Effects of amphetamine and phenylethylamine on catecholamine release in the glomerular layer of the rat olfactory bulb

The purpose of this study was to examine predictors of outcome in very low birth weight (< 1500 g) children. The very low birth weight sample consisted of 68 children weighing less than 750 g at birth and 65 children weighing 750 to 1499 g at birth who had been matched to the less than 750 g birth weight children in terms of hospital of birth, age, sex, and race. Mean ages for these two groups were 6.7 and 6.9 years, respectively. Outcomes were measured in terms of tests of cognitive function, neuropsychological abilities, and academic achievement and parent and teacher ratings of child behavior and school performance. A weighted sum of the number of major neonatal medical complications (Neonatal Risk Index) provided a composite measure of biological risk. Social risks were also assessed. Results indicated that the Neonatal Risk Index was the most consistent predictor of outcomes. Even after taking social risks into account, neonatal risk predicted overall cognitive ability and other achievement, neuropsychological, and behavior outcomes. Individual neonatal complications that predicted outcomes included severe cerebral ultrasonographic abnormality, chronic lung disease, necrotizing enterocolitis, and apnea of prematurity. Research and therapy to prevent or reduce neonatal complications and amelioration of social risks are of critical importance in improving outcomes of very low birth weight.     

Importance of !b-noradrenergic receptors in the olfactory bulb of sheep for recognition of lambs.

Within a 4-hr period after parturition, the ewe learns the odor of her lamb that will allow later recognition of her offspring from alien lamb. This study investigated the importance of the activation of olfactory bulb (OB) β-noradrenergic receptors in establishing this olfactory memory. Pregnant ewes (n?=?24) were cannulated bilaterally in the OB. Two days before parturition, OB were perfused continuously (10 μl/hr) with either a solution containing the selective β-noradrenergic antagonist propranolol (10–3 M) or vehicle. The results showed that, although 8 of 9 control ewes were still able to bond selectively to their lambs, only 7 of 15 propranolol-treated animals were able to bond (p?=?.04). These results suggest that activation of β-noradrenergic receptors in the OB during the period surrounding parturition is required to establish olfactory recognition of the lamb. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory regulation of maternal behavior in rats: I. Effects of olfactory bulb removal in experienced and inexperienced lactating and cycling females.

Used 57 Sprague-Dawley virgin female rats to study the effects of olfactory bulbectomy under various conditions. Bilateral bulbectomy induced either cannibalism or short latency maternal behavior in naive Ss. Following unilateral bulbectomy or 2-stage bilateral bulbectomy, short latency maternal behavior appeared but cannibalism did not. Pregnancy and parturition overcame cannibalism after bilateral bulbectomy in inexperienced Ss, but not in females exhibiting cannibalism as virgins. Experienced (2 days postpartum) bulbectomized Ss had shorter latencies for reinduction of maternal behavior than experienced intact Ss. Results suggest that olfactory bulbs have 2 functions in relation to maternal behavior: sensory (olfaction) and nonsensory. Female response to olfactory bulbectomy may be due to anosmia facilitating maternal behavior, or to removal of nonsensory influences resulting in cannibalism. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scopolamine injection into the olfactory bulb impairs short-term olfactory memory in rats.

A previous experiment showed that systemic administration of the muscarinic antagonist scopolamine altered delayed matching in an olfactory task in rats. The present experiment tested whether the impairment could result from blockade of the cholinergic transmission in the first relay structure of the olfactory system, the olfactory bulb. 25 rats served as Ss. The drug was infused directly into both olfactory bulbs before test sessions. Results show that the intrabulbar infusion reproduced the effect of the systemic administration. With a 4-sec delay between target odor and choice test, performances of treated rats remained unchanged; however, with a 30-sec delay, rats performed randomly. Results from a complementary electrophysiological experiment in anesthetized rats support the idea that scopolamine injected into the olfactory bulb was unlikely to have reached more central structures. Further evidence for the involvement of pure sensory areas in short-term memory is concluded. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the olfactory bulb in limbic mechanisms.

