Attenuation of Fos-like immunoreactivity in the trigeminal nucleus caudalis following trigeminovascular activation in the anaesthetised guinea-pig.
The present study has examined the involvement of sensory neurotransmitters in activating neurones in the trigeminal nucleus caudalis following stimulation of the trigeminovascular system in anaesthetised guinea-pigs. Electrical stimulation of the right trigeminal ganglion produced a unilateral expression of Fos-like immunoreactivity (Fos-LI) in the trigeminal nucleus caudalis. The tachykinin NK1 receptor antagonist, GR205171 (100 micrograms/kg i.v.) and the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 (1 mg/kg i.v.) each inhibited expression of Fos-LI following electrical stimulation. The calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP8-37 (1.3 mg/kg i.v.), administered following rostral intracarotid infusion of mannitol to disrupt the blood-brain barrier, tended to reduce Fos-LI evoked by electrical stimulation, although this failed to reach statistical significance. Capsaicin (10 nmol in 0.1 ml), administered intracisternally, produced a bilateral expression of Fos-LI in the trigeminal nucleus caudalis. This expression was unaffected by the peripherally acting NK1 receptor antagonist, GR82334 (0.2 mg/kg i.v.) or CGRP8-37 (1.3 mg/kg i.v.). The centrally penetrant NK1 receptor antagonist, GR205171 (100 micrograms/kg i.v.), inhibited significantly Fos-LI evoked by intracisternal capsaicin administration. It is concluded that the sensory neurotransmitters, substance P and glutamate are released centrally following activation of the trigeminovascular system and that each may be involved in activation of cells in the trigeminal nucleus caudalis.
Clayton
J S
JS
Systems Biology Unit, Glaxo Wellcome Medicines Research Centre, Stevenage, Herts, UK.
Gaskin
P J
PJ
Beattie
D T
DT
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D004558:Electric Stimulation; D018698:Glutamic Acid / Q000378:metabolism; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D064729:Neurokinin-1 Receptor Antagonists; D018377:Neurotransmitter Agents / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012039:Regional Blood Flow / Q000502:physiology; D013373:Substance P / Q000378:metabolism; D014279:Trigeminal Nucleus, Spinal / Q000098:blood supply* / Q000378:metabolism*
D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D064729:Neurokinin-1 Receptor Antagonists; D018377:Neurotransmitter Agents; D016760:Proto-Oncogene Proteins c-fos; D016194:Receptors, N-Methyl-D-Aspartate; D013373:Substance P; D018698:Glutamic Acid; D015740:Calcitonin Gene-Related Peptide