Alcohol-induced neuronal death in central extended amygdala and pyriform cortex during the postnatal period of the rat.

Mothers who consume alcohol during pregnancy may cause a neurotoxic syndrome defined as fetal alcohol spectrum disorder (FASD) in their offspring. This disorder is characterized by reduction in brain size, cognitive deficits and emotional/social disturbances. These alterations are thought to be caused by an alcohol-induced increase in apoptosis during neurodevelopment. Little is known about neuroapoptosis in the central extended amygdala and the pyriform cortex, which are key structures in emotional/social behaviors. The goal of this study was to determine the vulnerability of neuroapoptotic alcohol effects in those areas. Rats were administered alcohol (2.5g/kg s.c. at 0 and 2h) or saline on postnatal day (PND) 7, 15 and 20. The Amino-cupric-silver technique was used to evaluate neurodegeneration and immunohistochemistry to detect activated caspases 3-8 and 9 at 2h, 4, 6, 8, 12 and 24h after drug administration. We measured blood alcohol levels each hour, from 2 to 8h post second administration of alcohol in each of the ages studied. Results showed alcohol induced apoptotic neurodegeneration in the central extended amygdala on PND 7 and 15, and pyriform cortex on PND 7, 15 and 20. These structures showed activation of caspase 3 and 9 but not of caspase 8 suggesting that alcohol-induced apoptosis could occur by the intrinsic pathway. The pharmacokinetic differences between ages did not associate with the neurodegeneration age dependence. In conclusion, these limbic areas are damaged by alcohol, and each one has their own window of vulnerability during the postnatal period. The possible implications in emotional/social features in FASD are discussed.

[Understanding the pathophysiology of epilepsy in an animal model: pentylenetetrazole induces activation but not death of neurons of the medial extended amygdala]. / Descifrando la fisiopatología de la epilepsia en un modelo animal: el pentilentetrazol induce la activación pero no la muerte de las neuronas de la amígdala extendida medial.

INTRODUCTION: since middle of the 20th century the importance of amygdala in epilepsy it has suggested, although the basic mechanisms of this participation are still unknown. This ignorance increases when the different subdivisions of amygdala are considered, especially the medial amygdala. In this work we assess the involvement of the medial extended amygdala in an animal model of epilepsy and the consequences of its application in this brain structure. MATERIAL AND METHODS: forty eight adult Wistar male rats were used, of which 24 of them received i.p. injections of pentylenetetrazole, and 24 (controls) were injected with saline. After 2, 6, 12 and 24 h survival, animals were fixed; the brains were sectioned serially and stained for fos (immunochemistry) and for neuronal death with the A-Cu-Ag technique. Data were analysed using two-way ANOVA followed by the Fisher post hoc test. RESULTS: very few or no fos-immunoreactive neurons were seen in control animals. In experimental animals, fos was rapidly induced in structures of medial extended amygdala with peak levels at 2 h. Marked fos immunoreactivity persisted up to 12 h followed by a gradual return to baseline at 24 h. However, status epilepticus did not induced neuronal death. CONCLUSIONS: these results show involvement of medial extended amygdala in epileptic mechanisms with an inhibitory component. However, neuronal death is not a consequence of status epilepticus-induced by pentylentetrazole.

Descifrando la fisiopatología de la epilepsia en un modelo animal: el pentilentetrazol induce la activación pero no la muerte de las neuronas de la amígdala extendida medial / Understanding the pathophysiology of epilepsy in an animal model: pentylenetetrazole induces activation but not death of neurons of the medial extended amygdala

