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PubMed1981

Cerebellar interaction with the acoustic reflex.

The involvement of the cerebellar vermis in the acoustic reflex was analyzed in 12 cats, decerebrated or in pentobarbital anesthesia. Anatomical data suggested the existence of a connection of lobules VIII with the ventral cochlear nucleus. Single cell recording and evoked potential techniques demonstrated the existence of the acoustic projection to lobulus VIII. Electrical stimulation of this area changed the tension of the middle ear muscle and caused evoked potential responses in the caudal part of the ventral cochlear nucleus. Electrical stimulation of the motor nucleus of the facial nerve evoked a slow wave in the recording taken from the surrounding of the cochlear round window. A hypothesis is proposed which postulates the involvement of the acoustic reflex in space localization of acoustic stimuli and the action of cerebellar vermis in order to assure the stability and plasticity of the acoustic reflex arc.

Animals↗

PubMed1995

Afferent influences on brainstem auditory nuclei of the chicken: regulation of transcriptional activity following cochlea removal.

Neuronal survival in the cochlear nucleus of young animals is regulated by afferent activity. Removal or blockade of nerve VIII input results in the death of 20-40% of neurons in the cochlear nucleus, nucleus magnocellularis (NM), of the 10-14 days posthatch chick. Neuronal death in NM is preceded by complete failure of protein synthesis and degradation of ribosomes. In addition, there is a biphasic change in the immunoreactivity of ribosomes for a monoclonal antiribosomal RNA antibody, Y10B. Initially, the entire population of afferent-deprived NM neurons loses Y10B immunoreactivity, but, after 6 or 12 hours of afferent deprivation, lack of Y10B immunoreactivity specifically marks dying NM neurons. Whether RNA synthesis is also altered in afferent-deprived NM neurons has not previously been studied. To determine whether RNA synthesis in NM neurons is regulated by loss of afferent activity, we injected chicks with 3H-uridine following unilateral cochlea removal and measured the incorporation of RNA precursor with tissue autoradiography. As early as 1 hour after cochlea removal, there was a significant decrease in 3H-uridine incorporation by afferent-deprived NM neurons. After longer periods of afferent deprivation (6 or 12 hours), the majority of dying NM neurons (marked by loss of Y10B immunoreactivity) fail to incorporate RNA precursor. Six or 12 hours following cochlea removal, the subpopulation of surviving NM neurons incorporates 3H-uridine at increased levels over those observed 1 or 3 hours after cochlea removal. These findings suggest that nuclear function is regulated by afferent synaptic activity and that failure of RNA synthesis occurs early in the cell death process.

Afferent Pathways↗

PubMed1990

Neurotransmitter-specific uptake and retrograde transport of [3H]glycine from the inferior colliculus by ipsilateral projections of the superior olivary complex and nuclei of the lateral lemniscus.

Neurotransmitter-specific uptake and retrograde axonal transport of [3H]glycine were used to identify glycinergic projections to the inferior colliculus in chinchillas and guinea pigs. Six h after injection of [3H]glycine in the inferior colliculus, autoradiographically labeled cells were found ipsilaterally in the ventral nucleus of the lateral lemniscus, the lateral superior olive and the dorsomedial periolivary nucleus. These 3 regions accounted for 95% of the labeled projection neurons, with the remainder scattered elsewhere in the ipsilateral superior olivary complex. No labeled cells were found contralaterally even after survival times as long as 24 h. Retrograde transport of HRP from the inferior colliculus in these same cases confirmed the presence of additional projections that did not accumulate [3H]glycine. These included ipsilateral projections from the medial superior olive and cochlear nucleus and contralateral projections from the inferior colliculus, dorsal nucleus of the lateral lemniscus, lateral superior olive, periolivary nuclei and cochlear nucleus. The results implicate uncrossed projections from the ventral nucleus of the lateral lemniscus, lateral superior olive, and dorsomedial periolivary nucleus as the principal sources of inhibitory glycinergic inputs to the inferior colliculus.

Animals↗

PubMed2006

Use of neural response telemetry measures to objectively set the comfort levels in the Nucleus 24 cochlear implant.