Reviews recent data obtained after peripheral olfactory system damage which, when compared with bulbectomy data, suggest that the olfactory bulb has certain general modulatory functions in addition to its specific sensory role as initial processor of olfactory information. It is proposed that the olfactory bulb is involved in a forebrain arousal mechanism comprised mainly of hypothalamus and limbic system. Behavioral and electrophysiological evidence is discussed that supports the idea that the olfactory bulb may modulate the excitability of forebrain regions. Anatomical details of the system are considered, and its relationship to reinforcement mechanisms and to A. Routtenberg's (see PA, Vol 42:5112 and 47:244) Arousal System II is outlined. (5 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of olfactory bulb ablation upon emotionality and muricidal behavior in four rat strains.

Reported several differences in emotionality when 4 strains of rats (N= 160 males and females) (Holtzman, Long-Evans, Sprague-Dawley, Wistar) were compared. Olfactory bulb removal resulted in emotionality increases in male Holtzman and female Wistar Ss. However, the type of hyperemotionality or viciousness reported by some authors to result from bulbectomy was not seen. Despite the lack of hyperemotionality, more mouse killers were observed in the bulbectomized groups. With the exception of sham-operated Wistar Ss, males and females did not differ in emotionality ratings, but more males than females killed mice whether sham-operated or bulbectomized. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some behavioral effects of olfactory bulb damage in the rat.

Conducted 5 experiments in which male Holtzman rats (N = 50) with either olfactory bulb or septal lesions were tested on position-habit reversal, nonappetitive passive-avoidance, 1-way avoidance, and 2-way avoidance tasks. Ss with septal damage exhibited the expected behavioral abnormalities on all tasks. Ss with bulbar damage were deficient on 1-way avoidance, were facilitated on 2-way avoidance, and could not be distinguished from the normal Ss on the other 2 tasks. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurocalcin immunoreactivity in the rat main olfactory bulb

The morphological characteristics and distribution of neurocalcin (NC)-immunoreactive elements were studied in the rat main olfactory bulb (OB) using a polyclonal antibody and the avidin-biotin immunoperoxidase method. NC-positive elements were abundant in the glomerular layer (GL), where numerous immunostained external tufted cells and periglomerular cells were detected. Other less abundant NC-immunolabeled populations included middle and internal tufted cells, Van Gehuchten cells, horizontal cells, vertical cells of Cajal, deep short-axon cells and granule cells. This study demonstrates the presence of NC immunoreactivity in subsets of different neuronal types in the rat main OB. This calcium-binding protein has been found in interneurons, and no evidence of immunoreactivity to NC is detected in projecting neurons. Despite the large population of labeled external tufted cells, most of them belong according to morphological criteria to the local circuit group and some others to those with interbulbar and/or intrabulbar connections. The identification of neuronal subpopulations expressing NC provides a further characterization and shows the existence of biochemical differences within morphologically identical neurons. Thus, this marker may be a useful tool in unravelling the circuitries of the rodent OB in both normal and experimental conditions. The exact physiological function of NC in the olfactory system remains unknown. On the basis of similarities to recoverin, it could be involved in mechanisms responsible for sensory adaptation. Additionally, its calcium-binding abilities may contribute to improve the temporal precision of stimuli transmission, or be concerned with general calcium-related events occurring in specific interneuronal groups.     

Noradrenergic neuromodulation in the olfactory bulb modulates odor habituation and spontaneous discrimination.

