RESUMEN
Most hypnotic medications currently on the market target some aspect of GABAergic neurotransmission. Although all such compounds increase sleep, these drugs differentially affect the activity of the cerebral cortex as measured by the electroencephalogram. Whereas benzodiazepine medications such as triazolam tend to suppress slow wave activity in the cortex, the GABA(B) ligand gamma-hydroxybutyrate greatly enhances slow wave activity and the non-benzodiazepine, zolpidem, which binds to the omega1 site on the GABA(A) receptor/Cl(-) ionophore complex, is intermediate in this regard. Our previous studies have demonstrated that a small number of genes exhibit increased expression in the cerebral cortex of the mouse and rat during recovery sleep after sleep deprivation: egr-3, fra-2, grp78, grp94, ngfi-b, and nr4a3. Using these genes as a panel of biomarkers associated with sleep, we asked whether hypnotic medications induce similar molecular changes in the rat cerebral cortex to those observed when both sleep continuity and slow wave activity are enhanced during recovery sleep. We find that, although each drug increases the expression of a subset of genes in the panel of biomarkers, no drug fully replicates the molecular changes in the cortex associated with recovery sleep. Furthermore, high levels of slow wave activity in the cortex are correlated with increased expression of fra-2 whereas the expression of grp94 is correlated with body temperature. These results demonstrate that sleep-related changes in gene expression may be affected by physiological covariates of sleep and wakefulness rather than by vigilance state per se.
Asunto(s)
Corteza Cerebral/metabolismo , Expresión Génica/fisiología , Recuperación de la Función/fisiología , Sueño/fisiología , Análisis de Varianza , Animales , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Electroencefalografía/métodos , Chaperón BiP del Retículo Endoplásmico , Antígeno 2 Relacionado con Fos/genética , Antígeno 2 Relacionado con Fos/metabolismo , Proteínas HSP70 de Choque Térmico/genética , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Hipnóticos y Sedantes/farmacología , Masculino , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Miembro 1 del Grupo A de la Subfamilia 4 de Receptores Nucleares , ARN Mensajero/metabolismo , Ratas , Ratas Endogámicas WKY , Tiempo de Reacción/efectos de los fármacos , Receptores Citoplasmáticos y Nucleares/genética , Receptores Citoplasmáticos y Nucleares/metabolismo , Receptores de Esteroides/genética , Receptores de Esteroides/metabolismo , Recuperación de la Función/efectos de los fármacos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Sueño/efectos de los fármacos , Privación de Sueño/fisiopatología , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Brain opioid peptide systems are known to play an important role in motivation, emotion, attachment behaviour, the response to stress and pain, and the control of food intake. Opioid peptides within the ventral striatum are thought to play a key role in the latter function, regulating the affective response to highly palatable, energy-dense foods such as those containing fat and sugar. It has been shown previously that stimulation of mu opiate receptors within the ventral striatum increases intake of palatable food. In the present study, we examined enkephalin peptide gene expression within the striatum in rats that had been given restricted daily access to an energy-dense, palatable liquid food, chocolate Ensure(R). Rats maintained on an ad libitum diet of rat chow and water were given 3-h access to Ensure(R) daily for two weeks. One day following the end of this period, preproenkephalin gene expression was measured with quantitative in situ hybridization. Compared with control animals, rats that had been exposed to Ensure(R) had significantly reduced enkephalin gene expression in several striatal regions including the ventral striatum (nucleus accumbens), a finding that was confirmed in a different group with Northern blot analysis. Rats fed this regimen of Ensure(R) did not differ in weight from controls. In contrast to chronic Ensure(R), acute ingestion of Ensure(R) did not appear to affect enkephalin peptide gene expression. These results suggest that repeated consumption of a highly rewarding, energy-dense food induces neuroadaptations in cognitive-motivational circuits.
