A BSTR ACTTo identify the cortical sites where 5-hydroxytryptamine 2A (5-HT 2A ) serotonin receptors respond to the action of hallucinogens and atypical antipsychotic drugs, we have examined the cellular and subcellular distribution of these receptors in the cerebral cortex of macaque monkeys (with a focus on prefrontal areas) by using light and electron microscopic immunocytochemical techniques. 5-HT 2A receptor immunoreactivity was detected in all cortical layers, among which layers II and III and layers V and VI were intensely stained, and layer IV was weakly labeled. The majority of the receptor-labeled cells were pyramidal neurons and the most intense immunolabeling was consistently confined to their parallelly aligned proximal apical dendrites that formed two intensely stained bands above and below layer IV. The features highlighting the importance of 5-HT 2A receptors are contrasted by a disarray of data on its cortical and cellular distribution and by a lack of information on its subcellular localization (8-19). In the rat cortex, 5-HT 2A receptors have been reported to be expressed only by pyramidal cells according to an autoradiographic study (17) or only by interneurons according to an immunocytochemical study (19), but a recent mRNA in situ hybridization study of the human cortex (11) and an immunocytochemical study of the rat cortex have demonstrated the receptor both in pyramidal and nonpyramidal cells (20). 5-HT 2 agonist drugs directly activate pyramidal cells in the rat prefrontal cortex (21, 22), but only interneurons were found to be responsive in the rat piriform cortex (23-25). The light and electron microscopic 5-HT 2A -receptor-immunocytochemical experiments presented herein have enabled us to identify the neuronal elements containing 5-HT 2A receptor in the primate cortex at a level of resolution and specificity not possible in previous autoradiographic and in situ hybridization studies. MATERIALS AND METHODSFour adult rhesus monkeys (Macaca mulatta), housed and treated in accordance with institutional guidelines, were deeply anesthetized with Nembutal (100 mg͞kg, given intravenously) and perfused transcardially with normal saline followed by 4% paraformaldehyde͞0.1% glutaraldehyde prepared in 0.1 M sodium phosphate buffer (PB, pH 7.4). Coronal blocks containing frontal, parietal, temporal, and occipital cortical regions were cut at 50 m on a cryostat and Vibratome. The sections were treated for 1 h with a blocking serum (5% normal goat serum͞1% albumin͞0.1% lysine͞0.1% glycine in PB; also used in all antibody dilutions), incubated for 2 days at 4°C with 5-HT 2A receptor monoclonal antibodies raised in mouse (1:2,000 dilution; clone G186-1117; PharMingen), and processed by the avidin-biotin method using horse anti-mouse biotinylated antibodies (1:250 dilution; 1 h) and the Vectastain ABC Elite reagent (1:100 dilution, 1 h; Vector Laboratories). The immunoperoxidase reaction was visualized by using (i) 0.05% diaminobenzidine (DAB; Sigma) and 0.01% hydrogen peroxide in PB (resulting in a br...

Computer-assisted stereological and quantitative morphological approaches were used to analyse cerebellar glomeruli of the "simple type" in serial ultrathin sections. It was found that, of the total volume (110-200 micron3) of the glomeruli studied, 53% was occupied by granule cell dendrites, 34% by mossy terminal and 13% by Golgi axons. None of the four analysed glomeruli contained Golgi cell dendrites. The mossy terminals that were studied received, on the average, 53 granule cell dendrites. All of the dendrites originated from different granule cells and all made synaptic contacts with mossy terminal. However only about 60% of granule cell dendrites made synapses with Golgi axons. The surface of the mossy terminals occupied by synaptic junctions, was found to be 5.4-5.5%. Each granule cell dendrite emitted 3-5 terminal protrusions ("dendritic digits"). Each digit receives one or more synaptic contact from either the mossy terminal (67% of all digits), or from Golgi axon varicosities (25%). Only about 8% of all digits were contacted synaptically by both types of axonal terminals. All of the dendritic digits that were observed made synaptic connections. Each digit was, on the average, connected by symmetric attachment plaques to 4 neighbouring digits. Three-dimensional reconstructions of mossy terminal and some of contacting granule cell dendrites demonstrated that the dendrites curved around the central mossy terminal and were much longer than expected from earlier Golgi-impregnation studies. In addition to mossy terminals and Golgi axons, an axon terminal of small calibre that contained large, empty, spheroid vesicles were occasionally observed.(ABSTRACT TRUNCATED AT 250 WORDS)

We examined the cell-specific subcellular expression patterns for sodium- and potassium-coupled chloride (NaK2Cl) cotransporter 1 (NKCC1), Na+bicarbonate cotransporter (NBCe1), cystic fibrosis transmembrane conductance regulator (CFTR), and Na+/H+exchanger 3 (NHE3) to understand the functional plasticity and synchronization of ion transport functions along the crypt-villus axis and its relevance to intestinal disease. In the unstimulated intestine, all small intestinal villus enterocytes coexpressed apical CFTR and NHE3, basolateral NBCe1, and mostly intracellular NKCC1. All (crypt and villus) goblet cells strongly expressed basolateral NKCC1 (at approximately three-fold higher levels than villus enterocytes), but no CFTR, NBCe1, or NHE3. Lower crypt cells coexpressed apical CFTR and basolateral NKCC1, but no NHE3 or NBCe1 (except NBCe1-expressing proximal colonic crypts). CFTR, NBCe1, and NKCC1 colocalized with markers of early and recycling endosomes, implicating endocytic recycling in cell-specific anion transport. Brunner's glands of the proximal duodenum coexpressed high levels of apical/subapical CFTR and basolateral NKCC1, but very low levels of NBCe1, consistent with secretion of Cl−-enriched fluid into the crypt. The cholinergic agonist carbachol rapidly (within 10 min) reduced cell volume along the entire crypt/villus axis and promoted NHE3 internalization into early endosomes. In contrast, carbachol induced membrane recruitment of NKCC1 and CFTR in all crypt and villus enterocytes, NKCC1 in all goblet cells, and NBCe1 in all villus enterocytes. These observations support regulated vesicle traffic in Cl−secretion by goblet cells and Cl−and HCO3−secretion by villus enterocytes during the transient phase of cholinergic stimulation. Overall, the carbachol-induced membrane trafficking profile of the four ion transporters supports functional plasticity of the small intestinal villus epithelium that enables it to conduct both absorptive and secretory functions.

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