Noradrenergic projections from the locus coeruleus (LC) project to the olfactory bulb (OB), a cortical structure implicated in odor learning and perceptual differentiation among similar odorants. The authors tested the role of OB noradrenaline (NA) in short-term olfactory memory using an animal model of LC degeneration coupled with intrabulbar infusions of NA. Specifically, the authors lesioned cortical noradrenergic fibers in mice with the noradrenergic neurotoxin N-Ethyl-N-(2-chloroethyl)-2-bromobenzylamine hydrochloride (DSP4) and measured the effects on an olfactory habituation/spontaneous discrimination task. DSP4-treated mice failed to habituate to repeated odor presentations, indicating that they could not remember odors over the 5-min intertrial interval. The authors then infused NA bilaterally into the OBs of both DSP4-treated and nonlesioned control animals at two concentrations (10-3M and 10-5M, 2 μl/side). In DSP4-treated animals, NA administration at either concentration restored normal habituation and spontaneous discrimination performance, indicating that noradrenergic neuromodulation mediates these aspects of perceptual learning and that its efficacy does not require activity-dependent local regulation of NA release. Functional OB learning mechanisms may be necessary for normal odor recognition and differentiation among physically similar odorants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synaptic organization and neurotransmitters in the rat accessory olfactory bulb

The accessory olfactory bulb (AOB) is the first relay station in the vomeronasal system and may play a critical role in processing pheromone signals. The AOB shows similar but less distinct lamination compared with the main olfactory bulb (MOB). In this study, synaptic organization of the AOB was analyzed in slice preparations from adult rats by using both field potential and patch-clamp recordings. Stimulation of the vomeronasal nerve (VN) evoked field potentials that showed characteristic patterns in different layers of the AOB. Current source density (CSD) analysis of the field potentials revealed spatiotemporally separated loci of inward current (sinks) that represented sequential activation of different neuronal components: VN activity (period I), synaptic excitation of mitral cell apical dendrites (period II), and activation of granule cells by mitral cell basal dendrites (period III). Stimulation of the lateral olfactory tract also evoked field potentials in the AOB, which indicated antidromic activation of the mitral cells (period I and II) followed by activation of granule cells (period III). Whole cell patch recordings from mitral and granule cells of the AOB supported that mitral cells are excited by VN terminals and subsequently activate granule cells through dendrodendritic synapses. Both CSD analysis and patch recordings provided evidence that glutamate is the neurotransmitter at the vomeronasal receptor neuron; mitral cell synapses and both NMDA and non-NMDA receptors are involved. We also demonstrated electrophysiologically that reciprocal interaction between mitral and granule cells in the AOB is through the dendrodendritic reciprocal synapses. The neurotransmitter at the mitral-to-granule synapses is glutamate and at the granule-to-mitral synapse is gamma-aminobutyric acid. The synaptic interactions among receptor cell terminals, mitral cells, and granule cells in the AOB are therefore similar to those in the MOB, suggesting that processing of chemosensory information in the AOB shares similarities with that in the MOB.     

Early onset of the rat olfactory bulb projections

Using the fluorescent carbocyanine tracer DiI, we examined in detail the early development of the projections emanating from the rat olfactory bulb. The study commenced at embryonic day 13 when the first fibres can be detected and ended at embryonic day 20, when all major fibre systems have been established. The first axons arising from the prospective olfactory bulb area are seen at embryonic day 13. Labelled fibres are provided with elaborate axonal growth cones advancing through the ventrolateral part of the telencephalic vesicle. At embryonic day 14, while the main fibre tract has not developed much further, some isolated fibres are located quite distally from the prospective olfactory bulb. These early fibres apparently course within a narrow cell-free space that extends caudally along the ventrolateral part of the telencephalic vesicle. At embryonic day 15, a number of labelled fibres form a compact bundle, corresponding to the lateral olfactory tract, that ultimately reaches the prospective primary olfactory cortex. The fibres do not stop growing, but continue to extend caudally at embryonic day 17. The results of this study provide new information on the development of axonal tracts in the olfactory system. We show that the olfactory tract projection develops earlier than the morphological appearance of the olfactory bulbs. This suggests that the early development of olfactory projections might not depend on the arrival of the olfactory epithelium axons and thus, could be governed by factors intrinsic to the neurons and/or cues present in the target environment.     

