Brain Stem Of Cat Research Articles

John W. Severinghaus, M.D., 1922 to 2021.

John W. Severinghaus, M.D., 1922 to 2021.

Lymphoplasmacytic Meningoencephalitis and Neuronal Necrosis Associated With Parvoviral Infection in Cats.

Neurologic manifestations other than cerebellar hypoplasia are rarely associated with feline panleukopenia virus (FPV) infection in cats. Here the authors describe lymphoplasmacytic meningoencephalitis and neuronal necrosis in 2 cats autopsied after exhibiting ataxia and nystagmus. Gross changes consisted of cerebellar herniation through the foramen magnum, with flattening of cerebrocortical gyri and narrowing of sulci. Histologically, lymphoplasmacytic meningoencephalitis, extensive neuronal necrosis, and neuroaxonal degeneration with digestion chambers were present in the telencephalon and brain stem in both cats. Frozen brain tissue of both cats was positive for parvoviral antigen via fluorescent antibody testing, and formalin-fixed, paraffin-embedded tissue sections of brain were immunoreactive for parvovirus antigen and positive for parvoviral DNA on in situ hybridization. Frozen brain tissue from 1 case was positive for parvovirus NS1 and VP2 genes using conventional polymerase chain reaction, and subsequent DNA sequencing and phylogenetic analysis revealed that the viral strain was a FPV. Reverse transcription quantitative polymerase chain reaction on formalin-fixed, paraffin-embedded brain tissue revealed high levels of parvovirus in both cases, supporting an acute and active viral infection. Although rare, FPV infection should be considered in cases of lymphoplasmacytic meningoencephalitis and neuronal necrosis in cats.

Signatures of Somatic Inhibition and Dendritic Excitation in Auditory Brainstem Field Potentials.

Extracellular voltage recordings (Ve ; field potentials) provide an accessible view of in vivo neural activity, but proper interpretation of field potentials is a long-standing challenge. Computational modeling can aid in identifying neural generators of field potentials. In the auditory brainstem of cats, spatial patterns of sound-evoked Ve can resemble, strikingly, Ve generated by current dipoles. Previously, we developed a biophysically-based model of a binaural brainstem nucleus, the medial superior olive (MSO), that accounts qualitatively for observed dipole-like Ve patterns in sustained responses to monaural tones with frequencies >∼1000 Hz (Goldwyn et al., 2014). We have observed, however, that Ve patterns in cats of both sexes appear more monopole-like for lower-frequency tones. Here, we enhance our theory to accurately reproduce dipole and non-dipole features of Ve responses to monaural tones with frequencies ranging from 600 to 1800 Hz. By applying our model to data, we estimate time courses of paired input currents to MSO neurons. We interpret these inputs as dendrite-targeting excitation and soma-targeting inhibition (the latter contributes non-dipole-like features to Ve responses). Aspects of inferred inputs are consistent with synaptic inputs to MSO neurons including the tendencies of inhibitory inputs to attenuate in response to high-frequency tones and to precede excitatory inputs. Importantly, our updated theory can be tested experimentally by blocking synaptic inputs. MSO neurons perform a critical role in sound localization and binaural hearing. By solving an inverse problem to uncover synaptic inputs from Ve patterns we provide a new perspective on MSO physiology.SIGNIFICANCE STATEMENT Extracellular voltages (field potentials) are a common measure of brain activity. Ideally, one could infer from these data the activity of neurons and synapses that generate field potentials, but this "inverse problem" is not easily solved. We study brainstem field potentials in the region of the medial superior olive (MSO); a critical center in the auditory pathway. These field potentials exhibit distinctive spatial and temporal patterns in response to pure tone sounds. We use mathematical modeling in combination with physiological and anatomical knowledge of MSO neurons to plausibly explain how dendrite-targeting excitation and soma-targeting inhibition generate these field potentials. Inferring putative synaptic currents from field potentials advances our ability to study neural processing of sound in the MSO.

