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Suppression by the sumatriptan analogue, CP‐122,288 of c‐fos immunoreactivity in trigeminal nucleus caudalis induced by intracisternal capsaicin
Author(s) -
Cutrer F. Michael,
Schoenfeld David,
Limmroth Volker,
Panahian Nariman,
Moskowitz Michael A.
Publication year - 1995
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1995.tb13302.x
Subject(s) - area postrema , sumatriptan , solitary tract , capsaicin , chemistry , c fos , reticular formation , nucleus , trigeminal nerve , solitary nucleus , medicine , endocrinology , stimulation , anesthesia , agonist , brainstem , receptor , gene expression , biochemistry , gene , psychiatry
1 The effects of an intravenously administered sumatriptan analogue were examined on c‐fos‐like immunoreactivity (c‐fos‐LI), a marker of neuronal activation, evoked within trigeminal nucleus caudalis (TNC) and other brain stem regions 2 h after intracisternal injection of the irritant, capsaicin (0.1 ml, 0.1 m m ), in pentobarbitone‐anaesthetized Hartley guinea‐pigs. 2 C‐fos‐LI was assessed in eighteen serial sections (50 μm) using a polyclonal antiserum. A weighted average, reflecting total expression within lamina I, II o of TNC was obtained from three representative levels (i.e., at −0.225 mm, −2.475 mm and −6.975 mm.) 3 Capsaicin caused significant labelling within lamina I, II o , a region containing axonal terminations of small unmyelinated C‐fibres, as well as within the nucleus of the solitary tract, area postrema and medial reticular nucleus. A similar distribution of positive cells was reported previously after intracisternal injection of other chemical irritants such as autologous blood or carrageenin. 4 Pretreatment with a conformationally restricted sumatriptan analogue (with some selectivity for 5‐HT 1B and 5‐HT 1D receptor subtypes) CP‐122,288, reduced the weighted average by approximately 50–60% ( P <0.05) in lamina I, II o at ≥ 100 pmol kg −1 , i.v., but did not decrease cell number within area postrema, nucleus of the solitary tract or medial reticular nucleus. A similar pattern was reported previously following sumatriptan, dihydroergotamine or CP‐93,129 administration after noxious meningeal stimulation. 5 We conclude that modifications at the amino‐ethyl side chain of sumatriptan dramatically enhance the suppression of c‐fos expression within TNC, a finding consistent with its remarkable potency against neurogenic plasma protein extravasation within dura mater. CP‐122,288 and related analogues may serve as an important prototype for drug development in migraine and related headaches.