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At least 1,063 records · Page 59Linked to original sources
PubMed2005

Interaction between the antidepressant-like behavioral effects of beta adrenergic agonists and the cyclic AMP PDE inhibitor rolipram in rats.

RATIONALE: Type 4 phosphodiesterase (PDE4) is critical for hydrolysis of cAMP formed by stimulation of beta adrenergic receptors. However, it is not known if PDE4 is associated with beta adrenergic receptors in the mediation of antidepressant-like effects. OBJECTIVE: The aim of the study is to determine the relationship between PDE4 and beta adrenergic receptor-mediated cAMP signaling in mediating antidepressant-like effects. METHODS: The effects of the PDE4 inhibitor rolipram, alone or combined with dobutamine or clenbuterol, selective beta-1 and beta-2 adrenergic agonists, respectively, on behavior were examined in rats under a differential reinforcement of low rate (DRL) schedule and rats trained to discriminate rolipram from vehicle. Their effects on cAMP in primary cultures of rat cerebral cortical neurons also were determined. RESULTS: Rolipram (0.01-0.3 mg/kg), dobutamine (1-30 mg/kg), and clenbuterol (0.03-0.3 mg/kg) dose-dependently produced antidepressant-like effects on DRL behavior, decreasing response rate and increasing reinforcement rate. The effects of beta adrenergic agonists were potentiated by rolipram. Isobolographic analysis revealed that rolipram enhanced the antidepressant-like effect of dobutamine additively and that of clenbuterol synergistically. Consistently, a combination of ineffective doses of rolipram (0.03 mg/kg) and dobutamine (3 mg/kg) or clenbuterol (0.03 mg/kg) completely substituted for the rolipram discrimination stimulus. Further, incubation with an ineffective concentration of clenbuterol, but not dobutamine, in the presence of a subeffective concentration of rolipram, significantly increased cAMP in cultured cortical neurons. CONCLUSIONS: PDE4 plays an important role in regulating cAMP signaling by either beta-1 or beta-2 adrenergic receptors that mediate antidepressant-like actions; beta-2 adrenergic receptor-mediated cAMP signaling appears more responsive than beta-1 cAMP signaling to PDE4 inhibition.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1990

A vasopressin metabolite increases attentional selectivity.

Two behavioral paradigms were used to assess the effect of a vasopressin metabolite, AVP4-9, on selectivity of attention. The effects observed in a multiple-cue task indicated that AVP4-9 treatment increased the extent to which attention was controlled by the dominant cues in the environment. When these stimuli predicted reward, the peptide treatment facilitated learning, but when these cues were nonpredictive, the treatment hindered learning. In a redundant learning paradigm, administration of the lower dose of AVP4-9 (1 microgram/kg) prevented animals from learning about an added, equally predictive (i.e., redundant) set of cues, suggesting that this treatment caused selective attending to the originally presented stimuli, whose relationship with reward had already been learned. The results of these two studies provide converging evidence that AVP4-9 treatment increases the selectivity of attention, with preferential processing of dominant information. Parallels with the putative attentional effects of increased arousal are discussed.

Animals↗
PubMed2004

Effects of acute and chronic ketoconazole administration on hypothalamo--pituitary--adrenal axis activity and brain corticotropin-releasing hormone.

We have been investigating the effects of ketoconazole on cocaine reward in rats for several years now. However, we recently confirmed that ketoconazole-induced changes in cocaine self-administration and reinstatement do not always correspond with decreases in plasma corticosterone, which suggests that other mechanisms must be underlying the behavioral effects that we observe. This experiment was therefore designed to determine the effects of acute, repeated and chronic ketoconazole administration on corticotropin-releasing hormone (CRH) content in hypothalamic and extra-hypothalamic brain sites in rats following the same dosing regimen that we use in our behavioral studies. Although ketoconazole significantly increased the concentration of ACTH in trunk blood, there were no significant effects on plasma cortisol, corticosterone or testosterone. There was also a significant increase in CRH content in the median eminence after the acute administration of ketoconazole that just failed to reach statistical significance following repeated or chronic administration. However, acute, repeated and chronic treatment with ketoconazole each significantly increased CRH content in the medial prefrontal cortex (MPC), but did not consistently affect the peptide in any other brain region studied. Since the MPC and CRH have been implicated in the neurobiology of cocaine, CRH-induced alterations in dopaminergic neurotransmission may play an important role in this peptide's effects on cocaine responsiveness. Taken together with the results from previous studies, these data suggest that ketoconazole may affect cocaine reward, at least in part, through interactions with dopamine and CRH within the MPC.

