Febrile effects of polyriboinosinic acid: polyribocytidylic acid and interferon: relationship to somatostatin in rat hypothalamus

The changes in thermoregulatory effectors produced by an injection of polyriboinosinic acid: polyribocytidylic acid (Poly I:C) or interferon were assessed and compared in control rats, in rats with hypothalamic somatostatin (SS) receptor blockade and in rats with hypothalamic SS depletion. Intrahypothalamic (i.h., 0.05–0.50 μg) or intraperitoneal (i.p., 100–600 μg) administration of Poly I:C caused a dose-related rise in colon temperature in control rats at all ambient temperatures (T_a) studied. A Poly I:C-induced fever was produced by increased metabolism at a T_a of 8 °C, whereas at 30 °C, it was caused by cutaneous vasoconstriction. At a T_a of 22 °C, the fever was caused by increased metabolism and cutaneous vasoconstriction. On the other hand, i.h. administration of SS-14 antagonist (0.1–0.5 ng) caused a dose-related fall in colon temperature at T_a of 8 °C or 22 °C. At a T_a of 8 °C, the hypothermia was caused by decreased metabolism, whereas at 22 °C, it was caused by decreased metabolism and cutaneous vasodilation. At a T_a of 30 °C, the thermoregulatory effectors were not affected by SS-14 antagonist treatment. Furthermore, the fever induced by Poly I:C or interferon was significantly reduced by pretreatment of rats with an i.p. dose of cysteamine (30 mg. kg⁻¹) or an i.h. dose of SS-14 antagonist (0.1 ng). The results indicate that a somatostatinergic pathway in rat hypothalamus may mediate the fever induced by interferon or its inducer Poly I:C.     

Behavioral patterns proceeding from liver thermoreceptors

Subdiaphragmatic denervated, liver heated rats eat as much and as long as subdiaphragmatic denervated, non-heated rats. This points to vagus and/or splanchnic nerve afferentation from hepatic thermoreceptors. Left abdomen heated rats eat and drink as much as left abdomen non-heated rats. Since however they show some different behavior patterns, the intervention of other nerve fibers other than vagal and/or splanchnic fibers should be acknowledged in order to account for the different behavior pattern.     

大鼠下丘脑一氧化氮合酶（NOS）阳性神经元的分布

观察大鼠下丘脑各核团NOS阳性神经元的分布。采用还原型尼克酰胺腺嘌呤二核苷酸脱氢酶（NADPH－d）法，结果显示，大量NOS阳性神经元见于下丘脑外侧区、视上核（SO）和室旁核（Pa）；出现较多NOS阳性神经元的部位是视前大细胞核，见到少量NOS阳性神经元的部位是室周核、视前内侧区、视前外侧区和下丘脑前区。结论：NOS阳性神经元分布于下丘脑的许多核团。     

Androgen receptor blockade in the MPOA or VMN: effects on male sociosexual behaviors

Previously, our laboratory has shown that androgen receptors in the medial preoptic area (MPOA) and ventromedial nucleus (VMN) are necessary for copulation in male rats. The present study examined whether these receptors are required for other sociosexual behaviors. In Experiment 1, different regions of the VMN were implanted with the antiandrogen hydroxyflutamide (OHF). We found that implants located in anterodorsal portions of the VMN were more effective at inhibiting the restoration of copulation than implants in the posteroventral VMN. In Experiment 2, a second set of male rats was pretested for copulation and other sociosexual behaviors and was castrated. Experimental animals then received Silastic capsules filled with testosterone (T) plus intracranial (IC) implants filled with OHF to selectively block androgen receptors in either the MPOA or VMN. We found that androgen receptor blockade in the MPOA inhibited the restoration of copulation but had no effect on other sociosexual behaviors. OHF directed at the VMN inhibited the restoration of copulation and 50-kHz vocalizations but had no effect on scent marking. Two tests were used to assay sexual motivation: partner preference and conditioned place preference (CPP). Both methods revealed impairments in sexual motivation in the VMN group but not in animals receiving OHF in the MPOA. Taken together, these data suggest that androgen receptors in the MPOA are essential for copulatory performance, while androgen receptors in the VMN are important for copulation, sexual motivation, and androgen-dependent vocalizations.     

Electrical self-stimulation of single and multiple loci: long term observations

Rats with chronic hypothalamic electrodes were allowed continuous access to self-stimulation, food and water in a 3 lever chamber. A prolonged burst of self-stimulation, with little food and water intake, was followed by bursts of activity on all 3 levers. A 12 hr light-dark cycle imposed a diurnal periodicity on all behaviors except in animals self-stimulating at the highest daily rates where self-stimulation was equal in dark and light. Under constant light conditions there was a 30 min daily shift in the peak periodicity of all behaviors. Increasing the current by 10 μA led to another continuous self-stimulation session for one day, with a subsequent decline and stabilization after three days. Reduction of the current to its original setting abolished self-stimulation for one day, but within 5 days rates returned to control values. Animals with electrodes in the septal, anterior and posterior hypothalamic areas allowed continuous access to self-stimulation on all 3 electrodes displayed similar behavior in that after a long initial self-stimulation session alternating on all 3 electrodes, periodic bursts of activity occurred on all three electrodes. The diurnal periodicity of self-stimulation seemed to be determined by the current intensity. The similarity of self-stimulation to normal drive mechanisms is discussed.     