Asunto(s)
Cacao/metabolismo , Cuerpo Estriado/metabolismo , Sacarosa en la Dieta/metabolismo , Ingestión de Alimentos , Encefalinas/metabolismo , Precursores de Proteínas/metabolismo , Animales , Northern Blotting , Peso Corporal , Cognición , Ingestión de Alimentos/fisiología , Ingestión de Alimentos/psicología , Alimentos Formulados , Regulación de la Expresión Génica , Hibridación in Situ , Masculino , Motivación , Núcleo Accumbens/metabolismo , Ratas , Ratas Sprague-DawleyRESUMEN
Although sleep is thought to be restorative from prior wakeful activities, it is not clear what is being restored. To determine whether the synthesis of macromolecules is increased in the cerebral cortex during sleep, we subjected C57BL/6 mice to 6 hours of sleep deprivation and then screened the expression of 1176 genes of known function by using cDNA arrays. The expression of the heat shock proteins (HSP), endoplasmic reticulum protein (ERp72) and glucose-regulated protein (GRp78), was among the genes whose expression was significantly elevated in the cortex during sleep deprivation, whereas GRp78 and GRp94 mRNAs were elevated in the cortex during recovery sleep after sleep deprivation, as confirmed by conventional and quantitative real-time polymerase chain reaction and/or Northern analyses. A systematic evaluation of the expression of six heat shock protein family members (ERP72, GRp78, GRp94, HSP27, HSP70-1, and HSP84) in seven brain regions revealed increased mRNA levels in cortex, basal forebrain, hypothalamus, cerebellum and medulla during sleep deprivation, whereas increased mRNA levels during recovery sleep were limited to the cortex and medulla. Immunohistochemical studies identified increased numbers of GRp78-, GRp94-, and ERp72-immunoreactive cells in the dorsal and lateral cortex during sleep deprivation but, during recovery sleep, elevated numbers of these cells were found only in the lateral cortex. In the medulla, increased numbers of GRp94-immunoreactive cells were observed in nucleus tractus solitarius, dorsal motor nucleus of the vagus and the rostroventrolateral medulla during recovery sleep. The widespread increase of heat shock protein family mRNAs in brain during sleep deprivation may be a neuroprotective response to prolonged wakefulness. In contrast, the relatively limited heat shock protein family mRNA expression during recovery sleep may be related to the role of heat shock proteins in protein biogenesis and thus to the restorative function of sleep.
Asunto(s)
Encéfalo/metabolismo , Proteínas Portadoras/metabolismo , Proteínas de Choque Térmico/metabolismo , Glicoproteínas de Membrana/metabolismo , Chaperonas Moleculares/metabolismo , Privación de Sueño/metabolismo , Sueño , Animales , Northern Blotting , Chaperón BiP del Retículo Endoplásmico , Inmunohistoquímica , Masculino , Ratones , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Análisis de Secuencia por Matrices de Oligonucleótidos , Reacción en Cadena de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
There is a long-standing interest in the role of endogenous opioid peptides in feeding behavior and, in particular, in the modulation of food reward and palatability. Since drugs such as heroin, morphine, alcohol, and cannabinoids, interact with this system, there may be important common neural substrates between food and drug reward with regard to the brain's opioid systems. In this paper, we review the proposed functional role of opioid neurotransmission and mu opiate receptors within the nucleus accumbens and surrounding ventral striatum. Opioid compounds, particularly those selective for the mu receptor, induce a potent increase in food intake, sucrose, salt, saccharin, and ethanol intake. We have explored this phenomenon with regard to macronutrient selection, regional specificity, role of output structures, Fos mapping, analysis of motivational state, and enkephalin gene expression. We hypothesize that opioid-mediated mechanisms within ventral striatal medium spiny neurons mediate the affective or hedonic response to food ('liking' or food 'pleasure'). A further refinement of this hypothesis is that activation of ventral striatal opioids specifically encodes positive affect induced by tasty and/or calorically dense foods (such as sugar and fat), and promotes behaviors associated with this enhanced palatability. It is proposed that this brain mechanism was beneficial in evolutionary development for ensuring the consumption of relatively scarce, high-energy food sources. However, in modern times, with unlimited supplies of high-calorie food, it has contributed to the present epidemic of obesity.
