High ethanol preference and dissociated memory are co-occurring phenotypes associated with hippocampal GABAAR-δ receptor levels.

Alcohol use disorder (AUD) frequently co-occurs with dissociative disorders and disorders with dissociative symptoms, suggesting a common neurobiological basis. It has been proposed that facilitated information processing under the influence of alcohol, resulting in the formation of dissociated memories, might be an important factor controlling alcohol use. Access to such memories is facilitated under the effect of alcohol, thus further reinforcing alcohol use. To interrogate possible mechanisms associated with these phenotypes, we used a mouse model of dissociative amnesia, combined with a high-alcohol preferring (HAP) model of AUD. Dissociated memory was induced by activation of hippocampal extrasynaptic GABA type A receptor delta subunits (GABAAR-δ), which control tonic inhibition and to which ethanol binds with high affinity. Increased ethanol preference was associated with increased propensity to form dissociated memories dependent on GABAAR-δ in the dorsal hippocampus (DH). Furthermore, the DH level of GABAAR-δ protein, but not mRNA, was increased in HAP mice, and was inversely correlated to the level of miR-365-3p, suggesting an miRNA-mediated post-transcriptional mechanism contributing to elevated GABAAR-δ. The observed changes of DH GABAAR-δ were associated with a severe reduction of excitatory projections stemming from GABAAR-δ-containing pyramidal neurons in the subiculum and terminating in the mammillary body. These results suggest that both molecular and circuit dysfunction involving hippocampal GABAAR-δ receptors might contribute to the co-occurrence of ethanol preference and dissociated information processing.

Spatial memory extinction differentially affects dorsal and ventral hippocampal metabolic activity and associated functional brain networks.

Previous studies showed the involvement of brain regions associated with both spatial learning and associative learning in spatial memory extinction, although the specific role of the dorsal and ventral hippocampus and the extended hippocampal system including the mammillary body in the process is still controversial. The present study aimed to identify the involvement of the dorsal and ventral hippocampus, together with cortical regions, the amygdaloid nuclei, and the mammillary bodies in the extinction of a spatial memory task. To address these issues, quantitative cytochrome c oxidase histochemistry was applied as a metabolic brain mapping method. Rats were trained in a reference memory task using the Morris water maze, followed by an extinction procedure of the previously acquired memory task. Results show that rats learned successfully the spatial memory task as shown by the progressive decrease in measured latencies to reach the escape platform and the results obtained in the probe test. Spatial memory was subsequently extinguished as shown by the descending preference for the previously reinforced location. A control naïve group was added to ensure that brain metabolic changes were specifically related with performance in the spatial memory extinction task. Extinction of the original spatial learning task significantly modified the metabolic activity in the dorsal and ventral hippocampus, the amygdala and the mammillary bodies. Moreover, the ventral hippocampus, the lateral mammillary body and the retrosplenial cortex were differentially recruited in the spatial memory extinction task, as shown by group differences in brain metabolic networks. These findings provide new insights on the brain regions and functional brain networks underlying spatial memory, and specifically spatial memory extinction. © 2016 Wiley Periodicals, Inc.

Population pharmacokinetics of ramosetron.

Ramosetron is a selective serotonergic 5-hydroxy-tryptamine receptor 3 antagonist that is used to prevent and treat postoperative nausea and vomiting. This study aimed to characterize the population pharmacokinetics of ramosetron in patients undergoing surgery with general anesthesia. Patients aged 19-80 years received a single intravenous bolus of ramosetron (0.3, 0.45, or 0.6 mg) 30 min before the end of surgery. Blood samples were collected, and plasma concentrations of ramosetron were measured by high performance liquid chromatography-tandem mass spectrometry. Pooled data from 50 patients and 479 pharmacokinetic samples were used for population pharmacokinetic analysis using the nonlinear mixed effect modeling program (NONMEM(®)). The pharmacokinetics of ramosetron was best described by a three-compartment mammillary model with first-order elimination. Based on allometric principles, body weight was incorporated in the base model, along with fixed allometric exponents. The typical value of clearance was 0.19 L/h in a 60-kg subject, and it decreased approximately 3% for every year of age, starting at age of 57. The bootstrap method and visual predictive check showed that the final pharmacokinetic model was appropriate. A population pharmacokinetic model of ramosetron was constructed in adult surgical patients, providing a foundation for further defining the relationship between ramosetron dose and postoperative nausea and vomiting.

