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An azepine derivative, 6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-[4,5- d ]-azepine (B-HT 920; 100 nM), inhibited the evoked noradrenaline release from slices of rat posterior hypothalamus, and yohimbine (100 nM) potentiated the release from slices of rat anterior and posterior hypothalamus. In the posterior hypothalamus of 4- and 15–16-week-old spontaneously hypertensive rats (SHRs), as compared with age-matched Wistar-Kyoto rats (WKYs), the inhibitory effect of B-HT 920 and the facilitatory effect of yohimbine were decreased. In the anterior hypothalamus there was no significant difference in the yohimbine effect between WKYs and SHRs, at either age. It is concluded that α 2 -adrenoceptor-mediated autoinhibition of noradrenergic neurotransmission is diminished in the posterior hypothalamus of SHRs.

The effects of electrophoretically applied prostaglandin D2 (PGD2) on neuronal activity in the rat lateral preoptic area (LPOA) and posterior hypothalamic area (PHA) were examined. In the LPOA, 20% of the tested neurons were excited, 26% inhibited, and 6% showed bidirectional response. The direct effects often showed desensitization after repeated applications. Neurons excited by PGD2 were significantly sensitive (excitation) to acetylcholine (ACh). The ACh excitatory effect was sometimes (38%) attenuated, blocked, or reversed by concurrent PGD2 application. Excitatory or inhibitory effect of noradrenaline (NA) was not related to the effects of PGD2, however, modulation of the NA responses by PGD2 was common (58%). Inhibition, the predominant NA response, was changed to no effect or to excitation during simultaneous PGD2 application. Changes of the NA responses from inhibition to excitation, or from excitation to inhibition-excitation sequences were observed after PGD2 infusion into the third cerebral ventricle at low concentrations. In 43% of the cells, neurotransmission in the LPOA following ventral noradrenergic bundle stimulation was modified by PGD2 application. PGD2 application tended to reduce the duration of inhibition and to extend that of excitation. The direct effects of PGD2 in the PHA were similar to those in the LPOA. Desensitization was also observed in the PHA, but no interrelations were observed among the effects of PGD2, ACh, and NA. Modulation of ACh and NA responses by PGD2 was rarely seen in the PHA. Possible contributions of PGD2 to sleep and thermoregulation are discussed.

Bilateral radiofrequency lesions in the anterior and posterior basal hypothalamus decreased courtship and agonistic behaviors in both intact, sexually active, and castrated, androgen treated male Anolis carolinensis . Intact males receiving lesions in the anterior basal hypothalamus had atrophied testes, aspermia, and decreased epithelial cell height of the renal sex segment. Lesions of the posterior basal hypothalamus had no effect on testicular activity or the development of accessory organs. All animals demonstrating behavioral changes had lesion destruction in the ventromedial nucleus and the accompanying periventricular system. It is concluded that the basal hypothalamus in male A. carolinensis is involved both in the regulation of reproductive behavior and pituitary function.

Unit activity of the dorsal hippocampus in response to electrical stimulation of the posterior hypothalamus was recorded in 3--3.5 months old alert rabbits in chronic and acute experiments. Electrical stimulation of the sties of the posterior hypothalamus which had produced orienting behavior in preliminary tests, led to the appearance in the majority of cells at all hippocampal levels of tonic inhibitory and activational reactions with a long-term after-effect. With increased frequency of the stimulating current there was an increase in the number of responding elements and in the reactivity of neurones. The conditioning stimulation of the posterior hypothalamus increased the pronouncement and duration of hippocampal unit responses to sound stimuli. It is concluded that functional manifestations of the afferentation, ascending from the posterior hypothalamus to the hippocampus during the development of orienting reaction, are determined by a nonspecific character of its influences on the neurones of the dorsal hippocampus.

Immunoreactive beta-endorphin (beta-EP) in the ventricular fluid of six carcinomatous patients was measured using a specific radioimmunoassay. The subjects were undergoing a surgical procedure for relief of chronic intractable pain. This procedure involved the focal stimulation and coagulation of the posteromedial hypothalamus. Samples of ventricular fluid were collected before and after the stimulation and serially after the coagulation. Prior to stimulation, beta-EP-like immunoreactivity (beta-EP-LI) was below 200 pg/ml. In all of the six patients with pain relief, electrical stimulation led to a marked increase in immunoreactive beta-EP. In three patients beta-EP levels remained high after electrical coagulation for 6-24 hrs. These results suggest that beta-EP-like material, released into the ventricular fluid, may contribute to the initial pain blockade that results from stimulation and coagulation of the posteromedial hypothalamus.

