Reciprocal changes in feeding behavior produced by intrahypothalamic chemical injections.
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The present experiment was designed to investigate the role of Progesterone in the regulation of two aspects of the female's appetitive sexual behavior. Ovariectomized females were tested for partner preference using either a test in which sexual interaction was not possible ("sexual orientation") or a test which included the possibility of sexual interaction ("sexually rewarded choice behavior"). The females were either primed with OIL, Estradiol benzoate (EB) or with Testosterone propionate (TP). Additional groups of females which were primed with EB or TP were treated with Progesterone (P) four hours prior to testing. The results indicate that females which are either treated with EB or with TP, show a male-directed orientation, while OIL-treated females do not. Sexually rewarded choice behavior however, was not affected by hormonal treatment with EB or TP. Additional treatment with P did not further increase the female's male-directed sexual orientation. Sexually rewarded choices for males, in contrast, were drastically increased. EB + P- or TP + P-treated females also showed a significant increase in heterosexual interactions with males in the goal box. The present results support the hypothesis that P plays a role in the female's appetitive sexual behavior, only when the possibility for interaction with a male is present.
Daily food intake in rats was temporarily reduced by the introduction of an activity wheel and temporarily increased by the subsequent removal of the wheel. When this outcome is coupled with the positive relation between food deprivation and running-and food deprivation is seen as a loss of eating rather than as a physiological state-there is the suggestion that the total behavior output of the organism may be regulated as such. Specifically, when the rat is deprived of a behavior that recurrently comprises a large part of its total daily activity, an increase may occur in some other behavior.
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This study investigated measures of sexual behavior displayed by female rats in bilevel chambers, the statistical relationships among the measures, and their dependency on hormone priming. Normative data from a standard 35-min test of sexual behavior were gathered from 82 fully primed sexually experienced Long-Evans females and subjected to multiple correlational and factor analyses. Several consummatory measures of copulation were related significantly, whereas appetitive level changing was statistically independent of consummatory measures. Factor analyses were conducted using orthogonal rotations of correlational matrices derived either from (a) measures of female behavior alone or (b) measures of female and male behavior together. The first analysis revealed five factors that accounted for 84% of the intersubject variance: Receptivity, Pacing, Appetitive Level Changing, Lordosis Reflex, and Solicitation. The second factor analysis with male data included revealed seven factors that accounted for 95% of the intersubject variance: Pacing, Copulatory Rate, Mount Count, Receptivity, Appetitive Level Changing, Solicitation, and Lordosis Reflex. Subsequently, subsets of these females were maintained on different steroid priming regimens (oil, low estrogen, high estrogen, high estrogen and progesterone) prior to a standard test of sexual behavior. Although the expression of all sexual behaviors required estrogen priming, appetitive level changing, solicitation, and pacing required progesterone for their full expression. Finally, appetitive level changing developed following hormone treatment alone, regardless of whether the females received access to sexually active males, inactive castrated males, or other females. Use of bilevel chambers allows complex patterns of sexual behavior to be observed in female rats and may thus facilitate the identification of neurochemical or endocrine mechanisms associated with different aspects of female sexual motivation and performance.
In a recently developed in vitro analog of appetitive classical conditioning of feeding in Aplysia, the unconditioned stimulus (US) was electrical stimulation of the esophageal nerve (En). This nerve is rich in dopamine (DA)-containing processes, which suggests that DA mediates reinforcement during appetitive conditioning. To test this possibility, methylergonovine was used to antagonize DA receptors. Methylergonovine (1 nM) blocked the pairing-specific increase in fictive feeding that is usually induced by in vitro classical conditioning. The present results and previous observation that methylergonovine also blocks the effects of contingent reinforcement in an in vitro analog of appetitive operant conditioning suggest that DA mediates reinforcement for appetitive associative conditioning of feeding in Aplysia.
