Simultaneous enhancement of the bandwidth and responsivity in high-speed avalanche photodiodes with an optimized flip-chip bonding package

The enhancement in responsivity of photodiodes (PDs) or avalanche photodiodes (APDs) with the traditional flip-chip bonding package usually comes at the expense of degradation in the optical-to-electrical (O-E) bandwidth due to the increase of parasitic capacitance. In this work, we demonstrate backside-illuminated In0.52Al0.48As based APDs with novel flip-chip bonding packaging designed to relax this fundamental trade-off. The inductance induced peak in the measured O-E frequency response of these well-designed and well-packaged APDs, which can be observed around its 3-dB bandwidth (∼30 GHz), effectively widens the bandwidth and becomes more pronounced when the active diameter of the APD is aggressively downscaled to as small as 3 µm. With a typical active window diameter of 14 µm, large enough for alignment tolerance and low optical coupling loss, the packaged APD exhibits a moderate damping O-E frequency response with a bandwidth (36 vs. 31 GHz) and responsivity (3.4 vs. 2.3 A/W) superior to those of top-illuminated reference sample under 0.9 Vbr operation, to attain a high millimeter wave output power (0 dBm at 40 GHz) and output current (12.5 mA at +8.8 dBm optical power). The excellent static and dynamic performance of this design open up new possibilities to further improve the sensitivity at the receiver-end of the next-generation of passive optical network (PON) and coherent communication systems.

Reconfigurable scan lens based on an actively controlled optical phased array

Integrated photonics provides a path for miniaturization of an optical system to a compact chip scale and offers reconfigurability by the integration of active components. Here we report a chip-scale reconfigurable scan lens based on an optical phased array, consisting of 30 actively controlled elements on the InP integrated photonic platform. By configuring the phase shifters, we show scanning of a nearly diffraction-limited focused spot with a full width at half maximum spot size down to 2.7 µm at the wavelength of 1550 nm. We demonstrate the key functions needed for a laser-scanning microscope, including light focusing, collection, and steering. We also perform confocal measurements to detect reflection at selective depths.

Separated electrodes for the enhancement of high-speed data transmission in vertical-cavity surface-emitting laser arrays

In this work, a novel design for the electrodes in a near quasi-single-mode (QSM) vertical-cavity surface-emitting laser (VCSEL) array with Zn-diffusion apertures inside is demonstrated to produce an effective improvement in the high-speed data transmission performance. By separating the electrodes in a compact 2×2 coupled VCSEL array into two parts, one for pure dc current injection and the other for large ac signal modulation, a significant enhancement in the high-speed data transmission performance can be observed. Compared with the single electrode reference, which parallels 4 VCSEL units in the array, the demonstrated array with its separated electrode design exhibits greater dampening of electrical-optical (E-O) frequency response and a larger 3-dB E-O bandwidth (19 vs. 15 GHz) under the same amount of total bias current (20 mA). Moreover, this significant improvement in dynamic performance does not come at the cost of any degradation in the static performance in terms of the maximum near QSM optical output power (17 mW @ 20 mA) and the Gaussian-like optical far-field pattern which has a narrow divergence angle (full-width half maximum (FWHM): 10° at 20 mA). The advantages of the separated electrode design lead to a much better quality of 32 Gbit/sec eye-opening as compared to that of the reference device (jitter: 1.5 vs. 2.8 ps) and error-free 32 Gbit/sec transmissions over a 500 m multi-mode fiber has been achieved under a moderate total bias current of 20 mA.

Application of Trace Biological Evidence Collection Kit in DNA Examination of Trace Bloodstain Samples from the Scene

Objective To evaluate the effects of DNA examination of trace bloodstain samples from the scene collected with Trace Biological Evidence Collection kit. Methods Venous blood was made into bloodstains on the ground. The trace bloodstain samples were collected with Trace Biological Evidence Collection kit and common methods, respectively. DNA examination of trace bloodstain samples （50 from each group） was conducted on the constant temperature shaker for 2, 24, 48, 72, and 96 h, respectively, and the examination results of every group were compared. Results When the trace bloodstain samples were placed on the constant temperature shaker for 24, 48, 72, and 96 h, the DNA detection rates in the group which used Trace Biological Evidence Collection kit （100.00%, 100.00%, 100.00%, 96.00%） were significantly higher than those in the group using common methods （62.00%, 26.00%, 10.00%, 0）, the differences had statistical significance （P<0.05）. When the trace bloodstain samples were placed on the constant temperature shaker for 2 h, the differences of DNA detection rates between the two groups had no statistical significance （ P>0.05）. Conclusion The Trace Biological Evidence Collection kit can effectively improve DNA detection rate and extend detection time limit for trace bloodstain samples from the scene that have been stored for a relatively long time.