Implementation of rapid prototyping to produce a 3‐dimensional physical model of the anatomical distribution of functionally identified cat pre‐Bötzinger complex microinjection sites (714.4)

Previous work from our laboratory has used histological analyses to confirm functionally identified sites in the cat pre‐Botzinger complex (pre‐BotC). These sites have been represented in a 2‐D fashion based on our histological sections in conjunction with plates from Berman's stereotactic atlas (1968). To gain further insight into the anatomical distribution of these sites, we have used rapid prototyping technology to generate a 3‐D physical model representing the relevant regions/nuclei of the cat brainstem (based on Berman’s atlas) and the histological/stereotaxic coordinates associated with our microinjection sites. To accomplish this, plates from Berman’s atlas were scanned and compiled into a 3‐D configuration slide box, the stereotaxic coordinates of 348 pre‐BötC microinjection sites were entered into an x/y/z matrix based on histologically confirmed coordinates with the origin (0, 0, 0) referenced to the caudal pole of the retrofacial nucleus, midline, and dorsal surface of the medulla, and a 3‐D digital representation was generated and printed. We believe that this approach compliments both the 2‐D representations (previously used) and the digital 3‐D representation, and provides additional insight into the anatomical specificity of our functionally identified and histologically confirmed microinjection sites.Grant Funding Source: Supported by HL 63175

A unifying theory of ITD-based sound azimuth localization at the behavioral and neural levels

In many species, azimuthal sound source localization relies on the processing of fine temporal differences between the incoming signals at both ears (interaural time differences, ITDs). There exists no consensual theory of ITD-based localization that explains the behavioral and neural data alike. The classical view of a place code for localization [1] is questioned by electrophysiological data [2], while its alternative is functionally inefficient [3]. We propose as a functional principle that the system performs a maximum-likelihood estimation of the position of the source given the cues in the stimulus. This Bayesian approach implies that the behavioral and neural data are constrained by natural distributions of binaural cues, as observed in acoustical recordings of head related transfer functions (HRTFs). We first record and analyze HRTFs in humans and cats. Then we discuss the implications of our hypothesis on psychoacoustical data in humans and electrophysiological data in the cat. In a maximum-likelihood approach, the current observed cue is compared to the a priori distribution of cues (marginal prior normalization). It is thus fundamental to uncover what the cues are and how they are distributed across the spectrum. We recorded HRTFs in different species, and performed simulations of natural environments to quantify the robustness of ITD cues. We find that ITD is a frequency-dependent quantity that decreases by about 30% across the spectrum, and that such variations occur within the bandwidth of a cochlear filter. We also show how the distributions of cues vary across frequencies, in relation with various features of the environment such as reflections. Because the ITD as a constant delay is an insufficient cue, azimuth should be extracted by the system based on a frequency-dependent representation of ITD. We test this prediction in a psychoacoustical setup. Using a matching paradigm, subjects are asked to adjust the lateralization of two noises with different frequency contents, by varying the ITD of one of the stimuli. The HRTF data allows us to predict that the higher frequency sounds should be matched with a lower ITD than the lower frequency sound. We show how this prediction is met both qualitatively and quantitatively in our experiment. We give a model of the function of binaural cells in the cat brainstem. We predict the responses of those neurons to binaural beats at different frequencies from the cat HRTFs. We show how this simple model can explain already observed features of the electrophysiological literature [4], namely the presence of cells sensitive to frequency-dependent interaural delays. Finally, we propose a spiking neuron implementation of this maximum-likelihood principle. Cells are tuned to the frequency-dependent cues of their best position by means of both cochlear mismatches and axonal delays [5]. The Bayesian marginal prior normalization is implemented through the use of inhibition. Probing the model with various input sources, in a simulated virtual environment, we show that the network accurately localizes sound sources, comparably with an optimal Bayesian observer. Moreover, this model predicts qualitative differences in those observations for mammals of different sizes such as the cat and gerbil.

