Cerebral cortical concentrations of bioamines and their metabolites during arousal and after feeding in the little brown bat (Myotis lucifugus)

The concentrations of bioamines and their metabolites have been determined in March and April during arousal from hibernation in the cerebral cortex of the little brown bat (Myotis lucifugus). The patterns during arousal for dopamine and serotonin (5-HT) were similar with a significant fall in concentrations by 1 h of arousal, and an inverse relationship with their respective metabolites, 3,4-dihydroxyphenylacetic acid and 5-hydroxyindolacetic acid (5-HIAA). This suggests an acute release and metabolism of these bioamines with onset of arousal. During arousal, cerebral cortical concentrations of norepinephrine (NE) were not significantly changed. Levels of homovanillic acid were markedly depressed during hibernation and rose acutely with arousal. After arousal and 4 days of feeding in April, there was an increase in all bioamines and their metabolites studied except for NE. Of note is the marked decrease in the hibernating level of 5-HT and increase in its metabolite 5-HIAA from March to April, which may herald the natural termination of hibernation. Our results suggest that the brain of hibernators undergoes complex changes in the modulation of neurotransmitter systems which are consistent with both down- and up-regulation of neuronal activity in the maintenance of hibernation and the initiation of the arousal process.     

Functional zones in the auditory cortex of the echolocating bat, Myotis lucifugus

Neurophysiological mapping experiments in the auditory cortex of the frequency-modulated bat, Myotis lucifugus, reveal 3 functional subregions: a tonotopic zone located dorsally, a delay-sensitive zone more ventrally, and an intermediate zone of major overlap. The unique finding of an overlapping cortical region representing both spectral and time-delay information of echoes is intriguing in view of a recent behavioral study suggesting the convergence of such echo cues in auditory perception. (Simmons et al., Soc. Neurosci. Abstr., 13 [1987] 870).     

Mapping of the auditory area in the cerebellar vermis and hemispheres of the little brown bats, Myotis lucifugus

Mapping of auditory area in the cerebellar vermis and hemispheres of little brown bats, Myotis lucifugus, shows that a large area of the bat's cerebellum contains units responding to acoustic stimuli. These units had latencies between 4 and 34 msec and best frequencies between 33.0 and 92.5 kHz. The Q₁₀-dB values of their tuning curves ranged from 2.0 to 19.7. Most of the units studied fired only a few impulses during a stimulus with minimum thresholds between 22 and 90 dB SPL. Units in the cerebellar vermis tend to have higher best frequencies and shorter latencies than those in the cerebellar hemispheres. However, there is no evidence of clear tonotopic organization therein.     

鼠脑反复缺血再灌注海马6种氨基酸、单胺递质及其代谢产物变化的研究

目的：研究脑反复缺血后海马细胞外液氨基酸和单胺递质及其代谢产物的变化规律。方法：采用Ｐｕｌｓｉｎｅｌｌｉ和Ｂｒｉｅｒｌｅｙ４血管闭塞的方法,使鼠脑反复缺血,海马微管透极与高压液相电化学检测,观察细胞外谷氨酸（Ｇｌｕ）,天门冬氨酸（Ａｓｐ）,谷氨酰胺,牛磺酸、丙氨酸,丝氨酸,多巴胺（ＤＡ）,５－羟色胺（５－ＨＴ）及其代谢产物浓度的变化。结果：缺血期,Ｇｌｕ和Ａｓｐ骤然增高５０倍和３０倍。缺血期ＤＡ和５－ＨＴ含量分别增加３０倍和５０倍,随后逐渐下降,再灌注１００ｍｉｎ恢复到基线水平,与此同时,其酸性代谢产物３,４－二羟苯乙酸（ＤＯＰＡＣ）,高香草酸（ＨＶＡ）,５－羟吲哚乙酸（５－ＨＩＡＡ）在缺血期明显下降。结论：缺血期海马细胞外液兴奋性氨基酸和单胺递质急剧大量释放并触发膜离子通道改变。Ｃａ＾＋超载,自由基反应,共同     

Cerebral oxygen metabolism and cerebral blood flow in man during light sleep (stage 2)