In order to examine the cellular mechanisms by which estradiol (E2) exerts its acute negative feedback upon luteinizing hormone (LH) secretion, a temporal correlation was made among serum LH concentrations, pituitary responsiveness to luteinizing hormone-releasing hormone (LHRH), and the translocation of E2 to nuclear (NER) receptors of the pituitary (PIT), preoptic hypothalamic area (POA), and the caudal hypothalamic area (HYP). Rats on diestrous day 1 were ovariectomized (OVX) and killed 10 days later. LH and LHRH were measured by RIA. NER was measured by an exchange assay. Serum LH increased 10-12-fold 10 days following OVX as compared to diestrous controls. The injection of estradiol benzoate (Eb, 20 microgram in corn oil/rat, sc) did not affect LH concentrations at 30 min but decreased serum LH at both 60 and 180 min following its administration. Pituitary responsiveness to LHRH (measured as the increase in LH 10 min after iv injections of 100 ng LHRH/rat) was not altered at 60 min but was significantly decreased 180 min following Eb injection. Thus, serum LH decreased prior to a detectable alteration in pituitary responsiveness to LHRH. Translocation of E2 receptors to NER of the HYP and PIT began 60 min following Eb injection and was maximal at 180 min. In contrast, translocation of E2 receptors in the POA was maximal at 60 min, and had recovered to control values 180 min following Eb administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Brown adipose tissue (BAT) is an energy dissipating form of adipose tissue implicated in non-shivering thermogenesis as well as diet-induced thermogenesis. In the present study, in vivo interscapular BAT (IBAT) temperature was recorded prior to and following low level electrical stimulation (a 30 sec train of 60 Hz, 100 microA 0.5 msec isolated pulses) of various hypothalamic regions in rats. Significant increases in IBAT temperature were observed after stimulation of the anterior, medial preoptic, paraventricular and dorsomedial hypothalamus but not after stimulation of either ventromedial or caudal hypothalamus. For positive sites, IBAT temperature typically increased at 3-4 minutes following stimulation, peaked at 7-8 minutes after stimulation and declined at 20 minutes after stimulation. Although alterations in diet-induced thermogenesis have been reported after ventromedial hypothalamic lesions, the increases in BAT temperature noted in the present study suggest that inhibitory fibers that course through the paraventricular hypothalamus may form part of the central nervous system control of brown adipose tissue thermogenesis induced by overfeeding.

It has been demonstrated that in the frog Rana temporaria the anterior hypothalamus is involved into regulation of the depth of two forms of rest--one with plastic, the other with decreased muscle tone. Resting state with catatonic muscle activity is associated with activation of the posterior hypothalamus. Participation of the anterior hypothalamus in regulation of the resting state with the decreased tone of skeletal muscles may be taken as one of the indications that this form of rest plays the role of sleep in amphibians, being transformed during evolution of vertebrates into the sleep of poikilotherms.

Rats with posterior hypothalamic electrodes were trained to lever press for intracranial stimulation. Each rat was then subjected to a 60 min ICSS test where different series of stimulus intensities were presented using a 10 min on, 2 min off procedure. Ascending series of stimulus intensity changes produced significantly higher intracranial stimulation rates at a given current value than descending or randomized series. Results indicate that ordered presentations of stimulus intensities shift the rate/intensity function to the right or left and may distort the reinforcement value as measured by the lever press response at a given intensity.

Castrated male quail were injected with the synthetic oestrogen, diethylstylbestrol (DES) or the synthetic androgen, methyltrienolone (R 1881) or both compounds simultaneously. Both R 1881 and DES activated male sexual behaviour, inhibited LH and FSH secretion and increased hypothalamic aromatase activity. Additive effects between R 1881 and DES were observed for the induction of brain aromatase and for the inhibition of FSH secretion. As a consequence, mechanisms mediated by androgen and estrogen receptors must be involved in the control of these reproductive characteristics.

