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PubMed1989

Cholinergic and peptidergic projections from the medial septum and the nucleus of the diagonal band of Broca to dorsal hippocampus, cingulate cortex and olfactory bulb: a combined wheatgerm agglutinin-apohorseradish peroxidase-gold immunohistochemical study.

We have examined the distribution pattern and the density of various neuropeptide, neurotransmitter and enzyme containing neurons in the rat medial septum and the nucleus of the diagonal band of Broca to assess their possible involvement in the septohippocampal, septocortical and septobulbar pathways. Immunohistochemical methods were combined with the retrograde transport of a protein-gold complex injected in the hippocampus, the cingulate cortex or the olfactory bulb. Cholinergic neurons were the most numerous. Galanin-positive neurons were about two or three times less numerous than cholinergic cells. Both these cell types had a similar location though the choline acetyl transferase-like immunoreactive cells extended more caudally in the horizontal limb of the nucleus of the diagonal band of Broca. Immunoreactive cells for other neuroactive substances were few (calcitonin gene-related peptide, luteinizing hormone releasing hormone. [Met]enkephalin-arg-gly-leu) or occasional (dynorphin B, vasoactive intestinal polypeptide, somatostatin, neurotensin, cholecystokinin, neuropeptide Y and substance P). No immunoreactive cells for bombesin, alpha atrial natriuretic factor, corticotropin releasing factor, 5-hydroxytryptamine, melanocyte stimulating hormone, oxytocin, prolactin, tyrosine hydroxylase or arg-vasopressin were present. Choline acetyltransferase- and galanin-like immunoreactive cells densely participate to septal efferents. Cholinergic neurons constituted the bulk of septal efferent neurons. Galanin-positive cells were 22% of septohippocampal, 8% of septocortical, and 9% of septobulbar neurons. Galanin containing septohippocampal neurons were found in the medial septum and the nucleus of the diagonal band of Broca; galanin-positive septobulbar and septocortical cells were limited to the nucleus of the diagonal band of Broca. Occasional double-labellings were noticed with some peptides other than galanin. Luteinizing hormone-releasing hormone, calcitonin gene-related peptide and enkephalin were the most often observed; some other projecting cells stained for vasoactive intestinal polypeptide or dynorphin B. Luteinizing hormone-releasing hormone, calcitonin gene-related peptide and enkephalin were observed in septohippocampal neurons; luteinizing hormone-releasing hormone and vasoactive intestinal peptide were observed in septocortical neurons and calcitonin gene-related peptide, luteinizing hormone-releasing hormone and dynorphin B were observed in septo-bulbar cells. These results show that, in addition to acetylcholine, galanin is a major cellular neuroactive substance in septal projections to the hippocampus, the cingulate cortex and the olfactory bulb. The presence of septal projecting neurons immunoreactive for other peptides shows that a variety of distinct peptides may also participate, but in a smaller number, to septal efferent pathways.

Animals↗
PubMed1990

Neuronal responses related to the novelty and familarity of visual stimuli in the substantia innominata, diagonal band of Broca and periventricular region of the primate basal forebrain.

This study examined correlates of memory processes in neuronal activity recorded from the substantia innominata, the diagonal band of Broca and the periventricular region or the basal forebrain of monkeys performing recognition and/or visual discrimination tasks. Two types of neurons were found that responded differentially to stimuli on the basis of their novelty or their familiarity. Neurons (5/572) in the periventricular region rostral to the thalamus and caudal to the anterior commissure responded to familiar stimuli with increases in firing rate. Neurons in the substantia innominata (16/1058) and in the diagonal band (14/489) responded maximally to novel stimuli, with smaller responses to reappeared presentations of these stimuli. The properties of these two types of neurons were similar in three respects: (1) the magnitude of the differential response to novel and familiar presentations of stimuli were largest for stimuli presented on successive trials, and were attenuated for stimuli that had not been seen for some intervening trials; (2) both types of neurons responded to highly familiar stimuli as if they were novel if they had not been recently seen; (3) both types responded to two- and three-dimensional stimuli; and were recorded in rhesus monkeys trained on the recognition tasks and in untrained cynomolgus monkeys. An injection of HRP into the periventricular region of one monkey resulted in retrograde labeling of ventromedial regions of the prefrontal, cingulate and temporal cortices, of the amygdala, medial thalamus, supramammillary region of the midbrain. These data indicate that information about the novelty, familiarity or recency of presentation of visual stimuli is reflected in the responses of some basal forebrain neurons. Neurons in the substantia innominata and diagonal band of Broca could not be distinguished using the battery of applied tests, suggesting functional mechanisms common to both regions. The results of the anatomical experiment suggest that ventromedial limbic cortical and subcortical regions projecting to or through the periventricular region may be important for the transmission of information about visual stimuli and for memory function.

