Early maternal separation increases symptoms of activity-based anorexia in male and female rats.

Running activates the hypothalamic–pituitary–adrenal (HPA) axis, increasing the release of stress hormones known to exert anorexic effects. HPA axis reactivity is strongly influenced by early postnatal manipulations, including removal of pups from the dam for short (handling) or prolonged (maternal separation) durations during the preweaning period. The authors examined the effects of handling and maternal separation on food intake, body weight loss, and running rates of young adult male and female rats in the activity-based anorexia (ABA) paradigm. Postnatal treatment did not affect adaptation to a 1-hr restricted feeding schedule before the introduction of wheel running. During the ABA paradigm, maternally separated animals lost weight faster, ate less, ran more, and required fewer days to reach removal criterion compared with handled rats. Females were particularly vulnerable. These findings indicate that early postnatal treatment and sex influence ABA. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Running and addiction: Precipitated withdrawal in a rat model of activity-based anorexia.

Exercise improves cardiovascular health, strengthens muscles and bones, stimulates neuroplasticity, and promotes feelings of well-being. However, when taken to extremes, exercise can develop into an addictive-like behavior. To assess the addictive potential of exercise, withdrawal symptoms following injections of 1.0 mg/kg naloxone were compared in active and inactive male and female rats. Active and inactive rats were given food for 1 hr or 24 hr/day. Additionally, a group of inactive rats was pair-fed the amount of food consumed on the previous day by food-restricted active rats. Rats fed for 1 hr/day decreased food intake and lost weight. Additionally, food-restricted active rats increased wheel running. There was a direct relationship between the intensity of running and the severity of withdrawal symptoms. Active food-restricted rats displayed the most withdrawal symptoms, followed by active rats given 24-hr access to food. Only minimal withdrawal symptoms were observed in inactive rats. These findings support the hypothesis that exercise-induced increases in endogenous opioid peptides act in a manner similar to chronic administration of opiate drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preoptic rather than mediobasal hypothalamic amino acid neurotransmitter release regulates GnRH secretion during the estrogen-induced LH surge in the ovariectomized rat

Inhibitory and excitatory amino acid neurotransmitters have been suggested to participate in the feedback actions of estradiol (E2) on LH secretion. In the rat estrogen-receptive neurons have been demonstrated in the preoptic/anterior hypothalamic area (POA) and mediobasal hypothalamus/median eminence (MBH) and many of these neurons utilize gamma-aminobutyric acid (GABA) as neurotransmitter. The actions of excitatory amino acids (EAA) differ in ovariectomized (ovx) and ovx E2-substituted rats indicating that EAAs also participate in the positive feedback action of E2 on LH release. However, little information is available as to whether in vivo these transmitters exert their effects in the POA, where most of the GnRH perikarya are located, or in the MBH, i.e. at the nerve terminals. Therefore we conducted push pull cannula perfusions to compare the release rates of GABA, aspartate (ASP) and glutamate (GLU) in the MBH and POA. A subcutaneous implant of a silastic tube containing E2 resulted in LH surges in the afternoon of all treated animals. Prior to and during this LH surge the MBH release rates of neither GABA nor ASP nor GLU were significantly altered. In contrast, a conspicuous drop in preoptic GABA release occurred prior to and during the time of estrogen-induced LH surges and this was accompanied by enhanced preoptic secretion of ASP and GLU. In conclusion, we present the first data about amino acid release in the MBH during the E2-induced LH surge. Since only in the POA the LH surge is associated with changes in amino acid release, it appears that both inhibitory and excitatory amino acids act at the level of the GnRH cell bodies and/or dendrites and not on GnRH nerve terminals to mediate the feedback mechanism of E2 on LH release.     

Ventromedial hypothalamic hyperphagia in the hypophysectomized weanling rat.

Previous findings that ventromedial hypothalamic (VMH) lesions in weanling rats lead to obesity only after a delay of several weeks suggests either that the VMH is (a) undeveloped and not yet functioning; or (b) capable of functioning in weanlings, but inoperative for some reason. The present study demonstrates that 17 hypophysectomized weanling rats, which otherwise eat very little and grow at a markedly reduced rate, show hyperphagia with rapid onset following VMH lesions. Results support G. Kennedy's view that the presence of high levels of growth hormone in the weanling is responsible for VMH inactivity, either by eliminating the usual metabolic satiety signals and/or via a direct effect of the hormone on the VMH. Growth hormone involvement is suggested to account for the greater ease in producing hypothalamic hyperphagia in female than in male rats. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Looking to science rather than convention in adjusting IQ scores when death is at issue.

