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Evidence for excitatory 5‐HT 2 ‐receptors on rat brainstem neurones
Author(s) -
Davies Michael,
Wilkinson Lawrence S.,
Roberts Malcolm H.T.
Publication year - 1988
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.1476-5381.1988.tb11551.x
Subject(s) - excitatory postsynaptic potential , prazosin , metergoline , methysergide , ketanserin , chemistry , endocrinology , receptor , medicine , 5 ht2 receptor , 5 ht receptor , pharmacology , receptor antagonist , yohimbine , antagonist , serotonin , biology
1 The technique of microiontophoresis was used to investigate the identity of the receptor mediating the excitatory effects of 5‐hydroxytryptamine (5‐HT) upon neurones in the midline of the medullary brainstem of the rat in vivo . 2 The 5‐HT 1 ‐like receptor agonists 5‐carboxamidotryptamine (5‐CT) and 8‐hydroxy‐2‐(di‐n‐propylamino) tetralin (8‐OH‐DPAT) failed to excite the majority of neurones excited by 5‐HT. The mobilities of 5‐CT and 8‐OH‐DPAT when tested in vitro were found not to differ significantly from that of 5‐HT, suggesting that the lack of effect of these agonists was not due to a lower rate of release from the microelectrodes. 3 The excitatory responses to 5‐HT were attenuated by the 5‐HT 2 ‐receptor antagonists ketanserin and methysergide when applied microiontophoretically or administered intravenously (0.3 and 1 mg kg −1 respectively). Excitatory responses to glutamate and noradrenaline were not reduced. 4 The 5‐HT 3 ‐receptor antagonist MDL 72222 failed to attenuate selectively the excitatory response to 5‐HT when applied either by microiontophoresis or administered intravenously (1 mg kg −1 ). 5 Microiontophoretic application of the α 1 ‐adrenoceptor antagonist prazosin did not attenuate excitatory responses to either 5‐HT or noradrenaline. Intravenously administered prazosin (0.8 mg kg −1 ) also failed to attenuate excitatory responses to 5‐HT, but did block excitatory responses to noradrenaline. 6 These results suggest that 5‐HT 2 ‐receptors, but not 5‐HT 1 ‐like receptors, 5‐HT 3 ‐receptors or α 1 ‐adrenoceptors, are involved in the excitatory response of midline medullary neurones to 5‐HT.