Introducción: Desde mitad del siglo XX se ha apuntado a la importancia de la amígdala en la epilepsia, aunque los mecanismos básicos de esta participación en su mayoría son aún desconocidos. Esta ignorancia es aún mayor cuando se tienen en cuenta las distintas subdivisiones de la amígdala, especialmente sus partes mediales. En este trabajo evaluamos la participación de la amígdala extendida medial en un modelo animal de epilepsia, así como las consecuencias que tiene el epileptógeno en esta estructura cerebral. Material y métodos: Se utilizaron ratas adultas Wistar machos (n = 48); 24 animales recibieron inyecciones intraperitoneales de pentilentetrazol y 24, de salina. Luego de 2, 6, 12 y 24 h de sobrevida, los animales se fijaron, y sus cerebros se cortaron seriadamente y se procesaron para fos (inmunoquímica) y muerte neuronal con la técnica A-Cu-Ag. Los datos se analizaron con un ANOVA de 2 vías seguido de un test post-hoc (LSD de Fisher). Resultados: Muy poca activación fos se halla en animales controles. En animales experimentales, fos fue rápidamente inducida en la amígdala extendida medial a las 2 h. Esta activación fue sostenida hasta las 12 h y retornó a valores basales a las 24 h. Sin embargo, el estado epiléptico no produjo muerte neuronal. Conclusiones: Se demuestra así una participación de la amígdala extendida medial en mecanismos epilépticos en los cuales subyace un componente inhibitorio. Sin embargo, el estado epiléptico inducido no produce muerte neuronal en esta estructura (AU)

Introduction: Since middle of the 20th century the importance of amygdala in epilepsy it has suggested, although the basic mechanisms of this participation are still unknown. This ignorance increases when the different subdivisions of amygdala are considered, especially the medial amygdala. In this work we assess the involvement of the medial extended amygdala in an animal model of epilepsy and the consequences of its application in this brain structure. Material and methods: Forty eight adult Wistar male rats were used, of which 24 of them received i.p. injections of pentylenetetrazole, and 24 (controls) were injected with saline. After 2, 6, 12 and 24 h survival, animals were fixed; the brains were sectioned serially and stained for fos (immunochemistry) and for neuronal death with the A-Cu-Ag technique. Data were analysed using two-way ANOVA followed by the Fisher post hoc test. Results: Very few or no fos-immunoreactive neurons were seen in control animals. In experimental animals, fos was rapidly induced in structures of medial extended amygdala with peak levels at 2 h. Marked fos immunoreactivity persisted up to 12 h followed by a gradual return to baseline at 24 h. However, status epilepticus did not induced neuronal death. Conclusions: These results show involvement of medial extended amygdala in epileptic mechanisms with an inhibitory component. However, neuronal death is not a consequence of status epilepticus-induced by pentylentetrazole (AU)

Differential role of gonadal hormones on kainic acid-induced neurodegeneration in medial amygdaloid nucleus of female and male rats.

Sex hormones contribute to modulating brain functions throughout the life span. It has been suggested that estrogen prevents neuronal loss in different areas of the CNS such as the hippocampus. However there are less consistent data on its effects on the amygdala. Kainic acid (KA) is used to produce seizures that mimic those of temporal lobe epilepsy in humans. At high doses in animal models, KA induces neurotoxicity, particularly in the medial amygdaloid nuclei (MeA). It is uncertain whether the gonadal hormones are protective or not against this neurotoxicity in the MeA. Here we show that a single dose of KA induces neurodegeneration in the subnuclei of the MeA of rats with different degrees of intensity in males and females. A differential neuroprotective effect of the gonadal hormones was also observed. In diestrous rats, massive neuronal death similar to that in the ovariectomized females was detected. MeA neurons of proestrous rats, like the ovariectomized treated with estrogen, were significantly less affected by the KA. Testosterone produced a mild neuroprotective action, but dihydrotestosterone did not protect. A similar pattern was observed in all male groups. Together, the results indicate that estrogen protects MeA neurons from KA neurotoxicity. Androgens are only partially neuroprotective, with this effect being found only in testosterone, probably through its conversion to estrogen by aromatase.

Effect of retinal ablation on the expression of calbindin D28k and GABA in the chick optic tectum.