We measured cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) during light sleep (stage 2) in 8 young healthy volunteers using the Kety-Schmidt technique with 133Xe as the inert gas. Measurements were performed during wakefulness and light sleep as verified by standard polysomnography. Unlike our previous study in man showing a highly significant 25% decrease in CMRO2 during deep sleep (stage 3-4) we found a modest but statistically significant decrease of 5% in CMRO2 during stage 2 sleep. Deep and light sleep are both characterized by an almost complete lack of mental activity. They differ in respect of arousal threshold as a stronger stimulus is required to awaken a subject from deep sleep as compared to light sleep. Our results suggest that during non-rapid eye movement sleep cerebral metabolism and thereby cerebral synaptic activity is correlated to cerebral readiness rather than to mental activity.     

Further studies of bulk and orosensory decrement in producing satiation of feeding in Aplysia

Prior evidence has suggested that meal satiation in the marine mollusk Aplysia is associated with stretch of the crop. The current data, however, suggest that under some conditions, bulk in the crop can be dissociated from the propensity to feed. The crop was hyper-distended 6 h after a satiating meal of rehydrated seaweed; that is, the crop took in water and therefore contained a greater volume than it had contained immediately after satiation. Animals presented with food 6 h after an initial satiating meal consumed a new meal despite the fact that their crop was distended beyond the level at which they had previously terminated feeding. This unexpected result led to additional experiments designed to study possible orosensory decrement during presentation of food. Orosensory input was assessed by recording from the metacerebral cell (MCC) in free-moving animals. The MCC receives excitatory input in response to chemosensory stimulation of the lips, and exhibited a slow decrement during the course of a meal or during repeated lip stimulation without ingestion. Lesions of the cerebro-buccal connectives abolished the long-term MCC response decrement to lip stimulation. This result suggests that the MCC long-term response decrement to lip stimulation is a product of buccal-ganglion feedback and may not reflect sensory decrement of chemosensory pathways. Therefore, satiation may not produce a change in lip sensitivity to chemosensory input. Our data suggest that one important factor that determines satiation is a stretch stimulus of the posterior esophagus/anterior crop. This stretch stimulus may subside over several hours as the crop contents are redistributed or as receptors slowly adapt.     

Histoenzymological mapping of alkaline phosphatase and 5-nucleotidase in the medulla oblongata of a microchiropteran bat (Taphozous melanopogon temminck)

The contribution deals with the distribution of alkaline phosphatase and 5-nucleotidase in the medulla oblongata of Taphozousmelanopogon (a Microchiroptera), for the first time. The main highlights of the study are: (1) Cranial nerve nuclei demonstrate intense activity of alkaline phosphatase, whereas except nucleus tractus spinalis n. trigemini, rest of the nuclei show much variations of 5-nucleotidase distribution. (2) The vestibular nuclei are very intensely positive for 5-nucleotidase but exhibit variable activity of alkaline phosphatase. (3) Three subdivisions of nucleus olivaris inferior, i.e. nucleus olivaris accessorius medialis, nucleus olivaris accessorius dorsalis and nucleus olivaris inferior, which were not reported in the earlier neuroanatomical studies, have been identified. These nuclei show very intense alkaline phosphatase and relatively less intense 5-nucleotidase activities. (4) In general, the activity of alkaline phosphatase is stronger in neurons than in neuropil and that of 5-nucleotidase is stronger in neuropil than in neurons. (5) Blood capillaries are completely negative for alkaline phosphatase and intensely positive for 5-nucleotidase. A comparison is made between the distribution of these enzymes in the medulla oblongata of bat and other mammals so far studied.     

Distribution of norepinephrine and dopamine in cerebral cortical areas of the rat

Concentrations of norepinephrine and dopamine were determined using enzyme isotope assay in 27 microdissected cerebral cortical areas of the rat. A detailed map is presented for microdissection of rat cerebral cortex. Norepinephrine was found in low but still measurable quantities throughout the cortex. Differences between cortical areas are also low. Relatively highest levels were demonstrated in the pyriform, insular and entorhinal cortices. The distribution of dopamine was found to be uneven with a maximal regional difference of 1:24. Concentration of dopamine was in all areas lower than that of norepinephrine. The highest dopamine concentration (2,4 ng/mg protein) was measured in the rostral pyriform cortex but other mesocortical (cingulate, frontal, insular and entorhinal) dopaminergic areas also contained relatively high amounts. Except for the caudal occipital and caudal entorhinal cortices all regions studied contained measurable quantities of dopamine. Its low concentration relative to norepinephrine (below 15%) suggests that in the cortical areas studied dopamine is present as the precursor of norepinephrine.     