The electrocorticogram (ECoG) in a SART (specific alternation of rhythm in temperature)-stressed (repeatedly cold-stressed) rat, which is regarded as an experimental model for clinical vagotonic-type dysautonomia, was investigated in the present study by the power spectral technique. 1) Analysis of ECoG in SART-stressed rats during the resting-arousal state indicated a decrease in total power and a decrease in relative power in the delta band, and also an increase in relative power in the theta, alpha and beta bands. 2) In the slow-wave sleeping state, the ECoG of SART-stressed rats indicated a marked increase in total power, an increase in the delta band and decreases in theta, alpha and beta bands. 3) Electric stimulation of the posterior-hypothalamic area evoked alterations of ECoG similar to those caused by SART stress. ECoG response to electric stimulation in SART-stressed rats was less than that in unstressed rats. 4) Lesioning of the posterior-hypothalamic areas prevented SART stress-induced ECoG alterations. SART-stressed rats thus appear to be at a higher consciousness level on awakening but to sleep more soundly. They seem to exhibit greater fluctuation in brain activity than normal rats. There is also the possibility that the posterior-hypothalamic area is responsible to some degree for ECoG alterations in SART-stressed rats.

Neurons of the pericruciate cortex revealed a high degree of reactivity to stimulation of posterior hypothalamus (HP) and mesencephalic reticular formation (RF)--94 and 88% resp., and a marked convergence of upward discharges from HP and RF (73.5%) in anesthetized and immobilized cats. Latency and unit responses (2.4--4.0 msec) suggested a monosynaptic input from the two subcortical structures. Out of the corticofugal neurons activated antidromically, 27% were of the "divergent" type with collaterals in both the HP and RF and, therefore, reacting antidromically to stimulation of these structures. A predominance of cortical antidromic responses to stimulation of HP suggested a greater corticofugal influence on hypothalamic rather than on reticular neurons (84% and 42.3% resp.). Mean latency of antidromic reaction of cortico--hypothalamic neurons was 2.4 +/- 0.2 msec (0.8--6.0 msec), of cortico--reticular neurons--3.2 +/- 0.3 msec (1.0--6.0 msec). The conduction velocity (12.5 m/sec) was the same for both the HP and RF. Characteristics of neuronal organization of hypothalamo--cortical and reticulo--cortical systems of integration are discussed.

Forty-two male rats received one-stage or sequential unilateral (30 days between sides) lesions of the posterior hypothalamus and were tested 1, 3 and 5 weeks later on a swimming task and in the open field. Subjects with serial lesions were comparable to sham-operated rats in swimming ability at each observation point. Rats with one-stage lesions, in contrast, showed pronounced swimming deficits (time under water, body angle, hindlimb kicks/sec) at each test session, although some improvement was noted over time. With respect to open field activity, subjects with serial lesions did not demonstrate significant recovery until the third postoperative week, while rats with one-stage lesions were impaired at each test session. These data show that serial lesions of the posterior hypothalamus may be associated with more rapid recovery of function than one-stage lesions, but that the time course for such recovery may vary with the specific ability being evaluated.

Five experiments were conducted to determine the effects of hippocampal damage on timing and the memory for temporal events. In Experiments 1-3, rats were trained to discriminate between auditory signals that differed in both duration (2 or 8 s) and rate (2 or 16 cycles/s). Half of the rats were trained to discriminate duration, and half were trained to discriminate rate. After rats acquired the relevant discrimination, signals with intermediate durations and rates were presented to obtain psychophysical functions that related signal duration and/or rate to response choice. Rats then received either lesions of the fimbria-fornix or control operations. Postoperatively, the accuracy of duration and rate discriminations as measured by the difference limen (DL) was unaffected by the lesion, but the point of subjective equality (PSE) was shifted to a shorter duration and a slower rate by the lesion in Experiment 1. Both rats with lesions and rats with control operations showed cross-modal transfer of duration and rate from the auditory signals used in training to visual signals used in testing in Experiment 2. A 5-s delay was imposed between the end of a signal and the opportunity to respond in Experiment 3. The delay served as a retention interval for the rats trained in the rate discrimination, and the rats with fimbria-fornix lesions were selectively impaired by the addition of the delay as measured by an increase in the DL. The delay did not serve as a retention interval for rats trained in the duration discrimination because they were able to continue timing through the delay. A peak procedure was employed in Experiment 4. The maximum response rate of control rats was approximately at the time of scheduled reinforcement (20 s), but the maximum response rate of rats with fimbria-fornix lesions was reliably earlier than the time of scheduled reinforcement. When a 5-s gap was imposed in the signal, control rats summed the signal durations before and after the gap, whereas rats with fimbria-fornix lesions showed no retention of the signal duration prior to the gap. Experiment 5 continued the testing of the rats used in Experiments 1-4 and showed that rats with lesions had an impairment in a test of spatial working memory in an eight-arm radial maze. Taken together, these results demonstrate that a fimbria-fornix lesion interferes with temporal and spatial working memory, reduces the remembered time of reinforcement stored in reference memory, and has no effect on the animal's sensitivity to stimulus duration.