The effect of retinal ablation on qualitative and quantitative changes of calbindin D28k and GABA expression in the contralateral optic tectum was studied in young chicks. Fifteen days old chicks had unilateral retinal ablation and after 7 or 15 days, calbindin expression was analyzed by Western blot and immunocytochemistry. Neuronal degeneration was followed by the amino-cupric silver technique. After 15 days, retinal lesions produced a significant decrease in calbindin immunostaining in the neuropil of layers 5-6 and in the somata of neurons from the layers 8 and 10 of the contralateral tectum, being this effect less marked at 7 days post-lesion. Double staining revealed that 50-60% of cells in the layers 8 and 10 were calbindin and GABA positive, 30-45% were only calbindin positive and 5-10% were only GABAergic neurons. Retinal ablation also produced a decrease in the GABA expression at either 7 or 15 days after surgery. At 7 days, dense silver staining was observed in the layers 5-6 from the optic tectum contralateral to the retinal ablation, which mainly represented neuropil that would come from processes of retinal ganglion cells. Tectal neuronal bodies were not stained with silver, although some neurons were surrounded by coarse granular silver deposits. In conclusion, most of calbindin molecules are present in neurons of the tectal GABAergic inhibitory circuitry, whose functioning apparently depends on the integrity of the visual input. A possible role of calbindin in the control of intracellular Ca2+ in neurons of this circuit when the visual transmission arrives to the optic tectum remains to be studied.

Supracapsular bed nucleus of the stria terminalis contains central and medial extended amygdala elements: evidence from anterograde and retrograde tracing experiments in the rat.

Neurons that accompany the stria terminalis as it loops over the internal capsule have been termed collectively the supracapsular bed nucleus of the stria terminalis (BSTS). They form two cell columns, a lateral column and a considerably smaller medial column. The lateral column merges rostrally with the lateral bed nucleus of the stria terminalis and caudally with the central amygdaloid nucleus (central extended amygdala components). The medial column is continuous with the medial bed nucleus of the stria terminalis and the medial amygdaloid nucleus (medial extended amygdala districts). The connections of the BSTS were investigated in the rat by placing injections of Phaseolus vulgaris-leucoagglutinin (PHA-L) or retrograde tracers in different parts of the extended amygdala or in structures related to the extended amygdala. BSTS inputs and outputs were identified, respectively, by the presence of varicose fibers and retrogradely labeled neurons within the stria terminalis. The results suggest that the medial-to-lateral compartmentalization of BSTS neurons reflects their close alliance with the medial and central divisions of the extended amygdala. The medial BSTS contains primarily elements that correspond to the posterodorsal part of the medial amygdaloid nucleus and the medial column of the posterior division of the medial bed nucleus of the stria terminalis, and the lateral BSTS contains elements that correspond to the medial and lateral parts of the central amygdaloid nucleus and lateral bed nucleus of the stria terminalis. These results add strong support to the concept of the extended amygdala as a ring-like macrostructure around the internal capsule, and they are of theoretical interest for the understanding of the organization of the basal forebrain.

The neuronal organization of the supracapsular part of the stria terminalis in the rat: the dorsal component of the extended amygdala.

In the present normal anatomical light and electron microscopic study in the rat, histochemical (Nissl, Timm, Golgi) or immunocytochemical (microtubule-associated protein type 2, glutamate decarboxylase, glutamate receptor subunit 1, synaptophysin) stains were used to analyse neurons embedded within the stria terminalis and their associated neuropil. These cells are closely related to the bed nucleus of the stria terminalis and the centromedial amygdala, and have been termed the "supracapsular part of the bed nucleus of the stria terminalis". The largest part of this neuronal complex is located in the ventrolateral part of the stria, where it appears as a round or oval "lateral pocket" in virtually any type of light microscopic preparation because of its collection of neuronal cell bodies and dense neuropil, in addition to a lacework of unmyelinated axons. A much smaller but still distinct "medial pocket" is located in the medial corner of the stria. The large lateral subdivision of the supracapsular stria terminalis is directly continuous with the lateral bed nucleus of the stria terminalis and extends to the central amygdaloid nucleus, containing a column of neurons that is only broken up into cell clusters at the most caudal levels of the stria as it drops vertically toward the amygdala. The considerably smaller medial subdivision appears, in turn, to be directly continuous with the medial part of the bed nucleus of the stria terminalis. The medial column tapers off more rapidly than the lateral part, so that as the middle levels are approached, only small interrupted clusters of cells are seen. Solitary neurons can also be found in practically every part of the stria terminalis except among the ventrally located axons of the commissural component. Most of the neurons are small to medium in size, as viewed in transverse sections of the stria, but larger neurons are also encountered. In sections parallel to the stria, many neurons are fusiform in appearance. The dendrites are often aligned in a longitudinal fashion; many of the dendrites related to the cells in the lateral pocket are moderately to densely spined, whereas those in the medial pocket are more sparsely spined. The neuropil in both the lateral and medial pockets is characterized by boutons, bundles of unmyelinated axons, and dendrites. Based on their vesicle content, the boutons are divided into three major types: (A) round or slightly oval, agranular vesicles of uniform size; (B) pleomorphic, agranular vesicles, many of which are flattened; and (C) pleomorphic agranular vesicles, some of which are considerably larger than the ones in type B boutons. Type A boutons establish contacts with both dendritic spines and shafts, whereas types B and C usually contact dendritic shafts and sometimes somata. These synaptic components are similar to those described earlier for the central and medial amygdaloid nuclei. Overall, our results support the contention advanced in 1923 by Johnston [J. comp. Neurol. 35, 337481] that the cells accompanying the stria terminalis are interconnecting columns of a macrostructure encompassing the bed nucleus of the stria terminalis and centromedial amygdala. More recently, it has been appreciated that columns of neurons below the globus pallidus also belong to this macrostructure [Alheid G. F. et al. (1995) In The Rat Nervous System, 2nd edn, pp. 495 578, Academic, San Diego; de Olmos J. S. et al. (1985) In The Rat Nervous System, pp. 223-334, Academic, Sydney], which has been named the "extended amygdala".