Asunto(s)
Neostriado/fisiología , Péptidos Opioides/fisiología , Gusto/fisiología , Animales , Conducta Adictiva/psicología , Ingestión de Alimentos/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Conducta Alimentaria/fisiología , Humanos , Neostriado/efectos de los fármacos , Vías Nerviosas/efectos de los fármacos , Vías Nerviosas/fisiología , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/fisiología , Péptidos Opioides/farmacología , RecompensaRESUMEN
Pathways mediating the generation and/or maintenance of sleep reside within the preoptic/anterior hypothalamus (POAH). Reproduction, water balance, thermoregulation, and neuroendocrine functions are also associated with POAH, but it is not fully understood whether sleep is consolidated with these behavioral and physiological functions, or whether sleep-related circuitry is segregated from other POAH regions. Recent studies indicate that sleep mechanisms may be localized to the ventrolateral preoptic area (VLPO) and that this region sends inhibitory projections to waking/arousal-related neurons in the histaminergic tuberomammillary nucleus (TM), the noradrenergic locus coeruleus (LC), and the serotonergic dorsal raphe (DR). The present study is a quantitative investigation of preoptic area efferents to these monoaminergic groups. The results demonstrate that biotinylated dextran injections in the VLPO region reveal a robust innervation of TM that was as much as five times greater than innervation derived from other POAH subregions. The innervation of TM originated almost exclusively from injection sites in the region of galanin neurons. VLPO projections to the LC were moderately dense and were greater than in other POAH regions except for equivalent input from the medial preoptic area. Projections to the dorsal raphe were equivalent to LC innervation and were generally two to three times greater from VLPO than from other POAH regions, except for projections from the lateral preoptic region, which were similar in magnitude. The rostral and caudal levels projected more to the TM, whereas the midrostral region of VLPO strongly innervated the LC core. These findings, with recent studies demonstrating medial and lateral extensions of the sleep-related VLPO neuronal group, indicate that descending arousal state control may be mediated by this specific galaninergic/gamma-aminobutyric acid (GABA)ergic cell group.
Asunto(s)
Nivel de Alerta , Área Hipotalámica Lateral/fisiología , Locus Coeruleus/fisiología , Área Preóptica/fisiología , Terminales Presinápticos/fisiología , Núcleos del Rafe/fisiología , Animales , Vías Eferentes/citología , Vías Eferentes/fisiología , Área Hipotalámica Lateral/citología , Locus Coeruleus/citología , Masculino , Área Preóptica/citología , Núcleos del Rafe/citología , Ratas , Ratas Sprague-Dawley , SueñoRESUMEN
The sleep-waking discharge patterns of neurons in the posterior lateral hypothalamus (PLH) were investigated in the rat. Previous studies in the cat demonstrated that this region contained neurons that fired tonically at low rates (2-4 Hz) during waking, decreased firing in non-rapid eye-movement (NREM) sleep and nearly ceased firing during rapid eye-movement (REM) sleep. These "REM-off" neurons were proposed to be histaminergic neurons of the tuberomammillary nucleus (TM). Since many anatomical and physiological studies are performed in the rat, we sought to examine the sleep-waking discharge of these neurons in this animal. We found three main types of discharge patterns among PLH neurons. Waking-related neurons decreased their discharge in NREM sleep, and remained at low rates during REM sleep. A subpopulation of these neurons discharged very little during REM sleep (<0.2 Hz) (REM-off neurons). Waking/REM-related neurons decreased their discharge in NREM sleep and returned to waking rates in REM sleep. REM-related neurons decreased their discharge in NREM sleep and increased their discharge during REM sleep higher than waking rates. No NREM-related discharge patterns were recorded. Waking-related and waking/REM-related neurons were similar in location within the PLH and action potential duration. Some REM-off and other waking-related neurons were recorded within the boundaries of the histaminergic TM, however, not all waking-related and REM-off neurons were found within this region. Furthermore, neurons with waking/REM-related and state-indifferent discharge patterns were localized within the TM. These results suggest that waking-related and/or REM-off neurons may not be exclusively histaminergic in rats.