[The problems and countermeasures in the training of public health talents in colleges and universities in China]

Colleges and universities are the cradle for public health talents training. Under the epidemic situation, the new requirements for the construction of public health service system and the promotion of population health, urged us to rethink how to reform the training of public health talents in colleges and universities. This research focused on key problems of the construction and distribution, scale, orientation, and contents of training for various public health talents in colleges and universities. It was suggested to reinforce the balanced development of public health in colleges and universities in various areas in China, to refine interdisciplinary training, to intensively cultivate technical and research-oriented talents, to expand talents within and outside the colleges and universities, as well as to introduce and cultivate public health teachers simultaneously, so as to better play the role of colleges and universities in the training of the public health talents.

High-power and single-mode VCSEL arrays with single-polarized outputs by using package-induced tensile strain

In this work, we demonstrate a novel high-power vertical-cavity surface-emitting laser (VCSEL) array with highly single-mode (SM) and single-polarized output performance without significantly increasing the intra-cavity loss and threshold current (Ith). By combining a low-loss zinc-diffusion aperture with an electroplated copper substrate, we can obtain a highly SM output (side mode suppression ratio >50dB) with a very narrow divergence angle (1/e²:∼10^∘) under high output power (3.1 W; 1% duty cycle) and sustain a single polarization state, with a polarization suppression ratio of around 9 dB, under the full range of bias currents. Compared to the reference device without the copper substrate, the demonstrated array can not only switch the output optical spectra from quasi-SM to highly SM but also maintain a close threshold current value (Ith: 0.8 versus 0.7 mA per unit device) and slope efficiency. The enhancement in fundamental mode selectivity of our VCSEL structure can be attributed to the single-polarized lasing mode induced by tensile strain, which is caused by the electroplated copper substrate, as verified by the double-crystal x-ray measurement results.

Enhancement in speed and responsivity of uni-traveling carrier photodiodes with GaAs0.5Sb0.5/In0.53Ga0.47As type-II hybrid absorbers

We demonstrate a top-illuminated high-speed uni-traveling carrier photodiode (UTC-PD) with a novel design in the p-type absorber, which can effectively shorten the photon absorption depth at telecommunication wavelengths (1.31~1.55 μm) and further enhance the bandwidth-efficiency product of UTC-PD. In our proposed new UTC-PD structure, the p-type In_0.53Ga_0.47As absorption layer is replaced by the type-II GaAs_0.5Sb_0.5 (p)/In_0.53Ga_0.47As (i) hybrid absorber. Due to the narrowing of the bandgap and enhancement of the photo-absorption process at the type-II interface between the GaAs_0.5Sb_0.5 and In_0.53Ga_0.47As layers, our device shows an over 16.7% improvement in the responsivity compared with that of UTC-PD with the same thickness of pure In_0.53Ga_0.47As absorber (0.7 μm) and a zero optical coupling loss. Our demonstrated device with a simple top-illuminated structure offers a large active mesa (25 μm), a wide optical-to-electrical (O-E) bandwidth (33 GHz), a high responsivity (0.7 A/W), and a high saturation current (>5 mA) under 1.31 µm optical wavelength. These promising results suggest that our proposed PD structure can fundamentally overcome the trade-off among bandwidth, efficiency, and device active diameter of high-speed PDs.

Photonic technologies for autonomous cars: feature introduction

Photonic technologies that support the low cost manufacturing needed for automotive sensors have experienced explosive developments in recent years. To date most commercially available lidar system have been direct detection time-of-flight (ToF) sensors operating at 905 nm using mechanical mirrors for beam steering. However, these sensors suffer from important drawbacks. One issue is eye-safety, which limits maximum laser powers and hence operating range. Direct detection systems must also content with potential interference issues when lots of cars operate lidar systems simultaneously. In addition, mechanical scanners are frequently bulky and may be difficult to integrate within the form factors allowed by modern vehicles.

[Effect of Benzidine Test on DNA Analysis of Bloodstain]

OBJECTIVES

To explore the effect of benzidine test and related reagents on DNA analysis of bloodstain.

METHODS

A total of 970 bloodstain filter paper samples with 1 μL venous blood were collected, and 10 of them acted as control samples. After benzidine test and related reagent processing, DNA of 960 samples was extracted by Chelex-100 and silica bead methods and then multiplex amplified by AmpFℓSTR™ Identifiler™ Plus PCR kits. The results of STR typing were compared between different groups.

RESULTS

DNA were extracted immediately after benzidine test. Totally STR loci （3.80±1.34） were detected by silica bead method, while no STR loci were obtained by Chelex-100 method. Thirteen samples （21.7%） with whole STR typing results were obtained by drying after benzidine test, and the STR locus number （12.90±1.49） which obtained by silica bead method was much higher than by Chelex-100 method （4.70±1.96） （P<0.05）. When DNA was extracted immediately after the addition of glacial acetic acid, the STR locus number was （9.40±2.09） by silica bead method, but no STR typing result was obtained by Chelex-100 method. All 15 STR loci could be obtained by only adding glacial acetic acid after drying and only adding tetramethylbenzidine alcoholization liquid or 3% hydrogen peroxide liquid.