Analysis of Variance↗
PubMed1987

Time horizons in rats foraging for food in temporally separated patches.

An important tenet of optimal foraging theory is that foragers compare prey densities in alternative patches to determine an optimal distribution of foraging behavior over time. A critical question is over what time period (time horizon) this integration of information and behavior occurs. Recent research has indicated that rats do not compare food density in a depleting patch with that in a rich patch delayed by an hour or more (Timberlake, 1984). In the present research we attempted to specify over what time period a future rich patch would affect current foraging. The effect of future food was measured by early entry into the rich patch (anticipation) and by a decrease in food obtained in the depleting patch (suppression). The rats showed anticipation of a rich patch up to an hour distant, but suppressed current feeding only if the rich patch was 16 min distant or less. The suppression effect appeared mediated by competition for expression between anticipatory entries into the rich patch and continued foraging in the depleting patch. These results suggest that optimal foraging is based on a variety of specific mechanisms rather than a general optimizing algorithm with a single time horizon.

Animals↗
PubMed1993

Eating pathology in bulimia nervosa.

Degree of eating pathology in bulimia nervosa was assessed using the Eating Behavior Rating Scale (EBRS) across three videotaped eating sessions. Twelve bulimic and 12 non-eating disordered subjects participated in this study. All subjects were filmed during a baseline meal (ad libitum), a high-calorie meal, and a low-calorie meal (both fixed amounts). Mean EBRS scores were significantly higher for bulimics (12.6 +/- 1.7) than for controls (3.9 +/- 0.9), suggesting a higher degree of eating pathology in these patients. Affect during eating was significantly more negative in the bulimic patients. EBRS and affect scores were significantly correlated [r (11) = .813, p < .01]. Bulimics had a slower rate of eating than controls and took significantly longer to initiate eating. Scores of pathological eating correlated with scores on the Eating Attitudes Test and the Bulimic Investigatory Test-Edinburgh, indicating a relationship between objective measures of pathological eating and self-report measures of eating disorder symptoms.

Adult↗
PubMed1990

Evaluation of the interaction between D1 and D2 receptors in a drug discrimination paradigm.

Recent research has suggested that there is a synergistic interaction between D1 and D2 dopamine (DA) receptors and that D1 stimulation by endogenous DA is necessary for the expression of some D2-mediated behavioral effects. The purpose of the present experiment was to examine further the interactions between D1 and D2 receptors using drug discrimination (DD), a behavioral paradigm that is sensitive and selective for D1 and D2 agonist and antagonist activity. Two groups of male Sprague-Dawley rats (N = 8/group) were trained to discriminate the D2 agonist quinpirole (QUIN; either 0.05 or 0.012 mg/kg, ip, 10 min pre-session) from saline (1.0 ml/kg, ip, 10 min pre-session) in a two-lever, food-reinforced DD paradigm. QUIN (0.0015-0.1 mg/kg) produced a dose-related increase in QUIN-appropriate responding in both groups of rats. The D1 agonist SKF 38393 (SKF; 6.4-12.8 mg/kg, ip) given alone did not substitute for QUIN in either of the two training dose groups. The administration of SKF 30 min before QUIN had no effect on the QUIN dose-response function in either group of rats. These results indicate that stimulation of D1 receptors failed to potentiate a behavioral effect mediated by D2 receptors. The D1 antagonist SCH 23390 (SCH; 0.0015-0.05 mg/kg, ip) partially substituted for QUIN in the group trained with the 0.05 dose of QUIN, and to a larger extent in the group trained with the 0.012 dose of QUIN. SCH did not alter the effect of the training dose of QUIN except at a dose high enough to virtually eliminate lever pressing in the group trained to discriminate the high dose of QUIN. The failure of SCH to block QUIN suggests that D1 receptor stimulation by endogenous DA is not necessary for this D2 effect to be expressed. These results may be accounted for by assuming a presynaptic site of action for QUIN in the QUIN discrimination. Further, they demonstrate that the interaction between D1 and D2 receptors cannot be simply characterized as synergistic.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1999

Behavioral responses to aliphatic aldehydes can be predicted from known electrophysiological responses of mitral cells in the olfactory bulb.