Retention of maternal behavior in nulliparous and primiparous rats: Effects of duration of previous maternal experience.

Lactating primiparous and nonlactating pup-induced maternal nulliparous female CD rats were given 1, 4, or 9 days of maternal experience with rat pups before they were isolated from the young. 25 days later, Ss were reexposed to 3–8 day old foster pups, and latencies to show maternal behavior in the home cage and a T-maze test were scored. In the home cage, the latencies of all nulliparous groups were shorter upon reinduction. Comparisons of primiparous and nulliparous groups revealed that primiparous females (1, 4, and 9 days combined) carried a pup, crouched, retrieved, and grouped the pups and built a good nest faster than did nulliparous females (combined groups). The number of behavioral differences between specific primiparous and nulliparous groups decreased as the length of prior maternal experience increased. In the T-maze, latencies to retrieve a pup were shorter in primiparous females. Results indicate that the processes underlying establishment of the long-term retention of short-latency maternal behavior in these groups may be comparable. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of isoflurane on in vivo release of acetylcholine in the rat cerebral cortex and striatum

BACKGROUND: Acetylcholine (ACh) is one of the major excitatory neurotransmitters in the central nervous system, and changes in neural activity induced by anesthesia alter the release of ACh. However, the effects of isoflurane, one of the most widely used volatile anesthetics, on ACh release are not known. The present study attempts to clarify the dose-effect relationship of isoflurane on the in vivo release of ACh in rat brains. METHODS: Changes in the extracellular concentration of ACh and choline in the cerebral cortex and striatum induced by 0.5, 1.0, and 1.5 minimum alveolar concentration (MAC) of isoflurane were determined using a brain microdialysis technique. RESULTS: In the cortex, the ACh release decreased to 30.8+/-10.1 (mean+/-SEM), 10.2+/-4.1, and 8.1+/-2.9% of basal value by increasing doses of isoflurane, and in the striatum, to 73.3+/-4.4, 49.2+/-4.2, and 40.7+/-4.5%. The ACh release rapidly recovered control levels with the discontinuance of isoflurane. Choline concentration was not changed significantly by isoflurane except for a decrease to 74.8+/-4.6% in the striatum by 0.5 MAC. In both the cortex and striatum, the choline concentration decreased with the discontinuance of isoflurane to 70.3+/-13.3, and 68.2+/-5.4%, respectively. CONCLUSION: The fact that all classic anesthetics reported previously, as well as isoflurane, reduce ACh release supports the hypothesis that the suppression of cholinergic cells is, at least in part one of the mechanisms of anesthesia.     

Identification of olfactory receptor mRNA sequences from the rat olfactory bulb glomerular layer

In situ hybridization has demonstrated mRNA for olfactory receptors (OR) in the axon terminals of olfactory receptor neurons. Neurons that express the same OR appear to send their axons to two stereotyped glomeruli in the olfactory bulb (OB). Based on these observations, we tested the feasibility of using RT-PCR to isolate and sequence OR mRNA from small samples of the rat OB glomerular layer. Biomagnetic mRNA isolation followed by RT-PCR yielded partial sequences for 21 novel members of the OR family. The results suggest that the topography of OR mRNA can be mapped across the OB, to study synaptic specificity and odor representation in the olfactory system.     

Plasticity in the maternal circuit: Effects of maternal experience on Fos-Lir in hypothalamic, limbic, and cortical structures in the postpartum rat.

To determine what brain sites are activated during the acquisition and retention of a maternal experience in postpartum rats, 3 studies examined the number of cells showing Fos-like immunoreactivity (Fos-lir) in brains following reexposure to pups and pup-associated cues in maternally experienced and inexperienced rats. Day 1 postpartum rats were given a 2- or 4-hr interactive experience with pups and then reexposed to pups in a perforated box, or to a neutral stimulus (perforated box only) 4 or 10 days later. At the end of the test phase, brains were prepared for immunohistochemical detection of Fos-lir. The brain sites showing the most consistent difference between experienced and inexperienced rats were the medial preoptic area, the basolateral amygdala, the parietal cortex, and the prefrontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of olfactory bulb removal on ingestive behaviors, activity levels and self-stimulation in hamsters.

