulation in the pain relief at multiple sites. Two patients with failed back surgery syndrome obtained more easily stimulation-induced paresthesias in the back and the legs. Dual channel stimulation is cost saving in patients implanted with two electrodes. This is presented in a third patient with an electrode in the thalamus--as pain treatment for cervicobrachialgia and a second in the epidural space--as treatment for the failed back surgery syndrome. These electrodes were connected to the Mattrix stimulator.