A modified stereotaxic surgical and implantation technique for animal EEG studies in rabbits is described. The use of a stereotaxic "socklet unit" with a minimum of operational equipment, high accuracy, simple handling, and good tissue compatibility permits the repetition of EEG studies in the same animal with a large number of electrodes and over a period of several months. For example for this technique an experimental arrangement for recording visually evoked potentials is described. The importance of a careful selection of the experimental animals, of maintaining constant test conditions, and of the selecting of test parameters as a prerequisite for assessing induced alterations is emphasized and discussed.

A case of hypothalamic hamartoma with precocious puberty is presented and the literature of reported cases is reviewed. An 8-year-old boy was admitted to our hospital because of precocious puberty and mental retardation. His genital development was Tanner's stage 4 and pubic hair was Tanner's stage 3. Bone age was 11 years. Plain CT showed an isodense mass in the suprasellar cistern which was not enhanced following contrast administration. Metrizamide CT cisternography showed a filling defect in the suprasellar cistern. Endocrinological evaluation revealed high levels of serum luteinizing hormone (LH) and testosterone with a marked response of LH to LH-RH injection. A left frontotemporal craniotomy was performed and the tumor was partially removed. The tumor was gray, firm and well-circumscribed with poor vascularity. Postoperatively, a right oculomotor palsy and transient diabetes insipidus developed. He was discharged ambulatory one month later. Serum LH and testosterone returned to normal and the response of LH to LH-RH injection became normal. Hamartoma was diagnosed on histological examination. Electron micrographic study showed numerous dense granules with approximately 0.1 mu in diameter, in which Judge proved LH-RH by immunofluorescent study in 1977. Our case supports the hypothesis that hypothalamic hamartoma may cause precocious puberty by autonomous secretion of LH-RH and we consider that neurosurgical treatment is recommended.

Reproduction in the Japanese quail (Coturnix coturnix japonica), as in many other bird species, is controlled by the daily photoperiod. The present experiments have investigated the role of the posterior or tuberal hypothalamus in the neuroendocrine regulation of this photoperiodic response. By using various types of small knives the tuberal hypothalamus was isolated surgically in male quail maintained on short daylengths. The birds were then transferred to long daily photoperiods and after fourteen days the effects on gonadotrophin secretion assessed by measuring testicular growth and the circulating level of luteinizing hormone (LH). Complete deafferentation of the tuberal hypothalamus blocked testicular growth and the plasma level of LH remained low. Partial cuts that severed the afferents entering from anterior and antero-lateral directions also blocked gonadotrophin secretion but cuts severing posterior connections were without effect. Following deafferentation of sexually mature males the LH level fell rapidly to reach a basal concentration within two days. The normal rise in LH that follows the castration of quail on long days was blocked by complete tuberal deafferentation. Electrolytic lesions were placed medially in the tuberal hypothalamus. Those in the postero-dorsal part of the infundibular nuclear complex (p.d.-i.n.c.) completely blocked testicular growth, while those in the ventral portion of the nucleus (v.-i.n.c.) only partially disrupted gonadotrophin secretion.

Chronic experiments in dogs revealed that administration of neurotensin (3 and 10 mkg in 1.5 mkl) into the caudate nucleus altered the parameters of conditioned and unconditioned food reflexes: shortened the latency by 31% and augmented the reflexes by 56%. The microapplication of neurotensin in the same dosage into the posterior hypothalamus increased the stomach secretory function induced by histamine administration. The caudate nucleus and the hypothalamus seem to contain cells which have the receptors for neurotensin and take part in the mechanisms of conditioning and central influences on the digestive system's organs.

The effect of ventromedial (VMN) or basolateral (LHA) hypothalamic electrical stimulation on glucose and hormone production was examined in conscious and anesthetized male rats. Barbiturate treatment alone led to large increases of corticosterone and smaller but significant increases of glucose, insulin, and glucagon. When hypothalamic stimulation was combined with anesthesia, interactions between the hypothalamic sites and the awake-anesthetized conditions were observed. This was most evident with LHA placements, as awake rats exhibited mild hypoglycemia and hypoglucagonemia in response to low-level (approximately 10 microA rms) current, but no effects on these values were seen with VMN electrodes. With barbiturate anesthesia, the same level of stimulation led to severe hyperglycemia in both VMN and LHA rats and a mild hyperglucagonemia in the LHA group. No consistent effects of stimulation on immunoreactive insulin or corticosterone were detected at either hypothalamic site or in any anesthesia condition. The present results point out the important role anesthetics may play in studies defining functional aspects of the hypothalamus. Furthermore, our inability to elicit consistent autonomic responses with electrical stimulation, when compared with the effectiveness of both metabolic agents and pharmacologic stimuli, suggests that the sites integrating autonomic function may be diffusely distributed over the basal diencephalon.

