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Capsaicin activation of glutamatergic synaptic transmission in the rat locus coeruleus In vitro
Author(s) -
Marinelli Silvia,
Vaughan Christopher W.,
Christie MacDonald J.,
Connor Mark
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.022863
Subject(s) - capsaicin , excitatory postsynaptic potential , postsynaptic potential , chemistry , locus coeruleus , neurotransmission , medicine , glutamate receptor , endocrinology , receptor , neuroscience , inhibitory postsynaptic potential , biology , central nervous system , biochemistry
The vanilloid receptor protein (VR1) is a well‐characterised integrator of noxious stimuli in peripheral sensory neurones. There is evidence for the presence of VR1 in the central nervous system, but little information as to its role there. In this study we have examined the actions of agonists for VR1 receptors in the rat locus coeruleus (LC), using whole‐cell patch‐clamp recordings from acutely isolated neurones and neurones in slices. Superfusion with capsaicin resulted in a concentration‐dependent increase in the frequency of isolated miniature excitatory postsynaptic currents (mEPSCs) in LC neurones. The mean amplitude of the mEPSCs was not affected by capsaicin. The effects of capsaicin (1 μM) were abolished by the VR1 receptor antagonists capsazepine (10 μM) and iodoresiniferatoxin (300 n m ). Removal of extracellular Ca 2+ abolished the capsaicin‐induced increase in frequency of mEPSCs. Capsaicin superfusion had no consistent effects on evoked excitatory postsynaptic currents. Capsaicin superfusion also resulted in the release of an adrenoceptor agonist in the LC but did not affect the membrane currents of acutely isolated LC neurones. These data demonstrate that the VR1 receptor appears to be located presynaptically on afferents to the LC, and that activation of VR1 may serve to potentiate the release of glutamate and adrenaline/noradrenaline in this brain region.