The importance of the context in the hippocampus and brain related areas throughout the performance of a fear conditioning task.

The importance context has been broadly studied in the management of phobias and in the drug addiction literature. The way in which changes to a context influence behavior after the simple acquisition of a passive avoidance task remains unclear. The hippocampus has long been implicated in the contextual and spatial processing required for contextual fear, but its role in encoding the aversive component of a contextual fear memory is still inconclusive. Our work tries to elucidate whether a change in context, represented as differences in the load of the stimuli, is critical for learning about the context-shock association and whether this manipulation of the context could be linked to any change in metabolic brain activity requirements. For this purpose, we used an avoidance conditioning task. Animals were divided into three different experimental conditions. In one group, acquisition was performed in an enriched stimuli environment and retention was performed in a typically lit chamber (the PA-ACQ-CONTX group). In another group, acquisition was performed in the typically lit chamber and retention was undertaken in the highly enriched chamber (the PA-RET-CONTX group). Finally, for the control group, PA-CN-CONTX, acquisition, and retention were performed in the enriched stimuli environment. Our results showed that the PA-ACQ-CONTX group had longer escape latencies and poorer retention than the PA-RET-CONTX and PA-CN-CONTX groups after 24 h of acquisition under contextual changes. To study metabolic brain activity, histochemical labelling of cytochrome c-oxidase (CO) was performed. CO results suggested a neural circuit including the hippocampus, amygdala, thalamus, parahippocampal cortices, and mammillary nuclei that is involved in the learning and memory processes that enable context-dependent behavior. These results highlight how dysfunction in this network may be involved in the contextualization of fear associations that underlie several forms of psychopathology, including post-traumatic stress disorder, schizophrenia, and substance abuse disorders.

Lateral mammillary body neurons in mouse brain are disproportionately vulnerable in Alzheimer's disease.

The neural circuits governing the induction and progression of neurodegeneration and memory impairment in Alzheimer's disease (AD) are incompletely understood. The mammillary body (MB), a subcortical node of the medial limbic circuit, is one of the first brain regions to exhibit amyloid deposition in the 5xFAD mouse model of AD. Amyloid burden in the MB correlates with pathological diagnosis of AD in human postmortem brain tissue. Whether and how MB neuronal circuitry contributes to neurodegeneration and memory deficits in AD are unknown. Using 5xFAD mice and postmortem MB samples from individuals with varying degrees of AD pathology, we identified two neuronal cell types in the MB harboring distinct electrophysiological properties and long-range projections: lateral neurons and medial neurons. lateral MB neurons harbored aberrant hyperactivity and exhibited early neurodegeneration in 5xFAD mice compared with lateral MB neurons in wild-type littermates. Inducing hyperactivity in lateral MB neurons in wild-type mice impaired performance on memory tasks, whereas attenuating aberrant hyperactivity in lateral MB neurons ameliorated memory deficits in 5xFAD mice. Our findings suggest that neurodegeneration may be a result of genetically distinct, projection-specific cellular dysfunction and that dysregulated lateral MB neurons may be causally linked to memory deficits in AD.

A novel TaulacZ allele reveals a requirement for Pitx2 in formation of the mammillothalamic tract.