Examined the influence of olfactory bulb removal on running activity, body weight, food and water consumption, and lateral hypothalamic self-stimulation rates in 24 male and 4 female golden hamsters. 2 experiments were conducted in an attempt to characterize more completely the behavioral and physiological deficits which might be related to the total abolition of male sexual behavior produced by ablation of the olfactory bulbs. This operation depressed food consumption and body weight during the 1st 5-10 postoperative days only and had no effect on water intake. During the same postoperative period, running activity declined by 50% before returning to normal. Self-stimulation rates were reduced below normal during the 1st 2 postoperative days but returned to preoperative levels by 7 days. These transient effects of bulbectomy on the measured variables were contrasted with the permanent deficit in male sexual behavior which results from olfactory bulb removal. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of the olfactory bulb in consolidation processes associated with long-term memory in rats.

In a daily training paradigm, rats were trained to discriminate between spatially distinct electrical stimulations delivered to one olfactory bulb. Xylocaine injections were used to disrupt the olfactory bulb functioning in the region close to the electrode tips for 1 hr after each training session. The treatment started either just after the session or 2 hrs later. When compared with the performance of saline-injected rats, the performance of Xylocaine-injected rats was unimpaired except when the treatment started just after the daily session. In that case, acquisition of the task was slightly altered, and retention over a 5-day period was dramatically impaired. It is concluded that, within 1 hr following training, the olfactory bulb is engaged in consolidation processes critical for long-term retention of learned olfactory cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The importance of calmodulin in the accessory olfactory bulb in the formation of an olfactory memory in mice

Female mice form an olfactory memory to the pheromones of the mating male, during a critical period after mating. Failure to form this memory results in the male being treated as strange, and hence, his pheromones block pregnancy. Previous studies have shown that formation of this memory is dependent on synaptic mechanisms in the accessory olfactory bulb. A number of studies have pointed to calmodulin as a critical mediator of synaptic plasticity. In this study we have examined the effects of local infusions of drugs which block calmodulin-regulated processes, into the accessory olfactory bulb on the formation of this memory. Infusions of the calmodulin antagonist calmidazolium during the critical period prevented memory formation. However, the specific inhibitor of calcium/calmodulin-dependent protein kinase II, KN-62, or the selective inhibitor of calcium/calmodulin-dependent protein phosphatase 2B (calcineurin), FK506, was without effect on memory formation at any of the doses used. Instead of preventing memory formation, FK506 permitted the formation of a non-selective memory to strange male pheromones in the presence of mating, although FK506 alone could not induce a memory without the occurrence of mating. These results suggest that calmodulin in the accessory olfactory bulb is important in the formation of the olfactory memory to male pheromones. However, memory formation may be independent of calmodulin-kinase II. Calcineurin may play a role in processes antagonizing memory formation.     

Effects of caffeine and acetylcholine on glucose-stimulated insulin release from islet transplants in mice

The aim of this study was to examine the effects of image instructions on subjects able to use imagery spontaneously and those unable to use them spontaneously, on the self-control of skin temperature. The subjects were 20 undergraduate students. All subjects were instructed to raise their skin temperatures through four sessions. After the first session, subjects were assigned to one of the following three groups: the spontaneous image group (SI), instructed image group (II), and control group (C). The SI group comprised only of those subjects who used imagery spontaneously in the first session. Before the second session, the subjects in the SI and II groups were instructed to use imagery in the following sessions. The results showed that SI group subjects could raise their skin temperatures to higher levels than those in the other groups. These results suggest that subjects who use imagery spontaneously have a greater ability to control their skin temperatures, than other subjects who cannot raise their skin temperatures well, even if instructed in the use of imagery.