Increase In Response Duration Research Articles

NMDA receptor antagonists attenuate mechanical hyperalgesia in rats with unilateral inflammation of the hindpaw

The effects of N-methyl-d-aspartate (NMDA) receptor antagonists on mechanical hyperalgesia associated with tissue inflammation were studied. Following an injection of the inflammatory agent, complete Freund's adjuvant, into the rat hindpaw, there was a significant decrease in threshold and an increase in response duration to mechanical stimuli, suggesting that a state of mechanical hyperalgesia was induced. The intrathecal administration of the NMDA receptor antagonists, dizocilpine maleate and (±)-2-amino-5-phosphonopentanoic acid, significantly increased mechanical threshold and reduced response duration in the inflamed hindpaw, but had no effect on the non-injected paw. The results suggest that NMDA receptor activation may contribute to the mechanical hyperalgesia that follows peripheral tissue inflammation.

Differential tolerance to the behavioral effects of chronic pimozide and clozapine on multiple random interval responding in rats

The behavioral effects of 10 days of chronic administration of the typical neuroleptic, pimozide, and the atypical neuroleptic, clozapine, were compared on a schedule of multiple random interval responding for food reinforcement and on photocell activity in rats. The low doses of both neuroleptics (0.125mg/kg pimozide, 1.25mg/kg clozapine) had little effect on any of the dependent variables measured. The high doses (1.0mg/kg pimozide, 10.0mg/kg clozapine) significantly disrupted response rates and reinforcement rates and significantly increased response duration when the drugs were first administered. Chronic administration, however, resulted in different profiles for the two drugs. While tolerance developed to the disruptive effects of clozapine, tolerance did not develop to the disruptive effects of pimozide and, on some dependent measures, an increased sensitivity developed. No tolerance developed to the disruptive effects of either drug on photocell activity. The effects of the drugs depended on the reinforcement density of the operant schedule.

A-fibers mediate mechanical hyperesthesia and allodynia and C-fibers mediate thermal hyperalgesia in a new model of causalgiform pain disorders in rats

Unilateral tight ligation of about half of the sciatic nerve in rats rapidly produces sympathetically dependent neuropathic pain which lasts many months and resembles causalgia in humans. The sensory abnormalities detected at the plantar side of the hindpaws include: (1) nocifensive responses to repetitive light touch (allodynia); (2) bilateral reduction in withdrawal thresholds to repetitive von-Frey hair stimulation (mechanical hyperesthesia); (3) bilateral reduction in withdrawal thresholds to CO2 laser heat pulses; and (4) unilateral increase in response duration to an intense laser heat pulse (thermal hyperalgesia). Using neonatal capsaicin treatment, we determined the type of afferent fiber remaining in the partially injured nerve, which mediates these disorders. Capsaicin, which destroys most C- and some A delta-fibers in peripheral nerves, had no effect on the touch-evoked allodynia and mechanical hyperesthesia that are produced by partial sciatic nerve injury. These disorders were, therefore, mediated by myelinated fibers. In contrast, thermal hyperalgesia failed to develop in capsaicin-treated rats following partial nerve injury. Thus, thermal hyperalgesia produced by partial nerve injury appears to be mediated by heat-nociceptive C-fibers.

Haloperidol produces within-session increments in operant response duration in rats

On the basis of previously reported observations that haloperidol induces within-session decrements in operant response rate in rats, it was suspected that other measures of operant behavior may also display within-session changes after treatement with this neuroleptic. Accordingly, haloperidol (0.02, 0.04, 0.08, 0.16 mg/kg) was administered to six rats trained on a fixed-ratio 20 schedule of liquid food reinforcement, and response duration was recorded as a measure of drug effects independent of response rate. Significant within-session decrements in response rate and increments in response duration were observed as responding ensued. At the 0.08 mg/kg dose, 300% increases in response duration were seen during the last third of the responses made in a session. The progressive slowing of individual motor acts were interpreted as neuroleptic-induced Parkinsonism in the rat, and within-session decrements in response rate were likewise seen as a manifestation of the same pharmacological effects that increased response duration.

Selection for increased pheromone response in the male pink bollworm,Pectinophora gossypiella (lepidoptera: Gelechiidae)

The genetic basis of the duration and incidence of male wing fanning to pheromone in the pink bollworm moth, Pectinophora gossypiella (Saunders), was examined by artificial selection. Using a still-air bioassay, males from a laboratory colony were selected for increased duration of wing fanning when exposed to a 65:35 blend of (Z,E)- and (Z,Z)-7,11-hexadecadienyl acetates. The mean (+/- SE) duration of wing fanning in the selected line increased from 5.4 +/- 1.4 to 17.4 +/- 2.7 s after six generations. The increase in wing fanning duration was the result of an increase in response duration among responders and not the percentage of males that responded. Realized heritability of wing-fanning duration was 0.16 +/- 0.02. The amount and ratio of pheromone produced by females in the male-selected line did not change.