CONCLUSIONS

Benzidine test has significant influence on DNA analysis of bloodstain. The Chelex-100 method is not suitable for the DNA extraction of bloodstain after benzidine test. Drying after benzidine test and silica bead methods can effectively enhance the STR locus number of bloodstain.

Polymorphisms of 23 Y-chromosome STR Loci in A Han Population in Jiangsu Province

Objective To investigate the polymorphisms of 23 Y-STR loci in a Han population in Jiangsu province. Methods Blood samples were collected from 4821 unrelated healthy Han males in Jiangsu province. DNA templates were amplified by PowerPlex Y23 kit,and the amplification products were detected by 3500xL genetic analyzer. Then,we calculated the allele frequencies and gene diversities respectively,as well as the haplotype frequencies and haplotype diversities. Results The gene diversity of these 23 Y-STR loci ranged 0.4099-0.9696. A total of 4781 haplotypes were detected,of which 4743 were found once. The haplotype diversity was 0.99999812. Conclusion The 23 Y-STR loci used in this study are highly polymorphic in Han individuals in Jiangsu province and therefore suitable for population genetic study and forensic individual identification.

Monolithically integrated InAs/InGaAs quantum dot photodetectors on silicon substrates

We report InAs/InGaAs quantum dot (QD) waveguide photodetectors (PD) monolithically grown on silicon substrates. A high-crystalline quality GaAs-on-Si template was achieved by aspect ratio trapping together with the combined effects of cyclic thermal annealing and strain-balancing layer stacks. An ultra-low dark current of 0.8 nA and an internal responsivity of 0.9 A/W were measured in the O band. We also report, to the best of our knowledge, the first characterization of high-speed performance and the first demonstration of the on-chip photodetection for this QD-on-silicon system. The monolithically integrated waveguide PD shares the same platform as the previously demonstrated micro-ring lasers and can thus be integrated with laser sources for power monitors or amplifiers for pre-amplified receivers.

Coding for stable transmission of W-band radio-over-fiber system using direct-beating of two independent lasers

We demonstrate experimentally Manchester (MC) coding based W-band (75 - 110 GHz) radio-over-fiber (ROF) system to reduce the low-frequency-components (LFCs) signal distortion generated by two independent low-cost lasers using spectral shaping. Hence, a low-cost and higher performance W-band ROF system is achieved. In this system, direct-beating of two independent low-cost CW lasers without frequency tracking circuit (FTC) is used to generate the millimeter-wave. Approaches, such as delayed self-heterodyne interferometer and heterodyne beating are performed to characterize the optical-beating-interference sub-terahertz signal (OBIS). Furthermore, W-band ROF systems using MC coding and NRZ-OOK are compared and discussed.

High-depth-resolution 3-dimensional radar-imaging system based on a few-cycle W-band photonic millimeter-wave pulse generator

We demonstrate that a near-single-cycle photonic millimeter-wave short-pulse generator at W-band is capable to provide high spatial resolution three-dimensional (3-D) radar imaging. A preliminary study indicates that 3-D radar images with a state-of-the-art ranging resolution of around 1.2 cm at the W-band can be achieved.

Photonic chirped radio-frequency generator with ultra-fast sweeping rate and ultra-wide sweeping range

A high-performance photonic sweeping-frequency (chirped) radio-frequency (RF) generator has been demonstrated. By use of a novel wavelength sweeping distributed-feedback (DFB) laser, which is operated based on the linewidth enhancement effect, a fixed wavelength narrow-linewidth DFB laser, and a wideband (dc to 50 GHz) photodiode module for the hetero-dyne beating RF signal generation, a very clear chirped RF waveform can be captured by a fast real-time scope. A very-high frequency sweeping rate (10.3 GHz/μs) with an ultra-wide RF frequency sweeping range (~40 GHz) have been demonstrated. The high-repeatability (~97%) in sweeping frequency has been verified by analyzing tens of repetitive chirped waveforms.

