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Larger Response (larger + response)
Selected AbstractsExcitatory actions of substance P in the rat lateral posterior nucleusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2010Kush Paul Abstract The lateral posterior nucleus (LP) receives inputs from both neocortex and superior colliculus (SC), and is involved with integration and processing of higher-level visual information. Relay neurons in LP contain tachykinin receptors and are innervated by substance P (SP)-containing SC neurons and by layer V neurons of the visual cortex. In this study, we investigated the actions of SP on LP relay neurons using whole-cell recording techniques. SP produced a graded depolarizing response in LP neurons along the rostro-caudal extent of the lateral subdivision of LP nuclei (LPl), with a significantly larger response in rostral LPl neurons compared with caudal LPl neurons. In rostral LPl, SP (5,2000 nm) depolarized nearly all relay neurons tested (> 98%) in a concentration-dependent manner. Voltage-clamp experiments revealed that SP produced an inward current associated with a decreased conductance. The inward current was mediated primarily by neurokinin receptor (NK)1 tachykinin receptors, although significantly smaller inward currents were produced by specific NK2 and NK3 receptor agonists. The selective NK1 receptor antagonist RP67580 attenuated the SP-mediated response by 71.5% and was significantly larger than the attenuation of the SP response obtained by NK2 and NK3 receptor antagonists, GR159897 and SB222200, respectively. The SP-mediated response showed voltage characteristics consistent with a K+ conductance, and was attenuated by Cs+, a K+ channel blocker. Our data suggest that SP may modulate visual information that is being processed and integrated in the LPl with inputs from collicular sources. [source] Effect of doping location on photoconductive spectrum of SiGe quantum dotsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2007S. E. Schacham Abstract Comparative analysis of photoconductive (PC) spectra obtained from SiGe quantum dots grown on Si shows large dependence on the location of doping. The sample with doping in the silicon barrier has much larger response than the sample in which the doping was placed in the wetting layer, i.e. in the self assembled dots. This is due to the penetration of the wave-function into the barrier in the first structure, as shown by the 1-D simulation. Several peaks in the infrared were observed, ranging from 70 to 220 meV, associated with inter-level transitions of holes in the valance band of the dot or the wetting layer. The overall spectra and the relative intensity of the various peaks change drastically with bias magnitude and polarity. The PC signals increase super-linearly with bias, indicating that the carriers are released into the quasi-continuum through tunneling. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Interactions between histamine and bradykinin in stimulation of ischaemically sensitive cardiac afferents in felinesTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Liang-Wu Fu Cardiac spinal afferents are activated during myocardial ischaemia. Our previous studies have shown that during ischaemia, histamine and bradykinin (BK) stimulate cardiac spinal afferents. Because the two mediators are released together during ischaemia, the present study examined the interactions between these two mediators with respect to their influence on ischaemically sensitive cardiac afferents. Single-unit cardiac afferent activity was recorded from the left sympathetic chain or rami communicantes (T2,T5) in anaesthetized cats. Fifty-five ischaemically sensitive cardiac afferents (conduction velocity (CV) = 0.2,5.6 m s,1, 8 A,- and 47 C-fibres) were identified. Administration of histamine (10 ,g kg,1) and BK (1 ,g) in combination into the left atrium (LA) caused an additive response in 16 afferents compared with administration of either BK or histamine alone (2.62 ± 0.39 versus 1.67 ± 0.20 versus 1.24 ± 0.23 impulses s,1 (imp s,1), BK + histamine versus BK versus histamine). To further evaluate interactions between these mediators, we observed that injection of histamine (10 ,g kg,1, LA) 4 min after the administration of BK (1 ,g, LA) induced a significantly larger cardiac afferent response than the response to histamine before BK (1.24 ± 0.23 versus 1.96 ± 0.39 imp s,1, before versus after, n= 10). In contrast, six other afferents responded reproducibly to repeated injections of histamine (10 ,g kg,1, LA) in the absence of BK. BK sensitization of the afferent response to histamine lasted for less than 10 min. Cyclooxygenase blockade with indomethacin (5 mg kg,1, i.v.) abolished BK sensitization of the response to histamine (1.09 ± 0.11 versus 1.11 ± 0.10 imp s,1, n= 10). Conversely, the response of most (7/9) cardiac afferents to repeat application of BK (1 ,g, LA) 4 min after histamine (10 ,g kg,1, LA) was attenuated compared with the BK response before histamine (1.84 ± 0.25 versus 1.31 ± 0.18 imp s,1, before versus after, P < 0.05). Repeat BK (1 ,g, LA) induced a consistent response in five other afferents in the absence of histamine. Thus, BK interacts with histamine, and together they cause a larger response than either one alone. BK sensitizes cardiac afferents responding to histamine in a time-dependent fashion, and the BK sensitization effect is dependent on an intact cyclooxygenase pathway. Conversely, histamine reduces the response of most afferents to BK. [source] Activation of splanchnic and pelvic colonic afferents by bradykinin in miceNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2005S. M. Brierley Abstract, Background:, Lumbar splanchnic (LSN) and sacral pelvic (PN) nerves convey different mechanosensory information from the colon to the spinal cord. Here, we determined whether these pathways differ also in their chemosensitivity to bradykinin. Methods:, Using a novel in vitro mouse colon preparation, serosal afferents were recorded from the LSN and PN and distinguished based on their mechanosensitivity to von Frey filaments (70,4000 mg) and insensitivity to colonic stretch (1,5 g) or fine mucosal stroking (10 mg). Bradykinin was applied into a ring around mechanoreceptive fields. Results:, The LSN and PN afferents had different dynamic responses to mechanical stimuli: PN afferents required lower intensity stimuli, evoked larger responses, and displayed more maintained responses than LSN afferents. Bradykinin (1 ,mol L,1) excited 66% (27 of 41) of LSN afferents. Responses to probing were potentiated after bradykinin. The concentration-dependent (EC50: 0.16 ,mol L,1) response was reversed by the B2 -receptor antagonist HOE-140 (10 nmol L,1). Twelve bradykinin responsive afferents were mechanically insensitive. More LSN serosal afferents responded to bradykinin than PN afferents (11%, P < 0.001) , with larger responses (P < 0.05). No mechanically insensitive PN afferents were recruited by bradykinin. Conclusions:, Bradykinin potently stimulates most splanchnic serosal afferents via B2 -receptors, but few pelvic afferents. Mechanically insensitive afferents recruited by bradykinin are exclusive to the LSN. [source] | ||||||||||