The hypothalamic mammillary region is critical for spatial memory and vestibular processing. Pitx2 encodes a paired-like transcription factor that is highly expressed in the developing mammillary region and is required for subthalamic nucleus formation. Here we analyzed a loss of function Pitx2-TaulacZ knock-in allele to study the effects of Pitx2 deficiency on neuronal projections in the embryonic mammillary region. Pitx2-expressing neurons contribute axons to principal mammillary, mammillotegmental and mammillotectal tracts. Embryos with Pitx2 deficiency exhibit axonal fibers in the principal mammillary tract that are improperly bundled and disorganized, yet project caudally toward the tectum and tegmentum. Embryos with Nestin-Cre mediated conditional Pitx2 deficiency exhibit truncated mammillothalamic tracts (mtt) that fail to elongate, and reduced Pax6-positive cells at the branching point of the principal mammillary and mtt. These data suggest that Pitx2 mediates cell-autonomous and nonautonomous guidance cues necessary for mammillary collaterals destined to project to the anterior thalamus.

Acute ethanol induces behavioral changes and alters c-fos expression in specific brain regions, including the mammillary body, in zebrafish.

Ethanol is one of the most commonly abused substances in the world, and ethanol abuse and dependence disorders represent major societal problems. However, appropriate treatment is lacking as we still do not fully understand the molecular bases of these disorders. The zebrafish is one of the model organisms utilized for studying such mechanisms. In this study, we examined the effects of acute ethanol administration on the behavior of zebrafish, and we also analyzed correlated gene expression changes using whole-mount in situ hybridization focusing on a number of genes associated with different neurotransmitter systems, stress response, and neuronal activity. We found ethanol treatment to result in hyperactivity and reduced shoal cohesion compared to control. Analysis of c-fos expression demonstrated altered activity patterns in certain brain regions, including intense activation of the mammillary body in zebrafish with acute ethanol treatment. We also found reduced level of gad1b expression in the cerebellum of ethanol treated fish compared to control. However, we could not detect significant changes in the expression level of other genes, including vglut2b, th, crh, hdc, avp, pomc, and galn in ethanol treated fish compared controls. Our results suggest that zebrafish is a promising animal model for the study of mechanisms underlying alcohol induced behavioral changes and alcohol related human disorders.

Heterogeneity of the supramammillary-hippocampal pathways: evidence for a unique GABAergic neurotransmitter phenotype and regional differences.

The supramammillary nucleus (SuM) provides substantial projections to the hippocampal formation. This hypothalamic structure is involved in the regulation of hippocampal theta rhythm and therefore the control of hippocampal-dependent cognitive functions as well as emotional behavior. A major goal of this study was to characterize the neurotransmitter identity of the SuM-hippocampal pathways. Our findings demonstrate two distinct neurochemical pathways in rat. The first pathway originates from neurons in the lateral region of the SuM and innervates the supragranular layer of the dorsal dentate gyrus and, to a much lesser extent, the ventral dentate gyrus. This pathway displays a unique dual phenotype for GABAergic and glutamatergic neurotransmission. Axon terminals contain markers of GABAergic neurotransmission, including the synthesizing enzyme of GABA, glutamate decarboxylase 65, and the vesicular GABA transporter and also a marker of glutamatergic neurotransmission, the vesicular glutamate transporter 2. The second pathway originates from neurons in the most posterior and medial part of the SuM and innervates exclusively the inner molecular layer of the ventral dentate gyrus and the CA2/CA3a pyramidal cell layer of the hippocampus. The axon terminals from the medial part of the SuM contain the vesicular glutamate transporter 2 only. These data demonstrate for the first time the heterogeneity of the SuM-hippocampal pathways, not only from an anatomical but also a neurochemical point of view. These pathways, implicated in different neuronal networks, could modulate different hippocampal activities. They are likely to be involved differently in the regulation of hippocampal theta rhythm and associated cognitive functions as well as emotional behavior.

The supramammillo-septal-hippocampal pathway mediates sensorimotor gating impairment and hyperlocomotion induced by MK-801 and ketamine in rats.