Design and demonstration of ultra-fast W-band photonic transmitter-mixer and detectors for 25 Gbits/sec error-free wireless linking

A 25 Gbits/s error-free on-off-keying (OOK) wireless link between an ultra high-speed W-band photonic transmitter-mixer (PTM) and a fast W-band envelope detector is demonstrated. At the transmission end, the high-speed PTM is developed with an active near-ballistic uni-traveling carrier photodiode (NBUTC-PD) integrated with broadband front-end circuitry via the flip-chip bonding technique. Compared to our previous work, the wireless data rate is significantly increased through the improvement on the bandwidth of the front-end circuitry together with the reduction of the intermediate-frequency (IF) driving voltage of the active NBUTC-PD. The demonstrated PTM has a record-wide IF modulation (DC-25 GHz) and optical-to-electrical fractional bandwidths (68-128 GHz, ~67%). At the receiver end, the demodulation is realized with an ultra-fast W-band envelope detector built with a zero-bias Schottky barrier diode with a record wide video bandwidth (37 GHz) and excellent sensitivity. The demonstrated PTM is expected to find applications in multi-gigabit short-range wireless communication.

100 GHz ultra-wideband (UWB) fiber-to-the-antenna (FTTA) system for in-building and in-home networks

Fiber-to-the-antenna (FTTA) system can be a cost-effective technique for distributing high frequency signals from the head-end office to a number of remote antenna units via passive optical splitter and propagating through low-loss and low-cost optical fibers. Here, we experimentally demonstrate an optical ultra-wideband (UWB) - impulse radio (IR) FTTA system for in-building and in-home applications. The optical UWB-IR wireless link is operated in the W-band (75 GHz - 110 GHz) using our developed near-ballistic unitraveling-carrier photodiode based photonic transmitter (PT) and a 10 GHz mode-locked laser. 2.5 Gb/s UWB-IR FTTA systems with 1,024 high split-ratio and transmission over 300 m optical fiber are demonstrated using direct PT modulation.

Compact and passive-alignment 4-channel x 2.5-Gbps optical interconnect modules based on silicon optical benches with 45 degrees micro-reflectors

Compact and passive-alignment 4-channel x 2.5-Gbps optical interconnect modules are developed based on the silicon optical benches (SiOBs) of 5 x 5 mm2. A silicon-based 45 degrees micro-reflector and V-groove arrays are fabricated on the SiOB using anisotropic wet etching. Moreover, high-frequency transmission lines of 4 channel x 2.5 Gbps, and bonding pads with Au/Sn eutectic solder are also deposited on the SiOB. The vertical-cavity surface-emitting laser (VCSEL) array and photo-detector (PD) array are flip-chip assembled on the intended positions. The multi-mode fiber (MMF) ribbons are passively aligned and mounted onto the V-groove arrays. Without the assistance of additional optics, the coupling efficiencies of VCSEL-to-MMF in the transmitting part and MMF-to-PD in the receiving part can be as high as -5.65 and -1.98 dB, respectively, under an optical path of 180 microm. The 1-dB coupling tolerance of greater than +/- 20 microm is achieved for both transmitting and receiving parts. Eye patterns of both parts are demonstrated using 15-bit PRBS at 2.5 Gbps.

Transverse-junction superluminescent diodes at the 1.1 microm wavelength regime

We demonstrate, for the first time to our knowledge, GaAs-based transverse-junction (TJ) superluminescent diodes (SLDs) that operate at a wavelength of 1.1 microm. Due to lateral current injection by use of TJ, specified as transverse carrier flow spread in each quantum well horizontally instead of vertical well-by-well injection, nonuniform carrier distribution can be minimized among different multiple quantum wells (MQWs), which is a problem in vertical-junction (VJ) SLDs whose electroluminescent (EL) spectrum is governed by the center wavelength of QWs near the p side. In contrast with a VJ SLD, the EL spectrum of our device is determined by QWs that have a larger differential gain than the positions of QWs neighbored with a p side layer.

Spatial manipulation of nanoacoustic waves with nanoscale spot sizes

Coherent acoustic phonons are generated at terahertz frequencies when semiconductor quantum-well nanostructures are illuminated by femtosecond laser pulses. These phonons-also known as nanoacoustic waves-typically have wavelengths of tens of nanometres, which could prove useful in applications such as non-invasive ultrasonic imaging and sound amplification by the stimulated emission of radiation. However, optical diffraction effects mean that the nanoacoustic waves are produced with spot sizes on the micrometre scale. Near-field optical techniques can produce waves with smaller spot sizes, but they only work near surfaces. Here, we show that a far-field optical technique--which suffers no such restrictions--can be used to spatially manipulate the phonon generation process so that nanoacoustic waves are emitted with lateral dimensions that are much smaller than the laser wavelength. We demonstrate that nanoacoustic waves with wavelengths and spot sizes of the order of 10 nm and 100 nm, respectively, can be generated and detected.