For a better understanding of the encoding of odor quality in the olfactory system, it is critical to determine how electrophysiological responses to odorants are reflected in the behavioral responses to these odorants. In this article, we use a simple behavioral paradigm to show that the behavioral responses to similar odorants can be predicted from the electrophysiological responses of neurons in the olfactory bulb. Carbon chain length in aliphatic aldehydes has been used as a model for graded similarity among odorants. Recent electrophysiological experiments have shown that mitral cells in the rabbit olfactory bulb respond with similar response patterns to aliphatic aldehydes of similar chain length. On average, mitral cells responded with increased spiking activity to stimulation with two to three different aldehydes of neighboring chain length. We here show that the perception of these odorants can be predicted from the electrophysiological responses: rats that are conditioned to a given aldehyde generalize to aldehydes with one to two carbon differences in chain length from the conditioned aldehyde. When asked to discriminate between aldehydes of different chain lengths, rats learned to discriminate between any two odorants, but the rate of acquisition depended on the degree of similarity between the two odorants.

Aldehydes↗
PubMed2000

Ovarian dynamics and host use.

Oviposition behavior in herbivorous and frugivorous insects and parasitoids is dynamic at the level of the individual, responding to variation in host quality and availability. Patterns of variation in egg load in response to host presence and quality suggest that ovarian development also responds to variation in the host environment. Ovarian dynamics are mediated by feedback from oviposition, by host feeding, and by sensory input from the host. The last of these mechanisms, host sensory cuing, is known to occur in three major orders and provides strong evidence that ovarian dynamics are adaptive by design. Conditions favoring host effects on ovarian development include trade-offs between egg production and either survival or dispersal, uncertainty in the host environment, and a correlation in host conditions between the time that oogenesis is initiated and the time that eggs are laid. Some host defenses block ovarian development, suggesting that ovarian dynamics in host-specific insects should be viewed from a coevolutionary perspective.

Animals↗
PubMed2001

Nares occlusion eliminates heterosexual partner selection without disrupting coitus in ferrets of both sexes.

Using an airtight Y maze and a new method to induce peripheral anosmia in ferrets, we assessed the contribution of conspecific odors, either alone or in combination with visual and auditory signals, to heterosexual partner preference. Sexually naive ferrets were gonadectomized and treated with sex steroids, after which their nares were either bilaterally occluded using dental impression material or were sham-occluded. Behavioral and histological evidence suggested that nares occlusion blocked access of odors to the main olfactory epithelium for the duration of the study. Sham-occluded females and males preferred to approach odor only or odor plus visual plus auditory cues from opposite-sex conspecifics, whereas nares-occluded ferrets approached opposite- and same-sex cues equally. All ferrets subsequently mated successfully in tests conducted in a small chamber. When retested in the Y maze, sham-occluded females and males again preferred to approach odor-only or odor plus visual plus auditory cues from opposite-sex ferrets, whereas nares-occluded subjects showed no such preference even in tests when a brief physical interaction with tethered stimulus ferrets was allowed after each trial. Our results show that in the ferret, a carnivore, the detection and processing of volatile odors from conspecifics by the main olfactory system is required for heterosexual mate choice.

Acoustic Stimulation↗
PubMed1998

Postnatal foraging demands alter adrenocortical activity and psychosocial development.

Mother squirrel monkeys stop carrying infants at earlier ages in high-demand (HD) conditions where food is difficult to find relative to low-demand (LD) conditions. To characterize these transitions in psychosocial development, from 10- to 21-weeks postpartum we collected measures of behavior, adrenocortical activity, and social transactions coded for initiator (mother or infant), goal (make-contact or break-contact), and outcome (success or failure). Make-contact attempts were most often initiated by HD infants, but mothers often opposed these attempts and less than 50% were successful. Break-contact attempts were most often initiated by LD infants, but mothers often opposed these attempts and fewer LD than HD infant break-contact attempts were successful. Plasma levels of cortisol were significantly higher in HD than LD mothers, but differences in adrenocortical activity were less consistent in their infants. HD and LD infants also spent similar amounts of time nursing on their mothers and feeding on solid foods. By rescheduling some transitions in development (carry-->self-transport), and not others (nursing-->self-feeding), mothers may have partially protected infants from the immediate impact of an otherwise stressful foraging task.

Analysis of Variance↗
PubMed1991

Breeding readiness in squirrel monkeys: female-primed females are triggered by males.

