D‐serine is distributed in neurons in the brain of the sea lamprey

Abstract

The amino acid D-serine is an endogenous coagonist of N-methyl-D-aspartate (NMDA) receptors in mammals that has been shown to play an important role in synaptic function, behavior, learning, and memory. The distribution and cellular location of D-serine in the brain of the sea lamprey was investigated by using immunofluorescence methods. One major finding of our study, unlike early studies of mammals, was the localization of D-serine immunoreactivity in perikarya and dendrites of neurons, whereas D-serine immunoreactivity was not generally observed in the lamprey glia. D-serine-immunoreactive neurons were observed in different brain regions, including the olfactory bulb, medial pallium, thalamus, torus semicircularis, isthmus, and reticular formation. The colocalization of D-serine with gamma-aminobutyric acid (GABA) was also studied with a double-immunofluorescence technique. The relationship between D-serine and glycine immunoreactivities was studied in alternate parallel series of sections stained for either D-serine/GABA or glycine/GABA. Colocalization with GABA was observed in various D-serine-immunoreactive populations, and codistribution and possible colocalization with glycine was also observed in some populations, mainly in the dorsal isthmic gray, medial octavolateral nucleus, dorsal column nucleus, interpeduncular nucleus, and reticular formation. Although numerous fibers were strongly GABA- and glycine-immunoreactive, D-serine immunoreactivity was observed mostly in cell perikarya and dendrites. The present results indicate that the D-serine immunoreactive cells are small to medium-sized neurons, some exhibiting classical inhibitory neurotransmitters, in which D-serine might be acting as a modulator. The neuronal distribution of D-serine and its frequent colocalization and/or codistribution with the two main inhibitory neurotransmitters appeared early in vertebrates.

Glutamatergic neuronal populations in the forebrain of the sea lamprey, Petromyzon marinus: An in situ hybridization and immunocytochemical study

“…Instead, the ependymoglia of the sea lamprey is not labeled, which indicates that metabolic pools of glutamate in nonglutamatergic cells are probably too low to be demonstrated with present methods. As also shown previously for the amino acids glycine (Villar‐Cerviño et al,2006,2008a,b), L‐aspartate (Villar‐Cerviño et al,2008c), and D‐serine (Villar‐Cerviño et al,2010a), brain tissue of the sea lamprey also appears highly favorable for the immunocytochemical detection of glutamate in neuronal perikarya.…”

“…To assess the glutamatergic nature of the glutamate‐ir populations, we used in situ hybridization in the larval forebrain with probes for a lamprey VGLUT (Villar‐Cerviño et al,2010b). The lamprey VGLUT is highly homologous to the sequenced mammalian and nonmammalian VGLUTs and appears to be the only VGLUT sequence present in three different cDNA libraries obtained from adult and embryonic brains/heads of lampreys (Villar‐Cerviño et al,2010a,b). These probes provided a contrasting tool for the characterization of glutamatergic system in lampreys, which until now was dependent solely on glutamate antibodies.…”

A neurochemical map of the developing amphioxus nervous system

“…For instance, in embryos of the frog Xenopus laevis the first glycinergic cells appear in the caudal hindbrain region and subsequently extend to the spinal cord [48], which was also observed in lamprey embryos [49,50]. In C. intestinalis larvae, two pairs of glycinergic neurons have been reported in the tail [51] (Figure 13).…”

Cloning of the GABAB Receptor Subunits B1 and B2 and their Expression in the Central Nervous System of the Adult Sea Lamprey

“…In lampreys, the distribution of GABA immunoreactive neurons and fibers in the CNS of adults (Meléndez-Ferro et al, 2000; Robertson et al, 2007), their ontogeny (Meléndez-Ferro et al, 2002, 2003; Ruiz et al, 2004), the origin of the descending GABAergic projections to the spinal cord (Valle-Maroto et al, 2011) and the co-localization of GABA with others classic neurotransmitters in the same neuron (Villar-Cerviño et al, 2008, 2010, 2013, 2014; Barreiro-Iglesias et al, 2009a,b) have been widely studied. However, and despite the wide knowledge on the GABAergic system of lampreys, the cloning and molecular characterization of the GABA B receptors subunits of lampreys as well as their pattern of expression in the CNS have not been reported so far.…”