Assessment of pimozide's motor and hedonic effects on operant behavior in rats

The present study examined the effects of the neuroleptic pimozide on several measures of motor capacity and reinforcement efficacy in rats trained to respond according to a multiple random interval (RI) food reinforcement schedule (mean interreinforcement intervals of 10, 20, 40, 80, and 160 sec). Pimozide (0.125, 0.25, 0.5, and 1.0 mg/kg) produced a dose-dependent suppression of response rates for all five RI schedules and a dose-dependent increase in response duration. An independent measure of motor activity in photocell activity chambers also was decreased by pimozide in a dose-dependent manner. Photocell activity was significantly correlated with response duration and with the Matching Equation parameter k. Thus, all three measures of motor performance revealed similar decreases in motor capacity at the high dose of pimozide. Reinforcement efficacy also was reduced by the 1.0 mg/kg dose of pimozide as indicated by an increase in the Matching Equation parameter Re. The parameters k and Re were not significantly correlated, suggesting that these two Matching Equation parameters do provide independent measures of motor capacity and reinforcement efficacy, respectively. The present results demonstrate the importance of obtaining measures other than simple response rates in order to assess drug effects on operant behavior.

Effects of haloperidol on the biophysical characteristics of operant responding: Implications for motor and reinforcement processes

Food-deprived rats were reinforced with sweetened condensed milk for pressing a force-sensing operandum on a continuous reinforcement basis. Force was continuously recorded (every 0.00195 sec) during each response, and measures derived from the resulting force-time waveforms served as the basis for evaluating neuroleptic challenge in the form of haloperidol (0.04, 0.08, 0.16 mg/kg). Significant dose-related drug effects included a decrease in response rate, an increase in mean emitted peak force, and an increase in overall response duration. Additional quantitative analyses revealed that the drug-induced increase in response duration resulted primarily from a slowing in the animal's paw removal from the force-sensing operandum. The findings are analogous to deficits in Parkinson's disease and suggest a behavioral mechanism that might account for much of the rate attenuating effects of neuroleptics. Implications for motor and reward interpretations of the actions of dopamine antagonists are also discussed.

Effects of pimozide on emitted force, duration and rate of operant response maintained at low and high levels of required force.

The behavioral effects of pimozide (0.25, 0.5, and 1.0 mg/kg) were assessed in two separate experiments in which session mean peak force, maximum peak force, and response duration served as the dependent variables complementing operant response rate. In the first experiment, two groups of water-deprived rats were trained on a continuous reinforcement (CRF) schedule for reaching out and pressing downward on a force transducer with peak forces of at least 4 g (low-force group) or 40 g (high-force group). In the second experiment a pull-type response topography and fixed ratio 20 were used, and force requirements were 4 g for the low-force group and 100 g for the high-force condition. Under these conditions pimozide decreased response rate and increased response duration irrespective of response topography, required force, or schedule of reinforcement. Neither mean peak force nor maximum peak force were significantly decreased by the drug, and in the low-force CRF condition a small but significant dose-related rise in mean peak force was observed. It was hypothesized that neuroleptics exert their motor-impairing effects primarily in the temporal domain of behavior but do not appreciably affect the force dimension of performance capacity. And these temporal domain effects may be reflected in differences in the kinetic requirements for the overall behavior and not just the response itself. Additionally, the possibility that some of the observed effects could be accounted for by "anhedonia" was addressed.

Transcutaneous electrical nerve stimulation: A microneurographic and perceptual study

With the aim of studying peripheral physiological mechanisms involved in transcutaneous electrical nerve stimulation (TENS) for the suppression of pain, the authors have examined 14 healthy volunteers in the perceptual part and 8 in the microneurographic part of this study. For pain suppressing stimulation they have used ring electrodes and stimulators capable of producing rectangular, sine wave, triangular and hybrid wave forms. Pain was induced with electrical stimuli on the distal phalanx of the middle finger. TENS with rectangular, sine wave and triangular pulses activates mainly Aβ, but also some Aδ fibres. Pain suppressing capacity of different wave forms used was the same and was achieved with stimuli close to the threshold for pain. Pain was most effectively dimished when noxious and pain suppressing stimuli were applied to the same finger; this effect was smaller with the two stimuli on neighbouring fingers and very weak when pain suppressing stimulus was applied to the contralateral hand. Increases in stimulus frequency resulted in an increased and variable latency as well as intermittent blocking of those spike components which had been near threshold at low frequency stimulation. This is interpreted as being due to local changes in excitation threshold. In surface-recorded averaged electroneurograms this effect was seen as amplitude decrement and increased response duration, but was not due to impulse transmission failure in Aδ fibres as seen microneurographically. On continuous high frequency stimulation, the intensity of sensation elicited diminished, although there was no change in the microneurogram. The authors conclude that the peripheral contribution to the analgesic effects of TENS seems to be unimportant.