Asunto(s)
Área Hipotalámica Lateral/fisiología , Neuronas/fisiología , Sueño/fisiología , Vigilia/fisiología , Animales , Electrofisiología , Área Hipotalámica Lateral/citología , Masculino , Ratas , Ratas Sprague-Dawley , Sueño REM/fisiologíaRESUMEN
Numerous lesion, stimulation and recording studies in experimental animals demonstrate the importance of neurons within the preoptic/anterior hypothalamic area (POA) in the regulation of sleep induction and sleep maintenance. Recently, a discrete cluster of cells in the ventrolateral POA (vlPOA) of rats was found to exhibit elevated c-fos gene expression during sleep, indicating that these neurons are strongly activated during nonREM and/or REM sleep stages. We examined neuronal discharge during wakefulness and sleep throughout the dorsal to ventral extent of the lateral POA in rats, using chronic microwire technique. We found that neurons with elevated discharge rates during sleep, compared to waking, were localized to the vlPOA. As a group, vlPOA neurons displayed elevated discharge rates during both nonREM and REM sleep. Discharge of vlPOA neurons reflected the depth of sleep, i.e., discharge rates increased significantly from light to deep nonREM sleep. During recovery sleep following 12-14 h of sleep deprivation, vlPOA neurons displayed increased sleep-related discharge, compared to baseline sleep. Neurons in the vlPOA displaying increased neuronal discharge during sleep were located in the same area where neurons exhibit increased c-fos gene expression during sleep. Such neurons are likely components of a rostral hypothalamic mechanism that regulates sleep onset and sleep maintenance.
Asunto(s)
Núcleo Hipotalámico Anterior/fisiología , Hipotálamo/fisiología , Neuronas/fisiología , Sueño/fisiología , Vigilia/fisiología , Animales , Ritmo Circadiano , Electroencefalografía , Electromiografía , Masculino , Ratas , Ratas Sprague-DawleyRESUMEN
A group of medium-to-large cholinergic neurons situated in the dorsolateral mesopontine tegmentum comprises the pedunculopontine tegmental nucleus (PPT). The PPT pars compacta (PPT-pc), which occupies the lateral part of the caudal two-thirds of the nucleus, contains a dense aggregation of cholinergic neurons. In the present study, we have employed immunohistochemistry for choline acetyltransferase (ChAT) and electron microscopy to investigate the ultrastructure and synaptic organization of neuronal elements in the PPT-pc. Our results demonstrate that: (1) ChAT-immunoreactive (i.e., cholinergic) PPT-pc neurons are characterized by abundant cytoplasm and organelles, and have few axosomatic synapses (both asymmetric and symmetric); (2) ChAT-immunoreactive dendrites comprise 6-15% of total dendritic elements in the neuropil; the mean percentage of dendritic membrane covered by synaptic terminals is approximately 15%, and nearly all synapses with ChAT-immunoreactive dendrites are asymmetric; (3) within the boundaries described by cholinergic PPT-pc, there are noncholinergic neurons which, in contrast, exhibit a lucent cytoplasm and a higher frequency of axosomatic synapses (10.5% versus 3.7% for cholinergic neurons); and (4) noncholinergic neurons are morphologically heterogeneous with one subpopulation exhibiting a mean diameter that approximates that of cholinergic cells (i.e., > 15 microns and < 20 microns) and a very high frequency of axosomatic synapses (> 20%). Only 0.2-0.7% of terminal elements in the neuropil were ChAT-immunoreactive and these were not observed to synapse with cholinergic dendrites or somata. This relative paucity of terminal labeling and lack of cholinergic-cholinergic interactions seems inconsistent with the recognized and prominent physiological actions of acetylcholine on cholinergic PPT-pc neurons, and suggests a methodological limitation and/or a potential paracrine-like action of nonsynaptically released acetylcholine in the PPT region.