Optically heterodyne diagnosis of a high-saturation-power undoped InP sandwiched InGaAs p-i-n photodiode grown on GaAs

We demonstrate the optical heterodyne diagnostics and high saturation power characteristics of a novel undoped InP sandwiched In(0.53)Ga(0.47)As p-i-n photodiode with a partially p-doped photoabsorption layer, which is grown on a linearly graded metamorphic In(x)Ga(1-x)P buffered GaAs substrate layer and exhibits an excellent low dark current density of 3.6x10(-7) A/cm(2). Such a top-illuminated optical receiver exhibits an illuminating window of 60-mum diameter, which performs ultra-linear power handling capability up to 18 dBm at 1550 nm, providing a maximum photocurrent of 35 mA under a reverse bias of 9 volts. These result in extremely high current bandwidth and bandwidth-responsivity products of 350 mA*GHz and 4.8 GHz*A/W, respectively, at receiving frequency of up to 10 GHz.

Three-dimensional electric field visualization utilizing electric-field-induced second-harmonic generation in nematic liquid crystals

An electric-field-induced second-harmonic-generation signal in a nematic liquid crystal is used to map the electric field in an integrated-circuit-like sample. Since the electric-field-induced second-harmonic-generation signal intensity exhibits a strong dependence on the polarization of the incident laser beam, both the amplitude and the orientation of the electric field vectors can be measured. Combined with scanning second-harmonic-generation microscopy, three-dimensional electric field distribution can be easily visualized with high spatial resolution of the order of 1 microm.

Temporal changes of preproenkephalin mRNA and leu-enkephalin-like immunoreactivity in the neurons of the caudal spinal trigeminal nucleus and upper cervical cord after noxious stimuli

The changing levels of preproenkephalin (PPE) mRNA expression and leu-enkephalin-like immunoreactivity (L-ENK-LI) in the caudal spinal trigeminal nucleus (Vc) and the upper cervical cord subsequent to subcutaneous injection of formalin into orofacial region were examined using in situ hybridization histochemistry and immunohistochemistry. Formalin injection resulted in a significant increase in the number of neurons expressing PPE mRNA in the superficial (laminae I-II) and deep (lamina V) layers of the ipsilateral Vc and the first cervical cord (C1). The expression of PPE mRNA increased 2 h and 4 h after formalin injection in the neurons of deep layer and superficial layers of the Vc, respectively. An increased expression of PPE gene could still be observed 48 h after formalin injection. The PPE mRNA expression in the neurons of the C1 had similar temporal changes as in the Vc. In parallel, the L-ENK-LI did not show any significant changes in the Vc and C1. These results indicate that peripheral noxious stimulation trans-synapticaly activates the expression of PPE gene in the neurons of the Vc and C1 and suggest that enkephallin (ENK) plays an important role in the processing and modulation of the oroficial noxious stimulation.

[Co-existence of glutamate and substance P in electrophysiologically identified dorsal root ganglion neurons of rats]

Electrophysiological properties, reaction to substance P (SP) receptor agonist, and co-existence of glutamate (Glu) and SP in neurons of the spinal dorsal root ganglion (DRG) of the rat were investigated in vitro. The main results were: (1) According to the fiber conduction velocity, totally 135 intracellularly recorded DRG neurons were divided into A alpha/beta type (> 12 m/s) and C type (< 1.3 m/s). There were remarkable differences between the fast after hyperpolarization (fAHP) of action potential between the two types: fAHP of C type neurons had smaller amplititude and longer duration, whereas the fAHP of A alpha/beta type neurons had larger amplititude and shorter duration. (2) Among 22 DRG neurons of which overshoots of action potential appeared, specific SP receptor agonist Sar-SP induced depolorization in 42% (5/12) of the A alpha/beta type neurons and 80% (8/10) of the C type neurons. (3) Biocytin was intracellularly injected into the 22 Sar-SP administrated DRG neurons. After fixation and section, employing the immunofluorescent histochemical multi-staining technique for phosphate-activated glutaminase (PAG, a specific marker for glutamatergic neurons), SP and biocytin, 25% (3/12) of the A alpha/beta type neurons and 80% (8/10) of the C type neurons showed both PAG- and SP-like immunoreactivities. There was a great difference between the percentages of the PAG/SP co-existing A alpha/beta type neurons and C type neurons (P < 0.05). The present results indicated that there were some differences in chemicoanatomical and electrophysiological properties between A alpha/beta type and C type neurons, and SP might facilitate the discharge of DRG neurons through activating SP autoreceptors on their membrane.

[Peripheral substance P receptor mediating c-fos gene expression in the spinal dorsal horn induced by peripheral noxious stimulation]

Employing immunohistochemical staining for FOS protein, which is the expression product of c-fos proto-oncogene, the role of substance P receptor (SPR) in noxious information transmission at peripheral terminals of the dorsal root ganglion cells was investigated by means of a selective SPR antagonist L668, 169 and agonist Sar-SP. Unilateral injection of L668, 169 (10(-4) mol/L) into the plantar of hindpaw 10 min before injection of 4% formalin, the number of FOS-like immunoreactive (LI) neurons in the superficial laminae of dorsal horn was significantly decreased, but the changes were not obvious in the deeper laminae. Smaller doses of L668, 169 (10(-5), 10(-6) mol/L) were almost ineffective on FOS-LI neurons in both the superficial and the deeper laminae. However, Sar-SP (10(-4) mol/L) or formalin did result in the expression of c-fos gene in the superficial laminae of the dorsal horn. These results indicated that SP might contribute to the transmission of nociceptive information and induce noxious sensation, at least in part by activating SPR in peripheral terminals of the dorsal root ganglion cells.

Evidence of gamma-aminobutyric acidergic control over the catecholaminergic projection from the medulla oblongata to the central nucleus of the amygdala

It is known that the nucleus of the solitary tract (NTS) and the ventrolateral medulla (VLM) project to the central nucleus of the amygdala (Ce), conveying visceral information. Conversely, the Ce sends projections to the NTS and the VLM. To understand better the role of catecholamine and gamma-aminobutyric acid (GABA) in these reciprocal connections, experiments were performed by combining lectin-conjugated horseradish peroxidase (WGA-HRP) anterograde and retrograde transport with preembedding immunocytochemistry to detect tyrosine hydroxylase (TH), and postembedding immunocytochemistry to detect GABA. The light microscopic study suggested that the majority of neurons in the NTS and the VLM projecting to the Ce were TH immunoreactive (TH-IR). Most of them were located at the level of the obex. Under the electron microscope, the GABAergic and non-GABAergic terminals were found to form synaptic contacts with the TH-(IR) or Ce-projecting or TH-IR/Ce-projecting double-labelled neurons of the NTS and VLM. The GABAergic terminals mostly formed symmetrical synaptic contacts with the postsynaptic structure in which perikarya (14-19%), dendrites (79-84%), and spines (2%) were observed. Approximately 94% of the axon terminals in the NTS and 90% of those in the VLM arising from the Ce were GABAergic and appeared not to form synaptic contacts with the TH-IR or Ce-projecting neurons in these regions. The present results demonstrated that the catecholaminergic neurons of the NTS and VLM projecting to the Ce receive an extensive GABAergic innervation and that the amygdala projection to the medulla is mostly GABAergic.

GABAergic synapses upon neurons expressing substance P receptors in the nucleus of the solitary tract: an immunocytochemical electron microscope study in the rat

Morphological substrates for interactions between gamma-aminobutyric acid (GABA) and substance P upon neurons expressing substance P receptor (SPR) in the nucleus of the solitary tract (NST) were investigated by immunocytochemical electron microscopy. In the NST of the rat, many GABA-like immunoreactive axon terminals were in symmetric synaptic contacts with dendritic profiles; they were observed on nearly a half of the SPR-like immunoreactive dendritic profiles in the medial part of the caudal half of the NST.

Central origins of substance P-like immunoreactive fibers and terminals in the spinal trigeminal caudal subnucleus in the rat

After trigeminal rhizotomy, some substance P-like immunoreactive (SP-LI) fibers and terminals in the spinal trigeminal caudal subnucleus (Vc), specially in its superficial laminae (laminae I and II), still remained in the rat. Employing a combination of Fluoro-Gold retrograde tracing and immunofluorescence histochemical staining for SP, we found that the main central origins of these SP-LI fibers and terminals were midbrain periaqueductal gray (PAG), nucleus raphe magnus (NRM) and other raphe nuclei, and nucleus reticularis gigantocellularis pars alpha; all of them are important structures of the endogenous pain control system. The present results provided morphological evidence for PAG or NRM stimulation could inhibit neuronal activities in the Vc evoked by orofacial nociceptive stimulation and also suggested that SP might be an important neurotransmitter or neuromodulator for endogenous pain control system.

Catecholaminergic neurons in the nucleus tractus solitarii which send their axons to the midbrain periaqueductal gray express Fos protein after noxious stimulation of the stomach: a triple labeling study in the rat

In rats which were injected with horseradish peroxidase (HRP) into the midbrain periaqueductal gray (PAG) and then administered with formaldehyde into the stomach, Fos-like immunoreactivity was found in tyrosine hydroxylase-like immunoreactive neurons in the nucleus tractus solitarii (NTS) which were retrogradely labeled with HRP. The results indicate that catecholaminergic NTS neurons may mediate nociceptive visceral information to the PAG.