Cochlear implant programming necessitates accurate setting of programming levels, including maximum stimulation levels, of all active electrodes. Frequently, clinical techniques are adequate for setting these levels; however, they are sometimes insufficient (e.g., very young children). In the Nucleus 24, several methods have been suggested for estimation of comfort levels (C levels) from neural response telemetry (NRT); however, many require co-application of clinical measurements. Data was obtained from 21 adult Nucleus 24 recipients to develop reliable predictions of C levels. Multiple regression analysis was performed on NRT threshold, slope of the NRT growth function, age, length of deafness, length of cochlear implant use and electrode impedance to examine predictive ability. Only the NRT threshold and slope of the growth function measures were significant predictors yielding R2 values from 0.391 to 0.769. Results demonstrated that these measures may provide an alternative means of estimating C levels when other clinical measures are unavailable.

Adult↗

PubMed1992

Effects of noise and noise suppression on speech perception by cochlear implant users.

The recognition of phonemes in consonant-vowel-consonant words, presented in speech-shaped random noise, was measured as a function of signal to noise ratio (S/N) in 10 normally hearing adults and 10 successful adult users of the Nucleus cochlear implant. Optimal scores (measured at a S/N of +25 dB) were 98% for the average normal subject and 42% for the average implantee. Phoneme recognition threshold was defined as the S/N at which the phoneme recognition score fell to 50% of its optimal value. This threshold was -2 dB for the average normal subject and +9 dB for the average implantee. Application of a digital noise suppression algorithm (INTEL) to the mixed speech plus noise signal had no effect on the optimal phoneme recognition score of either group or on the phoneme recognition threshold of the normal group. It did, however, improve the phoneme recognition threshold of the implant group by an average of 4 to 5 dB. These findings illustrate the noise susceptibility of Nucleus cochlear implant users and suggest that single-channel digital noise reduction techniques may offer some relief from this problem.

Adult↗

PubMed1985

Evidence of collateral axonal projections to the superior olivary complex.

In this study we investigated the collateral axonal projections to the superior olivary complex using the combined anterograde and retrograde transport of wheat-germ agglutinin conjugated with horseradish peroxidase. Small injections of this tracer were placed in the lateral or medial superior olivary nuclei in cats, and the location of anterograde label in the alternate nuclei of the superior olivary complex was determined. Injections of [3H]leucine were also placed in these nuclei for control purposes. After wheat-germ agglutinin-horseradish peroxidase injections in the lateral superior olivary nucleus anterograde label was observed bilaterally in the medial superior olivary nuclei. Likewise, after injections in the medial superior olivary nucleus anterograde label was observed in the contralateral medial and lateral superior olivary nuclei. The topography of the anterograde label was always precise and varied predictably as a function of the injection site. Most retrogradely labeled cells were located in the ipsilateral anteroventral cochlear nucleus and the medial nucleus of the trapezoid body. Various interpretations of the data are considered. Our primary conclusion is that cells in the anteroventral cochlear nucleus are a major source of collaterals to both the ipsilateral and contralateral nuclei of the superior olivary complex.

Animals↗

PubMed2005

Neural response telemetry results with the nucleus 24 contour in a perimodiolar position.

OBJECTIVE: The purpose of the study was to analyze changes in neural response telemetry using the Cochlear Nucleus 24 Contour before and after stylet removal in a human model. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS: Twelve patients (23-72 years old) undergoing cochlear implantation, using the Nucleus 24 Contour implant, secondary to congenital and age-related hearing loss. INTERVENTION: Cochlear implantation with Cochlear Nucleus 24 Contour implant. MAIN OUTCOME MEASURE: Neural response telemetry thresholds were recorded initially with the stylet in and then with the stylet out during the implant procedure. RESULTS: Stimulus levels to obtain neural response telemetry threshold after stylet removal were statistically lower after the stylet was removed. CONCLUSION: The Nucleus 24 Contour achieves a perimodiolar position once the stylet is removed, and this leads to reduction in the current required to elicit a threshold neural response telemetry response.

Action Potentials↗

PubMed1996

Anatomical distribution of somatostatin receptors in the brainstem of the human fetus.

