Hippocampal amino acid concentrations after raphe and/or septal cell suspension grafts in rats with fimbria-fornix lesions

Two weeks after infracallosal electrolytic fimbria-fornix lesions, Long-Evans female rats received intrahippocampal suspension grafts of either fetal septal or mesencephalic raphe tissue, or a mixture of both. Ten months after lesion surgery, the concentrations of alanine, aspartate, GABA, glutamate, glutamine, glycine, serine and taurine were determined in a dorsal, a "middle" and a ventral region of the hippocampus. We found neither the lesions nor the grafts to have significantly modified the concentration of these amino acids which, in all groups, presented a regional heterogeneity in their hippocampal distribution. GABA, glutamate and glutamine were highest in the ventral hippocampus, whereas the other amino acids were highest in the dorsal region. Our results (i) show that fimbria-fornix lesions do not result in lasting effects on hippocampal concentrations of the assessed amino acids, (ii) confirm the regional heterogeneity in the distribution of these amino acids in the hippocampus and (iii) demonstrate that cell suspension grafts of fetal septal or mesencephalic raphe tissue, as well as grafts of a mixture of both of these tissues, do not exert a non-specific effect on either of the amino acid concentrations measured. These data complete those of the preceeding paper [Kiss et al. (1990) Neuroscience 36, 61-72] concerning the effects of the same grafts on hippocampal cholinergic, serotonergic and noradrenergic markers, as well as on several behavioural variables

Modulation of 5-hydroxytryptamine release in hippocampal slices of rats: Effects of fimbria-fornix lesions on 5-HT1b-autoreceptor and α2-heteroreceptor function

Fimbria-fornix lesions disrupt important parts of serotonergic and noradrenergic hippocampal afferents and elicit sprouting of sympathetic fibers from the superior cervical ganglion. Since 5-hydroxytryptamine (5-HT) release in the hippocampus is modulated by 5-HT1B auto- and alpha2-heteroreceptors, we investigated whether such lesions may alter these presynaptic mechanisms. Hippocampal slices of sham-operated (SHAM) and fimbria-fornix-lesioned (LES) rats (14 months after surgery) were preincubated with [3H]5-HT, superfused continuously, and stimulated electrically using two stimulation conditions: either (a) 360 pulses 3 Hz, or (b) 20 pulses 100 Hz (2 ms, 28 mA, 4 V/chamber). The amount of [3H]5-HT taken up by slices from LES rats was significantly reduced, whereas the evoked 5-HT release (in percent of tissue-3H) was unchanged compared to that of SHAM rats. The 5-HT1B agonist CP 93,129 or the alpha2-agonist UK 14,304 reduced the evoked 5-HT release more potently in slices from LES rats, but only using stimulation condition (a), which permits inhibition by endogenously released transmitters. In LES rats, the facilitatory effect of the 5-HT antagonist metitepine was weaker, whereas that of the alpha2-antagonist idazoxane was more pronounced than in SHAM rats. In LES rats, hippocampal 5-HT content was reduced to about 45% of SHAM levels, whereas that of noradrenaline was increased by about 30% (high-performance liquid chromatography). We conclude: (1) despite LES-induced changes in tissue levels of endogenous ligands, there is no down- or upregulation of 5-HT1B-autoreceptors or alpha2-heteroreceptors on serotonergic neurons in the denervated rat hippocampus. (2) The reduced endogenous autoinhibition (by 5-HT) seems to be compensated for by an increased heteroinhibition (by noradrenaline)

Intrahippocampal grafts containing cholinergic and serotonergic fetal neurons ameliorate spatial reference but not working memory in rats with fimbria-fornix/cingular bundle lesions

