Brain transections differentially alter lordosis and ear wiggling of 6-day-old rats.

The involvement of various brain regions in lordosis and ear-wiggling, which resemble components of adult female sexual behavior, was examined by making acute transections along the neuraxis from the olfactory tract to the medulla in 6-day-old rats. Four to 5 hrs after the transection procedure, pups were tested for lordosis and ear wiggling. Lordosis was reduced or eliminated in pups with cuts through the hindbrain or diencephalon (above the level of the mammillary bodies) but was relatively unaffected by cuts through the posterior hypothalamus and rostral tegmentum and by cuts rostral to the anterior hypothalamus. Ear wiggling was disrupted by transections throughout the hindbrain and was facilitated only in females by transections throughout the forebrain (anterior to the mammillary bodies). Data suggest that facilitation from the hypothalamus is required for lordosis in the infant rat and the forebrain inhibitory systems for ear wiggling are functional in female infants by 6 days of age. Similarities and differences between the neural control of lordosis and ear wiggling in infant and adult rats suggest that the infant sex-like behaviors may be precursors of adult female sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tolerance to amphetamine: Contingent suppression of stereotypy mediates recovery of feeding.

In this article, the effect of chronic injections of amphetamine on feeding and behavioral activation was analyzed. Rats were given milk either through an intraoral cannula or in a standard drinking tube, and the level of their behavioral activation was monitored before, during, and after access to the milk. Cannula- and bottle-fed rats given saline showed similar patterns of intake and activity. Bottle-fed rats given amphetamine (2 mg/kg) showed substantially greater suppression of intake than did cannula-fed rats, but recovered more rapidly, confirming earlier findings (Salisbury & Wolgin, 1985). Such recovery was accompanied by a suppression of stereotyped head scanning movements during access to milk, but not before and after milk access. In contrast, cannula-fed rats given amphetamine showed stereotyped head scans throughout the session for the duration of the experiment. These results suggest that tolerance to the suppression of intake by amphetamine involves learning to suppress stereotyped head movements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: I. Ingestive and behavioral responses to oral infusions.

Reports on 3 experiments with Charles River rat pups. When milk infusions were made through oral cannulas in the front of their mouths, 1–20 day old Ss actively ingested the diet, and their intake was related to the length of deprivation. Ss decreased their ingestive responding after they had consumed large volumes of milk. In addition, 1-, 3-, and 6-day-old Ss, when 24-hr deprived, exhibited an intense behavioral activation in response to milk infusion. The behavioral activation appeared to be stimulated primarily by taste and the opportunity to swallow. Milk infusions did not produce activation in older Ss; their behavior was more exclusively ingestive and food directed. Results demonstrate that (a) from birth, rat pups are capable of an active form of ingestion, independent of normal suckling from the mother; (b) such ingestion is controlled by physiological factors; (c) food has arousing properties in young animals; and (d) as pups grow older, their ingestive responding is refined from a generalized and nondirected activation to specific and directed feeding responses. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of the caudal medulla in negative feedback mechanisms triggered by spatial summation of nociceptive inputs

In the rat, applying noxious heat stimuli to the excitatory receptive fields and simultaneously to adjacent, much larger, areas of the body results in a surface-related reduction in the responses of lumbar dorsal horn convergent neurons. These inhibitory effects induced by spatial summation of nociceptive inputs have been shown to involve a supraspinally mediated negative feedback loop. The aim of the present study was to determine the anatomic level of integration of these controls and hence to ascertain what relationships they might share with other descending controls modulating the transmission of nociceptive signals. The responses of lumbar convergent neurons to noxious stimulation (15-s immersion in a 48 degrees C water bath) applied to increasing areas of the ipsilateral hindlimb were examined in several anesthetized preparations: sham-operated rats, rats with acute transections performed at various levels of the brain stem, and spinal rats. The effects of heterotopic noxious heat stimulation (tail immersion in a 52 degrees C water bath) on the C-fiber responses of these neurons also were analyzed. The electrophysiological properties of dorsal horn convergent neurons, including their responses to increasing stimulus surface areas, were not different in sham-operated animals and in animals the brain stems of which had been transected completely rostral to a plane -2. 8 mm remote from interaural line (200 micron caudal to the caudal end of the rostral ventromedial medulla). In these animals, increasing the stimulated area size from 4.8 to 18 cm2 resulted in a 35-45% reduction in the responses. In contrast, relative to responses elicited by 4.8 cm2 stimuli, responses to 18 cm2 were unchanged or even increased in animals with transections at more caudal level and in spinal animals. Inhibitions of the C-fiber responses elicited by heterotopic noxious heat stimulation were in the 70-80% range during conditioning in sham-operated animals and in animals with rostral brain stem transections. Such effects were reduced significantly (residual inhibitions in the 10-20% range) in animals with transections >500 micron caudal to the caudal end of the rostral ventromedial medulla and in spinal animals. It is concluded that the caudal medulla constitutes a key region for the expression of negative feed-back mechanisms triggered by both spatial summation of noxious inputs and heterotopic noxious inputs.     