Action Potentials↗
PubMed1975

Medial forebrain bundle projections to the nucleus of the diagonal band of Broca.

The electrophysiological characteristics of the medical forebrain bundle (MFB) projections to the nucleus of the diagonal band of Broca (nDBB) were studied in acutely prepared cats. MFB stimulation evoked field potentials which consisted of a large negative wave followed by a shallow positivity. Extracellular unitary discharges appeared out of the negativity. In addition, intracellularly recorded EPSPs showed no significant shift in the latency to onset with changes in stimulus intensity. These observations indicate that at least some of the MFB projections to the nDBB are excitatory with respect to their target cells.

Action Potentials↗
PubMed1997

An electrophysiological study of neurons in the horizontal limb of the diagonal band of Broca.

We examined the morphological and electrophysiological properties of neurons within the horizontal limb of the diagonal band of Broca (hDBB) and investigated the role of excitatory amino acid mediated synaptic transmission in this region. Whole cell patch-clamp recordings were obtained from hDBB neurons in rat forebrain slices. The hDBB cells examined in this study display a morphological and electrophysiological profile that is consistent with the type B, noncholinergic cell type. Cable analysis reveals that hDBB neurons are electrotonically compact and may therefore function as efficient relays for transmission of inputs to other forebrain target sites. Application of agonists for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), kainate, N-methyl-D-aspartate (NMDA), and metabotropic receptors all evoke inward currents in hDBB neurons. Pharmacological analyses of synaptic events indicate that evoked excitatory postsynaptic currents (EPSC) are either mediated by non-NMDA receptors alone or a combination of non-NMDA and NMDA receptors. In some neurons, the metabotropic receptor agonist, 1-aminocyclopentane-trans-1, 3-dicarboxylic acid, reduced EPSC amplitude without altering postsynaptic input conductance, thus suggesting a presynaptic locus of action. The electrical and pharmacological properties described for hDBB neurons may be physiologically relevant for the effective transmission of excitatory synaptic inputs to sites that receive projections from the hDBB.

Animals↗
PubMed1996

Excitatory actions of serotonin on GABAergic neurons of the medial septum and diagonal band of Broca.

The physiological and pharmacological actions of serotonin (5-HT) on neurons in the medial septum and diagonal band of Broca (MSDB) were examined using extracellular and intracellular recording techniques in an in vitro rat brain-slice preparation. In addition to previously described inhibitory effects, novel excitatory actions of 5-HT on GABA-type cells were observed. In intracellular recordings with KCl-containing electrodes, bath-applied 5-HT induced a bicuculline and tetrodotoxin-sensitive increase in the number of reverse IPSPs in both cholinergic- and noncholinergic-type neurons (presumably GABAergic). In brain slices where all structures neighboring the MSDB, including the lateral septum, had been excised, a similar increase in 5-HT-induced IPSPs occurred, indicating that 5-HT-induced IPSPs in both cholinergic- and noncholinergic-type neurons originate from GABAergic neurons within the MSDB itself. Accordingly, GABA-type neurons in the MSDB were found to be directly excited by 5-HT. MDL 100,907, a selective 5-HT2A antagonist, blocked 5-HT-induced excitations in a majority of neurons (58%). ICS 205-930, a 5-HT3/5-HT4 antagonist, or mianserin, a nonselective 5-HT antagonist, blocked most MDL-resistant responses, indicating a role for multiple 5-HT receptor subtypes. This study also provides the first electrophysiological evidence for synaptic interactions between 5-HT-activated GABAergic neurons and cholinergic neurons and amongst GABAergic neurons in the MSDB. The implications of the findings vis-à-vis intraseptal circuitry and septohippocampal circuitry are discussed.