Amygdaloid input to transiently tyrosine hydroxylase immunoreactive neurons in the bed nucleus of the stria terminalis of the rat.

Several studies have reported transient expression of tyrosine hydroxylase in a subpopulation of neurons in the bed nucleus of stria terminalis of preadolescent rats. The tyrosine hydroxylase immunoreactive (TH) neurons, which are of small to medium size and often display a typical bipolar configuration, are confined to the intermediate part of the lateral bed nucleus. By the use of a combination of experimental tracer techniques and immunocytochemical methods, we have demonstrated that these neurons receive a significant number of amygdaloid afferents, which establish mostly symmetric synaptic contacts on the cell bodies and sparsely spined dendritic shafts of the TH neurons. TH neurons also receive a small number of tyrosine hydroxylase-positive terminals of unspecified origin.

Use of an amino-cupric-silver technique for the detection of early and semiacute neuronal degeneration caused by neurotoxicants, hypoxia, and physical trauma.

A new amino-cupric silver protocol is described for detection of neuronal degeneration. We describe its selectivity in visualizing both early and semiacute degeneration after intracerebral or systemic administration of a variety of neurotoxicants in rats, and after transient ischemic episodes in gerbils. As early as 5 min after physical trauma, or 15 min following either intrastriatal injections of glutamate analogs or exposure to ischemic episodes, neuronal silver staining was evident at primary sites of trauma (i.g. injection sites) and at hodologically related secondary sites. With intoxication by peripheral injections of trimethyltin (IP) or intracerebral injections of Doxorubicin, reproducible patterns of degeneration are demonstrable after 24 h or after 9-13 days, respectively. The amino-cupric silver method permits simultaneous detection of all neuronal compartments against a clear background. Degeneration in the neuronal cell bodies, dendrites, axons and terminals, as well as the recruitment of new structures in a progressive pathologic process, could be accurately followed. The inclusion of new reagents increased the sensitivity vis-à-vis previous versions of the cupric-silver method. The advantages and disadvantages of the current method in comparison with other means of neurotoxic assessment are discussed in detail, with special emphasis on its unique ability to discriminate irreversible degenerative phenomena and degeneration of axonal components in cases where the cell body remains apparently intact. The amino-cupric silver method is an especially useful tool for surveying neuronal damage in basic neuroscience investigations and in neuropathologic and neurotoxic assessment.

Immunocytochemical localization of the plasma membrane calcium pump, calbindin-D28k, and parvalbumin in Purkinje cells of avian and mammalian cerebellum.