Effects of water deprivation and angiotensin II intracerebroventricular administration on brain nitric oxide synthase activity

Intracranial administration of L-arginine causes a reduction of the water intake induced by water deprivation or by intracerebroventricular (i.c.v.) injection of angiotensin II (angiotensin II), through the release of nitric oxide (NO) in the central nervous system. We studied the effects of i.c.v. angiotensin II (120 ng/rat) in association with i.c.v. L-arginine (2.5-10 microg/rat) on blood pressure. We also studied the effects of both peripheral and central angiotensin II injection (1.5-6 mg kg(-1) i.p. and 30-120 ng rat(-1) i.c.v., respectively) on NO synthase activity in the cortex, diencephalon and brainstem, after water deprivation (24 h), conditions producing activation of the renin-angiotensin system. L-arginine dose dependently antagonized the increase in blood pressure induced by i.c.v. angiotensin II (P < 0.001). Peripheral administration of angiotensin II produced a dose-dependent reduction of NO synthase activity in the brainstem and cortex (P < 0.001), but not in the diencephalon. Water deprivation produced similar effects on brain NO synthase activity. Angiotensin II i.c.v. injection caused NO synthase activity reduction in all brain regions studied (P < 0.001). Our findings suggest that NO and angiotensin II could play opposite roles in brain regulation of blood pressure and drinking behaviour.     

Dehydration anorexia in decerebrate rats.

Hypertonic saline (HS) administered intraperitoneal/ly (ip) reduced the intake of sucrose solution infused intraorally in tube-fed decerebrate rats, as it did in control animals. Similarly, either ip or intravenous HS markedly decreased the intake of laboratory chow by neurologically intact control rats. These observations complement recent findings that lesions of putative osmoreceptors in the ventral diencephalon, which eliminate thirst and blunt pituitary secretion of vasopressin and oxytocin in response to HS in rats, have no apparent effect on the HS-induced inhibition of food intake. Taken together they support previous studies indicating an important role for the caudal brainstem in the central control of food intake and suggest that such brainstem control may also include the inhibition of food intake induced by acute hyperosmolality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature denaturation of erythrocyte spectrin: rheology, deformability and resistance to detergents

The vigilance reaction is characterized by a large bradycardia, a pressor response, and inspiratory apnea in anesthetized rabbits and the inhibition of movement in conscious rabbits. This affective response pattern can be elicited by electrical stimulation of the dorsolateral hypothalamus (the hypothalamic vigilance area) or the ventrolateral periaqueductal gray (the periaqueductal gray vigilance area). The present study sought to advance our understanding of the functional relationship between the hypothalamic vigilance area (HVA) and the periaqueductal gray vigilance area (PVA) by measuring the effects of transverse transections of the caudal portion of the ventrolateral PAG (vlPAG) upon the cardiovascular responses elicited from the dorsolateral hypothalamus and the rostral vlPAG. Selective transverse transections of the caudal vlPAG significantly reduced the magnitudes of the bradycardia and pressor response elicited by stimulation of the PVA rostral to the transection site, but had minimal impact on the cardiovascular responses evoked by stimulation of the HVA. These findings suggest that the cardiovascular responses elicited by stimulation of the vlPAG are mediated by a neural pathway that is parallel, at least in part, to the one that subserves the response elicited from the HVA. The results also provide support for the view that the PAG is not an essential structure in the mediation of the autonomic components of affective behaviors involving behavioral inhibition.     

The ontogeny of feeding in rats: V. Influence of texture, home odor, and sibling presence on ingestive behavior.

