Behavioral tests show that noncontingent stimulation of self-stimulation sites in the lateral hypothalamus increases escape and avoidance from central or peripheral stimuli. The present study investigated the possibility that this phenomenon was mediated by an excitatory connection from the lateral hypothalamus to neurons in aversive regions of the brainstem. Most of the 24 rats participated in two phases of the experiment: unit recording under anesthesia ; and behavioral tests with intracranial stimulation in the waking state. Recordings of 120 units were obtained from the n. gigantocellularis reticularis (NGC) since stimulation of this region in the awake rat consistently elicited escape behavior. Unit responses could be divided into t\vo catagories: 61% responded to deep pinch or fout #shock (or both) but not to light brushing of the hair; and 39% responded to light brushing of the hair or were not responsive. Stimulation of behaviorally confirmed self-stimulation sites in lateral hypothalamus evoked short-latency (2 and 4 msec) excitation of 88% of the NGC units in the first category and only 15% in the second. Nearly all hypothalamic site.s not eliciting self-stimulation also failed to excite NGC units. The excitatory hypothalamic-bulboreticular connection may serve to increase the excitability of a nociceptive system during self-stimulation.
Manganese is known to reduce the spontaneous tension developed by atrial muscle ( 1 ) and to reduce the effect of catecholamines in both intestinal ( 2 ) and vascular (3) smooth muscles. In vascular smooth muscle the catecholamine, norepinephrine, increases the content (4) and reduces the efflux (4, 5 ) of 45Ca, suggesting that norepinephrineinduced tension results from an imbalance between calcium influx and efflux, with the net effect being an increase in the amount of intracellular calcium. Manganese decreases membrane permeability to calcium in a variety of tissues (6)(7)(8) and this action may be responsible for its attenuating effect on norepinephrine-induced tension. To investigate the possibility that a change in membrane permeability to calcium might be responsible for this attenuation in vascular smooth muscle, we determined the effect of manganese on calcium content of the tissue.Methods. Albino rabbits of either sex, weighing between 1 and 2 kg, were killed by a blow to the back of the head. The thoracic aorta was removed and placed in a physiological salt solution (PSS) comprised of (mM) :
Most of the neurons recorded from rat medial thalamus are inhibited by medial forebrain bundle and excited by reticular stimuli delivered at frequencies of 20-60 Hz. These opposite neural responses in single units parallel the opposite behavioral and motivational properties of the brain stimuli and may play a role in integrating reward and pain mechanisms. Brain stimulation Medial thalamus Rewarding Aversive brain stimulation
Opposite Medial Thalamic Unit Responses To Rewarding and Aversive Brain Stimulation Medial thalamus receives fibers from both medial forebrain bundle (MFB) and hindbrain and midbrain reticular formation (RET). The MFB and for the opposite 1\lFB and RET effects are similar to those eliciting self-stimulation and escape respectively in several operated rats tested both behaviorally and neurophysiologically.
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