Biomedical subjects

F Farabollini

Publications and source records attributed to F Farabollini.

At least 37 records · Page 2Linked to original sources

PubMed1986

Interaction of tonic immobility and dexamethasone in the modulation of hippocampal 5-HT activity in rabbits.

The immobility reaction (animal hypnosis) in the rabbit is related to basal levels of corticosterone and to modifications in 5-HT activity in the brain. In order to investigate the relationship between adrenocortical function, brain 5-HT activity and immobility response in rabbits, the susceptibility to the reaction and 5-HT and 5-HIAA levels in the hippocampus were studied in animals whose pituitary-adrenal function was altered by chronic DEX treatment. It was still possible to induce immobility in animals treated with DEX. The reduction in duration observed under the present testing schedule (two sessions of immobility separated by a one week interval) did not occur in the treated animals. There was a reduction in 5-HT turnover as a consequence of the immobility response and this confirms previous findings in other brain areas of the same species. In animals pretreated with DEX, so as to drastically reduce ACTH and corticosterone, not only was a reduction in 5-HT turnover prevented, but there was also an increase in 5-HT and 5-HIAA levels when immobility was induced. These results are discussed in terms of the influence of the pituitary-adrenal system in the neuroendocrine and behavioural aspects of the immobility reaction.

Adrenocorticotropic Hormone↗

PubMed1984

Changes in brain serotonin and 5-hydroxyindolacetic acid levels in the rabbit following tonic immobility.

The effect of tonic immobility on serotonin (5-hydroxytryptamine, 5-HT) and on 5- hydroxyindolacetic acid (5-HIAA) levels in different brain areas has been investigated, following two different schedules of treatment. The massed treatment consisted of a series of consecutive trials up to 15 min, the spaced treatment in 4 series of trials within 24 hours. Massed treatment produced a decrease in 5-HT in the mesencephalon and of 5-HIAA in the pons-medullary area, but similar changes were also elicited in animals treated with the procedure of induction not followed by immobility. The spaced treatment, which resulted in a potentiation of the immobility duration, i.e., sensitization, produced a reduction of 5-HT levels in the mesencephalon and of 5-HT turnover in the striatum. The procedure of the induction per se acts preferentially on 5-HIAA by increasing its levels. In the striatum, which appears selectively responsive to the spaced treatment of immobility, a negative correlation has been found between serotonin levels and immobility duration. Results suggest that elicitation of tonic immobility is associated with reduced levels of 5-HT in the brain.

Animals↗

PubMed1984

Hippocampal electrical activity and behavior in the presence of novel environmental stimuli in rabbits.

Male rabbits have been used in a simultaneous study of their behavioral and neural activity in different experimental situations related to attention and emotionality. The electrical activity of the dorsal hippocampus and frontal cortex was recorded in the following experimental situations: Neutral Environment (response to a novel environment); Object (response to a novel stimulus); Stuffed sparrow hawk; and live cat. Results show that behavioral and electrical responses depend upon: (a) the nature of the stimulus; and (b) whether or not the stimulus is moving. As for the immobile stimuli, the stuffed animal presentation significantly reduced both behavioral activity and percentage and frequency of rhythmic slow activity (RSA); prolonged periods of ECoG synchronization were also recorded. The introduction of the live cat greatly increased the percentage and frequency of RSA, especially when the cat was looking at the rabbit. The experimental situations caused differences in the distribution of RSA frequencies as well. The percentage of high RSA frequencies (greater than 6.5 Hz during immobility; greater than 7.2 Hz during movement) recorded in response to the immobile stimuli was negatively correlated to the amount of RSA. Results are discussed in the light of attentional and emotional theories.

Animals↗

PubMed1984

Physiological characteristics of pressure immobility. Effects of morphine, naloxone and pain.

This study is an attempt to detect the most important modifications of physiological parameters occurring during pressure immobility in rabbits and to compare them with those recorded during animal hypnosis. Like the latter, pressure immobility is characterized by the development of high voltage slow waves in the EEG, reduction in frequency and amount of rhythmic slow activity in the hippocampus (RSA) and depression of spinal polysynaptic reflexes. Systolic and diastolic blood pressures are not modified. Duration of two types of immobility is positively correlated within individuals. Treatment by a single dose of morphine (1 mg/kg) potentiates the duration and this effect is antagonized by naloxone (1 mg/kg). Repeated morphine injection up to tolerance reduces duration. Pressure immobility may also be produced under persistent nociceptive stimulation and is characterized by the development of high voltage slow waves in the EEG, as is typical in the absence of pain. Naloxone, (5 mg/kg) injected in a condition of persistent noxious stimulation, reduces immobility duration. In contrast to animal hypnosis, the duration of pressure immobility is neither potentiated by pain nor reduced by naloxone (1,5 or 20 mg/kg). It is suggested that the two immobilities are controlled by several mechanisms, some similar, some different.

Animals↗

PubMed1984

Effect of DSP-4, pCPA, and haloperidol on hippocampal electrical activity and behavior in rabbits.