Luteinizing hormone-releasing hormone (LH-RH) cells and their projections in the forebrain of the batMyotis lucifugus lucifugus

Luteinizing hormone-releasing hormone (LH-RH) neurons and their projections were studied by immunocytochemistry in the brains of little brown bats (Myotis lucifugus lucifugus: Chiroptera: Vespertilionidae ) as a first step in the study of relationships between these neurons and the seasonal reproductive events characteristic of this species. The majority of immunoreactive neurons in adult male, adult female, and fetal bats were ovoid bipolar cells with one thin and one thicker process, both of which gave rise to fine varicose fibers. LH-RH-immunoreactive perikarya were concentrated in the region of the arcuate nuclei in all bats examined. Perikarya were also consistently found dispersed in the mammillary region, anterior hypothalamus, preoptic areas, septum, diagonal band of Broca, and olfactory tracts; they were occasionally observed in the dorsal hypothalamus, organum vasculosum of the lamina terminalis (OVLT), habenula, amygdala, and cingulate gyrus. LH-RH-immunoreactive fibers projected heavily to the median eminence, infundibular stalk, and posterior pituitary. In extrahypothalamic areas, these fibers were especially abundant in the stria medullaris/habenula and stria terminalis/amygdala, but also contributed to the diagonal band of Broca and the olfactory tracts. Immunoreactive fibers that may be components of many different pathways clustered in the rostral septum and permeated the medial hypothalamus. LH-RH-containing fibers frequently entered the subfornical organ, but were observed less often in the OVLT and only occasionally in the pineal. The organization of the LH-RH system in the little brown bat resembles that of primates, but differs considerably from that in the rat. Anatomical characteristics of the LH-RH system in bats thus suggest that this animal may be a particularly suitable species for further study of neuroendocrine control of reproductive function as it may relate to primates, including humans.     

Egg laying hormone inhibits a neuron (C-PR) involved in multiple manifestations of food-induced arousal in Aplysia

Egg laying behavior is known to suppress feeding in Aplysia, but both behaviors have common responses involving head movements and posture. Egg laying hormone (ELH) applied in vitro to the isolated nervous system of Aplysia reduces the spontaneous and the evoked activity of the C-PR, a neuron implicated in postural responses during feeding. The inhibitory effect of ELH on the C-PR appears to be mediated by interneurons primarily located in the pedal/pleural ganglia, which contain all the known direct follower cells of the C-PR. Our results do not support the idea that postural response during feeding and egg laying are mediated by the activation of a common arousal element, the C-PR. In fact, the C-PR seems to be a specific element for the food-arousal state, and the inhibition of the C-PR by ELH may contribute to the suppression of appetitive feeding responses during egg laying.     

Neuromorphometric features and dimensional analysis of the vestibular end organ in the little brown bat (Myotis lucifugus)