Determined with Charles River rat pups in 3 experiments that terry-cloth texture, home odor, and the presence of siblings modulated Ss' ingestive behavior. Unlike warmth, which affected ingestion in pups until at least 15 days of age, the relative importance of other cues varied with age. At 3 days, ingestion was dependent on warmth but was not influenced by the other cues. At 6 days, texture and home odor enhanced ingestive behavior (intake, activity, mouthing, and probing), but the presence of siblings had no effect. Home odor or terry-cloth texture did not alter the ingestive behavior of 12-day-olds, but the presence of siblings enhanced milk intake. Thus, during development, the external sensory controls for ingestion became progressively more complex. Warmth served as a primary permissive cue for ingestion, but as Ss grew older, such other cues as odor, texture, or social stimuli also gained significance. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroanatomical distribution and variations across the reproductive cycle of aromatase activity and aromatase-immunoreactive cells in the pied flycatcher (Ficedula hypoleuca)

The anatomical distribution and seasonal variations in aromatase activity and in the number of aromatase-immunoreactive cells were studied in the brain of free-living male pied flycatchers (Ficedula hypoleuca). A high aromatase activity was detected in the telencephalon and diencephalon but low to negligible levels were present in the optic lobes, cerebellum, and brain stem. In the diencephalon, most aromatase-immunoreactive cells were confined to three nuclei implicated in the control of reproductive behaviors: the medial preoptic nucleus, the nucleus of the stria terminalis, and the ventromedial nucleus of the hypothalamus. In the telencephalon, the immunopositive cells were clustered in the medial part of the neostriatum and in the hippocampus as previously described in another songbird species, the zebra finch. No immunoreactive cells could be observed in the song control nuclei. A marked drop in aromatase activity was detected in the anterior and posterior diencephalon in the early summer when the behavior of the birds had switched from defending a territory to helping the female in feeding the nestlings. This enzymatic change is presumably controlled by the drop in plasma testosterone levels observed at that stage of the reproductive cycle. No change in enzyme activity, however, was seen at that time in other brain areas. The number of aromatase-immunoreactive cells also decreased at that time in the caudal part of the medial preoptic nucleus but not in the ventromedial nucleus of the hypothalamus (an increase was even observed), suggesting that differential mechanisms control the enzyme concentration and enzyme activity in the hypothalamus. Taken together, these data suggest that changes in diencephalic aromatase activity contribute to the control of seasonal variations in reproductive behavior of male pied flycatchers but the role of the telencephalic aromatase in the control of behavior remains unclear at present.     

Reconstruction of flexor/extensor alternation during fictive rostral scratching by two-site stimulation in the spinal turtle with a transverse spinal hemisection

Analyses of fictive scratching motor patterns in the spinal turtle with transverse hemisection provided support for the concept of bilateral shared spinal cord circuitry among neurons responsible for generating left- and right-side rostral, pocket, and caudal fictive scratching. Rhythmic bursts of hip flexor activity, the hip extensor deletion variation of fictive rostral scratching, were elicited by ipsilateral stimulation in the rostral scratch receptive field of a spinal turtle [transection at the segmental border between the second (D2) and third (D3) postcervical spinal segments] with a contralateral transverse hemisection one segment anterior to the hindlimb enlargement (at the D6-D7 segmental border). In addition, other sites were stimulated in this preparation: (1) contralateral sites in a rostral, pocket, or caudal scratch receptive field or (2) ipsilateral sites in a caudal scratch receptive field. A reconstructed fictive rostral scratch motor pattern of rhythmic alternation between hip flexor and hip extensor activation was produced by simultaneous stimulation of one site in the ipsilateral rostral scratch receptive field and another site in one of the other scratch receptive fields. This reconstructed rostral scratch motor pattern resembled the normal rostral scratch motor pattern produced by one-site rostral scratch stimulation of a spinal turtle (D2-D3 transection) with no additional transections. The observation of a reconstructed rostral scratch motor pattern produced by two-site stimulation in the spinal turtle with transverse hemisection supports the concept that hip extensor circuitry activated by stimulation of other scratch receptive fields is shared with circuitry activated by ipsilateral rostral scratch receptive field stimulation.     

Brainstem and hypothalamic regulation of sleep pressure and rebound in newborn rats.

Sleep pressure and rebound comprise the two compensatory or “homeostatic” responses to sleep deprivation. Although sleep pressure is expressed by infant rats as early as postnatal day (P)5, sleep rebound does not appear to emerge until after P11. We reexamined the developmental expression of these sleep-regulatory processes in P2 and P8 rats by depriving them of sleep for 30 min using a cold, arousing stimulus delivered to a cold-sensitive region of the snout. This method effectively increased sleep pressure over the 30-min period (i.e., increases in the number of arousing stimuli presented over time). Moreover, sleep rebound (i.e., increased sleep during the recovery period) is demonstrated for the first time at these ages. Next, we showed that precollicular transections in P2 rats prevent sleep rebound without affecting sleep pressure, suggesting that the brainstem is sufficient to support sleep pressure, but sleep rebound depends on neural mechanisms that lie rostral to the transection. Finally, again in P2 rats, we used c-fos immunohistochemistry to examine neural activation throughout the neuraxis during sleep deprivation and recovery. Sleep deprivation and rebound were accompanied by significant increases in neural activation in both brainstem and hypothalamic nuclei, including the ventrolateral preoptic area and median preoptic nucleus. This early developmental expression of sleep pressure and rebound and the apparent involvement of brainstem and hypothalamic structures in their expression further solidify the notion that sleep–wake processes in newborns—defined at these ages without reference to state-dependent EEG activity—provide the foundation on which the more familiar processes of adults are built. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of anorexia and behavioral activation in amphetamine-induced suppression of feeding: Implications for understanding tolerance.