Animals↗
PubMed1999

Zinc modulation of ionic currents in the horizontal limb of the diagonal band of Broca.

We examined modulation of ionic currents by Zn2+ in acutely dissociated neurons from the rat's horizontal limb of the diagonal band of Broca using the whole-cell patch-clamp technique. Application of 50 microM Zn2+ increased the peak amplitude of the transiently activated potassium current, I(A) (at + 30 mV), from 2.20+/-0.08 to 2.57+/-0.11 nA (n = 27). This response was reversible and could be repeated in 0 Ca2+/1 microM tetrodotoxin (n = 15). Zn2+ shifted the inactivation curve to the right, resulting in a shift in the half-inactivation voltage from 76.4+/-2.2 to -53.4+/-2.0 mV (n = 11), with no effect on the voltage dependence of activation gating (n = 15). There was no significant difference in the time to peak under control conditions (7.43+/-0.35 ms, n = 14) and in the presence of Zn2+ (8.20+/-0.57 ms, n = 14). Similarly, the time constant of decay of I(A) (tau(d)) at + 30 mV showed no difference (control: 38.68+/-3.68 ms, n = 15; Zn2+: 38.48+/-2.85 ms, n = 15). I(A) was blocked by 0.5-1 mM 4-aminopyridine. In contrast to its effects on I(A), Zn2+ reduced the amplitude of the delayed rectifier potassium current (I(K)). The reduction of outward K+ currents was reproducible when cells were perfused with 1 microM tetrodotoxin in a 0 Ca2+ external solution. The amplitude of the steady-state outward currents at +30 mV under these conditions was reduced from 6.40+/-0.23 (control) to 5.76+/-0.18 nA in the presence of Zn2+ (n = 16). The amplitudes of peak sodium currents (INa) were not significantly influenced (n = 10), whereas barium currents (I(Ba)) passing through calcium channels were potently modulated. Zn2+ reversibly reduced I(Ba) at -10 mV by approximately 85% from -2.06+/-0.14 nA under control conditions to -0.30+/-0.10 nA in the presence of Zn2+ (n = 14). Further analyses of Zn2+ effects on specific calcium channels reveals that it suppresses all types of high-voltage-activated Ca2+ currents. Under current-clamp conditions, application of Zn2+ resulted in an increase in excitability and loss of accommodation (n = 13), which appears to be mediated through its effects on Ca2+-dependent conductances.

4-Aminopyridine↗
PubMed1993

Distribution and colocalization of choline acetyltransferase immunoreactivity and NADPH diaphorase reactivity in neurons within the medial septum and diagonal band of Broca in the rat basal forebrain.

NADPH diaphorase histochemistry and choline acetyltransferase immunocytochemistry were used to assess quantitatively the presence of nitric oxide synthase in the cholinergic neurons of the magnocellular basal forebrain complex. Virtually all (97%) NADPH diaphorase reactive magnocellular neurons in the medial septum and the vertical and horizontal limbs of the diagonal band of Broca were choline acetyltransferase immunoreactive, whereas only a proportion of the choline acetyltransferase immunoreactive neurons were NADPH diaphorase reactive. Thus NADPH diaphorase histochemistry identified a subpopulation of the magnocellular cholinergic neurons. Occasionally, NADPH diaphorase reactive neurons were observed within the medial septum and diagonal band of Broca that were not choline acetyltransferase immunoreactive, and in general were morphologically distinct from the magnocellular neurons; such neurons are probably representatives within the medial septum and diagonal band of more widely distributed phenotypically distinct populations of NADPH diaphorase reactive neurons. The proportions of the neurons in which choline acetyltransferase and NADPH diaphorase colocalized in the medial septum and in the diagonal bands of Broca were similar in any one coronal section, but there was a considerable difference in the proportions throughout the rostrocaudal extent of these nuclei. In the most rostral sections of the medial septum and diagonal band, approximately 70% of the choline acetyltransferase immunoreactive neurons were NADPH diaphorase reactive, whereas the proportion decreased progressively to about 30% at the level of the decussation of the anterior commissure. To examine further the extent of colocalization throughout the magnocellular basal forebrain complex, sections of the magnocellular preoptic nucleus, substantia innominata, and nucleus basalis magnocellularis were examined. While there was little total colocalization of choline acetyltransferase immunoreactivity and NADPH diaphorase reactivity in any particular section (approximately 18%), almost all of the double labelled neurons were in the substantia innominata, with very few in the other nuclei. Thus although there is a caudal to rostral gradient of the proportion of magnocellular cholinergic neurons that are NADPH diaphorase reactive throughout the entire basal forebrain magnocellular complex, subregions, such as the substantia innominata and magnocellular preoptic nucleus, may not follow this trend. The recent demonstration that the NADPH diaphorase histochemical reaction localizes a nitric oxide synthase suggests that attention should be given to the NADPH diaphorase subpopulation in pathological and experimentally induced alterations of the basal forebrain.