Location of cat brain stem neurons that drive sweating

The brain stem premotor pathways controlling most noncardiovascular sympathetic outflows are unknown. Here, we mapped the brain stem neurons that drive sweating, by microinjecting excitant amino acid (L-glutamate or D,L-homocysteate: 0.4-3 nmol) into 420 sites over the pons and medulla of eight chloralose-anesthetized cats (70 mg/kg iv). Sweating was recorded by the electrodermal potential at the ipsilateral forepaw pad. Responses were classified as immediate (<5 s latency) or delayed (>10 s latency). Immediate responses were obtained from 16 sites (1-3 per animal) and were accompanied by no change in blood pressure. Those sites were clustered between the facial nucleus and the pyramidal tract in the rostral ventromedial medulla (RVMM). Microinjections into 33 surrounding sites caused delayed electrodermal responses of lesser amplitude, while the remaining 371 sites evoked none. To retrogradely label bulbospinal neurons that may mediate electrodermal responses, fluorescent latex microspheres were injected into the region of the intermediolateral cell column in the fourth thoracic segment in an earlier preparatory procedure on six of the animals. A cluster of retrogradely labeled neurons was identified between the facial nucleus and the pyramidal tract. Neurons in this discrete region of the RVMM, thus, drive sweating in the cat's paw and may do so via direct spinal projections.

Ocular and neural distribution of feline herpesvirus-1 during active and latent experimental infection in cats.

BackgroundHerpes simplex virus 1 (HSV-1) and varicella zoster virus (VZV) cause extensive intra-ocular and neural infections in humans and are closely related to Felid herpes virus 1 (FeHV-1). We report the extent of intra-ocular replication and the extent and morphological aspects of neural replication during the acute and latent phases of FeHV-1 infection. Juvenile, SPF cats were inoculated with FeHV-1. Additional cats were used as negative controls. Cats were euthanized on days 6, 10, and 30 post-inoculation.ResultsFeHV-1 was isolated from the conjunctiva, cornea, uveal tract, retina, optic nerve, ciliary ganglion (CG), pterygopalatine ganglion (PTPG), trigeminal ganglion (TG), brainstem, visual cortex, cerebellum, and olfactory bulb of infected cats during the acute phase, but not the cranial cervical ganglion (CCG) and optic chiasm. Viral DNA was detected in all tissues during acute infection by a real-time quantitative PCR assay. On day 30, viral DNA was detected in all TG, all CCG, and 2 PTPG. Histologically mild inflammation and ganglion cell loss were noted within the TG during acute, but not latent infection. Using linear regression, a strong correlation existed between clinical score and day 30 viral DNA copy number within the TG.ConclusionsThe correlation between clinical score and day 30 viral DNA copy number suggests the severity of the acute clinical infection is related to the quantity of latent viral DNA. The histologic response was similar to that seen during HSV-1 or VZV infection. To the author’s knowledge this is the first report of FeHV-1 infection involving intraocular structures and autonomic ganglia.

Animals, Identity and Persistence

A number of claims are closely connected with, though logically distinct from, animalism. One is that organisms cease to exist when they die. Two others concern the relation of the brain, or the brainstem, to animal life. One of these holds that the brainstem is necessary for life—more precisely, that (say) my cat's brainstem is necessary for my cat's life to continue. The other is that it is sufficient for life—more precisely, that so long as (say) my cat's brainstem continues to function, so too does my cat. I argue against these claims.

Projecting from the superior olivary complex to the inner ear in the cat: a retrograde fluorescent labelling study

To investigate the distribution and projective feature of cat olivocochlear neurons. Eleven adult cats were divided into two groups randomly. The experimental group of eight cats was injected of 1% cholera toxin B (CTB) to the left cochlea, while injected of 5% fluoro gold (FG) to the right cochlea. The control group of three cats was injected of saline to bilateral cochlea. After a survival time of 7 days, serial frozen sections were cut in the cat brainstem. All the sections were processed by immunofluorescent procedure for CTB and FG, and the labeled olivocochlear neurons were observed by fluorescent microscope. In the experimental group, the mean total of olivocochlear neurons labeled by CTB and FG was 3210 +/- 168, including lateral olivocochlear neurons (LOC, 2298 +/- 120) and medial olivocochlear neurons (MOC, 913 +/- 64). The labeled neurons were divided into three different types according to their feature of projection: neurons which only projected to the ipsilateral cochlea, neurons which only projected to the contralateral cochlea, and double-labeled neurons which projected both to the ipsilateral and contralateral cochlea, but the double-labeled neurons comprised 3.9% and 15.1% in the LOC and MOC system respectively. No labeled neurons were found in the control group. There are three types of neurons in the cat olivocochlear system. The neurons which projected to the bilateral cochlea may distribute both in the LOC and MOC system.