Asunto(s)
Tronco Encefálico/enzimología , Colina O-Acetiltransferasa/análisis , Neuronas/enzimología , Acetilcolina/análisis , Animales , Axones/enzimología , Tronco Encefálico/ultraestructura , Dendritas/enzimología , Inmunohistoquímica , Masculino , Terminaciones Nerviosas/enzimología , Neuronas/ultraestructura , Ratas , Ratas Sprague-Dawley , Sinapsis/enzimología , Sinapsis/ultraestructuraRESUMEN
The serotonergic dorsal raphe nucleus is considered an important modulator of state-dependent neural activity via projections to cholinergic neurons of the pedunculopontine tegmental nucleus (PPT). Light and electron microscopic analysis of anterogradely transported biotinylated dextran, combined with choline acetyltransferase (ChAT) immunohistochemistry, were employed to describe the synaptic organization of mesopontine projections from the dorsal raphe to the PPT. In a separate set of experiments, we utilized immunohistochemistry for the serotonin transporter (SERT), combined with ChAT immunohistochemistry at the light and electron microscopic levels, to determine whether PPT neurons receive serotonergic innervation. The results of these studies indicate that: (1) anterogradely labeled and SERT-immunoreactive axons and presumptive boutons invest the PPT at the light microscopic level; (2) at the ultrastructural level, dorsal raphe terminals in the PPT pars compacta synapse mainly with dendrites and axosomatic contacts were not observed; (3) approximately 12% of dorsal raphe terminals synapse with ChAT-immunoreactive dendrites; and (4) at least 2-4% of the total synaptic input to ChAT-immunoreactive dendrites is of dorsal raphe and/or serotonergic origin. This serotonergic dorsal raphe innervation may modulate cholinergic PPT neurons during alterations in behavioral state. The role of these projections in the initiation of rapid eye movement (REM) sleep and the ponto-geniculo-occipital waves that precede and accompany REM sleep is discussed.
Asunto(s)
Colina O-Acetiltransferasa/análisis , Proteínas de Transporte de Membrana , Núcleos del Rafe/química , Serotonina/análisis , Acetilcolina/análisis , Animales , Proteínas Portadoras/análisis , Inmunohistoquímica , Masculino , Glicoproteínas de Membrana/análisis , Microscopía/métodos , Microscopía Electrónica , Proteínas del Tejido Nervioso/análisis , Vías Nerviosas/química , Ratas , Ratas Sprague-Dawley , Proteínas de Transporte de Serotonina en la Membrana Plasmática , Sinapsis/químicaRESUMEN
The regional and developmental expression of epidermal growth factor (EGF) receptor in rat hippocampus was investigated utilizing immunocytochemical techniques at the light and electron microscopic levels. EGF receptor immunoreactivity in adult hippocampus was compared to that found at postnatal day 7 (P7). While the receptor was observed in P7 hippocampus, immunostaining was more prominent in the adult hippocampus, especially in the pyramidal CA2 field. Ultrastructural analysis of this region revealed that the receptor was localized to the cell bodies of both P7 and adult neurons rather than the axons or dendrites. The expression of EGF receptor in selected regions of the adult brain was verified by Western blotting. These results demonstrate the presence of EGF receptor in rat hippocampus as early as P7, localize the receptor to the pyramidal cell body, and establish the hippocampal formation, particularly CA2, as a major site of EGF receptor expression in rat brain.