48 male Sprague-Dawley albino rats administered chronic injections of either saline or dextroamphetamine (DAM) sulfate (2 or 4 mg/kg, intraperitoneally) were given milk either directly into the mouth through an intraoral cannula or in a standard drinking tube. Results reveal that bottle-fed Ss given DAM showed substantially greater suppression of intake than cannula-fed Ss. Saline-treated Ss showed almost identical milk intake with the 2 methods. Recovery of intake occurred in all drugged Ss except those given 4 mg/kg and fed by bottle. In the tolerant groups, Ss fed by bottle and given 2 mg/kg recovered at a faster rate than cannula-fed Ss at either dose. Findings demonstrate that in a normal drinking condition, the initial suppression of intake is caused by a combination of anorexia and behavioral interference and that tolerance occurs to both of these effects. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Opioid control of the fetal stretch response: Implications for the first suckling episode.

On their 1st experience with milk, fetal rats express a stretch response that is similar to the postnatal behavior exhibited by infant rats at the nipple. Fetuses also possess a functional opioid system that is activated by prenatal milk exposure. The opioid receptor antagonist naloxone and the specific kappa antagonist nor-binaltorphimine blocked the stretch response and prevented the increase in rearlimb activity that is typically induced by milk. The mu antagonist β-funaltrexamine blocked the stretch while permitting the expression of rearlimb activity. The kappa agonist U50,488 promoted rearlimb activity in the absence of milk, whereas the mu agonist [{d}-Ala–2,NMe-Phe–4,Gly–5-ol]-enkephalin (DAMGO) exerted little influence on fetal behavior. Fetuses pretreated with U50,488 stretched to nonmilk stimuli (saline or lemon), but fetuses pretreated with DAMGO did not. Opioid activation is part of a chain of events that culminates in the fetal stretch response and may be important in promoting milk ingestion during the newborn's 1st suckling episode. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sodium appetite elicited by intracerebroventricular infusion of angiotensin II in the rat: I. Relation to urinary sodium excretion.

Previous results show that icv infusion of angiotensin II (Ang II) elicits a substantial sodium appetite in the rat. The present study, with male Sprague-Dawley rats, demonstrated that this phenomenon consists of a small, early phase of sodium ingestion that is not the result of prior sodium loss but that thereafter urinary excretion of sodium exceeds intake and consequently the animals become hyponatremic and hypovolemic. The larger and more sustained bouts of sodium ingestion occurring 8–22 hrs after the start of the Ang II infusion appear to represent a behavioral compensation for this incurred sodium deficit. Results confirm the arousal of a sodium appetite by action of Ang II on the brain but indicate the need for caution in assigning to it a direct and exclusive role in the neuroendocrine control of sodium intake. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of milks inoculated with Lactobacillus acidophilus or a yogurt starter culture in lactose-maldigesting children

Dairy products containing live bacteria that possess lactase activity are used for dietary management of lactose maldigestion. The efficacy of acidophilus milk and the effect of consuming unfermented milk that had been inoculated with yogurt bacteria have not been examined in children. We compared scores for breath H2 excretion and symptoms of 20 lactose-maldigesting children following ingestion of 250 ml of uninoculated milk with two identical milks inoculated with 10(10) cells of Lactobacillus acidophilus or with a commercial yogurt starter culture containing 10(8) cells of Lactobacillus lactis and 10(10) cells of Streptococcus thermophilus. Nine of 10 subjects who were symptomatic following ingestion of uninoculated milk experienced a reduction in symptoms following ingestion of milk inoculated with L. acidophilus, without a decline in H2 excretion. Five of 6 subjects who were symptomatic following uninoculated milk had decreased symptoms and a significant reduction in H2 excretion following milk inoculated with the yogurt culture. For lactose-maldigesting children, milks inoculated with L. acidophilus or with a yogurt culture were associated with decreased symptoms compared with those with uninoculated milk.     