Involvement of the lemniscal and paralemniscal pathways in the perception of direction and neuronal activity in the barrel cortex in rodent single-whisker stimulation

We recorded the neuronal activities from, stimulated, and produced lesions in, various regions in the brainstem of thalamic cats. Neuronal activities were recorded during stepping on a motor-driven treadmill, and were averaged by using the flexor EMG as the trigger. In wide regions of the brainstem, an averaged response was obtained with similar latency as the ipsilateral flexor EMG; however, in the paralemniscal pontine reticular formation (PLRF) the averaged response preceded the flexor EMG. When repetitive electrical stimulation was applied to the PLRF on one side, coordinated movements of bilateral forelimbs were elicited. The ipsilateral forelimb was flexed and the contralateral forelimb extended. EMG recordings revealed that on the side ipsilateral to the stimulation, flexor EMGs appeared and increased gradually in amplitude, and the extensor EMG was suppressed, while the extensor EMG was increased and no flexor EMG was obtained on the side contralateral to the stimulation. When pulse train stimulation was alternatingly applied to the PLRF on bilateral sides, alternating forelimb movement, as in stepping, was evoked, depending on each stimulation. A small, unilateral lesion in the PLRF reduced forelimb stepping on a motor-driven treadmill, particularly the flexor muscle contraction in the forelimb ipsilateral to the lesion. Bilateral PLRF lesions abolished forelimb stepping on both sides. Unilateral transection of the ventral quadrant at the cervical cord abolished PLRF-elicited flexor EMGs and associated suppression of extensor EMG ipsilateral to the transection; however, the side contralateral to the transection remained intact. These results suggest that the PLRF exerts a patterned control of the bilateral forelimb muscles and plays a role in initiating and maintaining forelimb stepping.

The somatotopic organization of trigeminal premotoneurons in the cat brainstem

This study was performed to complement the results of prior intracellular recording and labeling studies by investigating the general distribution pattern of trigeminal premotoneurons in the cat brainstem using the retrograde tracing methods. The results of the present study reconfirmed the presence of premotoneurons in the trigeminal principal and oral nuclei following horseradish peroxidase injections into the jaw-opening (JO) or jaw-closing (JC) nucleus. Furthermore, we found that labeled cells from the JO nucleus and JC nucleus located in the reticular regions surrounding the trigeminal motor nucleus (Vmo; Vmo shell region) were arranged in a topographic fashion, while those in the parabrachial nucleus, supratrigeminal nucleus, lateral reticular formation caudal to the shell region and raphe nuclei were intermingled with each other. The labeling in the individual nuclei was bilateral with an ipsilateral predominance to each injection site, with the exception of the mesencephalic trigeminal nucleus, where the labeling was ipsilateral to the injection site in the JC nucleus. These results, combined with the data of the previous intracellular tracing studies, indicate that based on the presence of somatotopic organization, premotoneurons can be largely divided into two groups; those projecting to either the JO or the JC nucleus and those projecting to the two nuclei, and we offer the suggestion that roles of premotoneurons for jaw movements differ among the individual nuclei.

Mapping of neurokinin b in the cat brainstem

We studied the distribution of neurokinin B-immunoreactive cell bodies and fibers in the cat brainstem using an indirect immunoperoxidase technique. The highest density of immunoreactive fibers was found in the motor trigeminal nucleus, the laminar and alaminar spinal trigeminal nuclei, the facial nucleus, the marginal nucleus of the brachium conjunctivum, the locus coeruleus, the cuneiform nucleus, the dorsal motor nucleus of the vagus, the postpyramidal nucleus of the raphe, the lateral tegmental field, the Kölliker-Fuse nucleus, the inferior central nucleus, the periaqueductal gray, the nucleus of the solitary tract, and in the inferior vestibular nucleus. Immunoreactive cell bodies containing neurokinin B were observed, for example, in the locus coeruleus, the dorsal motor nucleus of the vagus, the median division of the dorsal nucleus of the raphe, the lateral tegmental field, the pericentral nucleus of the inferior colliculus, the internal division of the lateral reticular nucleus, the inferior central nucleus, the periaqueductal gray, the postpyramidal nucleus of the raphe, and in the medial nucleus of the solitary tract. This widespread distribution of neurokinin B in the cat brainstem suggests that the neuropeptide could be involved in many different physiological functions. In comparison with previous studies carried out in the rat brainstem on the distribution of neurokinin B, our results point to a more widespread distribution of this neuropeptide in the cat brainstem.