RATIONALE: Ketamine or MK-801 induced sensorimotor gating deficit, but the underlying neural mechanisms are not completely known. We have previously demonstrated that the medial septum (MS) mediated the phencyclidine-induced deficit in prepulse inhibition of the acoustic startle (PPI) in rats. OBJECTIVES: We investigated the involvement of the supramammillary area (SUM) to MS pathway in PPI impairment and behavioral hyperlocomotion induced by MK-801 or ketamine in rats and correlated the behavioral deficits with hippocampal gamma wave increase. MATERIALS AND METHODS: Ketamine (6 mg/kg, s.c.) or MK-801 (0.5 mg/kg, i.p.) was administered after infusion of saline or the GABA(A) receptor agonist, muscimol (0.25 microg), into the MS or SUM. Locomotion, PPI, and hippocampal electroencephalogram (EEG) were recorded. RESULTS: MK-801 or ketamine induced PPI impairment and behavioral hyperlocomotion, accompanied by an increase in hippocampal gamma waves (30-100 Hz). The changes in behavior and gamma waves induced by ketamine or MK-801 were antagonized by pre-infusion of muscimol, but not saline, into the SUM or MS. Infusion of muscimol into the SUM alone did not significantly affect PPI, but it suppressed spontaneous locomotor behavior and hippocampal EEG. Infusion of ionotropic glutamate receptor antagonists into the MS did not affect the PPI deficit or the gamma wave increase after MK-801. CONCLUSIONS: A non-glutamatergic component of the supramammillo-septal pathway mediates the hyperlocomotion and the deficits in PPI induced by MK-801 or ketamine. Inactivation of the MS or SUM normalized both the hippocampal gamma waves and the behavioral deficits (PPI impairment and hyperlocomotion).

A neuromodulatory role for oxytocin within the supramammillary nucleus.

Oxytocin functions as both a neurohypophysial hormone and central neuromodulatory peptide, and has been implicated in reproductive behaviours, anxiety and reward, as well as facilitation of the neuroendocrine milk-ejection reflex. A potential substrate for oxytocin is the supramammillary nucleus (SuM), a structure that contains oxytocin binding sites and serves as an important relay within the limbic system. Hence, this study investigated the neuromodulatory role of oxytocin within the SuM. Firstly, the effect of oxytocin on neuronal firing within the SuM was studied, using in vitro brain slices from virgin female rats. Oxytocin (10(-6)M) excited approximately 50% of SuM neurones, and similar results were obtained with the selective oxytocin agonist, Thr(4) Gly(7) oxytocin (TGOT) (10(-6) and 10(-7)M). The remaining neurones were unaffected. The TGOT response was blocked by application of the oxytocin antagonist, [d(CH(2))51,Tyr(Me)(2),Thr(4),Orn(8),Tyr-NH29]-vasotocin. Repeat doses of TGOT caused diminution of the response, indicative of desensitisation. In the second series of experiments, immunocytochemical techniques were used to study the oxytocinergic innervation of the SuM. The supramammillary decussation was found to contain numerous oxytocinergic fibres, and some could be seen coursing ventrally to enter the SuM. Whereas, some were clearly "en passant" fibres innervating the neurohypophysis, others followed a more convoluted and branching course, and appeared to terminate within the nucleus. Finally, in vivo microinfusion studies investigated whether oxytocin injected into the SuM facilitated the milk-ejection reflex, a well known action of central oxytocin. Oxytocin microinfusion in the region of the SuM caused a pronounced facilitation of the reflex, contrasting with the much smaller effects of microinfusions made rostral or caudal to the nucleus. Collectively, these results strongly support a neuromodulatory role for oxytocin within the SuM. This could have important implications for understanding the diverse neuroendocrine and behavioural functions of central oxytocin, including its role in reward.

Laminar Localization and Projection-Specific Properties of Presubicular Neurons Targeting the Lateral Mammillary Nucleus, Thalamus, or Medial Entorhinal Cortex.