The South American squirrel monkey (Saimiri) shows pronounced annual variations in reproductive activity. We investigated the contribution of social stimulation to breeding readiness, as reflected in behavior and gonadal hormones. A previous study indicated that formation of new heterosexual pairs can induce breeding readiness in males, but not in females. In the present study we examined the response of individually housed females to the formation of triads of unacquainted females and, subsequently, the response of these triads to the introduction of a single male. The formation of the all-female group was accompanied by a marked reduction in basal cortisol levels. Introduction of a male to such a group promptly induced breeding readiness in the females, as indicated by increased gonadal hormone production and cyclic variation in estrogen and progesterone levels. The contrasting responses of group-living or single females to a new male suggest that at least two processes are involved in the induction of breeding readiness by group formation in females. One is a "priming" effect resulting from interfemale stimulation: the other is a "triggering" effect resulting from the presence of a male.

Animals↗
PubMed1994

Importance of unpredictability for reward responses in primate dopamine neurons.

1. We used single neuron recording techniques in two behaving monkeys to investigate the conditions in which dopamine neurons respond to primary rewarding or potentially rewarding stimuli. Animals received drops of liquid either outside behavioral tasks or as rewards during learning or established performance of an auditory reaction time task. 2. Three quarters of dopamine neurons showed a short-latency, phasic response to liquid that was delivered outside the task without being predicted by phasic stimuli. The same neurons responded to liquid reward during learning but not when task performance was established, at which time the neuronal response occurred to the conditioned, reward-predicting, movement-triggering stimulus. 3. These data suggest that the responses of dopamine neurons to rewarding or potentially rewarding liquid are due to the temporally unpredicted stimulus occurrence. A known, reward-predicting, tonic context does not prevent dopamine neurons from responding to the rewarding liquid. The responses during learning apparently occur because reward is not yet reliably predicted by a conditioned phasic stimulus. Because the unpredicted occurrence of reward is of central importance for learning, these responses allow dopamine neurons to play an important role in reward-driven learning.

Animals↗
PubMed2005

Effects of stream hydraulic conditions on foraging strategies of false dace, Pseudorasbora parva, in the lentic ecosystem.

The effects of current velocity on the foraging behavior of false dace, Pseudorasbora parva, were examined in a zero velocity (stagnant) condition, and at four flow rates (5, 7, 11 and 16 cm per second). In stagnant water, the fish displayed a cruise-searching pattern, but they used a drift-feeding foraging tactic in flowing water. The shape of the transverse field of reaction field was elliptical in the stagnant condition, whereas their downward regions were restricted under the flowing conditions. The fish had a blind spot oriented directly in front of their reaction field. Although the relative swimming speed (with considering the against current velocity) increased with increasing flow velocity, the absolute search speed (ignore the against current velocity) showed about 1.2 fish body length per second at stagnant water and low flow velocity. The results of feeding rates showed stop-and wait (driff-feeding) foraging strategy is more efficient in flowing water because prey drift directly towards the fish and prey easily detected.

Animals↗
PubMed1997

Body weight and response acquisition with delayed reinforcement.

The relation between body weight and responding established with unsignaled delayed reinforcement was investigated. In three experiments, naive rats were deprived to either 70%, 80%, or 90% of ad libitum weight and were then exposed to tandem variable-interval 15-s differential-reinforcement-of-other-behavior 30-s schedules. The tandem schedule defined a resetting unsignaled delay-of-reinforcement procedure. In the first experiment, speed of magazine training, acquisition of lever pressing, and final rate of lever pressing were related to body weight. In the next experiment, lever pressing was established and maintained in rats that were magazine trained at 70% of ad libitum weight but that were then exposed to the delay procedure at 90% of ad libitum weight. Responding did not change consistently either across or within subjects in subsequent conditions in which body weight was manipulated. In the final experiment, lever pressing was established and maintained with delayed reinforcement in the absence of magazine training for each of 2 rats at 70% and for 1 of 2 rats at 90% of ad libitum weight. The results further illuminate the conditions under which responding can be established in the absence of training and when such responses are reinforced only following an unsignaled delay period.

Animals↗
PubMed2006

The effects of chronic administration of ethosuximide on learning and memory: a behavioral and biochemical study on nonepileptic rats.

Long-term use of antiepileptic drugs is common in the treatment of epilepsy. Clinical reports exist of cognitive impairment attributed to antiepileptic drugs. Hence, this study evaluates the effect of chronic administration of one antiepileptic drug, ethosuximide, on spatial and fear learning and memory in nonepileptic rats. High performance liquid chromatography with electrochemical detection was used for quantification of glutamate, glycine, taurine, gamma-aminobutyric acid, dopamine, and serotonin in the frontal cortex and hippocampus to elucidate the neurobiological basis of the effect of ethosuximide on learning and memory. We found that 21 days of ethosuximide treatment produced negative effects on fear memory (passive avoidance) at all doses (100, 200 and 250 mg/kg body weight), but had no effect on spatial learning (T-maze). Fear memory impairment was associated with decreased hippocampal dopamine levels. Ethosuximide (at all doses) had a minimal effect on the GABAergic and glutamatergic systems in all brain regions studied, with the exception of elevated levels of gamma-aminobutyric acid in the frontal cortex with the 250 mg/kg body weight dose. We have shown that long-term administration of ethosuximide adversely affects fear memory, but does not affect spatial learning and memory.