A monoclonal antibody produced against the human erythrocyte plasma membrane calcium pump (PMCA) was shown to react immunohistochemically with an epitope of the PMCA in avian and mammalian cerebellum. Western blot analysis of purified synaptosomes and homogenates from avian cerebellum revealed major immunoreactive proteins with molecular masses (130 kDa and 138 kDa) similar to those of purified erythrocyte PMCA. Dual-imaging confocal immunofluorescence microscopy of avian cerebellum showed that the PMCA antibody stained the periphery of the soma whereas calbindin-D28k was located in the cytosol. PMCA heavily stained the more distal dendrites of the Purkinje cells and, within the resolution of the fluorescence procedure, colocalized with calbindin-D28k. By using alkaline phosphatase-conjugated second antibody, PMCA was again localized to the peripheral soma, to a segmental pattern in dendrites, and to presumed spiny elements. The soma periphery and dendrites of Purkinje cells of the rat cerebellum were also prominently stained with anti-PMCA antibody and compared to parvalbumin localization. Dendritic depolarization and dendritic spiking behavior are significant Ca(2+)-dependent events of Purkinje cells. The rapid decline of intracellular free Ca2+ after the rapid rise time of Ca2+ transients is considered to be due to sequestration by Ca2+ buffers, uptake by intracellular stores, and Ca2+ extrusion mechanisms, the latter a function of PMCA now shown immunohistochemically to be a prominent feature of Purkinje cell dendrites.

Intracranial injection of Fluoro-Gold results in the degeneration of local but not retrogradely labeled neurons.

Small volumes of either Fluoro-Gold (hydroxy-stilbamidine) or physiological saline were pressure injected into the striatum of adult rats. This paradigm is essentially the same as that used by neuroscientists who inject small quantities of Fluoro-Gold into brain structures to reveal neuronal connections. Using a modified de Olmos' cupric-silver technique, virtually no degeneration could be detected as the result of saline injection at any time point examined. However, comparable injections of Fluoro-Gold resulted in conspicuous cell body and terminal degeneration within the striatum 1-10 days post injection. Terminal degeneration within the substantia nigra pars reticulata could also be seen 2-10 days after injection. Examination of cells of the compacta region revealed conspicuous retrograde uptake of Fluoro-Gold, although none of these cells exhibited any evidence of neuronal degeneration at any postoperative time examined.

Silver staining as a tool for neurotoxic assessment.

There is no denying that the silver methods lost their dominant role as tract-tracing methods in the past 10 to 15 years. But it seems equally clear that the silver technique is headed for a dramatic revival in many fields of neuroscience, where the scope and localization of neuronal degeneration are a central issue. Together with the immunostaining of proteins formed or altered in traumatized neurons, the modern silver techniques provide neurotoxicologists and neuropathologists with unparalleled opportunities to detect and study injured and dying neurons. Characterized by great sensitivity and distinct rendition of the morphology of degenerating neurons and their processes, the reduced silver methods constitute the ideal tool for screening irreversible neuronal damage caused by neurotoxic substances including drugs of abuse. Those interested in the rapidly expanding fields of "excitotoxicity" and neurodegenerative disorders (Taylor 1991) are also likely to find increasing use for the silver methods. The pattern of degeneration in so-called "system degenerations" may be predetermined by the neuronal connections (Saper et al. 1987), and as the disease progresses from the destruction of the originally affected neuron population, closely related systems and pathways may be recruited into the pathophysiologic cascade. Any type of trauma to the CNS has the potential to produce this type of "domino effect" of degeneration, through which additional systems are progressively recruited into a degenerative chain reaction of transneuronal degeneration. In other words, even longstanding disorders may exhibit signs of more recent degeneration, and the proper use of silver methods at autopsy may give some important clues regarding the etiology of disease; it may also provide new insights about the anatomy of the human brain. Little can be said at present about the chemical basis of argyrophilia in degenerating and "reactive" neurons, but there is every reason to pay more attention to this subject. One can expect that a continuing and concerted effort will result in a rational understanding of the molecular biological and physicochemical events that fortuitously provide the basis for the selective impregnation of degenerating neuronal elements. This knowledge can be the basis for the development of even more reliable and simple, yet sensitive, silver methods suited for neurotoxic risk assessment on a large scale.

Participation of the olfactory system in the control of approach behavior of the female rat to the male.