Acute experiments were conducted on adult cats. Injection of insulin microdose (0.025 U/kg with 0.025 ml of saline) into the posterior hypothalamic nucleus caused an increase in the blood sugar level 10 and 70 min after the injection. Changes of the blood sugar level correlated with the EEG activation of the posterior hypothalamic nucleus in response to the insulin injection, spreading to the lateral hypothalamus. However, hormonal stimulation of the posterior hypothalamic nucleus against the background of bilateral coagulation of the lateral hypothalamus produced no increase in the blood sugar level in 10 min. This is indicative of the participation of the lateral hypothalamus in the realization of hyperglycemic reactions in response to the insulin injection into the posterior hypothalamic nucleus.

In the present study, the cytoarchitectonic structure of the nuclei of the mamillary body has been studied on 4 age groups of Merino sheep and the following has been found: There is a significant intraspecific variability in the construction of mamillary body. Some of the animals studied have odd others paired mamillary bodies. Variability has been stated in the formation of the medial mamillary nucleus. The topographical relation of the mamillary nuclei to other hypothalamic structures during postnatal development did not change. Only the rostro-caudal length of the nuclei could be examined as changed. The quantity of Nissl substance increased in the cells of both mamillary nuclei studied which is related to maturation of the animals. Increased amounts of glial cells were observed during the postnatal period.

Wheat germ agglutinin (WGA) in a slow-release polyacrylamide gel pellet was implanted in the medulla or spinal cord of the rat. Large numbers of retrogradely labeled cells were visualized by immunocytochemical procedures in specific nuclei of the forebrain mainly ipsilateral to the implant site following implants as far caudal as the sacral segments of the spinal cord. Total average number of labeled forebrain cells (three brains per category; 100 micron per 150 micron of brain tissue were examined microscopically): medulla, 2,115; cervical, 1,878; lumbar, 1,017; sacral, 385. After WGA-gel implants in the medulla or cervical cord the majority of retrogradely labeled neurons were seen in the lateral hypothalamic area, the zona incerta, and in subdivisions of the paraventricular nucleus. A continuum of labeled cells extended from the caudal part of the paraventricular nucleus into the posterior hypothalamus and into the central gray of the midbrain. Labeled cells were also seen in the medial basal hypothalamus and the rostral part of the bed nucleus of the stria terminalis. A few labeled cells were observed in the medial and lateral preoptic areas, the rostral part of the paraventricular nucleus, and in the arcuate nucleus. Following WGA-gel implants in the lumbar or sacral cord many retrogradely labeled cells were observed mainly in the paraventricular nucleus, the lateral hypothalamus, zona incerta, medial basal hypothalamus, and posterior hypothalamic area. The continuum of labeled cells described above was also seen following these implants. Our data indicate that the lateral hypothalamus and zona incerta, as well as specific parts of the paraventricular nucleus, are major loci of neurons which project directly to the medulla and spinal cord of the rat. The consistency with which labeled cells were localized across all brains examined within categories of implant sites and the large numbers of labeled cells counted within these areas appeared to verify the sensitivity of our retrograde tracing method. Therefore, we interpret the paucity or absence of labeled cells in particular brain regions to indicate that cells of these regions do not project to the medulla or spinal cord.

Chemical sensitivity to acetylcholine (Ach) and angiotensin II (A-II) of the neurons from the perifornical area of the posterio-lateral hypothalamus was studied in rats after 30 days of alcoholization with 20% ethanol solution instead of water. The artificially formed alcohol motivation was accompanied by profound changes of the neuronal sensitivity to Ach and A-II. The latter changes were manifested by specific reorganization of time--interval patterns of neuronal activity. Changes of sensitivity to Ach were less obvious and involved prevalence of 30--40 msec intervals in the unit activity. These changes of chemical sensitivity to peptides and classical neurotransmitters may reflect profound changes in the system of intramembranous and intracellular cyclic nucleotides during alcoholization.

