Methodological optimization of applying neuroactive agents for the study of locomotor-like activity in the mudpuppies (Necturus maculatus).
We compared the effects of mode of delivery of neuroactive agents and the effects of dimethyl sulfoxide (DMSO), a vehicle for dissolving neuroactive agents, on locomotor-like activity in vitro. By superfusion, d-glutamate (0.3-0.9 mM) produced robust walking-like activity at superfusion rates 10-25 ml/min. In contrast, bolus application of the same or higher doses of glutamate (0.1-1.5 mM) failed to induce any rhythmic activity. Superfusion with AP-5, a NMDA receptor antagonist, produced dose-dependent inhibition of the ongoing walking-like activity induced by D-glutamate and completely blocked the activity at 20 microM. In contrast, bolus application of AP-5 did not block the walking-like activity at concentrations up to 120 microM. Similarly, superfusion of AP-5 inhibited the initiation of walking-like activity and completely blocked the initiation at 20 microM, while bolus application of AP-5 failed to do so at concentrations up to 120 microM. Superfusion of strychnine, a glycine receptor antagonist, blocked the walking-like activity at concentrations of 3-5 microM, while its bolus application altered NMDA-induced, but not glutamate-induced, walking-like activity to a synchronized pattern. DMSO significantly affected the walking-like activity in a dose-dependent manner at concentrations ranging 1-10% (v/v). These results demonstrate that the way by which the neuroactive agents are applied is a significant factor that determines the outcome of experiments on the neural control of locomotion. Also, the dose-dependent effects of DMSO on the activity of neural networks for locomotion should be taken into account in data interpretation.
Lavrov
Igor
I
Department of Physiological Science and Brain Research Institute, University of California, Los Angeles, CA 90095, USA.
Cheng
Jianguo
J
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D016503:Drug Delivery Systems / Q000295:instrumentation / Q000379:methods*; D004347:Drug Interactions / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005552:Forelimb / Q000294:innervation / Q000502:physiology; D018684:Glycine Agents / Q000494:pharmacology; D008124:Locomotion / Q000187:drug effects* / Q000502:physiology; D023421:Models, Animal; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009338:Necturus maculosus / Q000033:anatomy & histology / Q000502:physiology*; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology; D009480:Neuropharmacology / Q000379:methods*; D009482:Neurophysiology / Q000295:instrumentation / Q000379:methods*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009924:Organ Culture Techniques; D018009:Receptors, Glycine / Q000037:antagonists & inhibitors / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology; D016138:Walking / Q000502:physiology
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018684:Glycine Agents; D018377:Neurotransmitter Agents; D018009:Receptors, Glycine