Opioid peptide involvement in the bulbar inhibition of electrodermal activity in the cat.

By analogy with supraspinal and spinal inhibitory controls of pain, it was hypothesized that an opioid mechanism could be involved in the bulbar inhibitory control of the electrodermal activity. This activity was evoked as skin potential responses on the footpads of 13 cats by the central tegmental field stimulation (control responses) and inhibited by the simultaneous stimulation of bulbar reticular formation (experimental responses). Then, naloxone, an opioid peptide antagonist, was injected intravenously or intrathecally and its effects were analyzed on both control and experimental responses. Intravenous injections of naloxone increased significantly the amplitude of experimental responses from 6 to 12 min after the injection and had no effect on the amplitude of control responses. Intrathecal injections of naloxone induced significant increases of amplitude of experimental responses from 6 to 42 min after the injection. These results showed that a spinal opioid peptide link could be involved in bulbar inhibition mechanisms of electrodermal activity.

Instrumental conditioning of skin potential responses in curarized cats: non specific effects of a punishment procedure.

This study evaluates the effects of a punishment paradigm upon electrodermal activity (EDA) in curarized cats. In ten experimental subjects, any skin potential response (SPR) exceeding threshold value was punished by an electric shock. Ten control subjects received an electric shock or an electric stimulation of the mesencephalic reticular formation unrelated to the EDA. The results show that: a) No significant modifications of EDA occurred in subjects characterized by low initial activity; b) The frequency of SPR significantly decreased in high activity subjects used both for the experiments and the controls. Therefore, this diminution, in experimental subjects, cannot be due to a learning process. Neither can it be related to level of curarization or to rate of artificial ventilation. It is suggested that this effect results from a non-specific cortical inhibitory mechanism acting on the reticular activating system. The results obtained in three decorticated cats submitted to a punishment procedure are in accordance with such an hypothesis. Consequently the existence of operant autonomic learning remains unproven.

The ontogeny of spontaneous skin potential responses in kittens.

The evolution of frequency and amplitude of spontaneous skin potential responses (SPRs) was studied in kittens from birth to 30 days. Results showed that: i) at birth, electrodermal activity is very low, and significantly lower than in adults; ii) the evolution of electrodermal activity is rapid, the adult level being reached by the end of the third week. Frequency and amplitude evolve at approximately the same rate; iii) SPRs recorded on the forepaw were significantly more frequent and larger than those for the hindpaw up to 13 days; iv) changes in electrodermal activity as a function of sleep and waking showed that sleep is characterized by a moderate decrease of SPR amplitude and by a pronounced decrease in SPR frequency. The results are discussed in terms of maturation of the central nervous system.

Influence of skin temperature on latency and amplitude of skin potential responses in the cat.

The effect of skin temperature changes on skin potential response (SPR) amplitude and latency was examined in the cat. SPRs were elicited either by stimulating the reticular formation or the distal end of the median nerve. At room temperature, the latency due to the neuroglandular transmission and to the peripheral effector accounts for about half of the total latency of SPR evoked by reticular stimulation. This latency increases to several seconds at low skin temperatures (approximately 10 degrees C), decreases with temperature, and is minimal (300 msec) at high temperatures (over 40 degrees C). SPR amplitude increases with skin temperature, reaches a maximal value (usually around 30 degrees C) and then decreases at higher temperatures. The decrease of latency at higher temperatures confirms results previously obtained in humans. However, the mechanisms of amplitude decrease for high temperatures remain unclear.

Mesencephalic and bulbar reticular control of skin potential responses in kittens.

Reticular command of Skin Potential Responses (SPRs) was investigated in 30 kittens between 1 and 30 days of age which had been acutely implanted under chloralose anaesthesia (40 mg/kg). The results show that (a) SPRs can be elicited through electrical stimulation of the mesencephalic reticular formation (MRF) in kittens as early as a few hours after birth. As in the adult cat, these SPRs consist of a monophasic negative wave. Up until the age of 10 days SPRs recorded from the forepaws are significantly larger than those from the hindpaws. There is not difference in amplitude between ipsilateral and contralateral responses, relative to the stimulation site. (b) The first of a pair of MRF stimuli is followed by a subnormal period of 50 s, during which a second MRF stimulus of the same intensity evokes SPR of lower amplitude. (c) Stimulation of certain parts of the bulbar reticular formation (BRF) inhibits the SPRs evoked through MRF stimulation. The average percentage of inhibition was 65% in 10 kittens aged from 1 to 15 days. These results suggest that the reticular centers which control electrodermal activity are functional at birth and that certain characteristics of electrodermal activity are subject to post-natal maturation.

Stability of spontaneous electrodermal activity in the kitten.

Recordings of spontaneous electrodermal activity (EDA) were made in eight kittens, between 1 and 29 days of age, in order to obtain an estimation of reliability. Both frequency (number of SSPRs/min) and amplitude (in mV) of spontaneous electrodermal responses were computed during several waking-sleeping sessions. The results show that: (a) the reliability of records taken during the first week appears to be very low; (b) the frequency of SSPRs reaches the same level of stability as that of the adult at about three weeks of life; and (c) reliability of spontaneous EDA is considerably higher in sleeping than in waking kitten. The results are discussed in terms of ontogeny and 'trait' vs. 'state' characteristics of spontaneous EDA.

Reliability of spontaneous electrodermal activity in the cat as a function of waking and sleep stages.

This study was designed to examine the reliability of spontaneous electrodermal activity (EDA) as a function of the stages of sleep and waking in freely moving cats. Five adult cats were observed during waking--sleep sessions. The results show that: (a) for all stages, the reliability of EDA is slightly higher for amplitude of SSPRs than for frequency; (b) during drowsiness, a maximum of reliability is observed, as is a slight decrease during slow wave sleep; during paradoxical sleep, reliability decreases greatly to below that of the waking level; (c) the reliability of spontaneous EDA appears to be higher in waking cats than that quoted for human subjects. These results are discussed with reference to individual characteristics and state variables.