Hypothalamic obesity following knife cuts that minimize arterial damage

Parasagittal knife cuts that separate the medial hypothalamus from the lateral hypothalamus produce obesity. It has been assumed that the obesity results from the cutting of axons. However, these cuts also appear to sever arteries. The present study demonstrates that the severing of arteries is not necessary for the production of obesity. Knife cuts were placed at an angle so as to separate the medial hypothalamus from the lateral hypothalamus with minimal damage to arteries. These rats overate and became obese just as rapidly as rats with parasagittal cuts.     

In vivo release of neurotransmitters in the medial basal hypothalamus of the monkey

Summary In vivo release rates of norepinephrine (NE), epinephrine (E), dopamine (DA), gammaaminobutyric acid (GABA), glutamate (GLU) and beta-endorphin (E) in the medial basal hypothalamus (MBH) of unanaesthetized female macaca fascicularis monkey, and the effects thereon of estrogen (E2) treatment, have been estimated using pushpull perfusion methodology. DA, NE, E, GABA, GLU and E were all detectable in 30 min perfusate fractions. No direct correlation between their release rates and those of LH and PRL could be observed. E2 induced an initial decrease, then an increase, in LH and PRL secretion, and concomitant changes in the release patterns of DA, NE, E. GABA and GLU were apparent. This study demonstrates that in vivo push-pull perfusion methodology may be applied to the unanaesthetized monkey, and when combined with venous catheterization for serial blood sampling may prove to be a powerful tool in the investigation of the central molecular events governing neuroendocrine functions.     

Disruption of diurnal feeding and weight gain cycles in weanling rats by ventromedial and dorsomedial hypothalamic lesions

At the age of 28 days, male Sprague-Dawley rats received bilateral electrolytic lesions in the ventromedial (VMN) and dorsomedial (DMN) hypothalamic nuclei, repectively. Sham-operated rats served as controls. Food intake and body weight gains were measured for 13 days at the beginning of the light period (0800–2000 hr) and prior to the start of the dark period (2000-0800 hr). Both types of hypothalamic lesions caused a disruption of the naturally occurring diurnal feeding and weight gaining cycles. In accordance with previous data, the VMN rats remained normophagic and made normal weight gains while DMN animals were hypophagic and gained weight subnormally; linear growth was reduced in both types of lesioned animals, but only the VMN rats became obese. The data suggest the existence in the medial hypothalamus of an area that is involved in feeding and weight gaining cycles. From the standpoint of overall-caloric intake, this area consists of two types of neuronal assemblies that differ fuctionally as profoundly as they are anatomically separate.     

Hypothalamic knife cuts dissociate maternal behaviors, sexual receptivity, and estrous cyclicity in female hamsters

Female hamsters were tested for their response to pups as virgins, then received sagittal cuts either lateral to the medial preoptic area-medial anterior hypothalamus (anterior cuts) or lateral to the medial anterior hypothalamus-ventromedial nucleus (posterior cuts). Postoperatively females were tested: (a) as virgins, for changes in pup retrieval and cannibalism, (b) for mating behavior, (c) for maternal care and cannibalism of their own pups, and (d) for object hoarding. Anterior cuts converted retrieving virgins to cannibalistic ones and reduced nest builing. All females with anterior cuts cannibalized their litters within a few days of parturition. Half of these females did retrieve pups in home cage tests during the first 3 days postpartum. However, unlike controls, when tested in a neutral arena 5–6 weeks later, no pup retrieval was seen, although most would hoard objects. In contrast, posterior cuts reduced pup retrieval and cannibalism in virgins, and disrupted object hoarding. These cuts did not reduce postpartum pup retrieval, but did reduce postpartum cannibalism. Anterior cuts did not reduce sexual receptivity; posterior cuts reduced sexual receptivity without eliminating ovulation. Anterior cuts are interpreted as having a somewhat selective effect of reducing maternal responsiveness by cutting the lateral connections of neurons in the medial anterior hypothalamus and adjacent medial preoptic area, while posterior cuts disrupt sexual receptivity by cutting lateral connections of the ventromedial hypothalamus which travel in the region of the supraoptic commissures     

Body weight regulation in ground squirrels and hypothalamically lesioned rats: slow and sudden set point changes

Golden-mantled ground squirrels. Citellus lateralis, have a near annual cycle in body weight. In the present experiments their weights were temporarily forced off the usual levels either by food deprivation during a phase of weight gain or by offering extra palatable food during a phase of weight loss. When these treatments ceased the weights returned to levels appropriate for that time of year rather than to pretreatment values. Therefore the cycle of body weight in uniform and ad lib conditions reflects an underlying cycle in slowly climbing or sliding set points for body weight. In contrast to fattening ground squirrels, lesioned rats in the dynamic phase of hypothalamic hyperphagia did not compensate well for weight losses incurred during food deprivation. Weight gain during the dynamic phase appears to be roughly proportional to the discrepancy between actual and set weights, the latter being suddenly much elevated by the lesion.