Animals↗
PubMed1985

A catecholaminergic projection from the ventral tegmental area to the diagonal band of Broca: modulation by neurotensin.

The ventral tegmental area contains a high density of dopaminergic perikarya having ascending projections to a number of limbic forebrain regions. In this study, we use combined retrograde labeling with horseradish peroxidase (HRP) and immunohistochemical staining for tyrosine hydroxylase to examine the catecholaminergic projection from the ventral tegmental area to the diagonal band of Broca. When injection of HRP was restricted to the diagonal band, only neurons in the nucleus linearis, nucleus interfascicularis and ventromedial portion of the nucleus paranigralis were labeled. In contrast, HRP injection into the adjacent nucleus accumbens labeled neurons throughout these nuclei, plus the nucleus parabrachialis pigmentosus, nucleus retroruber and substantia nigra, pars compacta. Approximately 60% of neurons in the ventral tegmental area labeled from the diagonal band contained tyrosine hydroxylase, compared with 79% of the neurons labeled from the nucleus accumbens. Neurotensin is a tridecapeptide found in the ventral tegmental area which has been shown to activate dopamine neurons projecting to the nucleus accumbens. In this study, microinjection of neurotensin into ventral tegmental nuclei which contained neurons retrogradely labeled from the diagonal band significantly elevated the levels of dopamine metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, in the diagonal band. The results of this study demonstrate that a catecholaminergic projection exists from the ventral tegmental area to the diagonal band of Broca, and that this pathway can be stimulated by intra-ventral tegmental injection with neurotensin.

Animals↗
PubMed1994

The effects of lesions of the entorhinal cortex and the horizontal nucleus of the diagonal band of broca upon performance of a spatial location recognition task.

The effects of lesions of the horizontal nucleus of the diagonal band of Broca (HNDB) and the entorhinal cortex (ENTO) upon performance of a spatial location recognition task were assessed. Two hypotheses of entorhinal cortex function were considered in interpretation of the data. The first hypothesis assumes that the anatomical proximity and interconnections between the hippocampus and the entorhinal cortex are indicative of a functional similarity. The second hypothesis recognizes the interconnections of the hippocampus and the entorhinal cortex, but posits that the two structures have distinct functions. The hippocampus receives input primarily from the medial septum (MS), whereas the entorhinal cortex receives input from the HNDB and the MS. The study attempted to assess the function of the ENTO and the HNDB in a spatial location recognition task with the intent of comparing the findings to previous research of the hippocampus and MS. Performance of animals with HNDB lesions and the ENTO lesions was at chance levels for all serial positions. Results indicated that there are functional differences between the HNDB and other basal forebrain structures. Further, the performance deficit of the ENTO group does not differ from that observed following lesions of the hippocampus.

Animals↗
PubMed1997

The effects of temperature and synaptic blockade in vitro on neurons of the horizontal limb of the diagonal band of Broca in the rat basal forebrain.

