Glutamate-like immunoreactivity in chick cerebellum and optic tectum

Neurotransmitters, neuropeptides and calcium binding proteins in developing human cerebellum: a review

Many endogenous neurochemicals that are known to have important functions in the mature central nervous system have also been found in the developing human cerebellum. Cholinergic neurons, as revealed by immunoreactivities towards choline acetyltransferase or acetylcholinesterase, appear early at 23 weeks of gestation in the cerebellar cortex and deep nuclei. Immunoreactivities gradually increase until the first postnatal month. Enkephalin is localized in the developing cerebellum, initially in the fibers of the cortex and deep nuclei at 16-20 weeks and then also in the Purkinje cells, granule cells, basket cells and Golgi cells at 23 weeks onward. Another neuropeptide, substance P, is localized mainly in the fibers of the dentate nucleus from 9 to 24 weeks but substance P immunoreactivity declines thereafter. GABA, an inhibitory neurotransmitter of the central nervous system, starts to appear at 16 weeks in the Purkinje cells, stellate cells, basket cells, mossy fibers and neurons of deep nuclei. GABA expression is gradually upregulated toward term forming networks of GABA-positive fibers and neurons. Catecholaminergic fibers and neurons are also detected in the cortex and deep nuclei at as early as 16 weeks. Calcium binding proteins, calbindin D28K and parvalbumin, make their first appearance in the cortex and deep nuclei at 14 weeks and then their expression decreases toward term, while calretinin appears later at 21 weeks but its expression increases with fetal age. The above findings suggest that many neurotransmitters, neuropeptides and calcium binding proteins (1) appear early during development of the cerebellum; (2) have specific temporal and spatial expression patterns; (3) may have functions other than those found in the mature neural systems; and (4) may be able to interact with each other during early development.

Effects of dark rearing and light exposure on memory for a passive avoidance task in day-old chicks

Light exposure during embryogenesis is necessary for functional and morphological maturation in the domestic chick. In the present study, dark incubation was demonstrated to induce a weak amnestic effect on retention for a passive avoidance task and a diminution in discriminative memory ability in day-old chicks. Putative explanations based on possible motor, attentional, or visual impairment were excluded. Light exposure of dark-reared eggs, specifically during embryonic days E19 to E20, alleviated the retention and discrimination deficits. The processes which might mediate between prehatch light stimulation and posthatch behavioral effects are discussed.

Exposure to light prior to hatching induces asymmetry of receptor binding in specific regions of the chick forebrain

This paper describes neurochemical asymmetries present in forebrain regions of the newly hatched chick that result from environmental conditions; specifically from asymmetrical exposure of the chick embryo to light prior to hatching. Quantitative autoradiography was used to determine GABA and glutamate receptor subtype binding in a number of regions of the left and right forebrain hemispheres of chicks that had either the left (LES), or the right (RES), eye system exposed to light prior to hatching. On day 19 of incubation the embryo's head was withdrawn from the egg and the left or the right eye was occulded until hatching. [3H]MK-801, [3H]AMPA and [3H]muscimol binding assays were performed on frozen sections from 2 different coronal regions of the forebrain, sampled on day-1 posthatching. Significant [3H]MK-801, [3H]AMPA and [3H]muscimol binding asymmetries were determined in forebrain regions from chicks that had their RES exposed to light prior to hatching, particularly in forebrain regions which are known to receive afferent visual input. The reverse pattern of asymmetry was found for all 3 ligands in regions such as the ectostriatum of chicks that had their LES exposed to light, while asymmetry of muscimol and AMPA binding, present in many regions in right eye system chicks was not present in chicks that had the left eye system exposed to light during incubation. Thus, the presence and pattern of experience-dependent neurochemical asymmetries in the chick forebrain are specific to both region and receptor type.

An antibody to agmatine localizes the amine in bovine adrenal chromaffin cells

Agmatine, a newly identified amine in mammalian brain, is an endogenous ligand for imidazoline and alpha 2-adrenergic receptors. We sought to develop a polyclonal antibody to agmatine suitable for immunocytochemistry. Agmatine was conjugated to keyhole limpet hemocyanin and injected into rabbits. The polyclonal antiserum so generated dose-dependently recognized the agmatine conjugate but not carrier protein by dot blot. Its reaction with the conjugate was selectively antagonized by agmatine but not related compounds. The antiserum, but not pre-immune or pre-adsorbed antiserum, selectively stained cultured adrenal chromaffin cells. Our results indicate that agmatine immunoreactivity is contained in a sub-population of adrenal chromaffin cells and, thus, these antibodies are useful for immunocytochemical localization of the amine in mammalian tissues.