Biomedical subjects
Publications and source records attributed to R Duclaux.
Reproducible cerebral evoked responses have been recorded from the vertex in two men and one woman to endorectal electrical stimulation. The first component had a 36 ms latency for the woman, and an average latency of 90 ms for the men.
Explore the source record for details and available documents.
In this study, we examine the possible relation between depression and a diminution of subjective pleasure experienced during sensory stimulation. A subjective evaluation of 5 pure sounds presented at random 5 times to each subject was carried out with 10 depressive subjects, 10 non-depressive psychiatric subjects, and 10 non-depressive subjects, the three groups being matched for sex and age. In depressed subjects, the results showed no reduction in the number of experiences of subjective pleasure but a significant reduction in the repeatability of subjective pleasure associated with a given sound. These modifications seems to be specific to depression since psychiatric patients receiving neurotropic drug behave as control subjects. On the other hand, no such significant difference is found in the repeatability of a subjectively unpleasant experience. Finally, when all subjects are considered on the same continuum of depression, a significant negative correlation is found (P less than 0.01) between the degree of depression as measured by the Beck Depression Inventory and the number of sounds for which repeatability of subjective pleasure is obtained over 5 trials. Our results extend into the sensory realm the reduction in the repeatability of subjective pleasure already established for depressed subjects in the social realm; this is discussed in terms of positive reinforcement reduction associated with depression.
We measured the tonal auditory threshold for 500, 2000 and 4000 Hz, and made BAER recordings for both ears with unfiltered 125 dB SPL clicks, with 40 subjects between 18 and 23 years of age, 20 subjects having suffered minor cranial trauma during the preceding 48 hours and 20 being control subjects matched for age and sex. Compared to the control group, trauma patients showed a significantly higher auditory threshold: 19 dB SPL at 500 Hz, 9 dB SPL at 2000 and 4000 Hz. This threshold rise was bilateral. The head trauma patients showed, on average, one significantly earlier BAER wave I than did controls. This alteration was likewise bilateral. The latencies of waves II, III and V, the I-III, III-V, and I-V intervals, and the interaural wave latency and interval differences are comparable for trauma patients and control subjects. One to eight months after cranial trauma, 7 subjects manifested one sign of the subjective cranial trauma syndrome. Auditory threshold and BAER wave I earliness were not any greater for these subjects. Trauma patients seemed to show a reduction of the auditory field. They were hypersensitive to high stimulus intensities (shortening of BAER wave I) and less sensitive to low intensities (rise in tonal auditory threshold). This auditory alteration was bilateral. It can thus be thought that the trauma acts on the central nervous system to affect the operation of the cochlea via efferent pathways.
In the cat skin, the activity of 5 mechanothermal nociceptors has been studied to cold nociceptive stimuli. The frequency of discharge is very low (maximum of 2.0 Hz). The repetition of very cold stimulations decreased the discharge threshold of these receptors. After -5 degrees C stimulus, the mechanothermal nociceptors were completely inhibited during 3 to 7 minutes. These mechanothermal nociceptors should have an important function in cold pain.
In order to study peripheral nervous signals in response to a noxious or innocuous mechanical cutaneous stimulus we deviced an electromechanical stimulator of which stimulus duration, response frequency and delay are perfectly controlled. Using this device, stimulation of the finger has allowed us to record electrophysiological responses over the course of the median nerve.
Explore the source record for details and available documents.
Twenty-seven rats were treated by 475 mg kg-1 of subcutaneous capsaicin from 2 to 7 days of their life. After treatment, only 11 rats had survived. Their cutaneous heat, pressure, pricking and visceral hyperosmolarity nociceptive thresholds were measured between 50 and 170 days after treatment. The results showed a considerable, or even total, analgesia to cutaneous as well as visceral stimuli. The conclusion is that same pathways carried all the nociceptive messages independently of nature or localization of noxious stimuli.