The amounts of time spent by females in the sector of an open field close to the cage housing a normal male or a castrated male were measured in order to quantitate the tendency of the female to reach physical proximity to a sexually active male (androtropism). Intact proestrous or ovariectomized females primed with 100 micrograms of estradiol benzoate/kg b. wt. (EB) or EB plus 2 mg progesterone/kg b. wt. (P) spent significantly more time close to the sexually active (intact) male than in the proximity of the orchidectomized male. In order to determine whether olfactory clues were sufficient for female rats to distinguish between intact and castrated males, the males were removed from the stimulus cages, leaving the soiled bedding in place. Ovariectomized rats primed with EB or EB plus P clearly preferred proximity to the cage where the intact male had been living. No preference was evident after transection of olfactory nerves in proestrous rats or in ovariectomized rats primed with EB plus P. Resection of the vomeronasal organ also suppressed preference. These results indicate that olfactory input is necessary and sufficient for androtropism to occur, and suggest that the accessory olfactory system is involved in the analysis of olfactory signals used by female rats to identify the endocrine status of prospective sexual partners. In a different group of animals, it was demonstrated that destruction of the posteromedial cortical amygdaloid nucleus also suppressed preference for the intact male. It is proposed that this structure serves as a relay station for the analysis and integration of olfactory input significant for the motivational control of sexual behavior in the female rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventral premammillary nuclei mediate pheromonal-induced LH release stimuli in the rat.

The rise in the concentration of LH in the serum that takes place in ovariectomized, estrogen-primed rats exposed to the odors from a cage with bedding soiled by a male rat was completely prevented by bilateral lesions destroying the ventral premammillary (PMv) nuclei. These results suggest that the pheromonal stimuli generate stimuli that course through a pathway which involves the PMv nuclei before they reach the hypothalamus. In addition, the chemosensory information is apparently transmitted centrally by an uncrossed pathway in view of the fact that removal of one vomeronasal organ combined with lesions of the contralateral PMv nucleus, but not of the ipsilateral nucleus, suppressed the release of LH in rats exposed to male odors. Since pheromonal stimuli are known to activate the accessory olfactory system, of which the medial (Me) amygdaloid nucleus and the bed nucleus of the stria terminalis (BNST) are parts, the effect of stimulating these nuclei in rats bearing lesions of the PMv nucleus was also investigated. Unilateral lesions of the PMv nucleus prevented the release of LH in ovariectomized, estrogen-primed rats and the advancement of LH surge in proestrous rats induced by electrochemical stimulation (anodic d.c. 100 microA/30 s) of the ipsilateral Me amygdaloid nucleus but not those induced by stimulation of the contralateral Me amygdaloid nucleus. Similar results were obtained stimulating the medial part of the BNST in proestrous rats. It is concluded that the impulses evoked by pheromonal stimuli inducing LH release in the rat are conveyed by an uncrossed pathway and relay in the PMv nucleus before they reach the medial basal hypothalamus.

Inhibitory influence of the nuclei of the posterior hypothalamus on the pro-oestrous surge of LH.

The effect of transecting caudal afferents to the medial basal hypothalamus on the pro-oestrous surge of LH was studied in cyclic female rats. Rats with transverse cuts placed just in front of the mammillary bodies and caudal to the ventromedial hypothalamic nucleus showed an earlier time of onset of pro-oestrous surge of LH. Conversely, rats with transverse cuts placed 2 mm more caudally or with cuts along the lateral edges of the hypothalamus showed no altered release of LH. Advanced release of LH occurred also in rats in which the ventral premammillary nuclei or the posterior hypothalamic nuclei were bilaterally destroyed but not in those sham operated or with lesions in the dorsal premammillary nuclei. The number of ova ovulated was higher in rats bearing lesions of any of these nuclei but enhanced LH release was seen only in animals with lesions of the posterior hypothalamic nuclei. Electrochemical stimulation (anodic d.c., 100 microA, 15 s) applied at noon of pro-oestrus to the ventral premammillary nucleus, dorsal premammillary nucleus or posterior hypothalamic nucleus prevented ovulation and the preovulatory discharge of LH. It is concluded that inputs from nuclei of the posterior hypothalamus are inhibitory for LH release and could participate in determining the timing and magnitude of the pro-oestrous surge of the hormone.

