Capsaicin activation of glutamatergic synaptic transmission in the rat locus coeruleus In vitro

Abstract

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 nm). Removal of extracellular Ca2+ 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.

Potentiation of the glutamatergic synaptic input to rat locus coeruleus neurons by P2X7 receptors

“…Eventually, we confirmed the findings of Marinelli et al [21] in that capsaicin facilitated the sEPSC frequency in the LC. In addition, we showed that this effect was prevented by the selective TRPV1 antagonist capsazepine, but not by the P2 receptor antagonist PPADS.…”

“…The TRPV1 agonist capsaicin has earlier been shown to increase the mEPSC frequency in LC neurons under in situ conditions [21]. We found that, in contrast to 2-MeSATP and ATP, but in accordance with BzATP, capsaicin (10 μM) did not induce an inward current response of LC neurons (n =6; Fig.…”

Mechanisms of Prolonged Presynaptic Ca2+Signaling and Glutamate Release Induced by TRPV1 Activation in Rat Sensory Neurons

“…The proposed presynaptic function of mitochondria (Fig. 9F ) may also help to explain the previous observations by several groups that brief TRPV1 activation triggers long-lasting release of glutamate and prolonged synaptic activity in the spinal cord and brainstem slices (Ueda et al, 1993;Yang et al, 1998;Marinelli et al, 2002Marinelli et al, , 2003Nakatsuka et al, 2002).…”

Reduced Anxiety, Conditioned Fear, and Hippocampal Long-Term Potentiation in Transient Receptor Potential Vanilloid Type 1 Receptor-Deficient Mice

“…In line with these arguments, TRPV1-mediated effects of anandamide in the hippocampus turned out to be opposite to those induced via CB 1 by 2-arachidonylglycerol (Al-Hayani et al, 2001). In addition, whereas activation of TRPV1 promotes excitatory facilitation of synaptic transmission (Marinelli et al, 2002(Marinelli et al, , 2003, activation of CB 1 leads to a reduction in presynaptic calcium levels and, thus, to a reduction of synaptic transmission (for review, see Chevaleyre et al, 2006). Some fatty acid derivatives such as anandamide or N-arachidonyldopamine bind and activate TRPV1 and CB 1 receptors equally well and can, thus, be regarded as both endovanilloids and endocannabinoids (van der Stelt and Di Marinelli et al, 2006).…”