Asunto(s)
Envejecimiento/metabolismo , Animales Recién Nacidos/metabolismo , Receptores ErbB/metabolismo , Hipocampo/metabolismo , Animales , Hipocampo/ultraestructura , Inmunohistoquímica , Microscopía Electrónica , Ratas , Ratas Endogámicas , Distribución Tisular , Extractos de Tejidos/metabolismoRESUMEN
Differences in sleep-wake patterns in response to light-dark stimulation have been observed between albino Lewis and pigmented Brown Norway strains of rats, which may be associated with albinism. Since several anatomical differences have been demonstrated in the visual pathways of albino and pigmented mammals, the present study was undertaken to determine whether additional differences in visual pathways of these rat strains exist that might account for their behavioral differences. Using anterograde tracing techniques and image analysis, we have investigated the retinal projections of Lewis and Brown Norway rats. Our results demonstrate that the distribution of retinal terminals in the hypothalamic suprachiasmatic nucleus extends over a greater area in Lewis compared to Brown Norway rats. This zone of termination corresponds to a cytoarchitectonically definable ventrolateral subdivision of the suprachiasmatic nucleus (SCN), which is also greater in Lewis than in Brown Norway rats. These results may have implications for behaviors related to the SCN.
Asunto(s)
Albinismo/patología , Hipotálamo/patología , Pigmentación , Ratas Endogámicas Lew/anatomía & histología , Ratas/anatomía & histología , Retina/patología , Animales , Retina/fisiopatología , Núcleo Supraquiasmático/patología , Transmisión Sináptica , Vías Visuales/patologíaRESUMEN
Trk-immunoreactivity was observed in basal forebrain and striatal cholinergic neurons, whereas low-affinity NGF receptor immunoreactivity was observed in basal forebrain but not striatal cholinergic neurons. Since NGF exerts trophic actions on both basal forebrain and striatal cholinergic populations, the presence of Trk in these neurons lends strong support for an essential role of Trk in NGF-responsive neurons, but suggests that the low affinity receptor is not necessary for NGF actions in the striatum.
Asunto(s)
Cuerpo Estriado/metabolismo , Neuronas/metabolismo , Sistema Nervioso Parasimpático/metabolismo , Prosencéfalo/metabolismo , Receptores de Factor de Crecimiento Nervioso/metabolismo , Animales , Cuerpo Estriado/inmunología , Inmunohistoquímica , Masculino , Neuronas/inmunología , Sistema Nervioso Parasimpático/citología , Sistema Nervioso Parasimpático/inmunología , Prosencéfalo/inmunología , Ratas , Ratas Sprague-Dawley , Receptores de Factor de Crecimiento Nervioso/inmunologíaAsunto(s)
Acetilcolina/fisiología , Vías Aferentes/anatomía & histología , Conducta/fisiología , Fibras Colinérgicas/ultraestructura , Cognición/fisiología , Enfermedades del Sistema Nervioso/fisiopatología , Vías Aferentes/fisiología , Animales , Mapeo Encefálico , Corteza Cerebral/anatomía & histología , Corteza Cerebral/fisiología , Fibras Colinérgicas/fisiología , Hipocampo/anatomía & histología , Hipocampo/fisiología , Humanos , Modelos Biológicos , Neurotransmisores/fisiología , Primates , Prosencéfalo/anatomía & histología , Prosencéfalo/fisiología , Ratas , Sueño/fisiología , Tegmento Mesencefálico/anatomía & histología , Tegmento Mesencefálico/fisiologíaRESUMEN
The afferent connections of the pedunculopontine tegmental nucleus (PPT) and the adjacent midbrain extrapyramidal area (MEA) were examined by retrograde tracing with wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). Major afferents to the PPT originate in the periaqueductal gray, central tegmental field, lateral hypothalamic area, dorsal raphe nucleus, superior colliculus, and pontine and medullary reticular fields. Other putative inputs originate in the paraventricular and preoptic hypothalamic nuclei, the zona incerta, nucleus of the solitary tract, central superior raphe nucleus, substantia innominata, posterior hypothalamic area, and thalamic