An indirect projection from the nucleus of the solitary tract to the central nucleus of the amygdala via the parabrachial nucleus in the rat: a light and electron microscopic study

The morphological basis of how visceral information from the nucleus of the solitary tract (NTS) is relayed from the parabrachial nucleus (PBN) to the central nucleus of the amygdala (Ce) was studied at the light and electron microscopic levels using the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA-L), kainic acid degeneration, and retrograde tracing with horseradish peroxidase (HRP). After injection of PHA-L into the caudal NTS, anterogradely labeled fibers and terminals were predominantly distributed in the external lateral (el) and central lateral (cl) subnuclei of the PBN. After injection of HRP into the Ce, retrogradely labeled neurons in PBN were mainly distributed in the same areas. In double-labeling experiments, there was a clear overlap between neuronal elements labeled with HRP and PHA-L in the el and cl. At the electron microscopic level, the PHA-L-labeled axon terminals from the NTS mainly contained spherical agranular synaptic vesicles and formed asymmetric contacts with the postsynaptic dendrites or dendritic spines in PBN. After the lesioning agent kainic acid was injected into the NTS and HRP deposited in the Ce, it was found the afferent fibers from the NTS made direct synaptic contact with the lateral PBN neurons which in turn projected to Ce. Such evidence adds to our growing knowledge of regulation of visceral function in central nervous system and would be likely helpful for understanding the important roles of the NTS, PBN and Ce in the central control of cardiovascular, respiratory and gastrointestinal functions.

Visceral noxious stimulation induced expression of Fos protein in medullary catecholaminergic neurons projecting to nucleus accumbens in the rat: a study with triple labeling method of HRP tracing combined with Fos and TH immunohistochemistry

Horseradish peroxidase (HRP) was stereotaxically injected into the nucleus accumbens (Acb), and visceral noxious stimulation given by injecting formalin into the stomach. Sections of the medulla were subjected to HRP reaction combined with immunohistochemical reactions for Fos protein (ABC method) and tyrosine hydroxylase (TH, PAP method). The catecholaminergic neurons of the medulla (including vagal complex, ventrolateral medulla and reticular formation between them) which expressed Fos protein and projected to Acb were studied. The results showed that HRP retrogradely labeled cells were seen in the medulla bilaterally with apparent ipsilateral predominance and TH-LI and Fos-LI single labeled cells were bilaterally distributed; HRP/TH,TH/Fos double labeled neurons were more numerous than HRP/Fos double-labeled neurons. HRP/TH/Fos triple-labeled neurons were small in number and were mainly distributed in the nucleus tractus solitarii (nTS) and ventrolateral medulla (VLM), but only a few labeled cells were located in RF between nTS and VLM. It is concluded that TH-LI neurons in the medulla projected to Acb and some of them expressed Fos protein after noxious stimulation of the stomach.

Projection from the ventrolateral medullary neurons containing tyrosine hydroxylase to the central amygdaloid nucleus in the rat

By using a double-labeling produce of retrograde horseradish peroxidase (HRP) tracing and the immunocytochemical localization of tyrosine hydroxylase (TH), the present study ascertained that the axonal fibers of catecholaminergic neurons in the caudal ventrolateral medulla projected to the central amygdaloid nucleus in the rat. The majority of double-labeled cells were observed primarily around the level of the obex. 92% of HRP retrogradely labeled cells contained TH-like immunoreactive (TH-IR), but only 31% of TH-IR cells was labeled with HRP.

Serotonergic projections from the midbrain periaqueductal gray and nucleus raphe dorsalis to the nucleus parafascicularis of the thalamus

By a double-labeling method combining the retrograde tracing of horseradish peroxidase and the immunocytochemical technique, serotonin-like immunoreactive neurons in the midbrain periaqueductal gray (PAG) and nucleus raphe dorsalis (DR) of the rat were observed to send projection fibers to the nucleus parafascicularis of the thalamus bilaterally with an ipsilateral dominance. These serotonin-containing projecting neurons were observed mainly at the middle-caudal levels of the ventrolateral subdivision of the PAG and less at the middle-rostral levels of the DR.

Tyrosine hydroxylase-, neurotensin-, or cholecystokinin-containing neurons in the nucleus tractus solitarii send projection fibers to the nucleus accumbens in the rat

A double-labeling method combining the retrograde tracing of horseradish peroxidase (HRP) with the immunocytochemical technique was used in the present study. The results suggest that the neurons containing tyrosine hydroxylase (TH), neurotensin (NT) or cholecystokinin (CCK) in the nucleus tractus solitarii (NTS) of the rat send their axons to the nucleus accumbens bilaterally with ipsilateral dominance. HRP-TH, HRP-NT or HRP-CCK double-labeled cell bodies were mainly located in the medial and the commissural subnucleus of the NTS. HRP-TH double-labeled cells were the largest in number, followed by HRP-NT cells, with HRP-CCK cells present in the lowest numbers.

