摘要:

In the present study, we have shown by single afferent unit recording in the organs of Lorenzini that L-serine-o-phosphate (L-SOP) decreases the resting discharge frequency as well as electrically evoked responses. L-SOP in a concentration of 0.1–100$mUM antagonizes responses induced by L-glutamate (L-GLU) andN-methyl-D-aspartate (NMDA) and has no effect on the responses to application of kainate (KA) and quisqualate (Q). The results obtained confirm previous observations about the existence of NMDA receptors in the afferent synapse of the ampullae of Lorenzini.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

This study tested whether acetylcholine (ACh) could induce long-term modifications in neuronal excitability in the main olfactory bulb (OB). In anaesthetized rats, perfusion in the region of the mitral cell body layer was done with a push-pull cannula and the neuronal excitability was appraised through evoked field potentials (EFPs) elicited by stimulation of the laternal olfactory tract. Application of ACh (1 mM) for 15min following a 10min period of infusion with picrotoxin (GABAAantagonist, 0.4 mM) induced a large enhancement in the antidromic response of output cells which lasted for several hours. This result suggests that the cholinergic projections from the basal forebrain could be involved in processes supporting durable changes in OB response to odours.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Responses of Purkinje cells were compared in the monkey flocculus and ventral paraflocculus. During vestibuloocular reflex (VOR) eye movements, flocculus Purkinje cells exhibited simple spike modulation related to head velocity, while ventral paraflocculus Purkinje cells exhibited modulation with no such head velocity preference. During smooth tracking of a sinusoidally moving small target, ventral paraflocculus Purkinje cells exhibited simple spike modulation related to target velocity or position, while the flocculus Purkinje cells exhibited a smaller modulation with no such target preference. Visual suppression of the VOR enhanced the simple spike responses in the ventral paraflocculus, but not in the flocculus. These results suggest that the primate flocculus and the ventral paraflocculus control differentially VOR and smooth pursuit eye movements, respectively.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Spontaneous saccades of both eyes were recorded in head-restrained pigeons placed in 6 different visual conditions (darkness and biocular, uniocular, frontal or lateral viewing). Most saccades (95%) were biocular and directed forward (around the beak axis) and backward (around the horizontal line). In the dark, the proportions of forward and backward saccades were different, they became symmetrical when the visual input involved either the left eye, the lateral fields or both eyes. This spatial reorganization could be mediated by one `dominant' eye through the lateral and foveal vision. Although some biocular saccades were strictly convergent, divergent or conjugate, most of them showed a higher independence since they had different directions and amplitudes for each eve.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Normal nociceptors are sensitized by hyperalgesic mediators such as eicosanoids and tachykinins. The possibility that these mediators contribute to hyperalgesic pain associated with neural injury was investigated by examining their effects on the excitability of injured afferent nerve endings. In amounts that sensitize normal nociceptors and are hyperalgesic in normal skin, the eicosanoids prostaglandin I2(PGI2), and 8(R),15(S)-dihydroxyicosatetraenoic acid (8(R),15(S)-diHETE) both excited some C-fibers in chronic neuromas of rat sciatic nerve. In contrast, the selective tachykinin-receptor agonists septide and senktide did not excite C-fibers. None of the mediators affected A-fibers. We conclude that PGI2and 8(R),15(S)-diHETE may contribute to post-injury pain and hyperalgesia by an action on injured afferent endings.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

In this combined electrophysiological-ultrastructural study in the cat spinal cord, we detected enkephalin-like immunoreactivity using internally radio-labelled monoclonal antibodies in functionally characterized neurons which had been filled intracellularly with horesradish peroxidase. Of the 4 neurons included in this study, two were positive for enkephalin immunoreactivity; one was a nociceptive specific neuron in lamina I, the other a wide dynamic range neuron in lamina V. The other two cells were devoid of immunoreactivity for enkephalin; one was a wide dynamic range neuron and the other was a nonnociceptive neuron. These results thus provide a morphological substrate within the spinal dorsal horn for the release of an endogenous opioid following administration of substance P or noxious cutaneous stimulation.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Adult rats were trained on a white versus black card discrimination in a circular water tank. Three independent variables were manipulated: lesion (sham, lateral occipital, medial occipital), dose of ORG 2766 administered (0 or 25 $mUg in saline on alternate days for 18 days), and time of administration (during the post-surgical recovery interval or during post-operative testing). Both visual cortical lesions produced a prominent retention deficit and defective pattern vision. Neither post-surgical nor concurrent administration of ORG 2766 improved visual functions. These results, along with a growing body of evidence, challenge the generality of the positive influences of ORG 2766 upon behavioral recovery observed in animals with limbic lesions.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Acetylcholinesterase histochemistry suggests that the pretectal nucleus corticalis of teleost fish may be cholinergic. Because immunohistochemical analysis with antibodies against choline acetyltransferase provides a more reliable means of recognizing cholinergic central nervous structures, we investigated transverse brain sections of the African cichlid fish,Hemichromis lifaliliandHemichromis guttatuswith standard immunohistochemical techniques and found the nucleus corticalis to contain choline acetyltransferase. This supports the hypothesis that teleosts (unlike all other known vertebrates) have a cholinergic second-order sensory (i.e. visual) circuit.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Angiotensin II and eledoisin modulate drinking behaviour in rats that is mediated by monoaminergic and cholinergic neurons. In the present study we have shown that combined intracerebroventricular injections of either 0.1 or 1.0 $mUg doses of angiotensin and eledoisin resulted in a decrease of about 25–35% in activities of choline ace-tyltransferase, ATP-citrate iyase in the hippocampus. In addition, 1 $mUg quantities of these peptides depressed activity of carnitine acetyltransferase but did not alter activity of acetylcholinesterase. On the other hand, the application of 0.1 $mUg of angiotensin caused no change in activity of monoamine oxidase A, while 1.0 $mUg dose brought about its 67% activation. Eledoisin abolished this effect of angiotensin II. These data provide evidence that angiotensin II and eledoisin evoke non related adaptive changes in cholinergic and monoaminergic neurons of the hippocampus.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Tyrosine 109 in the acetylcholinesterase sequence ofDrosopbila melanogastercorresponds to an aspartate in vertebrate cholinesterases. Mutation of this amino acid to a glycine in the human butyrylcholinesterase gives rise to the `atypic‘ phenotype characterized by a reduced activity for charged compounds. We investigated the importance of tyrosine 109 in theDrosopbilasequence byin vitromutagenesis and its expression in theXenopusoocyte. We show here that tyrosine 109 contributes to the conformaiton of the active site and the charge of the residue at position 109 is important for catalytic properties. Sensitivity of the enzyme to organophosphorus and carbamatc compounds is modified depending on residues present in position 109, therefore this amino acid is a potential site of resistance for insects to insecticides.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID