title: Evidence for increased extracellular K(+) as an important mechanism for dorsal root induced alternating rhythmic activity in the neonatal rat spinal cord in vitro.
abstract: Intracellular recording from rat lumbar motoneurones showed that patterned electrical stimulation of one dorsal root induced alternating patterns typical of fictive locomotion, accompanied by a reduction in the antidromic spike afterhyperpolarization (AHP). Since the AHP depended linearly on extracellular K(+) ([K(+)](o)), from the AHP fall we calculated that [K(+)](o) rose to 7.9+/-0.4 mM, a value within the 7-10 mM range known to elicit fictive locomotion. To confirm the specificity of this approach we also tested concentrations of N-methyl-D-aspartate (2 microM) below threshold for fictive locomotion, and we observed that, despite strong excitation, the estimated [K(+)](o) was 6 mM, i.e. outside the range for fictive locomotion. We suggest that synaptic activity induced by a certain pattern of electrical stimulation of afferent fibres evoked persistent elevation in [K(+)](o) which triggered the locomotor network to generate rhythmic patterns.
authors.affiliation: Biophysics Sector and Istituto Nazionale di Fisica della Materia Unit, International School for Advanced Studies (SISSA), Via Beirut 4, 34014, Trieste, Italy. marche@sissa.it
authors.forename: C
authors.initials: C
authors.lastname: Marchetti
authors.forename: M
authors.initials: M
authors.lastname: Beato
authors.forename: A
authors.initials: A
authors.lastname: Nistri
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D008124:Locomotion; D008564:Membrane Potentials / Q000502:physiology; D009046:Motor Neurons / Q000378:metabolism*; D016202:N-Methylaspartate / Q000378:metabolism; D011189:Potassium Chloride / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000378:metabolism; D013126:Spinal Nerve Roots / Q000502:physiology*
chemical_list: D016202:N-Methylaspartate; D011189:Potassium Chloride