Age-related ultrastructural changes in hypocretinergic terminals in the brainstem and spinal cord of cats

In a previous study, we noted the presence of enlarged “spot-like” structures that are immunoreactive to hypocretin in specific regions of brainstem of aged cats; similar structures were not seen in the same regions of adult cats. In the present study, electron microscopy was combined with hypocretin immunohistochemistry to examine the ultrastructure of these enlarged “spot-like” structures, which were found to consist of enlarged axonal terminals. The terminals were comprised of a large pale core with a dark peripheral rim. Many granules were present within the core; most of these granular structures were not immunostained. On the other hand, the rim contained a high density of hypocretin immunoreactivity; in this peripheral region, large dense-core vesicles and small synaptic vesicles without dense cores were observed. In addition, mitochondria in the peripheral rim region exhibited high electron density, which is indicative of the presence of age-related degenerative changes. Synaptic contacts were observed between the enlarged terminals and adjacent dendrites. Most of these synapses were asymmetric (Gray type I), although a few of them were symmetric (Gray type II). These data suggest that hypocretin transmission is altered during aging, which would be expected to result in age-related changes in the functioning of the hypocretinergic system.

Distribution of hypocretin (orexin) immunoreactivity in the feline pons and medulla

The distribution of hypocretin-1 (hcrt-1) and hypocretin-2 (hcrt-2) immunoreactivities in the cat brainstem was examined using immunohistochemical techniques. Hcrt-1- and hcrt-2-positive fibers with varicosities were detected in almost all brainstem regions. However, no hcrt-1- or hcrt-2-immunoreactive neuronal somata were observed in the cat brainstem. Both hcrt-1- and hcrt-2-labeled fibers exhibited different densities in distinct regions of the brainstem. In most brainstem regions, the intensity of hcrt-1 immunoreactivity was higher than that of hcrt-2 immunoreactivity. The highest densities of hcrt-1- and hcrt-2-positive fibers were found in the nucleus raphe dorsalis (RD), the laterodorsal tegmental nucleus (LDT) and the locus coeruleus (LC), suggesting an important role for these peptides in functions related to sleep–wake behavior.

Colocalization of γ-aminobutyric acid and acetylcholine in neurons in the laterodorsal and pedunculopontine tegmental nuclei in the cat: a light and electron microscopic study

Cholinergic and γ-aminobutyric acid (GABA) mechanisms in the dorsolateral pontomesencephalic tegmentum have been implicated in the control of active (REM) sleep and wakefulness. To determine the relationships between neurons that contain these neurotransmitters in this region of the brainstem in adult cats, combined light and electron microscopic immunocytochemical procedures were employed. Light microscopic analyses revealed that choline acetyltransferase (ChAT) and GABA immunoreactive neurons were distributed throughout the laterodorsal and pedunculopontine tegmental nuclei (LDT and PPT). Surprisingly, approximately 50% of the ChAT immunoreactive neurons in these nuclei also contained GABA. Using electron microscopic pre-embedding immunocytochemistry, GABA immunoreactivity was observed in somas, dendrites and axon terminals in both the LDT and PPT. Most of the GABA immunoreactive terminals formed symmetrical synapses with non-immunolabeled dendrites. Electron microscopic double-immunolabeling techniques revealed that ChAT and GABA were colocalized in axon terminals in the LDT/PPT. Approximately 30% of the ChAT immunoreactive terminals were also GABA immunoreactive, whereas only 6–8% of the GABA immunoreactive terminals were ChAT immunoreactive. Most of the ChAT/GABA immunoreactive terminals formed symmetrical synapses with non-immunolabeled dendrites; however, ChAT/GABA immunoreactive terminals were also observed that contacted ChAT immunoreactive dendrites. With respect to ChAT immunoreactive postsynaptic profiles, approximately 40% of the somas and 50% of the dendrites received synaptic contact from GABA immunoreactive terminals in both the LDT and PPT. These findings (a) indicate that there are fundamental interactions between cholinergic and GABAergic neurons within the LDT/PPT that play an important role in the control of active sleep and wakefulness and (b) provide an anatomical basis for the intriguing possibility that a mechanism of acetylcholine and GABA co-release from the terminals of LDT/PPT neurons is involved in the regulation of behavioral states.