We studied the thermosensitivity of neurons in the rat horizontal limb of the diagonal band of Broca (HDB) in vitro under normal conditions and under conditions of a low calcium/high magnesium synaptic blockade (SB). Of 52 HDB neurons tested, 34 neurons (65%) were warm-sensitive (WS), three neurons (6%) were cold-sensitive (CS), 11 neurons (21%) were temperature-insensitive (TI) and four additional neurons (8%) were both warm- and cold-sensitive (WS/CS). Of 34 neurons tested for thermosensitivity under SB, 11 were WS, 4 were CS and 19 were TI. Nearly half (48%) of the WS neurons maintained warm sensitivity under SB, 43% became TI and 9% became CS. Baseline firing rates of neurons significantly decreased during SB and then increased during recovery from SB. In addition, a distinct anatomical distribution of thermosensitive neurons was found in the HDB. The most ventral aspect of the HDB (interaural +0.9-1.3 mm) had proportionally fewer temperature sensitive neurons (65% vs. 88%) than areas more dorsal (interaural +1.3-1.7 mm), and only one of seven ventral HDB neurons (14%) remained thermosensitive during SB. In the dorsal HDB, 65% of the neurons maintained thermosensitivity during SB. These results demonstrate that the HDB contains inherently thermosensitive neurons, and that a difference in thermal characteristics exists between the ventral and dorsal HDB neurons.

Action Potentials↗
PubMed1999

Ionic mechanisms of action of neurotensin in acutely dissociated neurons from the diagonal band of Broca of the rat.

Whole cell recordings were performed on acutely dissociated neurons from the horizontal limb of the diagonal band of Broca (hDBB) from rats to elucidate the ionic mechanisms of action of neurotensin. Neurotensin caused a decrease in whole cell voltage-activated outward currents and failed to elicit a response when Ca2+ influx was blocked by changing the external solution to the one containing 0 mM Ca2+ and 50 microM Cd2+, suggesting the involvement of Ca2+-dependent conductances. Charybdotoxin, a specific blocker of voltage-sensitive calcium-activated K+ channels (IC), caused a decrease in outward currents comparable with that caused by blocking calcium influx and occluded the neurotensin-induced decrease in outward currents. Similarly, 50 microM tetraethylammonium ions also blocked the neurotensin response. Also neurotensin reduced whole cell barium currents (IBa) and calcium currents (ICa). Amiloride and omega-conotoxin GVIA, but not nimodipine, were able to eliminate the neurotensin-induced decrease in IBa. Thus T- and N- but not L-type calcium channels are subject to modulation by neurotensin, and this may account for its effects on IC. The predicted changes in action potential as a result of the blockade of currents through calcium channels culminating into changes in IC were confirmed in the bridge current-clamp recordings. Specifically, neurotensin application led to depolarization of the resting membrane potential, broadening of spike and a decrease in afterhyperpolarization and accommodation. These alterations in action potential characteristics that resulted in increased firing rate and excitability of the hDBB neurons also were produced by application of charybdotoxin. Neurotensin effects on these properties were occluded by 2 - [(1 - 7 - chloro - 4 - quinolinyl) - 5 - (2, 6 - di - methoxyphenyl) pyrazol-3-yl) carbonylamino] tricyclo (3.3.1.1.)decan-2-carboxylic acid, a nonpeptide high-affinity neurotensin receptor antagonist. Neurotensin blockade of IC, possibly through ICa, is a potential physiological mechanism whereby this peptide may evoke alterations in the cortical arousal, sleep-wake cycle, and theta rhythm.

Action Potentials↗
PubMed1986

Morphological characterization of cholinergic neurons in the horizontal limb of the diagonal band of Broca in the basal forebrain of the rat.

A monoclonal antibody against choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme, was used to identify cholinergic neurons in the nucleus of the horizontal limb of the diagonal band of Broca at the light and electron microscopic levels. ChAT-labelled somata were fusiform, triangular or round in shape and varied considerably in size. Depending on the type of the cell, one to four dendrites emerged from the soma, but an axon could rarely be seen. The nuclei of most cells were round or oval, showed invaginations and displayed prominent nucleoli. The karyoplasm of the larger fusiform and triangular neurons contained abundant organelles including parallel arrays of granular endoplasmic reticulum. The synaptic input to labelled perikarya and proximal dendrites was sparse. It consisted chiefly of asymmetrical synaptic contacts, sometimes with postjunctional densities, but a few symmetrical synapses were also noted. ChAT-positive axon terminals were not identified which suggests that axon collaterals are rare within the nucleus of the horizontal limb of the diagonal band of Broca.

Animals↗
PubMed1990

Luteinizing hormone release in the anesthetized cat following stimulation in the diagonal band of Broca, dorsal septum and fornix.