Rats were chronically implanted with a lateral cerebral ventricular guide cannula. After recovery they were trained to self-inject morphine sulfate. A week after this training period, self-injection behavior was studied during nociceptive stimulation. In response to a nociceptive stimulation rats increased their intracerebroventricular self-administration of morphine. This effect is specific for morphine since under identical conditions rats did not increase NaCl administration. Naloxone pretreatment inhibits self-administration of morphine in 5 rats. However, two rats increased morphine self-intake. These results show that rats can directly perceive a decrease of pain sensation induced by the morphine self-administration. This experimental situation is therefore similar to the therapeutic situation in humans, in which the criterion of efficacy of an analgesic is a reduction of the conscious pain sensation. Experimental self-administration during painful stimulation might therefore be used for preclinical evaluation of the efficacy of an analgesic drug.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The principle of behavioural therapy was used in anti-tobacco treatment. An assessment of the first 100 patients is given here. From the beginning of treatment, which was individual and lasted for one week, the subjects, with three exceptions, stopped smoking between the treatment sessions. After treatment was completed, 93 subjects maintained this abstinence for at least 15 days; 74 patients have not started to smoke again, with a follow-up period ranging from 2 to 18 months. The degree of motivation of the patients would seem to be the only parameter related to relapse.
Explore the source record for details and available documents.
1. The receptive fields of 48 specific cold units, located in the hairy and glaborous skin of fore- and hindlimbs of rhesus monkeys, were mapped and scale drawings made. Forty-five percent had single spotlike receptive fields of 1-2 mm diameter or were up to 2 mm wide and 3-5 mm long, and formed straight, crescent, or right-angle shapes. The remaining 55% had two to five discrete spots or small areas innervated by a single fiber. Area or number of receptive fields per unit did not vary significantly along the limb axis. 2. Of the 48 specific cold units, 15 were held sufficiently long to record their dynamic responses to intensity-rate series of temperature changes from several adapting temperatures (ATs) between 20 and 45 degrees C. Six cold units showed a paradoxical increase in the steady-state response at the 45 degrees C compared to that at the 40 degrees C AT. Of the 15 cold units, 7 discharged in bursts at the 35 degrees C or lower ATs. The proportion of short intervals (intraburst intervals) increased as the adapting temperature decreased. 3. Both the latency and the temperature change at the onset of the dynamic response to cooling remained relatively constant for ATs up to and including 35 degrees C. The response latencies were approximately 200-400 ms, while the temperature changes at response onset were -0.02 to -0.06 degrees C. Both increased sharply at the 40 degrees C and still more at the 45 degrees C ATs. 4. The rate of increase in the frequency of the dynamic response to cooling by the fast rate increased to maximum at the 30 degrees C AT and then decreased at the higher ATs. For the slow rate the highest rate of increase in frequency occurred at the 20 degrees C AT. The fast rate of cooling always induced a faster rate of increase in frequency than slow rate of cooling. 5. Four indices of response magnitude were used in the analysis of the dynamic responses. These were peak frequency, cumulative impulses in the first 4 s following stimulus onset, average frequency during stimulations plus 3 s, and the total impulses during stimulation. The first three indices gave similar representations of the dynamic responses to the rate and intensity of cooling and the effect of the AT. The slow rate of cooling invariably yielded a smaller index of response magnitude than the fast rate. The difference became more pronounced as the intensity of cooling increased. The stimulus intensity-response magnitude functions were nonlinear. This nonlinearity was more pronounced at the low than at the high ATs. As the AT was increased, the response indices approached linearity at the 35 and 40 degrees C ATs. The greatest sensitivity of cold units to cooling was from the 35 degrees C AT. The fourth index, total impulses during stimulation minus steady state, gave a different picture. This index of response magnitude was linearly related to stimulus intensity for both rates of cooling from all adapting temperatures except for the slow rate of cooling from the 45 degrees C AT...