The neuronal circuit of augmenting effects on intrinsic laryngeal muscle activities induced by nasal air-jet stimulation in decerebrate cats

We previously demonstrated that during nasal air-jet stimulation, both the activities of intrinsic laryngeal adductor and abductor muscles persistently increase, whereas the respiratory cycle prolongs and the activity of diaphragm decreases [Am. J. Rhinol. 9 (1995) 203–208; Neurosci. Res. 31 (1998) 137–146]. The purpose of this study was to clarify the neuronal circuit underlying the augmentation of intrinsic laryngeal muscles evoked by nasal air-jet stimulation. The immunohistologic analysis of Fos-expression was reported to determine the distribution of activated neurons in cat brainstem evoked by sneeze-inducing air puff stimulation of the nasal mucosa [Brain Res. 687 (1995) 143–154]. In sneezing cats, immunoreactivity was evoked in projection areas of the ethmoidal afferents, e.g. the subnuclei caudalis, interpolaris and in interstitial islands of the trigeminal sensory complex. Immunoreactivity was also enhanced in the solitary complex, the nucleus retroambiguus, the pontine parabrachial area and the lateral aspect of the parvocellular reticular formation [Brain Res. 687 (1995) 143–154]. In the present study, we focussed on the parvocellular reticular nucleus (PRN) as a relay of the neural circuit contributed to the augmentation of intrinsic laryngeal muscles evoked by nasal air-jet stimulation. We recorded the neuronal behavior of PRN during the nasal air-jet stimulation in precollicular-postmammillary decerebrate cats. As the results, 24% (17/71) of recorded neurons which were activated orthodromically by the electrical stimulation to anterior ethmoidal nerve, increased their firing rates in response to the nasal air-jet stimulation. Furthermore, spike-triggered averaging method revealed that four of these 17 PRN neurons activated intrinsic laryngeal muscles, suggesting that such neurons have excitatory projections to the intrinsic laryngeal muscle motoneurons in the nucleus ambiguus. These results suggest that the some of PRN neuron play a role in augmentation of the intrinsic laryngeal muscles activities during nasal air-jet stimulation.

Cardiovascular physiology and sleep

Sleep is a natural periodic suspension of consciousness during which processes of rest and restoration occur. The cognitive, reparative and regenerative accompaniments of sleep appear to be essential for maintenance of health and homeostasis. This brief overview will examine the cardiovascular responses to normal and disordered sleep, and their physiologic and pathologic implications. In the past, sleep was believed to be a passive state. The tableau of sleep as it unfolds is anything but a passive process. The brain's activity is as complex as wakefulness, never "resting" during sleep. Following the demise of the 'passive theory of sleep' (the reticular activating system is fatigued during the waking day and hence becomes inactive), there arose the 'active theory of sleep' (sleep is due to an active general inhibition of the brain) (1). Hess demonstrated the active nature of sleep in cats, inducing "physiological sleep" with electrical stimulation of the diencephalon (2). Classical experiments of transection of the cat brainstem (3) at midpontine level inhibited sleep completely, implying that centers below this level were involved in the induction of sleep (1, 4). For the first time, measurement of sleep depth without awakening the sleeper using the electroencephalogram (EEG) was demonstrated in animals by Caton and in humans, by Berger (1). This was soon followed by discovery of the rapid eye movement sleep periods (REM) by Aserinski and Kleitman (5), demonstration of periodical sleep cycles and their association with REM sleep (6, 7). Multiple studies and steady discoveries (4) made polysomnography, with its ability to perform simultaneous whole night recordings of EEG, electromyogram (EMG), and electrooculogram (EOC), a major diagnostic tool in study of sleep disorders. This facility has been of further critical importance in allowing evaluation of the interaction between sleep and changes in hemodynamics and autonomic cardiovascular control. Consequently the effects of sleep could be objectively differentiated from the effects of rest and recumbency. Furthermore, the specific effects of sleep onset and termination, and the effects of different sleep stages, could be assessed. Technological advances, with consequently enhanced and relatively non-invasive approaches to cardiovascular regulation, have greatly broadened our understanding of the effects of sleep stage on cardiovascular function. Continuous monitoring of simultaneous measures of polysomnographic and cardiovascular variables enables characterization of the effects of dynamic changes and rapid transitions in sleep stage, such as arousals. The capacity for measuring acute and immediate changes in autonomic, EEG and hemodynamic responses to sleep and arousal on a continuous basis has played an important role in enabling us to understand the interplay between changes in EEG and changes in the more peripheral measurements of neural and circulatory variables, such as sympathetic nerve traffic, heart rate (HR) and blood pressure (BP). Measurements of heart rate variability (HRV) (8-10), baroreflex sensitivity (BRS) (11-16), and intraneural measurement of sympathetic nerve traffic to muscle (MSNA) (17-22) and skin (SSNA) (23-24) have further advanced our understanding of mechanisms linking sleep and cardiovascular physiology.