Neuromorphometric parameters of the vestibular system were determined from serial sections of temporal bones from four little brown bats. Well-developed eminentiae cruciatae project from the cristae ampullares of the anterior and posterior membranous ampullae. A total of 4,500 bipolar ganglion cells were enumerated within the vestibular ganglion. The widths of the cell somas varied from 2.5 to 20 micrometers, with 70% of them having widths between 5.0 and 12.5 micrometers. Two maxima were observed in a curve of ganglion cell density as a function of the length of the ganglion. The first maximum indicated a density of 4,800 cells per mm2 at a length 0.20 from the apex of the ganglion (in the pars dorsalis); the second, a density of 4,750 cells per mm2 at 0.38 mm (in the pars ventralis). The morphometric parameters studied were the radii of curvature of the semicircular ducts, the cross-sectional diameters of the semicircular canals and ducts, the dimensions of the cristae ampullares and their membranous ampullae, and dimensions pertaining to the statoconial organs. Surface areas (measured from graphic projections) were determined as 0.098 mm2 and 0.016 mm2 and hair cell count 500 and 1,300 cells for the saccular and utricular maculae, respectively. The radii of curvature of the three semicircular ducts, R, were dissimilar, with the anterior duct having the largest radius (R = 0.91 mm) and the posterior duct the smallest one (R = 0.69 mm). The average cross-sectional diameters of the anterior, lateral, and posterior ducts were measured as 0.11 mm, 0.14 mm, and 0.13 mm, respectively. Some of the morphological parameters were used to ascertain information regarding the dynamics of semicircular--canal function. In particular, the coefficients theta and II in the torsion pendulum model (Steinhausen, '31; Egmond et al., '49), and the time constants xi L congruent to II/delta and xi S congruent to theta/II of the torsion pendulum model were estimated for the little brown bat from these parameters. Where appropriate, comparisons were made to time constants obtained for other species.     

Variations of monoamines and their metabolites in the human brain putamen

The levels of the monoamines dopamine (DA), serotonin (5-HT) and norepinephrine (NE) and the monoaminergic metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were measured with HPLC-ECD in 42 samples from human brain putamen. The influence of gender and of age was investigated and correlations between the monoamines were established. The DAergic system shows a significant difference between males and females, with females having lower DA and higher DOPAC levels and a higher DOPAC/DA ratio than males. No gender-related differences of 5-HT and its metabolites were observed, nor of NE. Three different age groups (group 1: 0–9.9 years; group 2: 10–59.9 years; group 3: 60 years and older) were defined according to previous studies on ontogenesis and senescence in human brain. An increase in 5-HT levels, decrease in 5-HIAA levels a d a decrease in the 5-HIAA/5-HT ratio were observed after the first decade of life. Changes in the DAergic system were seen in senescence, with decreasing DA levels and an increase in the HVA/DA ratio. DOPAC, HVA and the DOPAC/DA ratio are unaffected. NE is similar in all age groups. The analysis of the relation of the levels of the three monoamines proved a strong correlation between the DAergic and 5-HTergic systems. The nature of this relationship might have an impact on neuro-psychiatric disorders and brain function.     

脑缺血再灌注大鼠皮质NMDA受体亚单位NR2A/B蛋白的表达变化

目的 采用免疫细胞化学技术，探讨急性脑缺血再灌注不同时间段大鼠脑顶皮质NMDA受体亚单位NR2A及NR2B蛋白的表达变化。方法 雄性Wistar大鼠70只,随机分成正常对照组、假手术对照组、脑缺血再灌注对照组；以颈动脉引流法行全脑缺血7min再灌注造模，术后分6h、24h、72h3个时间段取脑．脑组织恒冷箱连续冠状切片,免疫细胞化学ABC反应，图像分析系统行顶皮质Ⅰ区V层免疫阳性面积检测。结果 （1）麻醉及假手术可导致顶皮质NR2A、NR2B蛋白表达短暂增多，24h内恢复正常；（2）缺血再灌注后6h前后形成表达高峰,24h恢复正常，随后表达急剧减少，持续至72h以后。结论（1）脑缺血再灌注可导致顶皮质神经元NR2A、NR2B蛋白表达变化，且表达存在明显的时间依赖性；（2）缺血再灌注早期皮质NR2A、NR2B蛋白高度表达可能是导致迟发性神经元丢失的重要原因。     

Neuropeptide Y-like immunoreactivity in the diencephalon of the little brown bat (Myotis lucifugus): localized variations with physiological state.

The current study used light microscopic immunocytochemistry to demonstrate and compare neuropeptide Y-like immunoreactivity (NPY-IR) in the diencephalon of the little brown bat (Myotis lucifugus) at different stages in its annual cycle of activity and hibernation. Animals were sacrificed in each of three discrete physiological states: euthermic, hypothermic, and hibernating. In general, NPY-IR was abundant in the hypothalamus and sparse in other diencephalic areas. Immunoreactivity was present in a number of pathways which project to or originate from diencephalic nuclei; these include the ansa peduncularis, medial forebrain bundle, inferior thalamic peduncle, stria terminalis, stria medullaris, mammillary peduncle, and dorsal longitudinal fasiculus. Dense fiber plexuses were present throughout the hypothalamus; however, NPY-IR was conspicuously absent from the suprachiasmatic nucleus. Immunoreactive perikarya were located in the supraoptic, dorsomedial, ventromedial, and arcuate nuclei, in the external division of the ventral lateral geniculate nucleus, and in the pineal gland. Localized changes in density and/or distribution of NPY-IR were correlated with changes in physiological state.     