Release of LH in the female rat by olfactory stimuli. Effect of the removal of the vomeronasal organs or lesioning of the accessory olfactory bulbs.

The release of LH in ovariectomized, estrogen-primed rats exposed to male or female rats was studied. The concentration of LH in the serum was measured in blood samples obtained by an indwelling jugular cannula. A blood sample was taken at 12.00 h and then every hour up to 18.00 h following exposure to another rat on the opposite side of a double wire mesh screen. LH in the serum of control non-exposed rats showed a small rise between 16.00 and 18.00 h as compared to earlier values. Rats exposed to intact or castrated male rats exhibited an enhanced release. Exposure to ovariectomized rats failed to induce any change in the release of LH but exposure to ovariectomized, estrogen-primed rats produced a significant increase. No effect on LH release was seen in animals exposed to a female diestrous rat or to a pregnant rat. Rats exposed to an empty cage which had been soiled by housing a male rat for 3 days, showed an enhanced release of LH similar to those exposed to a cage containing the male rat, indicating the importance of olfactory stimuli in the response. Ovariectomized rats whose vomeronasal organs had been removed or whose accessory olfactory bulbs were lesioned, failed to show any effect on the release of LH when exposed to a male rat. It is concluded that olfactory stimuli arising from male or female rats are capable of modulating the release of LH in female rats and that perception of these stimuli involves the vomeronasal organ-accessory olfactory bulb system.

Dual action of electrochemical stimulation of the bed nucleus of the stria terminalis on the release of LH.

The effect of stimulation of the bed nucleus of the stria terminalis (BNST) on ovulation and LH release was studied in unanesthetized, freely moving rats. Electrochemical stimulation (anodic d.c., 100 microA/30 sec) was applied at 11.30 h through chronically implanted monopolar, stainless steel electrodes. Serial blood samples were obtained by way of a plastic cannula implanted in the jugular vein. Stimulation on the day of proestrus prevented ovulation and the preovulatory discharge of LH when the stimulus was applied to the lateral part of the BNST but advanced the surge of LH in those rats stimulated in the medial part of the nucleus. In ovariectomized estrogen-primed rats stimulation in the medial part of the BNST produced LH release but no effect was seen when the stimulus was applied in the lateral part. It is concluded that the BNST is part of a dual system with antagonistic effects on LH secretion.

Sensory control of the hypothalamus and the neuroendocrine system.

A study was made of the control of the hypothalamus and neuroendocrine complex by the specialized receptors: the eye, the ear and the olfactory complex. The ancient and modern evidence that light, acting on the optic system, can influence hypothalamic, hypophyseal, endocrine reactions was reviewed and the recently acquired evidence that an optic-hypothalamic-autonomic-pineal-hypothalamic circuit exists which controls liberation of "releasing hormones". Evidence was presented to show that the ear and eye, extero-and interoceptive influences affect lactation and oxytocin secretion by action through the hypothalamus. It was also shown that electrochemical stimulation of the olfactory bulbs can affect both sexual behavior and gonadotropin secretion. Finally, it was shown that the olfactory system exerts some control over water intake, sodium appetite and antidiuretic hormone secretion. Progress in a long term cooperative study of the role of exteroceptor control of neuroendocrine functions was reported.

Sensory control of the hypothalamus and the neuroendocrine system.

A study was made of the control of the hypothalamus and neuroendocrine complex by the specialized receptors: the eye, the ear and the olfactory complex. The ancient and modern evidence that light, acting on the optic system, can influence hypothalamic, hypophyseal, endocrine reactions was reviewed and the recently acquired evidence that an optic-hypothalamic-autonomic-pineal-hypothalamic circuit exists which controls liberation of [quot ]releasing hormones[quot ]. Evidence was presented to show that the ear and eye, extero-and interoceptive influences affect lactation and oxytocin secretion by action through the hypothalamus. It was also shown that electrochemical stimulation of the olfactory bulbs can affect both sexual behavior and gonadotropin secretion. Finally, it was shown that the olfactory system exerts some control over water intake, sodium appetite and antidiuretic hormone secretion. Progress in a long term cooperative study of the role of exteroceptor control of neuroendocrine functions was reported.