The progressive obsolescence of IQ test norms and associated score inflation (i.e., the Flynn effect) may have literal life and death significance in capital mental retardation determinations (i.e., Atkins hearings). Hagan, Drogin, and Guilmette (2008) asserted that IQ score corrections for the Flynn effect were inconsistent with a “standard of practice” they deduced from custom, convention, and authority. More accurately, this reflected a proposed practice guideline or recommendation for practice, rather than a standard of practice. Whether a proposed guideline or recommendation for practice, these are better informed by an analysis of the available science than accepted convention. The authors reviewed research findings regarding the occurrence of the Flynn effect in the “zone of ambiguity” (IQ = 71–80), and proposed a best practice recommendation for discussing and reporting Flynn effect correction of IQ scores in capital mental retardation determinations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental increases and decreases in solutions of conditional syllogism problems.

281 students (Grades 8, 10, and 12 and college sophomores) were given a 16-item conditional reasoning test which contained 1 each of the arguments generated by the orthogonal arrangement of (a) stating the major premise in each of the 4 combinations of positive and negative instances of the antecedent or consequent, and (b) stating the 2nd premise in each of the 4 cases of affirming or denying the antecedent or consequent. Analysis of results indicated little development after Grade 8 for the easy affirm-antecedent problems, substantial increase on the deny-antecedent and affirm-consequent problems from below chance at the 8th grade to mediocre performance levels for college sophomores and a surprising monotonic decrease in performance on the deny-consequent problems from Grade 8 to the college sophomore year. An error analysis was performed which revealed that the poor performance of younger Ss and even adults may be partially an artifact of students misinterpreting the "if, then" conditional statements as biconditional ("if and only if, then") propositions. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Refractory period of hypothalamic thirst pathway in the rat.

Estimated the refractory period of the hypothalamic thirst pathway in 4 male albino rats by the double-pulse stimulating technique and by behavioral measurements of the response elicited by such stimulation. Results suggest a discrete neural substrate involved in stimulus-bound drinking with a refractory period of .9 msec. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hydroxide rather than histidine is coordinated to the heme in five-coordinate ferric Scapharca inaequivalvis hemoglobin

The ferric form of the homodimeric Scapharca hemoglobin undergoes a pH-dependent spin transition of the heme iron. The transition can also be modulated by the presence of salt. From our earlier studies it was shown that three distinct species are populated in the pH range 6-9. At acidic pH, a low-spin six-coordinate structure predominates. At neutral and at alkaline pHs, in addition to a small population of a hexacoordinate high-spin species, a pentacoordinate species is significantly populated. Isotope difference spectra clearly show that the heme group in the latter species has a hydroxide ligand and thereby is not coordinated by the proximal histidine. The stretching frequency of the Fe-OH moiety is 578 cm-1 and shifts to 553 cm-1 in H218O, as would be expected for a Fe-OH unit. On the other hand, the ferrous form of the protein shows substantial stability over a wide pH range. These observations suggest that Scapharca hemoglobin has a unique heme structure that undergoes substantial redox-dependent rearrangements that stabilize the Fe-proximal histidine bond in the functional deoxy form of the protein but not in the ferric form.     

Dietary lead increases ethanol consumption in the rat.

When 36 male Sprague-Dawley rats fed either a diet containing 500 parts per million Pb (as lead acetate) or an unadulterated control diet for 50 days were offered a 15% ethanol (ETOH) solution in a nonchoice (1-bottle) test situation, Pb-diet Ss consumed greater amounts of the ETOH solution than did controls. In a subsequent choice (3-bottle, 2-fluid) test situation offering a nonpreferred ETOH solution or tap water as alternatives, Pb-diet Ss again ingested greater amounts of the ETOH solution. Findings are discussed in terms of possible Pb-induced increases in emotionality and the potential stress-reduction properties of ETOH. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Expression of renewal is dependent on the extinction-test interval rather than the acquisition-extinction interval.