The distribution of somatostatin binding sites was studied in the pons and medulla oblongata of three human fetuses (gestional ages 26, 28 and 30 weeks). The study was carried out by in vitro quantitative autoradiography using either [125I-Tyr0,D-Trp8]somatostatin-14 or [125I-Tyr11]somatostatin-14 as radioligands. Somatostatin binding sites were observed in a number of nuclei subserving sensory, motor or integrative functions within the pons and medulla. In addition, discrete tracts also contained significant amounts of binding sites. Among structures involved in sensory processes, a high density of binding sites (40-60 fmol/ mg wet tissue) was measured in the dorsal cochlear nucleus and in the nucleus tractus spinalis trigemini caudalis. Moderate to high levels of binding sites (30-40 fmol/mg wet tissue) were detected in the other sensory cranial nerve nuclei. A moderate density of sites (15-30 fmol/mg wet tissue) was measured in most motor nuclei, the highest concentrations being observed in the dorsal motor nucleus of the vagus nerve, the facial nucleus, the hypoglossal nucleus and the nucleus ambiguus. The griseum pontis and the nucleus corporis pontobulbaris contained very high (> 60 fmol/mg wet tissue) and high concentrations of somatostatin binding sites, respectively, while the other relay nuclei contained low to moderate levels of binding. In monoaminergic nuclei, very high and moderate to high concentrations of somatostatin binding sites were measured in the nucleus locus coeruleus and in its dorsal subnucleus, respectively. Moderate densities of sites were detected in the ventral subnucleus of the nucleus locus coeruleus and in the different parts of the raphe. In the white matter, low levels of binding were measured in the inferior cerebellar peduncle, the lateral and median lemnisci and the tractus solitarius. Conversely, moderate to high concentrations of somatostatin binding sites were measured in the median and superior cerebellar peduncles. The pyramis contained a very high density of recognition sites. A marked heterogeneity in the density of binding sites was observed within a few structures particularly in the medial accessory olivary of nucleus and the medial longitudinal fasciculus. Selective ligands were used to determine the pharmacological profile of the [Tyr11]somatostatin-14 binding sites in various brainstem regions. In the dorsal cochlear nucleus and the pyramis, all somatostatin binding sites belonged to the SSA subtype. Conversely, in the lateral paragigantocellular nucleus, all somatostatin binding sites belonged to the SSB subtype. The other regions studied contained various proportions of SSA and SSB subtypes. In conclusion, the present study shows that high concentrations of somatostatin receptors are present in many regions of the human fetus brainstem. These data support the concept that somatostatin could be involved in the maturation of brain structures.

Age Factors↗

PubMed2000

GABA mediates presynaptic inhibition at glycinergic synapses in a rat auditory brainstem nucleus.

Many inhibitory nerve terminals in the mammalian anteroventral cochlear nucleus (AVCN) contain both glycine and GABA, but the reason for the co-localization of these two inhibitory neurotransmitters in the AVCN is unknown. We have investigated the roles of glycine and GABA at synapses on bushy cells in the rat AVCN, using receptor immunohistochemistry and electrophysiology. Our immunohistochemical results show prominent punctate labelling of postsynaptic clusters of glycine receptors and of the receptor clustering protein gephyrin over the surface of bushy cells. In contrast, weak diffuse membrane immunolabelling of GABAA receptors was observed. Whole-cell recordings from bushy cells in AVCN slices demonstrated that evoked inhibitory postsynaptic currents (IPSCs) were predominantly (81 %) glycinergic, based on the decrease in amplitude of the IPSCs in bicuculline (10 microM). This observation was supported by the effect of strychnine (1 microM), which was to decrease the evoked IPSC (to 10 % of control IPSC amplitude) and to produce a greater than 90 % block of spontaneous miniature IPSCs. These results suggest a minor role for postsynaptic GABAA receptors in bushy cells, despite a high proportion of GABA-containing terminals on these cells. Therefore, a role for metabotropic GABAB receptors was investigated. Activation of GABAB receptors with baclofen revealed a significant attenuation of evoked glycinergic IPSCs. The effect of baclofen was presynaptic, as indicated by a lack of change in the mean amplitude of spontaneous IPSCs. Significantly, the decrease in the amplitude of evoked glycinergic IPSCs observed following repetitive nerve stimulation was reduced in the presence of the GABAB antagonist, CGP 35348. This indicates that synaptically released GABA can activate presynaptic GABAB receptors to reduce transmitter release at glycinergic synapses. Our results suggest specific pre- versus postsynaptic physiological roles for GABA and glycine in the AVCN.

