Stimulation of a nicotinic ACh receptor causes depolarization and activation of L‐type Ca2+ channels in rat pinealocytes.

Abstract

1. Membrane voltage (Vm) recordings were obtained from isolated rat pinealocytes using the patch-clamp technique. In parallel to the electrophysiological experiments, intracellular Ca2P measurements were performed using fura-2. The mammalian pineal organ transduces information about the ambient photoperiod into a neuroendocrine message by rhythmic synthesis and secretion of melatonin (for review see Arendt, 1995). In mammals the sympathetic innervation of the pineal organ is mandatory to maintain the lightsynchronized circadian rhythm of melatonin production that is highest during the second half of the night. In rats, noradrenaline acts upon melatonin biosynthesis by stimulating both al-and /,3-adrenergic receptors. Stimulation of /,3-receptors increases intracellular cAMP, which mediates the activation of serotonin-N-acetyl-transferase, the rate-limiting enzyme of melatonin biosynthesis.Activation of az1-receptors potentiates the /,3-adrenergic effect via an increase in intracellular calcium concentration ([Ca2+]1) (for review see Klein, 1985). Thus, the essential role of noradrenaline for stimulation of melatonin biosynthesis has been firmly established. In contrast, it is still unclear whether and how neuronal pathways other than the noradrenergic sympathetic innervation (for review see Korf, 1996) are involved in the regulation of melatonin biosynthesis and pineal functions in mammals. Several morphological investigations point toward the existence of a parasympathetic innervation of the mammalian pineal gland, which may originate from the pterygopalatine ganglion and employ acetylcholine as primary neurotransmitter (for review see M0ller, 1992). Further evidence for a cholinergic innervation of the pineal organ has been obtained by recent immunocytochemical studies (E. Weihe, M. K.-H.

Bimodal Concentration-Response of Nicotine Involves the Nicotinic Acetylcholine Receptor, Transient Receptor Potential Vanilloid Type 1, and Transient Receptor Potential Ankyrin 1 Channels in Mouse Trachea and Sensory Neurons

“…A high nicotinic sensitivity can be enabled by a supportive action of voltage-gated calcium channels coexpressed in sensory neurons (Fucile et al, 2005). The fractional calcium conductance of heteropentameric-as opposed to homopentameric-nAChRs (here a 3 b 4 ) is restricted, but if they depolarize the neuron by sodium influx, those calcium channels will be activated and will provide cytosolic calcium increase and eventually CGRP release (Stetzer et al, 1996;Letz et al, 1997;Fucile et al, 2005).…”

ACACNA1Fmutation identified in an X-linked retinal disorder shifts the voltage dependence of Cav1.4 channel activation

“…Moreover, L-type calcium channel currents have been recorded in pinealocytes (31). We therefore investigated whether CACNA1F͞Cacna1f are transcribed in the pineal gland.…”

Cholinergic signal transduction cascades in rat pinealocytes: functional and ontogenetic aspects

“…[20,29]. These events trigger the release of glutamate that, by its action on metabotropic glutamate type 3 receptors, activates an inhibitory cyclic AMP cascade and suppresses NE-induced NAT activation and melatonin synthesis [41,42].…”

“…The components involved in the nicotinic response have been identified using a combination of patch-clamp recordings and calcium imaging [20]. These [4,20]. The [27,28] to low levels in adulthood [8,19,35] [13].…”

“…Moreover, new data will be presented on the ontogenetic development of cholinergic signalling mechanisms in rat pinealocytes. The components involved in the nicotinic response have been identified using a combination of patch-clamp recordings and calcium imaging [20]. These [4,20].…”