Anatomical and histological characteristics of the nervous system of the Chilean giant mussel, Choromytilus chorus (Molina 1782) (Bivalvia, Mytilidae) / Características anatómicas e histológicas del sistema nervioso del mejillón gigante, Choromytilus chorus (Molina 1782) (Bivalvia, Mytilidae)

The anatomy and histology of the nervous system in the mussel Choromytilus chorus were studied. Juvenile specimens of C. chorus and adult broodstock were collected in Laraquete Cove, Chile (37°09'S; 37°11'O). The juveniles were used for histological analysis and the adults for a macroscopic description of anatomical. The histological description was carried out by Gallego´s trichrome technique. The macroscopic analysis showed that nervous system network includes three pairs of ganglia of orange color and little size (20-40 mm) (cerebral, pedal and visceral) located in the anterior, middle and posterior zone of the specimen, respectively. The histological analysis showed many type de cells inside the ganglia (neurosecretory, granulated and glial cells). The ganglia network could be involving in regulating several physiological processes in the mussels through of their neurosecretions.

Se estudió la anatomía e histología del sistema nervioso en el coro Choromytilus del mejillón. Se recolectaron especímenes juveniles de C. coros y reproductores adultos en Laraquete Cove, Chile (37 ° 09'S, 37 ° 11'O). Los especímenes juveniles se utilizaron para el análisis histológico y los adultos para una descripción macroscópica de anatómica. La descripción histológica se realizó mediante la técnica de tricrómico de Gallego. El análisis macroscópico mostró que la red del sistema nervioso incluye tres pares de ganglios de color naranjo y poco tamaño (20-40 mm) (cerebral, pedal y visceral) localizados en la zona anterior, media y posterior de la muestra, respectivamente. El análisis histológico mostró muchos tipos de células dentro de los ganglios (células neurosecretoras, granuladas y gliales). La red de ganglios podría estar involucrada en la regulación de varios procesos fisiológicos en los mejillones a través de sus neurosecreciones.

Facilitation of AMPA receptor-mediated steady-state current by extrasynaptic NMDA receptors in supraoptic magnocellular neurosecretory cells

In addition to classical synaptic transmission, information is transmitted between cells via the activation of extrasynaptic receptors that generate persistent tonic current in the brain. While growing evidence supports the presence of tonic NMDA current (INMDA) generated by extrasynaptic NMDA receptors (eNMDARs), the functional significance of tonic I(NMDA) in various brain regions remains poorly understood. Here, we demonstrate that activation of eNMDARs that generate I(NMDA) facilitates the α-amino-3-hydroxy-5-methylisoxazole-4-proprionate receptor (AMPAR)-mediated steady-state current in supraoptic nucleus (SON) magnocellular neurosecretory cells (MNCs). In low-Mg2+ artificial cerebrospinal fluid (aCSF), glutamate induced an inward shift in I(holding) (I(GLU)) at a holding potential (V(holding)) of -70 mV which was partly blocked by an AMPAR antagonist, NBQX. NBQX-sensitive I(GLU) was observed even in normal aCSF at V(holding) of -40 mV or -20 mV. I(GLU) was completely abolished by pretreatment with an NMDAR blocker, AP5, under all tested conditions. AMPA induced a reproducible inward shift in I(holding) (I(AMPA)) in SON MNCs. Pretreatment with AP5 attenuated I(AMPA) amplitudes to ~60% of the control levels in low-Mg2+ aCSF, but not in normal aCSF at V(holding) of -70 mV. I(AMPA) attenuation by AP5 was also prominent in normal aCSF at depolarized holding potentials. Memantine, an eNMDAR blocker, mimicked the AP5-induced I(AMPA) attenuation in SON MNCs. Finally, chronic dehydration did not affect I(AMPA) attenuation by AP5 in the neurons. These results suggest that tonic I(NMDA), mediated by eNMDAR, facilitates AMPAR function, changing the postsynaptic response to its agonists in normal and osmotically challenged SON MNCs.