Responses to glossopharyngeal stimulus in the early embryonic chick brainstem: spatiotemporal patterns in three dimensions from repeated multiple-site optical recording of electrical activity

Abstract

In an effort to assess the spatial patterning of glossopharyngeal responses in the early embryonic chick brainstem, we used a multiple- site optical recording system with a 12 x 12 element photodiode array and a voltage-sensitive merocyanine-rhodanine dye (NK2761) to monitor neural transmembrane voltage activities. Seven and 8 d old embryonic chick brainstems were sliced into 1400–1600 microns thick sections with the glossopharyngeal and vagal nerves attached, and then stained with the dye. Neural voltage-related optical signals were evoked by a positive brief (depolarizing) square current pulse applied to the glossopharyngeal nerve with a microsuction electrode, and then recorded simultaneously from many loci in the objective two-dimensional image plane of a compound microscope. In addition to the multiple-site optical recording technique, we tried to introduce an optical sectioning method by changing the focal plane of the microscope to obtain three-dimensional information. Thus, we have been able to assess semiquantitatively the three-dimensional profiles of two glossopharyngeal response areas corresponding to the nucleus of the glossopharyngeal nerve (nucleus nervi glossopharyngei) and the nucleus of the tractus solitarius. Furthermore, glutaminergic excitatory postsynaptic potentials were determined within the response area corresponding to the nucleus of the tractus solitarius. In addition, we also compared the glossopharyngeal and vagal response areas and found that the cores of the related nuclei are separated in three dimensions.

Development of Functional Synaptic Connections in the Auditory System Visualized With Optical Recording: Afferent-Evoked Activity Is Present From Early Stages

“…The optical signals were eliminated at 630 -640 nm, where the NK2761-dependent extrinsic absorption signal is absent (Momose- Sato et al 1995), indicating that the detected optical signals are indeed dye-absorption changes related to the membrane potential and do not correspond to changes in light scattering related to mechanical or other factors. When we applied hyperpolarizing current pulses, no optical signal was observed within the medulla, although an electrotonic potential-related component was found within the ganglion.…”

“…In our previous studies, we applied a voltagesensitive dye-imaging technique to chicken and rat embryos and established its feasibility for recording electrical activity from the embryonic CNS (for reviews see Momose-Sato et al 2001. In these studies, we assessed the onset and early development of action potential activity and postsynaptic function related to various cranial and spinal nerve inputs and outputs Miyakawa et al 2004; Mochida et al 2001;Momose-Sato et al 1991, 1994, 2004Sato et al 1995Sato et al , 1998Sato et al , 1999. The brain stem neural circuits related to the vestibulocochlear nerve (N. VIII) provide an excellent model to investigate the mechanisms of neural circuit formation because of their accessibility and well-described internuclear connectivity (Boord and Rasmussen 1963;Rubel and Fritzsch 2002;Ryugo and Parks 2003).…”

Optical Mapping Reveals Developmental Dynamics of Mg2+-/APV-Sensitive Components of Glossopharyngeal Glutamatergic EPSPs in the Embryonic Chick NTS

“…To detect the largest optical responses from the N. IX-related NTS, we set the focal plane at the level of the glossopharyngeal nerve root ( Fig. 1; also see Sato et al 1995). In the present experiments, we used the 128ch optical recording system using a 12 ϫ 12-element silicon photodiode array (MD-144-4PV, Centronic, Croydon, UK), which was constructed in our laboratory (for reviews, see Kamino 1991;Momose-Sato et al 2001).…”

“…We showed three-dimensional profiles of the glossopharyngeal/vagal response areas corresponding to the NTS (sensory nucleus), the dorsal motor nucleus of the vagus nerve (DMNV: motor nucleus), and the nucleus of the glossopharyngeal nerve (Nucl IX: motor nucleus) in chick and rat embryos Momose-Sato et al 1991, 1999Sato et al 1995Sato et al , 1998Sato et al , 2002aSato et al ,b, 2004. In these studies, we proved the following characteristics of the embryonic chick NTS.…”

“…In these studies, we proved the following characteristics of the embryonic chick NTS. 1) In both the N. IX-and N. X-related NTS, optical signals were composed of fast and slow signals, and the fast signal corresponded mainly to the presynaptic action potential and the slow signal to the glutamatergic excitatory postsynaptic potential (EPSP) Momose-Sato 1994;Sato et al 1995). 2) In both the N. IX-and N. X-related NTS, the glutamatergic EPSPs consisted of non-N-methyl-D-aspartate (NMDA) and NMDA receptor components MomoseSato et al 1994).…”