The posterior (caudal) hypothalamus of the lizard, Lacerta sicula R. was investigated by means of Golgi methods. The periventricular grey is formed mainly by isodendritic bipolar and multipolar neurons, while in the lateral hypothalamus a more stellate form of neuronal elements is encountered. CSF-contacting neurons are restricted to the tuberal area and to the paraventricular organ. In the latter area they are highly differentiated and endowed with laterally branched processes. The overall pattern of the lizard hypothalamus (organization of neuropil, lateral nuclei, appearance of cell clusters, morphology of the neuronal elements) represents an intermediate stage in the phylogenetic development of the hypothalamus, being more advanced than the amphibian stage.

Dopamine-beta-hydroxylase (DBH) activity was determined in the locus coeruleus, anterior hypothalamus and posterior hypothalamus of cold-stressed rats. In the acute cold stress, rats were exposed to an ambient temperature of 5 degrees C in a cold room for 5-20 min. In the chronic cold stress, rats were exposed to the same cold temperature for 4 hr once every day in the morning for periods ranging from 1 to 3 weeks. There was decreased DBH activity in the locus coeruleus following acute cold stress and increased activity in both the locus coeruleus and the anterior hypothalamus following the chronically repeated cold stress.

Electric stimulation of the midbrain reticular formation, of the anterior and posterior hypothalamus of unrestrained cats entailed local raise of cerebral temperature, increase in the local blood flow, and various changes of the central arterial and venous pressure. The stimulation parameters were lower than thresholds for motor responses. The threshold and suprathreshold stimulation of the stem structures led in 60% of cases to diminishing of the local cerebral blood flow together with the pressor shifts in arterial pressure and the raise of local cerebral temperature. The diminishing of the cerebral blood flow contrdictory to increasing demands of the brain tissue for energy supply, could be accounted for by the generalized excitation of the sympatho-adrenal system and indicated inadequacy of the electric brain stimulation when studying hemodynamic components of the emotional-behavioral responses.

Stimulation of somatic nerves evoked in the cat L2--L3 white rami a late two--wave response. High frequency stimulation of the hypothalamus induced an increase of the blood pressure, facilitation of the first component and suppression of the second component of the late response. The components of the early response were insignificantly affected by the stimulation. The paired stimuli technique revealed interaction of descending and peripheral afferent excitation of sympathetic preganglionic neurons. The role of baroreceptor and hypothalamic excitation in spinal sympathetic mechanisms is discussed.

Unit activity of posterior, tuberal and anterior parts of the hypothalamus was studied during stimulation of the pelvic nerve in anesthetized and immobilized cats. Comparative analysis showed that neurons of the posterior hypothalamus were more responsive (89.6%) and had a shorter mean latency (33.3 +/- 2.4 msec) than neurons of more rostral parts of the hypothalamus. The focus of maximal pelvic-induced unit activity seems to be located in the posterior hypothalamus. The unit responses of the posterior hypothalamus evoked by pelvic nerve stimulation had long recovery cycles and were suppressed at low frequencies of stimulation. These findings suggest a polysynaptic organization of pelvic afferent projection in the hypothalamus. A high degree of convergence of the visceral and somatic afferent signals onto single neurons was found during stimulation of pelvic and sciatic nerves. The functional role of neurons of integrative types is discussed.

The influence of the sympathetic nervous system and the posterior hypothalamus on the rate of conditioning and the magnitude of conditioned reflexes was studied on dogs by motor defensive method. Extirpation of the superior cervical sympathetic ganglion reduced the conditioned reflex magnitude, delayed the elaboration of positive reflexes facilitating the formation of the inhibitory process. Stimulation of the posterior hypothalamus with electrical current of medium strength (50 mcA) promoted the enhancement of positive conditioned reflexes, and while not substantially affecting the rate of their formation, facilitated elaboration of internal inhibition.

Neuronal responses of different hypothalamic nuclei to frontobasal cerebral cortex (proreal, posterior orbital, basal and temporal regions) were studied in acute experiments on cats narcotized by membutal mixed with chloraloze. Neurons which could be activated antidromically during stimulation of another region were recorded. On the basis of their response a number of neuronal chains (circles) functioning in forebrain was distinguished. The first chain is orbital gyrus--preoptical zone--proreal gyrus. The second chain has the same cortical components as the first one, but switching over in the hypothalamus takes place in the region of mamillary bodies. The third chain is basal temporal cortex--lateral hypothalamus--prefrontal cortex.

