Modulation of responses of feline ventral spinocerebellar tract neurons by monoamines.
Ventral spinocerebellar tract neurons located in laminae V-VII of cat lumbar spinal cord were tested for the effects of ionophoretically applied monoamines and receptor selective agonists. Extracellularly recorded responses, monosynaptically evoked by group I afferents in a muscle nerve, were compared before, during, and after ionophoresis. They were analyzed with respect to changes in the number of evoked spikes and in the latency. Both serotonin (5-HT) and noradrenaline (NA) were found to facilitate responses of all neurons tested. Ionophoresis of three serotonin subtype receptor agonists (5-carboxamidotryptamine maleate, 5 methoxytryptamine HCl, and alpha-methyl 5-hydroxytryptamine) and of two NA receptor agonists (phenylephrine and isoproterenol) likewise had a facilitatory effect. However, three other 5-HT receptor agonists (8-hydroxy-dipropylaminotetraline hydrobromide), 2-methyl 5-hydroxytryptamine, and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl and two NA receptor agonists (tizanidine and clonidine) had the opposite effect because they depressed responses of the tested neurons. These results show that information forwarded by means of the ventral spinocerebellar tract may be modulated by monoamines and that several receptor subtypes, located pre- or postsynaptically, may be involved. The results also demonstrate that transmission by means of group I muscle afferents may not only be facilitated by monoamines but also depressed by selective receptor subtype activation.
Hammar
Ingela
I
Department of Physiology, Göteborg University, 405 30 Göteborg, Sweden. ingela.hammar@physiol.gu.se
Chojnicka
Barbara
B
Jankowska
Elzbieta
E
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000322:Adrenergic Agonists / Q000494:pharmacology; D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism* / Q000494:pharmacology; D002415:Cats / Q000033:anatomy & histology / Q000378:metabolism*; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D008297:Male; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013126:Spinal Nerve Roots / Q000187:drug effects / Q000502:physiology; D020824:Spinocerebellar Tracts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D000322:Adrenergic Agonists; D015306:Biogenic Monoamines; D017981:Receptors, Neurotransmitter; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D009638:Norepinephrine