An experimental model, including novel and fearful stimuli, has been used to study the effect of noradrenaline, serotonin, and dopamine depletion on hippocampal electrical activity and behavior in freely moving rabbits. DSP-4 (N-(2-chloroethyl)-N-ethyl-2- bromobenzylamine hydrochloride, 40 mg/kg ip), a selective hippocampal noradrenaline depletor, decreased the overall exploratory activity and significantly increased RSA (rhythmic slow activity) percentage. The high frequencies of the hippocampal RSA were significantly reduced. When this noradrenaline depletion was coupled with a serotonin depression by p-chlorophenylalanine (pCPA), the above described effect was potentiated. In particular, the frequency distribution of RSA was characterized by a further reduction of the high values with a concomitant increase of the low frequency band. Moreover, a more evident decrease of the exploratory activity and a similar increase of RSA percentage was observed. These results show that the hippocampal electrical activity is modulated by noradrenaline and serotonin by an inhibitory effect on RSA occurrence and a frequency selection. The block of dopamine receptors by chronic haloperidol administration (5 mg/kg ip/day) did not seem to exert any effect on RSA parameters. Results are discussed in the light of attentional and emotional theories.

Amines↗

PubMed1983

Modulation of presynaptic cholinergic receptors by adrenergic drugs.

Some adrenergic drugs were tested for their ability to interact with the stimulatory activity of scopolamine on Ach output from brain cortex. The noradrenergic neurotoxin DSP4 was the most potent in depressing the effect of the anticholinergic drug and behaved like a potent alpha 2-agonist and alpha 1-antagonist on nervous peripheral structures. This finding supports the view of a connection between presynaptic adrenergic and muscarinic receptors.

Acetylcholine↗

PubMed1981

Modifications of brain steroidogenesis and plasma steroids after p-chlorophenylalanine-methyl-ester treatment in male rats and rabbits.

The effect of p-chlorophenylalanine (p-CPA) on testosterone (T) hypothalamic metabolism and on plasma levels of T, estradiol (E2) and corticosterone (B) was studied in male rats and rabbits: both were sacrificed 48 hours after the last injection. In both rats and rabbits a significant increase in T leads to E2 transformation (aromatization) was evident after p-CPA treatment. This increase could be responsible for the stimulatory effect on sexual behavior which has been described in literature following p-CPA administration. Moreover p-CPA caused a decrease of circulating T and E2 in both species.

Animals↗

PubMed1981

Neuroendocrine changes following habituation of animal hypnosis in male rabbits.

Neuroendocrine changes have been studied in male rabbits during daily repeated inductions of animal hypnosis. All the animals attained the habituation but after different times, showing a different individual sensitivity to the treatment. Once habituation was reached, further treatment did not elicit any recovery. Corticosterone plasma levels gradually increased during treatment, reached a peak at habituation and did not change afterwards. Because corticosterone was not modified after habituation was established, despite further manipulation of the animals, it can be assumed that the increase of corticosterone is due to hypnosis. ACTH did not follow the same pattern of variation as corticosterone: an increase was found at habituation, but this was not statistically significant. Estradiol decreased and the testosterone/estradiol (T/E) ratio increased on the final day with respect to Day 1, whereas testosterone plasma levels were not modified by the treatment. However, there was a general increase of testosterone metabolites (dihydrotestosterone, estradiol) studied in vitro in the anterior hypothalamus of rabbits sacrificed at the end of the treatment. Thus the different responsiveness associated with repeated induction of animal hypnosis changes basal levels of ACTH, steroid hormones and central testosterone metabolism.

Adrenocorticotropic Hormone↗

PubMed1981

Effects of pain, morphine and naloxone on the duration of animal hypnosis.

Previous research has shown that animal hypnosis (tonic immobility) in the rabbit may be elicited in a condition of prolonged nociceptive stimulation. These experiments show that long-lasting irritative pain, produced within 15 min of formalin injection, potentiates the duration of hypnosis. Morphine, in the absence of painful stimuli, also potentiates hypnosis duration and this effect is antagonized by naloxone. Naloxone reduces hypnosis duration, but only at high doses (15 mg/kg). In a condition of irritative pain, the potentiation of hypnosis duration is abolished by naloxone (5 mg/kg). Hypnosis response is abolished in 6 out of 7 morphine-tolerant rabbits, but prolonged pain restores the response. The hypothesis that an opioid mechanism may be activated during animal hypnosis is discussed.

Animals↗

PubMed1979

Plasma corticosterone and its relation to susceptibility to animal hypnosis in rabbits.

Plasma corticosterone has been correlated with the susceptibility to animal hypnosis in male rabbits. Subjects (Ss) were considered susceptible when mean hypnosis duration was above 30 sec or when initial duration (duration of trial 1) was greater than 0. A positive significant correlation was found between mean and initial duration. A significant difference was found between corticosterone levels in susceptible and unsusceptible Ss: higher values were associated with susceptible SS and with SS with initial duration greater than 0. These results indicate a higher susceptibility to animal hypnosis in rabbits with a more active adrenocortical system.

Animals↗

PubMed1979

Slowly adapting receptors in cat hip joint.

1. The activity of slowly adapting joint receptors was recorded from fibers of the posterior articular nerve of the hip in deeply anesthetized cats. The static stimulus was any position of the femur maintained at least 2 min after passive displacement. Most of the fibers are active in all the positions where the femur may be placed. Modulation in the discharge frequency occurs in any axis of displacement, and higher activity is recorded at extreme positions. The maximal discharge may be reached in several positions of the femur far away from one another. 2. Adaptation to static stimuli occurs in all the receptors. Joint receptors fire at very regular, steady rates; the mean coefficient of variation was 0.079. 3. In most of the receptors, when the femur is displaced along a single axis, the frequency of discharge varies as a monotonic function of joint position. This relationship could be described either by linear and logarithmic or by linear and power functions, according to the criteria adopted to indicate the intensity of the stimulus. 4. Repetition of identical static stimuli results in different responses. 5. The static properties of the receptors are not modified by the section of periarticular muscles. 6. Hip joint receptors are able to code hip joint position.

Adaptation, Physiological↗

PubMed1978