The presubiculum (PrS) is part of an interconnected network of distributed brain regions where individual neurons signal the animals heading direction. PrS sends axons to medial entorhinal cortex (MEC), it is reciprocally connected with anterior thalamic nuclei (ATNs), and it sends feedback projections to the lateral mammillary nucleus (LMN), involved in generating the head direction signal. The intrinsic properties of projecting neurons will influence the pathway-specific transmission of activity. Here, we used projection-specific labeling of presubicular neurons to identify MEC-, LMN-, and ATN-projecting neurons in mice. MEC-projecting neurons located in superficial layers II/III were mostly regular spiking pyramidal neurons, and we also identified a Martinotti-type GABAergic neuron. The cell bodies of LMN-projecting neurons were located in a well-delimited area in the middle portion of the PrS, which corresponds to layer IV. The physiology of LMN projecting, pyramidal neurons stood out with a tendency to fire in bursts of action potentials (APs) with rapid onset. These properties may be uniquely adapted to reliably transmit visual landmark information with short latency to upstream LMN. Neurons projecting to ATN were located in layers V/VI, and they were mostly regular spiking pyramidal neurons. Unsupervised cluster analysis of intrinsic properties suggested distinct physiological features for the different categories of projection neurons, with some similarities between MEC- and ATN-projecting neurons. Projection-specific subpopulations may serve separate functions in the PrS and may be engaged differently in transmitting head direction related information.

Distribution of urocortin 3 neurons innervating the ventral premammillary nucleus in the rat brain.

Urocortin 3 (Ucn 3) is a recently described peptide of the corticotropin-releasing factor family. Neurons expressing Ucn 3 mRNA and peptide are distributed in specific brain areas, including the median preoptic nucleus, the perifornical area (PFx), and the medial nucleus of the amygdala (MEA). Fibers immunoreactive to Ucn 3 are confined to certain brain nuclei, being particularly dense in the ventral premammillary nucleus (PMV). In studies involving electrolytic lesions and analysis of Fos distribution according to behavioral paradigms, the PMV has been potentially implicated in conspecific aggression and sexual behavior. However, the role that Ucn 3 plays in this pathway has not been explored. Therefore, we investigated the origins of the urocortinergic innervation of the PMV of Wistar rat in an attempt to map the brain circuitry and identify likely related functions. We injected the retrograde tracer cholera toxin b subunit into the PMV and found that 88% of the Ucn 3-immunoreactive fibers in the PMV originate in the dorsal MEA, and that few originate in the PFx. As a control, we injected the anterograde tracer biotin dextran amine into both regions. We observed that the PMV is densely innervated by the MEA, and scarcely innervated by the PFx. The MEA is a secondary relay of the vomeronasal system and projects amply to hypothalamic nuclei related to hormonal and behavioral adjustments, including the PMV. Although physiological studies should also be performed, we hypothesize that Ucn 3 participates in such pathways, conveying sensory information to the PMV, which in turn modulates behavioral and neuroendocrine responses.

Astroglial distribution and sexual differences in neural metabolism in mammillary bodies.

The sexual differences in cerebral nuclei are produced by the organizational and the activational function of gonadal hormones. The different performances by male and female rats in memory tasks requiring use of the mammillary bodies (MBs), could be due to structural and functional sexual dimorphic differences. Our work quantifies the number of glial fibrillary acidic protein immunoreactive (GFAP-IR) astrocytes, and neuronal metabolic activity measured by the cytochrome oxidase (CO) histochemistry in the MBs in rats of both sexes. We find that there is no difference in astroglial number in the medial mammillary nucleus (MMN) and in the lateral mammillary nucleus (LMN) of males, females in estrus and diestrus adult rats. However, we do find statistically significant differences between the sexes in the neuronal oxidative metabolism influenced by the estrous cycle. We, therefore, conclude that there are functional and not structural sex differences in the MBs.

Female odors stimulate CART neurons in the ventral premammillary nucleus of male rats.

Olfactory information is known to influence both male and female sexual behavior. Chemosensory compounds known as pheromones activate distinct brain pathways, inducing innate and stereotyped behaviors, as well as hormonal changes. Studies have shown that female odors induce Fos expression in various brain nuclei of conspecific males, including the ventral premammillary nucleus (PMV). Although poorly investigated, previous studies have suggested that the PMV plays a role in aggressive and sexual behavior. In this study, we used Fos protein expression as a marker for neurons responsive to female odors in sexual inexperienced male rats exposed to soiled bedding. We observed that female odors induced intense Fos immunoreactivity throughout the PMV. Most of these neurons also express cocaine- and amphetamine-regulated transcript (CART) immunoreactivity. In addition, we used in situ hybridization and observed that, following exposure to female odors, CART mRNA increased only in the ventral PMV. Our results suggest that female odors stimulate CART production in the PMV of inexperienced males. Considering that the PMV CART neurons also express the leptin receptor, as well as the fact that they project to areas related to reproduction, we hypothesize that PMV CART neurons integrate nutritional and environmental (olfactory) information, being apt to modulate male reproductive behavior.

