Possibly first discussed as an intrinsic potential by Watanabe (1958) in lobster CG, and further described in studies of the Squilla (stomatopod) CG (Watanabe et al., 1967a, b), driver potentials are relatively slow, sustained, regenerative depolarizations that may arise from a gradual pacemaker potential or be evoked by a depolarization, such as an excitatory synaptic potential (or an applied depolarizing stimulus) (Fig.
Intracellular recordings from the small, posterior neurons have consistently shown a slowly depolarizing pacemaker potential that develops after the post-burst hyperpolarization and leads to the initiation of the next burst (Fig.
The question raised by the contrast in behavior of unstretched hearts and isolated ganglia is whether stretchinduced depolarization of dendrites and collateral processes normally induces bursting activity of the ganglion, while in isolated ganglia, the pacemaker potentials that functionally replace this stretch response in fact represent an injury current.
One of the ionic mechanisms giving rise to pacemaker potentials is hyperpolarization-activated cationic current, now generally referred to as [I.sub.h], which has been implicated in many of the vertebrate neurons studied (reviews: Santoro and Tibbs, 1999; Luthi and McCormick, 1998; Kaupp and Seifert, 2001).
Electrotonic coupling links all cells of the ganglion and passes slowly changing potentials such as stretch-induced or pacemaker potentials and DPs, and these can continue to recur synchronously and rhythmically when impulse propagation has been eliminated with TTX.
Pacemaker potentials for the periodic burst discharge in the heart ganglion of a stomatopod, Squilla oratorio.
In previous study, we suggested that poncirus trifoliate modulates pacemaker potentials through 5-H[T.sub.3] and 5-H[T.sub.4] receptor-mediated pathways via external [Na.sup.+] and [Ca.sup.2+] influx .
Therefore, we undertook to investigate the effects of the SCRT on the pacemaker potentials of cultured ICCs derived from murine small intestine and to identify the receptors involved.
Effect of SCRT on Pacemaker Potentials in Cultured ICCs.
The Involvement of G Protein on SCRT-Induced Depolarizations in Pacemaker Potentials in Cultured ICCs.
Since the membrane depolarizations by SCRT was related to intracellular [Ca.sup.2+] mobilization, we examined whether the effects on pacemaker potentials require phospholipase C (PLC) activation.
Involvements of Mitogen-Activated Protein Kinases (MAPKs) in SCRT-Induced Depolarizations in Pacemaker Potentials in Cultured ICCs.