Physiology & behavior
-
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.
-
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)