Three-month-old Long-Evans female rats sustained aspirative lesions of the dorsal septohippocampal pathways and, 2 weeks later, received intrahippocampal suspension grafts containing cells from the mesencephalic raphe, cells from the medial septum and the diagonal band of Broca, or a mixture of both. Lesion-only and sham-operated rats were used as controls. All rats were tested for locomotor activity 1 week, 3 and 5 months after lesion surgery, for spatial working memory in a radial maze from 5 to 9 months, and for reference and working memory in a water tank during the 9th month after lesioning. Determination of hippocampal concentration of acetylcholine, noradrenaline, and serotonin was made after completion of behavioral testing. Compared to sham-operated rats, all rats with lesions, whether grafted or not, exhibited increased levels of locomotor activity and made more errors in the radial maze. The lesioned rats were also impaired in the probe trial (30 first seconds) of the water-tank test made according to a protocol requiring intact reference memory capabilities. While rats with septal or raphe grafts were also impaired, the rats with co-grafts showed performances not significantly different from those of sham-operated rats. With a protocol requiring intact working memory capabilities, all lesioned rats, whether grafted or not, were impaired in the water-tank test. In the dorsal hippocampus of lesion-only rats, the concentration of acetylcholine and serotonin was significantly reduced. In rats with septal grafts or co-grafts, the concentration of acetylcholine was close to normal, as was that of serotonin in rats with raphe grafts or co-grafts. These results confirm previous findings showing that co-grafts enabled the neurochemical properties of single grafts to be combined. Data from the water-tank test suggest that cholinergic and serotonergic hippocampal reinnervations by fetal cell grafts may induce partial recovery of spatial reference, but not working memory capabilities in rats

The effects of intrahippocampal raphe and/or septal grafts in rats with fimbria-fornix lesions depend on the origin of the grafted tissue and the behavioural task used

Long-Evans female rats sustained electrolytic lesions of the fimbria and the dorsal fornix and, two weeks later, received intrahippocampal suspension grafts of fetal tissue. The grafts were prepared from regions including either the medial septum and the diagonal band of Broca (septal grafts), or the mesencephalic raphe (raphe grafts), or from both these regions together (co-grafts). All rats were submitted to a series of behavioural tests (home cage and open-field locomotion, spontaneous alternation, radial-arm maze and Morris water maze performance) run over two periods after grafting (one to nine weeks and 20-35 weeks). Two weeks after completion of behavioural testing, histological (acetylcholinesterase and Cresyl Violet staining) and/or neurochemical (choline acetyltransferase activity, high-affinity synaptosomal uptake of choline and serotonin, noradrenaline, serotonin and 5-hydroxyindolacetic acid concentrations) verifications were performed on the hippocampus. Compared to sham-operated rats, lesion-only rats exhibited hyperactivity which was transient in a familiar environment (home cage) and lasting in an unfamiliar one (open field), decreased rates of spontaneous T-maze alternation, and impaired memory performance in both the radial-arm maze and the Morris water maze. These rats also showed decreased cholinergic and serotonergic markers with a maximal depletion in the septal two-thirds of the hippocampus. Noradrenaline concentration tended to be increased in the dorsal third of the hippocampus, but was not modified in the other two-thirds. While septal grafts specifically increased the cholinergic markers and raphe grafts the serotonergic ones, neither of these grafts produced a lasting effect on any behavioural variable. Conversely, the co-grafts, which increased both the cholinergic and serotonergic markers in the septal two-thirds of the hippocampus, completely normalized the Morris water maze probe trial performance, but failed to affect any of the other behavioural variables. Our present results confirm that grafts of fetal neurons injected into the denervated hippocampus may induce a neurochemical recovery that depends on the anatomical origin of the grafted cells, and that co-grafting two fetal brain regions allows the combination of their individual neurochemical properties. Furthermore, our results show that these neurochemical effects of the co-grafts may be involved in the recovery of behavioural function observed in the water maze. However, somewhat paradoxically, those effects appear inefficient for inducing any recovery in other behavioural tasks, even in the radial-arm maze; which is assumed to measure similar spatial functions

Effects of grafts containing cholinergic and/or serotonergic neurons on cholinergic, serotonergic and noradrenergic markers in the denervated rat hippocampus

