Physiology & behavior
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Physiology & behavior · Jan 1988
Quantitative relationship between the stimulus intensity and the response magnitude in the tail flick reflex.
The purpose of the present study was to investigate the quantitative relation between the stimulus intensity and the response magnitude of the tail flick reflex. The EMG of a tail muscle was recorded from the extensor caudae medialis (ECM) muscle in the side contralateral to heat stimulation, and the area of integrated EMG for 1 sec was measured as the magnitude of EMG activity. ⋯ The magnitude of an integrated EMG was decreased by about 50% of the control by an intraperitoneal administration of morphine (0.5 mg/kg). These results suggest that tail flick reflex is closely related to painful sensation, and that EMG activity of the ECM muscle is applicable as an electrophysiological indicator to noxious stimulation of the tail and an expressible indicator of the magnitude of pain.
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In three experiments we investigated the role of the GABAergic system in regulating penile reflexes and copulation in rats. All males had the suspensory ligament of the penis removed 3 weeks before the experiments, thereby permitting the novel observation of penile body erections in addition to penile glans responses. In Experiments 1 and 2, rats were assigned to one of the following treatment groups: control (saline-injected); baclofen, a GABA-B receptor agonist (1 or 2 mg/kg); THIP, a GABA-A receptor agonist (5 mg/kg); or (+)bicuculline, a GABA-A receptor antagonist (0.25 mg/kg). ⋯ These findings suggest that baclofen inhibited the mechanisms mediating penile glans responses more than those mediating penile body erections. Bicuculline was without effect in both experiments; THIP significantly increased erections in Experiment 2 but had no reliable effect in Experiment 1. Because baclofen inhibited penile responses in ex copula tests, Experiment 3 was designed to assess the effects of the same dosages of this agent on male copulatory behavior.(ABSTRACT TRUNCATED AT 250 WORDS)
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Physiology & behavior · Oct 1986
Dose-related stimulation of feeding by systemic injections of monosodium glutamate.
Monosodium glutamate (MSG) is an excitotoxin capable of both stimulating and lesioning neurons in circumventricular organs (CVOs) after systemic administration. In this study, MSG and equiosmotic concentrations of NaCl were administered subcutaneously to adult rats in order to observe the effects on food and water intake. MSG (0.5, 1, 2 and 6 g/kg), but not NaCl, stimulated feeding. ⋯ Neonatal MSG treatment, which is known to be more damaging to circumventricular neurons than adult treatment, greatly reduced or abolished subsequent MSG-induced stimulation of feeding in adults. Both MSG and NaCl stimulated drinking. Since the magnitude of the drinking response was similar for both solutes and was directly related to the osmotic strength of the solutions, we conclude that the drinking response after MSG was mediated by cellular dehydration.
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Physiology & behavior · Jan 1986
Effects of shock controllability on rat brain noradrenaline turnover under FR-1 and FR-3 Sidman avoidance schedules.
We examined changes in brain noradrenaline (NA) turnover as a function of shock controllability and the task complexity (fixed ratio, FR-1 and FR-3) under a 21-hr continuous discriminated Sidman avoidance schedule with shock intensity of 0.7-1.0 mA, shock duration of 1.0 sec, shock-shock interval of 1.5 sec, response-shock interval of 100 sec and signal-shock interval of 10 sec, by measuring levels of a principal metabolite of NA, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), in discrete brain regions of male Wistar rats. In an FR-1 operant schedule, experimental rats which could avoid or escape shock by pulling a disk manipulandum only once showed significantly lower levels of MHPG-SO4 in the hypothalamus, amygdala, thalamus, locus coeruleus (LC) region and cerebral cortex than did yoked rats which received the same amount of shock but could not perform any effective avoidance and/or escape responses. ⋯ The FR-3-experimental rats exhibited levels of MHPG-SO4 similar to those seen in the FR-3 yoked rats in all brain regions. These two groups of shocked rats showed significantly higher levels of MHPG-SO4 in all brain regions with the exception of the basal ganglia, as compared to the FR-3 control rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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A series of experiments compared sleep deprivation of rats by sleep contingent shock and by non punitive procedures. Sleep overrode shock in approximately 24 hours. Animals were kept awake by non punitive procedures for 12 and 15 days. Recovery measures were higher for the non punitive procedures.