The sites of origin of a-melanocyte-stimulating hormone-containing axonal components in the lateral area of the midbrain periaqueductal gray of the rat

The sites of origin of alpha-melanocyte-stimulating hormone (alpha-MSH)-containing axonal components in the lateral area of the midbrain periaqueductal gray (PAG) were studied in the rat by the retrograde tracing method of horseradish peroxidase, combined with the immunocytochemical technique. The results indicated that alpha-MSH-containing axonal components in the PAG arose not only from the arcuate nucleus of the hypothalamus but also from the ventral zona incerta, the periventricular, perifornical and lateral hypothalamic regions.

Serotonin-, substance P- and tyrosine hydroxylase-like immunoreactive neurons projecting from the midbrain periaqueductal gray to the nucleus tractus solitarii in the rat

Serotonin-, substance P- and tyrosine hydroxylase-like immunoreactive neurons in the midbrain periaqueductal gray (PAG) were observed to send their axons to the nucleus tractus solitarii in the rat by the retrograde horseradish peroxidase tracing method combined with the immunocytochemical technique. These neurons were most frequently observed in the ventrolateral subnucleus and ventral portion of the medial subnucleus of the PAG at the entire rostrocaudal levels.

Serotonin-, substance P- and tyrosine hydroxylase-like immunoreactive neurons projecting from the periaqueductal gray to the ventromedial hypothalamic nucleus in the rat

Direct projections from serotonin-, substance P- and tyrosine hydroxylase-like immunoreactive neurons in the midbrain periaqueductal gray (PAG) to the ventromedial hypothalamic nucleus (VMH) in the rat were investigated by the retrograde horseradish peroxidase tracing method combined with the immunocytochemical technique. Serotonin-, substance P- and tyrosine hydroxylase-like immunoreactive PAG neurons sending their axons to the VMH were distributed in the ventrolateral subnucleus and ventral portion of the medial subnucleus of PAG at the middle and caudal levels.

Projections from serotonin- and substance P-like immunoreactive neurons in the midbrain periaqueductal gray onto the nucleus reticularis gigantocellularis pars alpha in the rat

Serotonin- and substance P-like immunoreactive (5HT-LI and SP-LI) neurons in the midbrain periaqueductal gray (PAG) of the rat were observed to send their axons to the nucleus reticularis gigantocellularis pars alpha (Rgc alpha) by the retrograde horseradish peroxidase (HRP)-tracing method combined with the 5HT- or SP-immunohistochemical technique. These 5HT- or SP-LI PAG neurons were distributed mainly in the ventrolateral subdivision and ventral portion of the medial subdivision at the middle and caudal levels of the PAG, and additionally in the nucleus raphe dorsalis (DR).

Serotonin-, substance P- or leucine-enkephalin-containing neurons in the midbrain periaqueductal gray and nucleus raphe dorsalis send projection fibers to the central amygdaloid nucleus in the rat

By a double-labeling method combining the retrograde tracing of horseradish peroxidase and the immunocytochemical technique, serotonin-, substance P- or leucine-enkephalin-like immunoreactive neurons in the midbrain periaqueductal gray (PAG) and the nucleus raphe dorsalis (DR) of the rat were found to send projection fibers to the central amygdaloid nucleus bilaterally with an ipsilateral dominance. These PAG neurons were chiefly distributed in the ventrolateral PAG subdivision and the ventral parts of medial PAG subdivision at the middle and caudal levels of PAG.

Midbrain periaqueductal gray neurons with substance P- or enkephalin-like immunoreactivity send projection fibers to the nucleus accumbens in the rat

Employing a combination of retrograde tracing and immunocytochemistry, midbrain periaqueductal gray (PAG) neurons with substance P- or leucine-enkephalin-like immunoreactivity in the rat were found to send projection fibers to the nucleus accumbens bilaterally with an ipsilateral dominance. These neurons were most frequently seen in the ventrolateral and ventral parts of the medial PAG subdivisions at all rostrocaudal levels of PAG.

Collateral projections from the midbrain periaqueductal gray to the nucleus raphe magnus and nucleus accumbens in the rat. A fluorescent retrograde double-labelling study

Collateral projections of single neurons in the midbrain periaqueductal gray (PAG) to the nucleus accumbens (ACB) and nucleus raphe magnus (NRM) were observed in the rat by a fluorescent retrograde double-labelling technique. After injecting propidium iodide into the ACB and bisbenzimide into the NRM, doubly labelled PAG neurons were most frequently seen in the ventrolateral subnucleus and ventral part of the medial subnucleus at the middle and caudal levels of the PAG.

Serotoninergic projections from the midbrain periaqueductal gray to the nucleus accumbens in the rat

A combined method of retrograde tracing of horseradish peroxidase (HRP) and serotonin (5-HT) immunocytochemistry indicated that some 5-HT-like immunoreactive neurons in the midbrain periaqueductal gray (PAG) of the rat send their axons to the nucleus accumbens. These PAG neurons are mainly located in the ventromedial and ventrolateral subdivisions at the middle and caudal levels of PAG.