The effects of exogenous neuropeptide Y on feeding and sexual behavior in the red-sided garter snake (Thamnophis sirtalis parietalis)

Actively courting adult male red-sided garter snakes were injected with one of two dosages of neuropeptide Y (NPY) or saline into the third cerebral ventricle. Courtship and feeding responses were assessed prior to surgery, 4–5 h and 24 h post-surgery. Feeding behavior was tested by the presentation of a favored food, an earthworm. NPY significantly reduced courtship behavior scores at both low (0.16 nmol) and high (0.77 nmol) doses 4–5 h after surgery. Snakes also took much longer to reach the criterion courtship score at the high dose. Feeding occurred only in snakes treated with NPY. At the low dose 29% ate at 4–5 h and 24 h after surgery; 43% of the snakes treated with the high dose ate 4–5 h post-surgery. When tested the day following injection, animals were courting at levels comparable to presurgery levels and refused food.     

Anatomic evidence for a neurotoxic effect of (±)-fenfluramine upon serotonergic projections in the rat

Immunocytochemistry was used to determine whether (±)-fenfluramine causes structural damage to serotonergic (5-HT) neurons. Sections from rat forebrain were examined 4 h, 36 h and 2 weeks after various dose regimens of fenfluramine. At all time points there was a reduction of fine 5-HT axon terminals in the forebrain, while beaded axons were spared. The presence of markedly swollen, fragmented 5-HT axons 36 h after injection is indicative of axonal degeneration, and provides morphologic evidence for a neurotoxic effect of (±)-fenfluramine upon 5-HT axon terminals.     

Stimulation of feeding behavior and food consumption in the goldfish, Carassius auratus, by orexin-A and orexin-B

The neuropeptides, orexin-A and orexin-B, have been demonstrated to have a physiological role in the regulation of food intake in mammals. The effects of human orexin-A and orexin-B intracerebroventricular (i.c.v.) injection on the feeding behavior of goldfish (Carassius auratus) were investigated. I.c.v. injection of orexin-A and orexin-B both caused a significant increase in appetite, as indicated by an increased number of feeding acts. Orexin-A and orexin-B both significantly stimulated food consumption, as indicated by increased total food intake during a 60-min observation period; the actions of orexin-A were dose dependent. Orexin-A was more potent than orexin-B in stimulation of both feeding behavior and food intake. These results indicate that orexin peptides are involved in the hypothalamic regulatory pathways of feeding behavior in goldfish.     

Glutamate suppression of feeding and the underlying output of effector neurons in Helisoma

This study tested the consequences of 3 stress conditions on feeding consumption in the freshwater snail Helisoma. Two stresses (placement in a hypotonic environment and body wall incision) were without effect on food consumption. In contrast, placement of animals in a hypertonic environment (20% seawater) caused a transient suppression of feeding. Since the osmolarity and composition of molluscan blood is known to be altered under conditions of osmotic stress, we reasoned that a blood-borne agent might be responsible for the observed suppression of feeding. We tested this hypothesis by chromatographic analysis of blood and, based on this analysis, subsequent assay of putative neuromodulatory agents on the patterned motor activity (PMA) expressed by effector neurons of the buccal ganglion. Our analysis shows that a rise and fall of blood acidic amino acids corresponds to the suppression of feeding. Furthermore, bath application of glutamate at its elevated physiological level (100-150 microM) to buccal ganglia caused complete and prolonged suppression of PMA in effector neurons. This suppression is attributable to activation of chloride and potassium currents which shunt patterned synaptic inputs to the effector neurons. We conclude that glutamate, in an endocrine-like fashion, can exert a powerful neuromodulatory action on the feeding effector neurons of Helisoma.