Development of synaptic contacts in the human brain during the early stages of embryogenesis

In vagotomized cats, after removal of the brain portion 5 mm rostral to the visual nerves crossing, the eupnoea type of respiration was preserved. Transection in the area of the visual nerves crossing was followed by a stable acceleration of respiration. Starting from the level of the posterior border of the visual nerves crossing and more caudal, successive transections of the brain entailed sharp decrease in the breathing rate, increase of the respiratory volume, and complicated changes of the lungs ventilation.     

Preoptic and subthalamic connections with the caudal brainstem are important for copulation in the male rat.

Bilateral lesions of either the medial preoptic area/anterior hypothalamus (MPAH) or a subthalamic region that includes the caudal zona incerta eliminate copulation in male rats. Pathways connecting the MPAH and subthalamus with the caudal brainstem may help regulate sexual behavior. Exp 1 showed that bilateral coronal transections of the pontine tegmentum reduce mating and that the combination of a unilateral tegmental cut with a contralateral excitotoxin lesion of either the MPAH (Exp 2) or subthalamus (Exp 3) virtually eliminates copulation. Asymmetric bilateral damage appears to eliminate mating through a bilateral effect common to the transection and the lesion: the destruction of connections linking the MPAH and subthalamus with the caudal brainstem. These results indicate that preoptic and subthalamic connections with the caudal brainstem are important for copulation in the male rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of behavioral arousal: The role of environmental stimuli.

During the course of ontogenesis the developing rat has been reported to pass through a transient period of intense behavioral arousal which peaks at 15 days of age, a phenomenon that has been interpreted to reflect a sequential caudal to rostral development of excitatory and inhibitory systems in the mammalian brain. In the present 4 experiments with male and female Sprague-Dawley rats, it was shown that (a) this period of intense hyperactivity occurred only when the animal was tested alone in an unfamiliar environment, the degree of arousal was proportional to the dissimilarity between the home cage and the test environment, and isolation per se was insufficient to elicit the arousal response; (b) environmental temperature had a minimal influence on the degree of behavioral arousal in either familiar or unfamiliar environments; (c) unlearned responses to pheromonal or other naturally occurring nest odors did not suppress the high levels of locomotor activity evoked by unfamiliar environments in the 15-day-old rat pup; and (d) it is fear or distress evoked by the unfamiliar environment rather than curiosity that underlies this developmental phenomenon. It is concluded that the sequential increase and decrease in locomotor activity that occurs during ontogenesis cannot be used to support the principle of caudal to rostral development of excitatory and inhibitory centers in the CNS. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress-induced asymmetric frontal brain activity and aggression risk.

Impersonal stressors, not only interpersonal provocation, can instigate aggression through an associative network linking negative emotions to behavioral activation (L. Berkowitz, 1990). Research has not examined the brain mechanisms that are engaged by different types of stress and serve to promote hostility and aggression. The present study examined whether stress exposure elicits more left than right frontal brain activity implicated in behavioral approach motivation and whether this lateralized brain activity predicts stress-induced aggression and hostile/aggressive tendencies. Results showed that (a) participants in the impersonal (assigned to stress by a computer) and interpersonal (assigned to stress by a provoking confederate) stress conditions both showed more left than right frontal electroencephalogram activity after condition assignment and stress exposure and (b) the 2 stress groups exhibited subsequent increases in aggression relative to the no-stress group. Importantly, left frontal asymmetry in response to stress exposure predicted increases in subsequent aggressive behavior, a finding that did not emerge in the no-stress condition. Thus, both the interpersonal and impersonal stressors impacted state changes in brain activity related to behavioral approach, suggesting that stress reactivity involving approach activation represents risk for behavioral dysregulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of licking and volume intake controls in rats ingesting glucose and maltodextrin.

The volume of fluid that rats acquire with each lick was systematically varied across short-term tests with 12.5% glucose (Experiment 1) or 12.5% maltodextrin (Experiment 2). For glucose, rats increased the number of licks emitted as lick volume was reduced such that meal size remained remarkably stable across all (8, 4, and 2 μl) but the smallest (1 μl) lick volume conditions tested. Rats similarly compensated for lick volume reduction (8 to 4 μl) with maltodextrin by approximately doubling the number of licks emitted. Meal duration and a number of lick-microstructural parameters (initial ingestion rate, mean burst duration, terminal lick and ingestion rates and burst duration) were not correlated with the intake outcome insofar as they varied significantly across conditions over which intake remained stable. Thus, in response to lick volume manipulation, rats demonstrated an impressive degree of behavioral flexibility in what may be regarded as a defense of meal size. (PsycINFO Database Record (c) 2010 APA, all rights reserved)