A recent finding suggested that when extinction occurs shortly after acquisition, renewal of an extinguished fear response (fear-potentiated startle) to a light conditioned stimulus (CS) is diminished (Myers, Ressler, & Davis, 2006). The present study attempted to extend this finding using a white-noise CS and freezing as the behavioral measure of fear. In Experiments 1A and 1B, we observed renewal whether extinction occurred 10 min or 24 hr after acquisition. In contrast, renewal was not observed if test occurred 10 min after extinction (Experiment 2). Experiment 3 demonstrated that expression of extinction at the 10-min extinction-test interval was attenuated by a pretest subcutaneous injection of the γ-aminobutyric acid (GABA) inverse agonist FG7142. These findings suggest that renewal is influenced more by the extinction-test interval than the acquisition-extinction interval. Further, the failure to see renewal 10 min after extinction suggests that there is a separate context memory that undergoes a different consolidation function than the CS-no US memory formed during extinction. Finally, the expression of extinction appears to be GABA dependent regardless of the extinction-test interval or the test context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Endothelin-1 increases susceptibility of isolated rat hearts to ischemia/reperfusion injury by reducing coronary flow

Endothelin-1 (ET-1) is the most potent vasoconstrictor known to date, and it was proposed that this peptide plays a major role in myocardial ischemia/reperfusion injury. ET-1 could increase myocardial susceptibility to ischemia by two mechanisms: via coronary flow reduction and/or via direct, metabolic effects on the heart. In isolated, buffer-perfused rat hearts, function was measured with a left ventricular balloon, and energy metabolism (ATP, phosphocreatine, inorganic phosphate, intracellular pH) was estimated by 31NMR-spectroscopy. Under constant pressure perfusion, hearts were subjected to 15 min of control perfusion, 15 ("moderate injury") or 30 ("severe injury") min of global ischemia, followed by 30 min of reperfusion. Hearts were pre-treated with ET-1 (boluses of 0.04, 4, 40 of 400 pmol) 5 min prior to ischemia. In the control period, ET-1 reduced coronary flow, ventricular function, phosphocreatine and intracellular pH dose-dependently: during ischemia/reperfusion, coronary flow, functional recovery and high-energy phosphate metabolism were adversely affected by ET-1 in a dose-related manner. To study effects of ET-1 not related to coronary flow reduction, additional hearts were perfused under constant flow conditions (ET-1 0 or 400 pmol) during 15 min of control, 15 min of ischemia and 30 min of reperfusion. When coronary flow was held constant, functional and energetic parameters were similar for untreated and ET-1 treated hearts during the entire protocol, i.e. the adverse effects of ET-1 on function and energy metabolism during ischemia/reperfusion were completely abolished. In both constant pressure and constant flow protocols, 400 pmol ET-1 reduced the extent of ischemic intracellular acidosis. The authors conclude that ET-1 increases the susceptibility of isolated hearts to ischemia/reperfusion injury via reduction of coronary flow.     

Intraventricular neuropeptide Y decreases need-induced sodium appetite and increases pica in rats.

Neuropeptide Y (NPY) is a potent endogenous stimulator of food intake. In addition to stimulating increased food intake, when paired with a novel-flavored solution, NPY produces an aversion to that flavor. Hence, exogenous NPY elicits 2 seemingly opposing behaviors, increased feeding and the formation of a conditioned taste aversion. One interpretation of these data is that NPY produces some form of malaise or visceral illness. NPY's orexigenic and malaise-inducing properties were tested in rats with 2 measures sensitive to malaise, increased kaolin consumption (pica behavior) and failure to express need-induced sodium intake. Administration of NPY resulted in increased food intake, increased kaolin consumption, and decreased need-induced sodium intake. These data support the hypothesis that exogenous NPY has both orexigenic and malaise-inducing properties. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain transplants enhance rather than reduce the impairment of spatial memory and olfaction in bulbectomized rats.