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1. The goal of this study was to quantitatively characterize the response properties of somatosensory and multisensory neurons in cortical area 7b (or PF) of monkeys that were behaviorally trained to perform an appetitive tolerance-escape task. Particular emphasis was given to characterizing nociceptive thermal responses and correlating such responses to thermal pain tolerance as measured by escape frequency. 2. A total of 244 neurons that responded to somatosensory stimulation alone or to both somatosensory and visual stimulation (multisensory) were isolated and studied in the trigeminal region of cortical area 7b. Thirty neurons responded only to visual stimulation. Thermoreceptive neurons formed approximately 13% (31 of 244) of the neurons that had somatosensory response properties. Thermal nociceptive neurons made up approximately 9% (21 of 244) of the neurons that had somatosensory response properties or approximately 68% (21 of 31) of the neurons that had thermoreceptive response properties. Thermal nociceptive neurons responded either exclusively to noxious thermal stimuli (high-threshold thermoreceptive, HTT) or differentially to nonnoxious and noxious thermal stimuli (wide-range thermoreceptive, WRT). Multimodal HTT neurons had nonnociceptive (low-threshold mechanoreceptive, LTM) and/or nociceptive (nociceptive-specific, wide-dynamic-range) mechanical receptive fields, whereas multimodal WRT neurons had only nonnociceptive (LTM) mechanical receptive fields. Thermal nonnociceptive neurons (low-threshold thermoreceptive, LTT) made up approximately 3% (8 of 244) of the neurons that had somatosensory properties or approximately 26% (8 of 31) of the neurons that were thermoreceptive. The background discharge of two thermoreceptive neurons (6%, 2 of 31) was inhibited by innocuous thermal stimulation. 3. Thermal nociceptive neurons (HTT and WRT) were functionally differentiated by statistical analyses into subpopulations that did encode (HTT-EN, WRT-EN) and did not encode (HTT-NE, WRT-NE) the magnitude of noxious thermal stimulus intensities. The mean slopes and median regression coefficients for the stimulus-response (S-R) functions of HTT-EN and WRT-EN neurons, respectively, were significantly greater than those for the S-R functions of HTT-NE and WRT-NE neurons. In contrast to HTT-NE and WRT-NE neurons, HTT-EN and WRT-EN neurons reliably encoded the magnitude of noxious thermal intensity by grading their mean discharge frequency. 4. The S-R functions of HTT-EN and WRT-EN neurons, unlike those of HTT-NE and WRT-NE neurons, closely approximated stimulus intensity-escape frequency functions.(ABSTRACT TRUNCATED AT 400 WORDS)
Ten-day-old rats sustained bilateral electrolytic lesions of the parabrachial nuclei in the pons (PBN). Growth measures and tests of sensorimotor, feeding and drinking behaviors, sodium appetite, and gustatory capacities were made between ages 1 and 150 days. PBN rats displayed a transient period of attenuated suckling, as evidenced by body weight loss. When tested soon after weaning, PBN rats were hyperdipsic in response to cellular dehydration and during food deprivation. This effect, however, was temporary. When tested as adults, PBN rats were hypodipsic in response to extracellular fluid volume depletion, they displayed alterations in sodium appetite, showed "exaggerated" preferences and aversions to saccharin and NaCl solutions, and they displayed attenuated quinine aversions. These results are generally similar to the behaviors of rats sustaining more central gustatory pathway lesions as adults. The functional significance of the PBN in the developing rat for preference/aversion and sodium appetite behaviors are discussed.
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Intake and taste reactivity tests were used to determine the effects of bilateral lesions of the gustatory portions of the nucleus of the solitary tract (NST), the parabrachial nucleus (PBN), and the ventral posteromedial nucleus of the thalamus (VPMpc) on several complex ingestive behaviors. In the 1st experiment, lesions of the PBN and the NST blocked, and VPMpc lesions impaired, the behavioral expression of salt appetite. In the 2nd experiment, alanine was paired with injections of LiCl. Control rats as well as rats with NST and VPMpc lesions acquired the taste aversion, but rats with PBN lesions did not. In the 3rd experiment, all animals increased their food intake after injections of 2 U/kg insulin and 250 mg/kg 2-deoxy-D-glucose, and their food intake was suppressed after nutritive stomach loads.
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The striatum is involved in the control of appetitively motivated behavior. We found previously that tonically active neurons (TANs) in the monkey striatum show discriminative responses to different stimuli that are appetitive or aversive. However, these differential responses may reflect the sensory qualities of the stimulus rather than its motivational value. In the present study, we sought to define more precisely the relationship between the particular aspect of the response of TANs and the motivational value of stimuli. For this purpose, three monkeys were presented with two types of aversive stimuli (loud sound and air puff) and one appetitive stimulus (fruit juice). In most instances, the TAN responses to the loud sound and the air puff were similar, in terms of response pattern and duration, whereas responses to the liquid reward showed distinct features. Using classical appetitive conditioning, we reversed the motivational value of a stimulus so that a previously aversive stimulus was now associatively paired with a reward and found that this manipulation selectively modifies the expression of TAN responses to the stimulus. These data indicate that the characteristics of neuronal responses undergo modifications when the valence of the stimulus is changed from aversive to appetitive during associative learning, suggesting that TANs may contribute to a form of stimulus encoding that is dependent on motivational attributes. The adaptation of TAN responses such as observed in the present study likewise reflects a neuronal system that adjusts to the motivational information about environmental events.
The tonically active neurons in the monkey striatum respond to stimuli presented during the performance of appetitively motivated behavior. To test whether these neurons are selectively responsive to the appetitive properties of stimuli, we studied their responsiveness to three different stimuli presented in an unsignalled manner to monkeys not performing any behavioral tasks: (1) an appetitive liquid, eliciting licking movements; (2) an aversive air puff directed towards the face, eliciting eyelid closure and facial movements; (3) a neutral sound, eliciting no overt behavioral reactions. The great majority of the tonic striatal neurons tested in two monkeys showed pronounced responses to the delivery of liquid (338 of 388 neurons, 87%) or the onset of the air puff stimulus (168 of 204, 82%). In contrast, few neurons (15 of 68, 22%) were modulated by the sound. The majority (80%) of the neurons tested with appetitive and aversive stimuli (n=189) responded to both types of stimulus. The characteristics of neuronal responses to the liquid were generally not similar to those described for the air puff in terms of response pattern and response duration. This suggests the existence of differences in the encoding of the affective significance of stimuli. It is concluded that tonic striatal neurons might function to differentiate stimuli that are important to the animal from those that are not, regardless of the specific motivational attributes of relevant stimuli.
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