The release of luteinizing hormone (LH) in response to electrical stimulation of septal nuclei (the diagonal band of Broca, DBB, and dorsal septal nucleus) and the subcallosal fornix has been studied in gonadectomized female cats. The cats were anesthetized with Althesin. Electrodes were placed on the medial and lateral aspects of the subcallosal fornix and paired bipolar stimulating electrodes were aimed at the DBB or dorsal septal nucleus. The effect of electrical stimulation of these regions on the secretion of LH was studied by radioimmunoassay of LH in serial blood samples taken before, during and after stimulation. Stimulation in the DBB or in the dorsal septal nucleus resulted in a peak of LH release during stimulation followed by further spontaneous peaks. All peaks showed an exponential decline. The frequency of spontaneous peaks following stimulation could reach the level found in unanesthetized cats. Stimulation of the subcallosal fornix produced a significant depression in the amplitude of LH release. The effects of DBB, dorsal septal and fornix stimulation are all exerted, we suggest, by projections to LHRH containing neurons in the preoptic region.

Alfaxalone Alfadolone Mixture↗
PubMed1990

The endomembrane system of cholinergic and non-cholinergic neurons in the medial septal nucleus and vertical limb of the diagonal band of Broca: a cytochemical and immunocytochemical study.

Coronal vibratome sections of the rostral part of the medial septum (MS) and vertical limb of the diagonal band of Broca (VDB) nuclei were studied by an immunocytochemical technique using a monoclonal antibody against choline acetyltransferase (ChAT) and a double histochemical method for detection of acid phosphatase (AcPase) and nucleoside diphosphatase (NDPase) activity. The electron microscopic morphology of ChAT-immunoreactive and non-immunoreactive neurons was compared with similar neurons showing both AcPase and NDPase activity. ChAT-labeled and non-labeled neurons were well differentiated by the organization of the endomembrane system and especially by the structure of the rough endoplasmic reticulum (RER) and associated lamellar bodies. These results support the theory that the peculiar ultrastructure of the lamellar bodies in each neuron is related to the pattern of organization of the endomembrane system and its function. The significance of the lamellar bodies is discussed, and the data of the present work, together with findings described by other investigators. These data suggest that these bodies are predominant in efferent projection neurons in the basal forebrain nuclei.

Acid Anhydride Hydrolases↗
PubMed1996

Three daily melatonin infusions alter gonadal development but not GnRH neuron number in the medial preoptic area or diagonal band of Broca in Siberian hamsters.

Among juvenile Siberian hamsters reproductive development is associated with an increased number of unipolar GnRH-immunoreactive neurons in the diagonal band of Broca and medial preoptic area. In the present study, GnRH neuron morphology was assessed in male juvenile hamsters which were treated with three daily melatonin (MEL) infusions to initiate or delay gonadal development. Hamsters gestated in short days were transferred to constant light (LL) at day 14 of age and infused on days 18-20 with MEL for 6 h/day. This treatment stimulated testis development compared to that in saline-infused controls. By contrast, testis growth was suppressed by three 12 h MEL infusions in long-day gestated hamsters in LL from day 14. The number of unipolar and bipolar GnRH neuron subtypes was the same irrespective of MEL infusion or preweaning photoperiod. Thus, gonadal response to three MEL infusions is independent of changes in GnRH neuron number.

Animals↗
PubMed1996

Serotonin1A receptors are expressed by a subpopulation of cholinergic neurons in the rat medial septum and diagonal band of Broca--a double immunocytochemical study.

The possible colocalization of 5-hydroxytryptamine1A receptors and choline acetyltransferase in the same neurons of the medial septum and diagonal band of Broca was investigated using double immunocytochemical techniques, either on the same section or on adjacent thin sections of the rat brain. The presence of both antigens in the same neurons was demonstrated at the light and electron microscopic levels. The proportion of cholinergic neurons that express 5-hydroxytryptamine1A receptors was similar in the different parts of the septal complex (around 25%). By contrast, the proportion of 5-hydroxytryptamine1A receptor-positive neurons also exhibiting choline acetyltransferase immunoreactivity was much higher (40-44%) in the dorsal and ventral groups of cholinergic cells, than in the intermediate group (18%). In line with the topographical distribution of cholinergic projections, this result points out the potential involvement of 5-hydroxytryptamine1A receptors in the control of the septohippocampal cholinergic projection by serotonin. This connection might be relevant to learning and memory, and in the appearance of age-dependent or neurodegenerative cognitive deficits, which have been shown to involve alterations in both the serotoninergic and the cholinergic systems.