Animals↗

PubMed2000

The case of the missing pitch templates: how harmonic templates emerge in the early auditory system.

Periodicity pitch is the most salient and important of all pitch percepts. Psychoacoustical models of this percept have long postulated the existence of internalized harmonic templates against which incoming resolved spectra can be compared, and pitch determined according to the best matching templates [J. Goldstein, J. Acoust. Soc. Am. 54, 1496-1516 (1973)]. However, it has been a mystery where and how such harmonic templates can come about. We present here a biologically plausible model for how such templates can form in the early stages of the auditory system. The model demonstrates that any broadband stimulus, including noise and random click trains, suffices for generating the templates, and that there is no need for any delay lines, oscillators, or other neural temporal structures. The model consists of two key stages: cochlear filtering followed by coincidence detection. The cochlear stage provides responses analogous to those recorded in the auditory nerve and cochlear nucleus. Specifically, it performs moderately sharp frequency analysis via a filterbank with tonotopically ordered center frequencies (CFs); the rectified and phase-locked filter responses are further enhanced temporally to resemble the synchronized responses of cells in the cochlear nucleus. The second stage is a matrix of coincidence detectors that compute the average pairwise instantaneous correlation (or product) between responses from all CFs across the channels. Model simulations show that for any broadband stimulus, a degree of high coincidence occurs among cochlear channels that are spaced precisely at harmonic intervals. Accumulating coincidences over time results in the formation of harmonic templates for all fundamental frequencies in the phase-locking frequency range. The model accounts for the critical role played by three subtle but important factors in cochlear function: the nonlinear transformations following the filtering stage, the rapid phase shifts of the traveling wave near its resonance, and the spectral resolution of the cochlear filters. Finally, we discuss the physiological correlates and location of such a process and its resulting templates.

Cochlea↗

PubMed1985

The auditory pathology of brain death as revealed by auditory evoked potentials.

A case of brain death is reported in which the auditory brainstem response, middle latency component, and slow vertex response were recorded before and after the cessation of cortical activity, and in which histological examination of the temporal bone and central auditory pathways was performed post mortem. Brain death of at least 48 hours' duration was demonstrated by neurological examination, flat electroencephalographic recording, and persistent absence of auditory evoked responses. The postmortem examination was performed 3 hours after death. The pathological studies of the whole length of the auditory pathway revealed total autolysis of the organ of Corti, marked cell loss in the dorsal cochlear nucleus, and moderate cell loss in other nuclei of the central auditory pathway. It should be considered that total autolysis of the organ of Corti and severe cell loss of the cochlear nucleus may occur if the auditory brainstem response becomes absent in comatose patients.

Adult↗

PubMed1991

Volumetric and histological changes in the cochlear nuclei of visually deprived rats: a possible morphological basis for intermodal sensory compensation.

The cochlear nucleus of 90 day-old rats was studied to determine whether bilateral visual deafferentation at birth induced compensatory structural changes in the auditory system. Computer-assisted reconstructions of the cochlear nucleus were used to demonstrate the three-dimensional organization of the nucleus and for calculating volumes of the subdivisions. In enucleated rats the volume of the granular region of the nucleus (GCD) increased 22.6% relative to controls, and the volume of the anterior ventral nucleus (AVCN) also increased by 10.0%. The posterior ventral nucleus (PVCN) and dorsal nucleus (DCN) were not affected. Since the volume change in GCD was substantial, this region was subjected to further analysis. Two types of granular cells were identified in the GCD of both control and enucleated rats with Kluver-Barrera staining. Type 1 cells contained an ovoid dark nucleus with clumpy chromatin and possessed only a very thin rim of cytoplasm. Type 2 cells were larger with pale spheroidal nuclei and with a more prominent cytoplasmic rim. There was an obvious stratification of these two cell types in the superficial layers over the lateral aspect of the AVCN in both groups. In contrast to this, the subpeduncular corner was not distinctively laminated and contained predominantly Type 2 cells. In enucleated animals the nuclear size of Type 1 cells increased by 3.8% while the size of Type 2 nuclei was not affected. Granule cell numbers increased by 28% in the visually deafferented rats. The GCD seems to be more highly developed in species which are dependent on non-visual modalities for spatial location. The regional hypertrophy of the GCD and AVCN seen in the present study may indicate that intermodal sensory compensation is taking place in the auditory system of visually deafferented rats.