The behaviour in the form of tappings with forepaws after electric stimulation of 5 s duration was studied in rabbits with electrodes chronically implanted in the diencephalon. This species-specific behaviour is described following stimulations of threshold strength and gradually increasing to three thresholds. It has been found out that frontal, medial and posterior nuclei of the hypothalamus possess the greatest ability for eliciting such behaviour. During stimulation motor signs of avoidance behaviour dominate. The tappings are observed only in the post-stimulation period. Stimulation with two thresholds strength elicits the greatest number of tappings. There is a reliable relation between the number of tappings and total duration of the reaction. The possibility of reinforcing properties of the tappings based on emotional fear reaction to stimulation is discussed.

LRF producing neurons were characterized in the squirrel-monkey (Saimiri sciurus) and Cebus apella monkey, by means of a rabbit antiserum against unconjugated synthetic LRF, previously adsorbed on polyvinylpyrrolidone. These neurons, which vary in number according to the species and physiological or experimental conditions, are mainly concentrated in the mediobasal hypothalamic area (infundibular and premammillary nuclei in particular) and the vascular organ of the lamina terminalis. The neurons of the first group give rise to axons which terminate round the capillaries of the primary portal plexus of the infundibulum. Those of the second group give rise to axons which terminate round the capillaries of the primary and secondary plexuses of the vascular organ of the lamina terminalis and in the ependyma which lines its ventricular side. Some specifically immunoreactive axons apparently run towards the telencephalon (passing in front of and behind the anterior white commissure), the mescencephalon and the epithalamus. Some of the latter give rise to terminal ramifications in the area of the median habenular nucleus.

Under chloralose narcosis, employing the evoked potentials method, studies have been made on the projection of the posterior hypothalamus to the frontal cortex in 1-30 days old kittens. The animals were divided into 3 age groups: 1-9, 10-19 and 20-30 days. Studies of the EPs in different points of pericruciate zone showed that these potentials are observed in all the investigated points from the first days of postnatal life. The latent period of responses in the youngest animals varied from 40 to 80 ms, exhibiting insignificant fluctuations depending on the cortical zone investigated. From the very beginning of postnatal life, in the same cortical zone the EPs may be observed in response to stimulation of the ischiadic nerve as well. In older animals, the latent period of the EPs decreases in all the points, the decrease being most significant near the crucial fissure. To the 30th day of postnatal life, the EPs in this zone with respect to their latency and configuration became quite similar to those in adult animals. In the third age period, the latency varies from 6 to 10 ms in the focus of maximum activity; with the removal of the recording electrode from this zone the latent period of the hypothalamo-cortical responses increases up to 30-40 ms. Overlapping of the EPs in response to central and peripheral stimulation was observed at all age periods.

Using a single unit recording technique in freely moving Cats, we have demonstrated the presence of two groups of neurons in the ventrolateral part of the caudal hypothalamus. One is characterized by a tonic discharge during waking and paradoxical sleep, the other is highly selective to the waking state. This group of neurons showed a slow tonic and regular discharge during wakefulness, a significant decrease in firing rate during stage I slow-wave sleep and a complete cessation of firing during stage II slow-wave sleep and subsequent paradoxical sleep.

Bombesin was microinjected into the lateral ventricle, preoptic area, and posterior hypothalamus of cold-exposed rats. Preoptic and ventricular injections produced dose-dependent depressions in metabolism with subsequent hypothermia. Furthermore, injections into the preoptic area elicited greater depressions in body temperature than equivalent doses injected into the lateral ventricle. No changes in oxygen consumption or body temperature resulted from posterior hypothalamic administration of the peptide. The data suggest that the preoptic area may be an important site of action for bombesin and that bombesin-induced hypothermia is mediated, at least in part, by a reduction in metabolic rate.

It was demonstrated by electroencephalography that a single injection of 0.125 mg/kg reserpine reduced the activating and augmented the inhibitory mechanisms in the rabbit brain. A possible correlation between the neurophysiological structure of "reserpine depression" and the clinical forms of the depressive syndrome is discussed.

SUMMARY 1. The effects of methoxyverapamil or hydralazine on pressor responses to posterior hypothalamic stimulation and injected pressor agents were studied in normotensive male Wistar rats. 2. Methoxyverapamil inhibited both phases of pressor response to hypothalamic stimulation and pressor responses to injected noradrenaline or angiotensin II. 3. Hydralazine inhibited the secondary phase (due to adrenomedullary catecholamine) and not the primary phase (due to increased sympathetic vasomotor activity) of pressor response to hypothalamic stimulation. However, it inhibited the pressor responses to exogenous noradrenaline or angiotensin II. 4. The data indicate that hydralazine is ineffective in inhibiting the pressor response elicited by noradrenaline endogenously released at the sympathetic nerve endings.