Animals↗
PubMed1997

Cardiovascular responses to glutamate stimulation of diagonal band of Broca.

Experiments were done in alpha-chloralose-anesthetized, paralyzed, and artificially ventilated rats to investigate the effect of L-glutamate stimulation of the diagonal band of Broca (DBB) on arterial pressure (AP) and heart rate (HR). Stimulation of the horizontal limb of the DBB (hDB) elicited decreases in both mean AP (MAP; -32.3 +/- 2.5 mmHg; n = 37) and HR (-32.5 +/- 3.8 beats/min; n = 33) at 84% of the sites stimulated. Stimulation of the vertical limb of the DBB (vDB) elicited significantly smaller decreases in MAP (-9.7 +/- 1.0 mmHg; n = 19) and HR (-13.5 +/- 1.8 beats/min; n = 7) at approximately 13% of the sites stimulated. Intravenous administration of the muscarinic receptor blocker atropine methylbromide had no effect on the magnitude of the MAP and HR responses to stimulation of the hDB. In contrast, administration of the nicotinic receptor blocker hexamethonium bromide abolished both the depressor and the bradycardic responses elicited by stimulation of the hDB. These data indicate that the hDB contains neurons that exert cardiovascular depressor effects and that these circulatory effects are mediated by the inhibition of sympathetic vasoconstrictor fibers to the vasculature, and cardioacceleratory fibers to the heart.

Animals↗
PubMed1991

Ultrastructural localization of tyrosine hydroxylase immunoreactivity in the rat diagonal band of Broca.

The present study sought to establish the cellular basis for the catecholaminergic (i.e., noradrenaline and dopamine) modulation of neurons in the horizontal limb of the diagonal band of Broca (HDB) in the rat brain. The light and electron microscopic localization of antigenic sites for a polyclonal antibody directed against the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH), were examined in the HDB using a double-bridged, peroxidase-antiperoxidase method. By light microscopy, numerous punctate, varicose processes with intense TH-immunoreactivity (TH-I) were detected in the HDB. Additionally, a few small, bipolar, or multipolar TH-immunoreactive neurons were observed. Ultrastructural analysis of single sections revealed that the TH-labeled processes were axons and axon terminals. Axons (n = 134) with TH-I were primarily unmyelinated. Terminals with TH-I (n = 169) were 0.3-1.4 microns in diameter and contained many small, clear vesicles and 0-5 larger dense-core vesicles. The types of associations (i.e., asymmetric synapses, symmetric synapses, and appositions which lacked a membrane specialization in the plane of section analyzed) formed by the TH-labeled terminals were quantitatively evaluated. The TH-labeled terminals: (1) formed associations with unlabeled perikarya and dendrites (134 out of 169), (2) were closely apposed without glial intervention to unlabeled and TH-labeled terminals (11 out of 169), or (3) had no neuronal associations in the plane of section analyzed (24 out of 169). The relatively rare (n = 4) associations with unlabeled perikarya were mostly characterized by symmetric synaptic specializations. The majority of the TH-labeled terminals were associated with the shafts of small dendrites (66% of 134). Moreover, most of the associations on dendrites and dendritic spines were further characterized by asymmetric synaptic specializations; however, many were also appositions without any apparent glial intervention in the plane of section analyzed. Additionally, the TH-labeled terminals were often associated with only one dendrite, which, in the same plane of section, was sparsely innervated by other terminals. Astrocytic processes usually surrounded the portions of the terminals and dendrites not involved in the region of association. The TH-immunoreactive perikarya were small (7-12 microns), ovoid, and had an indented nucleus with some heterochromatin. Their scant cytoplasm contained mitochondria, Golgi complexes, and endoplasmic reticulum. A few immunoreactive dendrites, presumably derived from the local neurons, were also detected. Both TH-immunoreactive perikarya and dendrites were associated primarily with unlabeled terminals, although a few terminals with TH-I also contacted them.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