Adaptation, Physiological↗

PubMed1995

Convergence and divergence of ascending binaural and monaural pathways from the superior olives of the mustached bat.

The lateral superior olive and medial superior olive give rise to pathways that terminate in the dorsal nucleus of the lateral lemniscus and central nucleus of the inferior colliculus. In most mammals, neurons in both the medial and lateral superior olives are binaural, but in the mustached bat most neurons in the medial superior olive are monaural. The aims of this study were to determine how the inputs to the medial superior olive contribute to its monaurality and to determine whether the ascending projections from the lateral and medial superior olives overlap or remain segregated at their targets. Injections of two different tracers were placed in tonotopically matched areas of the lateral and medial superior olives in the same animal. Retrograde transport from injections in the medial superior olive labeled spherical cells in the contralateral anteroventral cochlear nucleus and principal cells in the ipsilateral medial nucleus of the trapezoid body. Few cells were labeled in ipsilateral cochlear nucleus. Anterograde transport resulted in tonotopically specific distributions of label with the same laterality as in nonecholocating mammals. In the dorsal nucleus of the lateral lemniscus, label from the lateral and medial superior olives largely overlapped. In the inferior colliculus, label from the lateral and medial superior olives largely overlapped. In the inferior colliculus, label from the two sources overlapped in the high and low frequency ranges, but in the frequency range around 60 kHz, label from the medial superior olive extended more dorsally than that from the lateral superior olive. These results indicate that projections of the lateral and medial superior olives overlap extensively at their targets.

Animals↗

PubMed1985

In vivo studies on amino acid transmitters in the central auditory system of the guinea pig.

The extracellular concentrations of endogenous amino acids were measured in vivo in the guinea pig cochlear nucleus during sound stimulation. The purpose was to explore whether certain amino acids might be employed as neurotransmitters by the auditory nerve. A dialysis sampling probe was used to collect a dialysate of the cochlear nucleus. The amino acids were determined fluorometrically after precolumn derivation and high-performance liquid chromatography separation. A short pulse of p-chloromercuryphenylsulfonate (p-CMS) was used to reduce the reuptake of amino acids. The concentration of glutamic and aspartic acid increased twofold to threefold during sound stimulation, while gamma-aminobutyric acid was unaffected. The results support a role for glutamic and/or aspartic acids as neurotransmitters in the auditory nerve.

4-Chloromercuribenzenesulfonate↗

PubMed1984

Effects of kanamycin on cochlear nuclear evoked responses and behavioral responses in C57BL/6J mice.

The effect of kanamycin on auditory function was investigated in C57BL/6J mice. Results showed that kanamycin treatments (400 mg/kg/day, injected between 10 to 13 days of age) caused severe cochlear damage, particularly to the outer hair cells, and elevation of cochlear nucleus evoked-response thresholds. The treatment also rendered the treated animals susceptible to audiogenic seizures, suggesting a change in the animals' reactivity to intense sounds. However, unlike the effect of noise, exposure to kanamycin did not cause the treated animals to show abnormal augmentation of cochlear nucleus evoked-response amplitude when stimulated at high intensities.

Acoustic Stimulation↗

PubMed1991

Brainstem auditory evoked potentials correlate with morphological changes in Gunn rat pups.

The relationship of brainstem structure and function in bilirubin encephalopathy is incompletely understood. The present experiments compare quantitative measures of brainstem structures with brainstem auditory evoked potentials (BAEPs) in infant jaundiced (jj) and nonjaundiced (Nj) Gunn rats. Ten jj's from 4 litters were injected with sulfadimethoxine at 11-12 days of age to raise their brain bilirubin concentration. Littermate controls were jj's given saline, and Nj's given sulfadimethoxine or saline. At 15-17 days of age BAEPs were recorded, and rats were prepared for histological examination, as was reported in the previous paper (Conlee and Shapiro, 1991). Significant differences between groups were seen for BAEP wave I latency (P = 0.002). I-II interwave interval (P = 0.001), and amplitudes of waves I, II, III, and IV (each P less than 0.0005) due to increased latencies and decreased amplitudes in the jj-sulfa group. Animals with the most severe BAEP abnormalities had the most severe histological abnormalities. Cochlear nucleus volume had a positive linear correlation with the amplitude of BAEP waves I, II, and IV, and an inverse correlation with wave I latency and I-II interwave interval (P less than or equal to 0.001). The highest correlations were BAEP I-II interwave interval and amplitude of waves I and II with cochlear nucleus volume (r = -0.78, 0.71 and 0.70, respectively, P less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1981

A histochemical study on the innervation of the cerebral blood vessels in bats.