Animals↗
PubMed2006

Schedule-induced alcohol drinking: non-selective effects of acamprosate and naltrexone.

Acamprosate and naltrexone are therapeutically effective drugs that promote abstinence and prevent drinking relapse among alcohol-dependent patients, and dose-dependently decrease alcohol self-administration in animals. The purpose of this experiment was to investigate the behavioral specificity of acamprosate and naltrexone treatment in mice on alcohol drinking elicited in a schedule-induced polydipsia (SIP) task. Food-deprived male C57BL/6J (B6) mice were divided into three groups assigned to a 5% alcohol SIP, water SIP, or a 1-hour limited access regulatory water drinking task. Injections (intraperitoneal) of acute (0, 50, 100, 200, 400 mg/kg) and chronic (2 x 100 mg/kg, 10 days) acamprosate, or naltrexone (0, 1.0, 2.5, 5.0 mg/kg) were administered. Behavioral drug specificity was determined by comparing alterations in alcohol or water consumption in SIP with alterations in limited access drinking. Additionally, drug effects on drinking-specific measures (g/kg consumption and lick efficiency) were compared with those of non-drinking measures (head entries for food and locomotor activity) during SIP. In comparison with saline injections, acute acamprosate (400 mg/kg) reduced both alcohol and water drinking in both SIP and the regulatory drinking conditions, but had no significant effects on non-drinking measures. Chronic administration of acamprosate reduced both alcohol and water drinking during SIP, but did not significantly affect regulatory drinking or non-drinking measures. Naltrexone (1.0, 2.5, 5.0 mg/kg) reduced alcohol and water drinking in both paradigms, and at the highest dose, significantly reduced head entries for food. These results indicate that acamprosate (acute and chronic) and naltrexone are relatively non-selective in their effects on alcohol self-administration in this task.

Acamprosate↗
PubMed1994

Application of scalar timing theory to individual trials.

Our purpose was to infer the characteristics of the internal clock, temporal memory, and decision processes involved in temporal generalization behavior on the basis of the analysis of individual trials. Three groups of 10 rats each were trained on a peak procedure with reinforcement at 15, 30, or 60 s, with several nonfood trial durations. On nonfood trials, the mean response rate gradually increased to a maximum near the time that reinforcement sometimes occurred and then gradually decreased. Individual trials were characterized by a period of high response rate, preceded and followed by a low response rate. The covariance pattern among measures of the temporal characteristics of the high response rate (start, stop, middle, and spread) supported a parallel, scalar timing model in which animals used on each trial a single sample from memory of the time of reinforcement and separate response thresholds to decide when to start and stop responding. An alternative model, the quasi-serial model (J. Gibbon & R. M. Church, 1992), was not consistent with the obtained relationships between covariances or with the scalar property seen across different nonfood signal durations.

Animals↗
PubMed1999

The role of the response-reinforcer relation in delay-of-reinforcement effects.

The role of the response-reinforcer relation in maintaining operant behavior under conditions of delayed reinforcement was investigated by using a two-operandum (i.e., two-key) procedure with pigeons. Responding on one key was reinforced under a tandem variable-interval differential-reinforcement-of-other-behavior (tandem VI DRO) schedule. The schedule defined a resetting unsignaled delay-of-reinforcement procedure in that a response was required when the interfood interval of the VI schedule lapsed, but further responding during the DRO component on either key reset the time interval. This ensured a fixed delay duration between any response and reinforcement. Responding on another key, physically identical to the first one except for spatial location, otherwise was without consequence. The location of the key correlated with the delay-of-reinforcement procedure varied between sessions according to a semirandom sequence. Differences in response rates between the two keys were greater, with proportionally higher rates on the key correlated with the delay-of-reinforcement procedure, the longer the delay-of-reinforcement procedure remained correlated with the same key. Differences in responding on the two keys also increased within individual sessions. These results suggest that the response-reinforcer relation is the primary determinant of responding when responding is acquired and maintained with delayed reinforcement.

Animals↗