parafascicular nucleus. The major afferent to the medially adjacent MEA originates in the lateral habenula, while other putative afferents include the perifornical and lateral hypothalamic area, periaqueductal gray, superior colliculus, pontine reticular formation, and dorsal raphe nucleus. MEA inputs from basal ganglia nuclei include moderate projections from the substantia nigra pars reticulata, entopeduncular nucleus, and a small projection from the globus pallidus, but not the subthalamic nucleus. Dense anterograde labeling was observed in the substantia nigra pars compacta, entopeduncular nucleus, subthalamic nucleus, globus pallidus, and caudate-putamen only following WGA-HRP injections involving the MEA. The results of this study demonstrate that the PPT and MEA share many potential afferents. Remarkable differences were found that support distinguishing between these two nuclei in future studies regarding the functional organization of the midbrain and pons. The results, for example, confirm our previous observations that the largely reciprocal connections between the midbrain and basal ganglia distinguish the MEA from the PPT. Afferents from the lateral habenula and contralateral superior colliculus represent extensions of more traditional basal ganglion circuitry which further delineate the MEA from the PPT. The results are discussed with respect to the important role of the midbrain and pons in behavioral state control and locomotor mechanisms.
Asunto(s)
Vías Aferentes/anatomía & histología , Encéfalo/anatomía & histología , Mesencéfalo/anatomía & histología , Puente/anatomía & histología , Ratas Endogámicas/anatomía & histología , Tegmento Mesencefálico/anatomía & histología , Animales , Nivel de Alerta , Transporte Axonal , Ganglios Basales/anatomía & histología , Encéfalo/fisiología , Peroxidasa de Rábano Silvestre , Área Hipotalámica Lateral/anatomía & histología , Masculino , Actividad Motora , Sustancia Gris Periacueductal/anatomía & histología , Puente/fisiología , Tractos Piramidales/anatomía & histología , Ratas , Sueño , Tegmento Mesencefálico/fisiología , Vigilia , Aglutinina del Germen de Trigo-Peroxidasa de Rábano Silvestre Conjugada , Aglutininas del Germen de TrigoRESUMEN
The principal relay nuclei of the thalamus receive their cholinergic innervation from two midbrain cholinergic groups: the pedunculopontine tegmental nucleus and the laterodorsal tegmental nucleus. The different thalamic nuclei exhibit populations of cholinergic axons which vary in density and morphology when examined at the light microscopic level. However, the ultrastructure of the cholinergic terminals in different thalamic nuclei has not been described. This study was undertaken to confirm that synaptic contacts are formed by cholinergic axons in several principal thalamic relay nuclei, to describe their ultrastructural morphology, and to identify the types of postsynaptic elements contacted by cholinergic synaptic terminals. The thalamic nuclei examined in this study are the dorsal lateral geniculate nucleus, ventroposteromedial nucleus, ventroposterolateral nucleus, and anteroventral nucleus. Our results confirm that cholinergic axons form synaptic terminals in these thalamic nuclei. Cholinergic synaptic terminals contact structures outside the characteristic synaptic glomeruli, are never postsynaptic, and have morphologies and postsynaptic targets which differ among the thalamic nuclei. In the ventroposterior nuclei, cholinergic terminals form asymmetric synaptic contacts onto larger dendrites in the extraglomerular neuropil. In the anteroventral nucleus, cholinergic terminals form both symmetric and asymmetric synaptic contacts onto dendrites and somata. Cholinergic terminals in the anteroventral nucleus are larger than those in other nuclei. In the dorsal lateral geniculate nucleus, cholinergic terminals contact both somata and dendrites in the extraglomerular neuropil, but the synaptic contacts in this nucleus are symmetric in morphology.