Distribution of glutamic acid decarboxylase mRNA in the forebrain of the rainbow trout as studied by in situ hybridization

Abstract

By using degenerate primers designed from glutamate decarboxylase (GAD) sequences of mammals, Xenopus and Drosophila, a 270‐bp cDNA fragment was cloned by reverse transcriptase‐polymerase chain reaction (RT‐PCR) from cerebellum total RNA of rainbow trout. This partial cDNA shows 90% identity with mammalian GAD 65 and presents the Asn‐Pro‐His‐Lys (NPHK) sequence corresponding to the pyridoxal‐binding region of porcine DOPA decarboxylase or mammalian GAD. The distribution of GAD 65 mRNA‐expressing neurons in the forebrain of the trout was studied by in situ hybridization using either digoxigenin‐ or 35S‐labeled probes. The results demonstrate that gamma‐amino butyric acid (GABA) neurons are widely distributed throughout the forebrain, with a high density in the periventricular regions. In this study, we report their precise distribution in the telencephalon and diencephalon. GAD mRNA‐expressing cells were particularly abundant in the preoptic region and the mediobasal hypothalamus, two major neuroendocrine and estrogen‐sensitive regions in fish. The presence of GAD mRNA‐expressing neurons was observed in visually related structures such as the suprachiasmatic nucleus, the pretectal region, and the thalamus. Immunohistochemistry with antibodies directed against mouse GAD failed to demonstrate the presence of immunoreactive cell bodies, but showed a very high concentration of GAD‐immunoreactive fibers in many brain regions, notably in the preoptic area, hypothalamus, and neurohypophyseal digitations of the pituitary, in particular in the proximal pars distalis. These results indicate that GABA neurons are ideally placed to modulate neuroendocrine activities at the hypothalamic and pituitary levels and to participate in the processing of sensorial information. J. Comp. Neurol. 410:277–289, 1999. © 1999 Wiley‐Liss, Inc.

Neurochemical Organization and Connections of the Cerebral Preglomerular Complex of the Masu Salmon

“…In the anterior preglomerular nucleus (F) of the masu brain, we found GABA-ergic type-I neurons. The results of immunohistochemical labeling of GABA in nuclei of the masu preglomerular complex agree with the data obtained on other fish species [23][24][25]. In the glomerular nucleus, considerable amounts of GABA/ benzodiazepine receptors were found [26].…”

“…In the medial and anterior nuclei of the preglomerular complex of the Danio fries, neurons with expresion of the vesicular transporter GAD67 were found [23]. Medina et al also found GABA-ergic neurons in the preglomerular complex of the silver eel (Anguilla anguilla) [24], while GAD was found in the trout preglomerular nucleus [25]. Taking into account these data, we can suppose that GABA does not exclusively function in the masu preglomerular complex as a neuromodulator/neuromediator; this agent can also be considered a factor controlling the morphogenesis in this region.…”

Expanded expression of Sonic Hedgehog inAstyanaxcavefish:multiple consequences on forebrain development and evolution

“…We did not observe at any stage Lhx6-positive cells that could constitute the fish counterpart of tangentially migrating GABAergic cortical interneurons (Anderson et al, 1999;Anderson et al, 1997;Anderson et al, 2001;Marin and Rubenstein, 2001;Marin and Rubenstein, 2003). In fish, these GABAergic pallial interneurons constitute a relatively scarce neuronal population (Anglade et al, 1999), and the absence of pallial Lhx6 expression, together with the absence of Dlx gene expression in the fish pallium (Akimenko et al, 1994;Alunni et al, 2004;Zerucha and Ekker, 2000) (present data), suggest that these interneurons do not share common genetic specification mechanisms with their mammalian counterparts. In fact, an Lhx6.1 isoform of Lhx6 in mouse was reported to be expressed both in the cortex and the olfactory bulbs .…”

The distribution of GAD67‐mRNA in the adult zebrafish (teleost) forebrain reveals a prosomeric pattern and suggests previously unidentified homologies to tetrapods

“…The distribution of GABAergic cells has been investigated in the forebrain of the eel (Medina et al, 1994), trout (Anglade et al, 1999) and goldfish (Martyniuk et al, 2007). These studies focused on the distribution of GABAergic cells in telencephalic and hypothalamic regions and did not lead to an improved anatomical characterization of subpallial units to distinguish among striatum, pallidum and septum as recently discussed (Wullimann and Mueller, 2004b).…”