Redundant afferentation from reflexogenic zones of the lung and skeletal muscles alters effects of electric stimulation of the midbrain reticular formation and posterior hypothalamic nucleus in the cat due to readjustment of the cortico--subcortical interrelationships and to an increase in the excitability of the brain structures. The data suggest that the functional activity of the vasomotor center depends on the character of afferentation from different reflexogenic zones.

Three goats were chronically implanted with thermodes to alter the temperatures of the anterior and posterior hypothalamus independently of each other. At an air temperature of +14 degrees C the anterior hypothalamus was cooled with different intensities, while the posterior hypothalamus was simultaneously either warmed (39 degrees C) or cooled (29 degrees C). In both conditions cooling anterior hypothalamus increased heat production. However, the increase was smaller, when the posterior hypothalamus was cooled. The inhibiting effect was most pronounced during the first parts of the periods and diminished with time. Nevertheless, in a separate series of experiments, the effects of posterior hypothalamic cooling were found to persist over periods of 3 h. At an air temperature of +3 degrees C the posterior hypothalamus temperature was altered between 28 and 42 degrees C, while anterior hypothalamus temperature was kept close to its control level. Shivering and heat production decreased with cooling and increased with warming of the posterior hypothalamus. The results suggest that those neurons which reside in the posterior hypothalamus and mediate shivering, are sensitive to temperature. Thermosensitivity of these allegedly integrative neurons affects shivering and heat production in a way inverse to the thermosensitivity of the temperature sensing neurons in the anterior hypothalamus.

A 5-sec electrical shock applied to the rabbit medial hypothalamus induced series of stereotype behavioral responses in the form of synergic blows with hindlimbs. Adaptation to the stimulation occurred in repetition of the stimuli every 1.5-2.0 min. Pharmacological experiments revealed that intraperitoneal administration of cortisol (10 and 20 mg/kg) enhanced the stimulation-induced behavioral response and shortened its latency.

Six Rhesus monkeys were trained in a running recognition task with visual-spatial configurations as the stimuli to be remembered. Following pre-operative training half the monkeys were subjected to fornix transection and half to a control operation. Fornix transection produced a severe and apparently permanent impairment. These results add to the evidence that fornix transection produces defects in memory which cannot be explained as secondary consequences of impairments of perception.

Horseradish peroxidase was injected in the corticotropic area of the pigeon's hypothalamus (n. posterior medialis hypothalami) and reacted with 3,3′-diaminobenzidine and hydrogen peroxide in brain sections. Cells labelled with peroxidase reaction product were found in hippocampal and medial septal regions. One possible function for such fibre connections might be to convey some limbic inhibitory influences to the corticotropic neuronal population of the hypothalamus.

The cardiovascular effects of electrical stimulation of the posterior hypothalamus, intravenous administration of norepinephrine (NE), and direct sympathetic nerve stimulation (SNS) were compared in spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY) given captopril (osmotic minipump, 1.25 micrograms/h icv) or vehicle for 4 wk beginning at age 7 wk. Mean arterial pressure (MAP) and renal and mesenteric flows (pulsed Doppler flow probes) were monitored in anesthetized rats. Following chronic administration of captopril the MAP was 141 +/- 4 mmHg in SHR receiving captopril and 183 +/- 6 mmHg in SHR receiving vehicle. Posterior hypothalamic stimulation, intravenous NE, and SNS resulted in lesser increases in MAP and renal and mesenteric vascular resistances in SHR treated with captopril. Response curves were shifted to the right, and the initial slopes and rate of change of slopes of the curves were less in captopril-treated SHR than vehicle-treated rats. The decrease in sensitivity to posterior hypothalamic stimulation was greater than the decrease in response to NE or SNS. The decrease in vascular reactivity in captopril-treated SHR was not due to increased sensitivity of the baroreflex for control of vascular resistance nor to a decrease in arterial pressure per se. WKY treated with captopril also showed lesser increases in MAP and renal and mesenteric vascular resistances in response to posterior hypothalamic stimulation, intravenous NE, and SNS. The depressor effects of intracerebroventricular captopril in SHR may be due, in part, to an attenuation in sympathetic vasoconstrictor tone. This attenuation involves both a decrease in vascular smooth muscle responsiveness to NE as well as a decrease in central stimulation of sympathetic outflow.