Expression of c-Fos protein in medial septum/diagonal band of Broca and CA3 region, associated with the temporary inactivation of the supramammillary area.

The supramammillary (SuM) area is part of the diencephalic nuclei comprising the mammillary bodies, and is a key structure in the memory and spatial learning processes. It is a critical region in the modulation/generation of hippocampal theta rhythm. In addition, many papers have recently shown a clear involvement of this structure in the processes of spatial learning and memory in animal models, although it is still not known how it modulates spatial navigation and response emotional. The aim of the present research was to study the effect of the temporary inactivation of the SuM area on synaptic plasticity of crucial structures in the formation of spatial memory and emotional response. Sprague-Dawley rats were asigned in three groups: a control group where the animals were not subjected to any treatment, and two groups where the rats received microinjections of tetrodotoxin (TTX) in the SuM area (5ng diluted in 0.5µl of saline) or saline (0.5µl). The microinjections were administered 90min before the perfusion. Later, cellular activity in medial septum/diagonal band of Broca (MS/DBB) and CA3 region of the dorsal hippocampus was assessed, by measuring the immediate early gene c-fos. The results show a clear hiperactivity cellular in medial septum/diagonal band of Broca and a clear hypoactivity cellular in the CA3 region of the hippocampus when there was a functional inactivation of the SuM area. It suggests that the SuM area seems to be part of the connection and information input pathways to CA3 region of the hippocampal formation, key for proper functioning in spatial memory and emotional response.

Comparable reduction in Zif268 levels and cytochrome oxidase activity in the retrosplenial cortex following mammillothalamic tract lesions.

Damage to the mammillothalamic tract (MTT) produces memory impairments in both humans and rats, yet it is still not clear why this diencephalic pathway is vital for memory. One suggestion is that it is an important route for midbrain inputs to reach a wider cortical and subcortical network that supports memory. Consistent with this idea, MTT lesions produce widespread hypoactivity in distal brain regions as measured by the immediate-early gene, c-fos. To determine whether these findings were selective to c-fos or reflected more general changes in neuronal function, we assessed the effects of MTT lesions on the expression of the immediate-early gene protein, Zif268 and the metabolic marker, cytochrome oxidase, in the retrosplenial cortex and hippocampus. The lesions decreased levels of both activity markers in the superficial and deep layers of the retrosplenial cortex in both its granular and dysgranular subregions. In contrast, no significant changes were observed in the hippocampus, despite the MTT-lesioned animals showing marked impairments on T-maze alternation. These findings are consistent with MTT lesions providing important, indirect inputs for normal retrosplenial cortex functioning. These distal functional changes may contribute to the memory impairments observed after MTT lesions.

Thiazine Red(+) platelet inclusions in Cerebral Blood Vessels are first signs in an Alzheimer's Disease mouse model.

Strong evidence shows an association between cerebral vascular diseases and Alzheimer´s disease (AD). In order to study the interaction of beta-amyloid (Aß) plaques with brain vessels, we crossbred an AD mouse model (overexpressing amyloid precursor protein with the Swedish-Dutch-Iowa mutations, APP_SweDI) with mice expressing green fluorescent protein (GFP) under the flt-1/VEGFR1 promoter in vessels (GFP_FLT1). Our data show, that only very few Aß plaques were seen in 4-months old mice, focused in the mammillary body and in the lateral septal nucleus. The number of plaques markedly increased with age being most prominent in 12-months old mice. Thiazine Red was used to verify the plaques. Several Thiazine Red(+) inclusions were found in GFP(+) vessels, but only in non-perfused 4-months old mice. These inclusions were verified by Resorufin stainings possibly representing cerebral amyloid angiopathy. The inclusions were also seen in non-crossbred APP_SweDI but not in wildtype and GFP_FLT1 mice. In order to characterize these inclusions Flow Cytometry (FACS) analysis demonstrated that platelets were specifically stained by Thiazine Red(+), more pronounced when aggregated. In conclusion, our data show that Thiazine Red(+) inclusions representing aggregated platelets are a first pathological sign in AD before plaque development and may become important therapeutic targets in early AD.