The possibility to compensate the loss of olfactory and non-olfactory functions due to removal of the olfactory bulb by embryonal brain grafts was investigated in adult rats. Spatial working memory was examined in an 8-arm radial water maze task 6 weeks after bulbectomy. During 15 daily trials, performance gradually improved in bulbectomized controls (n?=?10) and in rats with olfactory bulb transplants (n?=?9), but did not attain that of intact controls (n?=?10). No improvement was observed in the rats with substantia nigra grafts (n?=?8). 11 wks after bulbectomy, the same rats were tested in the water tank navigation task. The performance improved during ten 12-trial sessions in bulbectomized rats less than in intact controls, but more than in the transplanted rats. The olfactory food retrieval test performed 14 wks after bulbectomy revealed almost full recovery of smell in bulbectomized rats, but not in the transplanted animals. It is concluded that the spatial memory deficit is probably due to bulbectomy-induced interference with septohippocampal function which is not alleviated, but rather enhanced by transplantation. Results suggest that the effect of brain grafting is not always beneficial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metabolic and endocrine aspects of the ventromedial hypothalamic syndrome in the rat.

Subjected 8 male Long-Evans hooded rats to parasagittal knife cuts that separated the medial from the lateral hypothalamic areas; following surgery, some Ss were given free access to food while others were restricted to normal quantities. Compared with 6 sham-operated controls, the restricted-food Ss exhibited hyperinsulinemia as early as 36 hr after surgery without any change in plasma glucose levels. The blood samples of free-food Ss which had become obese, showed hyperinsulinemia, mild hyperglycemia, and elevated levels of free fatty acids. These results suggest that the interruption of mediolateral hypothalamic connections produces hyperinsulinemia directly, and that further increases in insulin, glucose, and free fatty acid levels are caused by overeating. The surgical cuts produced an increase in aggressive behavior but no change in the circulating levels of testosterone. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in posterior hypothalamic self-stimulation following experimental cerebral infarction in the rat.

Bipolar stimulating electrodes were placed bilaterally in the posterior hypothalamus of male Sprague-Dawley rats following which the Ss were shaped for intracranial self-stimulation (ICSS). When ICSS rates were stable for 1 wk, the right middle cerebral artery was ligated. During the 25-day postinfarction period, the rate of ICSS at specified current values was compared with preoperative rates. At 2 days after operation, there was a 33% decrease in the maximum frequency of ipsilateral ICSS. By 8 days after experimental stroke, there was a 16% increase in the maximal rate of ICSS above the preoperative values, and the rate returned to control levels by 20 days after surgery. The minimum current necessary to elicit the maximal rate of response also changed in a biphasic manner (i.e., minimum required current was greater than preoperative control levels until 8 days after operation but then dropped below control level until 20 days postoperative). There were no changes in the current or rate of response in the contralateral electrode. Results are discussed in relation to what may be the underlying neurophysiological changes causing these biphasic alterations in ICSS. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A hypothalamic follicle-stimulating hormone-releasing decapeptide in the rat

Previous studies indicated that there is a separate hypothalamic control of follicle-stimulating hormone (FSH) release distinct from that of luteinizing hormone (LH). An FSH-releasing factor (FSHRF) was purified from rat and sheep hypothalami, but has not been isolated. We hypothesized that FSHRF might be an analogue of mammalian luteinizing hormone-releasing hormone (m-LHRH) and evaluated the activity of many analogues of m-LHRH and of the known LHRHs found in lower forms. Here we demonstrate that lamprey (l) LHRH-III has a potent, dose-related FSH- but not LH-releasing action on incubated hemipituitaries of male rats. l-LHRH-I on the other hand, had little activity to release either FSH or LH. m-LHRH was equipotent to l-LHRH-III to release FSH, but also had a high potency to release LH in contrast to l-LHRH-III that selectively released FSH. Chicken LHRH-II had considerable potency to release both LH and FSH, but no selectivity in its action. Salmon LHRH had much less potency than the others tested, except for l-LHRH-I, and no selectivity in its action. Because ovariectomized, estrogen, progesterone-treated rats are a sensitive in vivo assay for FSH- and LH-releasing activity, we evaluated l-LHRH-III in this assay and found that it had a completely selective stimulatory effect on FSH release at the two doses tested (10 and 100 pmols). Therefore, l-LHRH-III is a highly potent and specific FSH-releasing peptide that may enhance fertility in animals and humans. It may be the long sought after m-FSHRF.