Effect of temperature on habituation of the LC-VR reflex of the frog spinal cord

The lateral column-ventral root reflex of the frog spinal cord is a neurophysiologically well-characterized model system that demonstrates eight of the nine parameters of habituation. Because knowledge about the temperature dependence of biological processes can yield clues about the underlying biochemical mechanisms, the current paper investigates the effects of temperature on lateral column-ventral root reflex habituation. Lowering the temperature from 15° to 5°C resulted in profound, quantitative alterations in the appearance of the lateral column-ventral root reflex. These changes included a decrease in response amplitude, an increase in response duration, and an increase in response latency. In spite of these changes, it was concluded that the responses at 15° and 5° were generated by the same, monosynaptic lateral column-motoneuronal system. These changes built up gradually with each degree of cooling and were consistent with the known temperature dependencies of various neurophysiological processes. Lowering the temperature from 15° to 5°C also increased the depression induced by conditioning stimulation for pulse trains of two to ten pulses in length. This increase in habituation with cooling was poorly correlated with changes in response amplitude, and it was therefore concluded that the altered habituation did not result from a stimulus-intensity like effect. Furthermore, understanding the mechanism by which temperature was able to alter habituation did not seem possible without resolving the effects of temperature on the depression induced by each successive stimulus from the effects of temperature on the rate of recovery between stimuli.

The effect of discrimination training on the response rate and response duration of the rat

Response rate (responses per minute) and response duration (time in seconds per press) were recorded in rats shifted from multiple variable-interval variable-interval (mult VI VI) to multiple extinction variable-interval (mult EXT VI). This procedure produced positive contrast (i.e., a decrease in response rate in EXT and an increase in VI) in 11 of 12 rats and, in addition, produced an increase in response duration (i.e., bar holding), which, for the most part, was confined to the EXT component of the mult EXT VI condition. One of the 12 rats showed negative induction (i.e., a decrease in response rate in both the EXT and VI components), and also an increase in response duration in both the EXT and VI components of the mult EXT VI condition. The results indicate that generalization of behavior from the EXT to the VI component can produce negative induction, and that such generalization must be prevented if positive contrast is to occur in the rat.

Response to Delayed Auditory Feedback in Patients with Hemispheric Lesions

The effect of delayed auditory feedback (DAF) on the performance of verbal and nonverbal tasks at two levels of difficulty by patients with left or right hemispheric lesions and non brain-damaged controls was compared. All subjects showed DAF effects, as measured by increases in response duration and intensity. While controls showed an increase in DAF effects as a function of increased task difficulty, the brain-damaged patients failed to show such an increase on tasks on which they were presumably impaired (verbal tasks for lefts, nonverbal for rights). Findings suggest a clear dissociation between DAF effects in unilateraly lesioned patients due to the nature of the stimulus material and its difficulty level.

Effect of different pupil to eye size ratios on tonic immobility in chickens

Seven simulated eyes with varying pupil size to eye ratios were tested for their effects on the duration of tonic immobility. A pair of eyes with a ratio of approximately 11/20 mm was the only configuration which produced reliable increases in response duration. The results were discussed as they relate to the possible role of eye contact in predator-prey encounters.

SOME PUNISHING EFFECTS OF RESPONSE‐FORCE1

The present experiment explored the punishing effect of different response-force requirements by means of a two-operant design analogous to a two-component chain schedule. The first component of the chain required a lever pull through 0.25 in. (0.64 cm) at 1 lb (4.45 N) of force. The second component required a lever pull through an additional 0.75 in. (1.90 cm) with the force varied between sessions from 1 lb to 50 lb (4.45 N to 223 N). Completion of the second component of the chain was reinforced after variable intervals averaging 1 min. The average rate of first-component response decreased as the force requirement for second-component responses was increased. This rate reduction did not appear to be due to increased response duration, "fatigue", or differing rates of reinforcement. If the force requirement for the second-component response is viewed as a consequence for the first-component response, then the results of the experiment show that a high force requirement is a punisher.