Rewarding effects of AMPA administration into the supramammillary or posterior hypothalamic nuclei but not the ventral tegmental area.

We examined whether injections of the excitatory amino acid AMPA are rewarding when injected into the posterior hypothalamus and ventral tegmental area. Rats quickly learned to lever-press for infusions of AMPA into the supramammillary or posterior hypothalamic nuclei but failed to learn to lever-press for similar injections into the ventral tegmental areas. AMPA injections into the supramammillary nucleus, but not the ventral tegmental area, induced conditioned place preference. The rewarding effects of AMPA appear to be mediated by AMPA receptors, because coadministration of the AMPA antagonist CNQX blocked the rewarding effects of AMPA, and administration of the enantiomer R-AMPA did not mimic the rewarding effects. AMPA injections into the supramammillary nucleus, but not the ventral tegmental area, also increased extracellular dopamine concentrations in the nucleus accumbens. Pretreatment with the D1 dopamine antagonist SCH 23390 [R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine] led to extinction of AMPA self-administration. These findings implicate posterior hypothalamic regions in reward function and suggest that reward mechanisms localized around the ventral tegmental area are more complex than has been assumed recently.

Galanin immunohistochemistry and electron microscopic studies in developing human fetal mammillary bodies.

Development and maturation of nuclear groups in the mammillary complex of second and third trimester human fetal hypothalamus were studied using Nissl stain, galanin immunocytochemistry and transmission electron microscopy. While the identity of the supra and medial mammillary nucleus was established at 24 weeks of gestation (w.g.) in Nissl stained preparation, galanin immunoreactive (Gal-ir) neurons were seen in the supra and medial mammillary nucleus of 27 through 39 w.g. fetuses. Immunoreactive perikarya in the lateral mammillary nucleus appear later at 34 w.g. and show relatively meager population. Gal-ir neurons of the supramammillary nucleus were divisible in dorsal and ventral subgroups. There was a progressive increase in galanin expressing neurons in more and more ventral positions, along the medial margin of either mammillary body so that in term fetal specimens, the ventral subgroup appeared to be continuous with the medial mammillary nucleus. Galanin positive neurons were relatively sparse in the core of the mammillary bodies. Transmission electron micrographs revealed neurons with varying degree of indentation of the nuclear envelope. Vigorous synaptogenesis was seen in the supramammillary region of the mammillary bodies. The height and width of the synaptic complex also showed a progressive increase. Although galanin neurons were reported from the supramammillary nucleus of adult human mammillary complex, no immunoreactivity was detected in the medial and lateral components of the mammillary body. We suggest that expression of galanin in the medial and lateral components may be of transient occurrence and may serve a significant role in the synaptogenesis.

Monoamine metabolism in human brain.

Norepinephrine (NE), dopamine (DA), tyrosine hydroxylase (TH), catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) levels were measured in human brain tissue obtained at autopsy from a series of 39 patients dying of various medical and accidental causes. The nine following brain areas were studied: globus pallidus, thalamus, hypothalamus, hippocampus, substantia nigra, floor of the fourth ventricle, orbital cortex, caudate nucleus, and mammillary bodies. Enzyme activity correlated positively with age in all brain areas for MAO (with both benzylamine and tryptamine substrates) but no consistent pattern of correlation was found for COMT and TH. Mean MAO activity was significantly higher in women than men. There is increased brain MAO activity during late childhood and adolescence. These data are consistent with previous evidence suggesting that age and sex are important determinants of amine metabolism in the human central nervous system.