Nitric oxide synthase (NOS) coexists with activated neurons by skeletal muscle contraction in the brainstem of cats

Contraction of skeletal muscle evokes increases in arterial blood pressure and heart rate. Some regions of the brainstem have been implicated for expression of the cardiovascular responses to muscle contraction. Previous studies have reported that static muscle contraction induced c-Fos protein in the nucleus of tractus solitarii (NTS), lateral reticular nucleus (LRN), lateral tegmental field (FTL), subretrofacial nucleus (SRF), A1 region and periaqueductal gray (PAG) of the brainstem. Furthermore, neuronal NADPH-diaphorase (NADPH-d), which is considered as a marker of neuronal nitric oxide synthase (nNOS), has been localized in those same regions. In this study, static muscle contraction was induced by electrical stimulation of the L7 and S1 ventral roots in anaesthetized cats. Distribution of c-Fos protein within neurons containing nNOS was evaluated by double labeling methods in order to determine if nNOS containing neurons in the brainstem were activated during muscle contraction. The results indicate that c-Fos protein colocalized with NADPH-d positive staining within the neurons of the SRF and PAG, but not within the NTS neurons. Distinct number of neurons with c-Fos protein was in close proximity to NADPH-d positive staining in the NTS, SRF, and PAG. Coexisting of c-Fos protein and NADPH-d positive staining was not observed in the LRN, FTL and A1 region. These findings demonstrate that nNOS containing neurons were activated by muscle contraction in the selective regions of the brainstem, and nNOS positive staining had close anatomic contacts with the neurons activated by contraction. This result provides neuroanatomic evidence suggesting that nitric oxide modulates the cardiovascular responses to muscle contraction within the NTS, SRF and PAG of the brainstem.

Age-related changes in hypocretin (orexin) immunoreactivity in the cat brainstem

Terminals of hypothalamic hypocretin-containing neurons are observed within brainstem nuclei involved in the control of sleep and wakefulness. Because aged humans, cats and other species exhibit changes in sleep and wakefulness in old age, we were interested in examining age-related changes in hypocretin/orexin projections to the following brainstem regions which are associated with the regulation of sleep and wakefulness: the dorsal raphe nucleus, the laterodorsal tegmental nucleus, the pedunculo-pontine tegmental nucleus and the locus coeruleus. Based upon the results of immunohistochemical determinations, in all the regions examined, round or oval ‘spot-like’ structures were observed in aged cats. Many of these ‘spot-like’ structures resembled enlarged varicosities of a nature that would be expected to disrupt hypocretin neurotransmission. In addition, a site-specific decrease in immunostaining was observed in the locus coeruleus in old cats compared with adult controls; this result likely reflects a decrease in the number of labeled fibers, which indicates that there occurs a degeneration of hypocretinergic function in conjunction with old age. The proceeding changes may account for some of sleep–wake disturbance which are observed in aged animals as well as elderly humans.

Fos-immunoreaction on the laryngeal reflex arc in the lower brainstem of cat

Fos-immunoreaction on the laryngeal reflex arc in the lower brainstem of cat