The adrenergic and cholinergic nerves innervating the cerebral blood vessels of four species of Japanese chiropterids (Rhinolophus ferrumequinum, Murina leucogaster, Vespertilio superans and Miniopterus schreibersi) have been investigated using specific histochemical techniques. In all these species of bats arteries of the internal carotid system are poorly developed, whereas those of the vertebro-basilar system are well developed. The adrenergic and cholinergic nerves innervating these cerebral arteries, however, all originate from the stem nerve bundles entering the cranial cavity along the internal carotid artery. Both nerve plexuses are among the densest of any vertebrate species so far investigated. Adrenergic nerve plexuses are usually composed of complicated meshworks of fine fibres, while cholinergic ones are composed of rather longitudinally arranging meshworks of both thick and thin fibres, exhibiting a very high acetylcholinesterase activity. Small parenchymal arteries and arterioles are also dually innervated by adrenergic and cholinergic nerve fibres of peripheral origin. Intracerebral capillaries, on the other hand, are in several places directly connected with both adrenergic and cholinergic fibres of parenchymal origin. Capillaries in the cerebral and cerebellar cortices, diencephalon and cochlear nucleus in v. superans exhibit a heavy non-nervous acetylcholinesterase activity in their walls, but in R. ferrumequinum and M. schreibersi, the response is weak or negative, except for that in the cochlear nucleus.

Acetylcholinesterase↗

PubMed1994

Effects of selective adenosine A1 and A2 receptor agonists and antagonists on local rates of energy metabolism in the rat brain.

The quantitative [14C]2-deoxyglucose autoradiographic technique was applied to the measurement of the cerebral metabolic effects of adenosine A1 and A2 receptor agonists and antagonists in adult rats. The adenosine A1 receptor agonist and antagonist, 2-chloro-N6-cyclopentyladenosine (CCPA) and 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) as well as the adenosine A2 receptor agonist, 2-[p-(2-carboxyethyl)phenylethylamino]-5'-ethylcarboxamidoadenosin e (CGS 21680), were injected at the dose of 0.01 mg/kg. The adenosine A2 receptor antagonist, 3,7-dimethyl-1-proparglyxanthine (DMPX) was injected at the dose of 0.3 mg/kg. These doses were chosen in accordance with the known affinity of the drugs for their respective receptor and to avoid peripheral effects. The adenosine A1 receptor agonist, CCPA, induced decreases in glucose utilization in three brain areas, the globus pallidus and two hypothalamic nuclei. The adenosine A2 receptor agonist, CGS 21680, induced more general depressant effects on energy metabolism which were significant in 17 brain areas, such as cerebral cortex, hippocampal and white matter regions plus motor and limbic structures. The adenosine A2 receptor antagonist, DMPX, decreased glucose utilization in the globus pallidus while increasing energy metabolism in the cochlear nucleus. The adenosine A1 receptor antagonist, DPCPX, depressed glucose utilization in the globus pallidus and dentate gyrus, and increased rates of energy metabolism in six regions, mainly hypothalamic, thalamic areas and in the cochlear nucleus. There was a mismatch between cerebral metabolic consequences of adenosine A1 and A2 receptor agonists and the localization of corresponding adenosine receptors. The metabolic effects of the adenosine A2 receptor agonist and antagonist were consistent with the known involvement of that type of receptor in the control of locomotion and its effects on neuronal firing in the hippocampus and cerebral cortex. The effects of the adenosine A1 receptor agonist were very discrete and mostly related to the transient decrease in blood pressure induced by the drug. The increases in glucose utilization induced in limbic regions by the adenosine A1 receptor antagonist are probably linked to the regulation by adenosine of arousal and cardiorespiratory function. These results are in good agreement with the neuroregulatory function of the adenosine system as previously shown by other methods.

Adenosine↗