Long-Evans female rats sustained aspirative lesions of the septohippocampal pathways and, 2 weeks later, received intrahippocampal suspension grafts prepared from the regions including either the medial septum and the diagonal band of Broca (group S), or the mesencephalic raphe (group R), or from both these regions together (group S + R). Sham-operated (group SHAM) and lesion-only (group LES) rats were used as controls. Six months after grafting, high affinity synaptosomal uptake of choline (HACU) and serotonin (HASU), choline acetyltransferase (ChAT) activity and, using HPLC, the content of serotonin ([5-HT]), 5-hydroxyindolacetic acid ([5-HIAA]) and noradrenaline ([NA]) were determined in three rostro-caudal segments of the hippocampus (designated hereafter as the dorsal, the 'middle' and the ventral segments). In all three segments of the dorsal hippocampus, septohippocampal lesions decreased HACU, ChAT activity, HASU and [5-HT]; [5-HIAA] was decreased only in the middle and ventral hippocampal segments. The lesions also resulted in an above normal increase of [NA]. Septal grafts increased HACU and ChAT in the three hippocampal regions, had no effect on serotonergic markers and attenuated the lesion-induced increase of [NA] in only the dorsal and middle hippocampal segments. Raphe grafts increased HASU, [5-HT] and [5-HIAA] in the dorsal and middle hippocampal segments, had no effects on cholinergic markers and did not affect the lesion-induced increase of [NA]. Co-grafts increased HACU, ChAT activity, HASU, [5-HT] and [5-HIAA], and attenuated the lesion-induced increase in [NA]. These data demonstrate that grafts of fetal neurons placed into the denervated hippocampus may induce a neurochemical recovery which depends upon the anatomical origin of the grafted cells. They also show that co-grafting allows to combine the neurochemical properties of two fetal brain regions grafted separately. Furthermore, our findings suggest that graft-derived cholinergic reinnervation of the hippocampus prevents the lesion-induced increase of noradrenaline concentration which is likely to result from sympathetic sprouting. Thus, our data confirm the results of a previous experiment carried out at a post-grafting delay of 10-11 months, and show that the graft-induced effects reported previously are already massively present by 6 months after surgery

The Effects of Intrahippocampal Grafts, Training, and Postoperative Housing on Behavioral Recovery After Septohippocampal Damage in the Rat

This study examined whether the expression of behavioral effects of grafts rich in cholinergic neurons placed into the hippocampus of rats with septohippocampal damage may be modulated by postoperative housing or training conditions. Among 91 Long-Evans female rats, 61 sustained a bilateral aspirative lesion of the fimbria-fornix fibers and all overlying tissue, while 30 were given sham operations. Ten days after surgery, fetal septal suspension grafts were performed in the hippocampus of half the lesioned rats. Two days later, all rats were randomly assigned to one of three housing or training conditions: standard, standard with daily training, and enriched. Two and 5 months later, the rats were tested for learning using a Hebb-Williams maze. At both these delays, performance was clearly impaired in lesioned rats and was found to be ameliorated by grafts only in rats which had received daily training. Cresyl violet staining and acetylcholinesterase histochemistry showed that, irrespective of the housing or training conditions, all grafts had survived and provided the denervated hippocampus with a substantial cholinergic reinnervation. Our results suggest that the beneficial behavioral effects of intrahippocampal suspension grafts of septal cells may depend on the postsurgical training or handling conditions of the graft recipients. This result might be of importance for interpreting some behavioral effects of grafts, since in most studies in which grafts were found to induce beneficial behavioral effects (especially on learning capacity), these effects were generally observed at the end of a rather long testing period. Moreover, the present findings show that this delay, before graft function is expressed, might be linked not only to the time needed by grafts to establish a functional reinnervation in the host brain, but also to the training and/or handling conditions of the graft recipient

Sympathetic Sprouting: Time Course of Changes of Noradrenergic, Cholinergic, and Serotonergic Markers in the Denervated Rat Hippocampus

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MDMA (ecstasy) effects in pubescent rats: Males are more sensitive than females

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Effects of grafts containing cholinergic and/or serotonergic neurons on cholinergic, serotonergic and noradrenergic markers in the denervated rat hippocampus

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The effects of intrahippocampal raphe and/or septal grafts in rats with fimbria-fornix lesions depend on the origin of the grafted tissue and the behavioural task used

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