Response characteristics of lateral hypothalamic neurons to odors in unanesthetized rabbits

1983 ◽  
Vol 50 (3) ◽  
pp. 609-617 ◽  
Author(s):  
S. Kogure ◽  
N. Onoda
Keyword(s):  
Electrical Stimulation ◽  
Response Curves ◽  
Hypothalamic Area ◽  
Response Characteristics ◽  
Lateral Hypothalamic ◽  
Inhibitory Type ◽  
Excitatory Responses ◽  
Type Response ◽  
Concentration Series ◽  
Stimulation Of

Extracellular responses of 103 neurons to eight odors were studied in the lateral hypothalamic area (LHA) of unanesthetized rabbits. In response to electrical stimulation of the olfactory bulb (OB), 97 units were excited with latencies of 3.7-68.0 ms (mean, 19.4 ms) and the activity of 6 units was suppressed. In the LHA, 90 units of 103 were found that responded to from one to eight odors. The number of units that responded to three odors was the most numerous (22%) among these odor-sensitive units. Lateral hypothalamic (LH) neurons showed high response probabilities to cineole (0.72), cyclotene (0.68), and isovaleric acid (0.54). Of the recorded units, 94% showed an excitatory-type response to both electrical stimulation of the OB and odor stimuli of the olfactory mucosa, while only 6% showed an inhibitory-type response to both stimuli. These results suggest that the olfactory effect on the LHA is predominantly excitatory. Responses to a concentration series of odors were examined in 24 LH neurons. In most cases, response intensity did not increase monotonically with increasing odor concentration. Instead, the concentration-response curves of most units showed a peak or inflections during the concentration series. Compared with results obtained from other olfactory structures in different species, it appears that LH neurons do not contribute much to odor discrimination in rabbits.

Avoidance and approach learning motivated by stimulation of identical hypothalamic loci

1959 ◽  
Vol 197 (1) ◽  
pp. 153-157 ◽  
Author(s):  
George W. Brown ◽  
Bertram D. Cohen
Keyword(s):  
Electrical Stimulation ◽  
Lateral Hypothalamus ◽  
Opportunity To Learn ◽  
Hypothalamic Stimulation ◽  
Experimental Conditions ◽  
Approach Response ◽  
Lateral Hypothalamic ◽  
Stimulating Electrodes ◽  
Second Procedure ◽  
Stimulation Of

Cats with stimulating electrodes implanted in the lateral hypothalamus were subjected to two types of experimental procedures. In the first procedure the cats were given an opportunity to learn to avoid hypothalamic stimulation which produces a typical ‘hypothalamic rage’ response. The second procedure allows the same cats to learn to approach an area where the hypothalamic stimulus is administered. In both procedures, electrical stimulation was delivered through identical electrodes, yet each animal learned the appropriate avoidance or approach response, depending upon the experimental conditions. Therefore, lateral hypothalamic stimulation may act as an energizing, drive-arousing, operation to produce both avoidance and approach learning in cats.

Responses of medullary raphe neurons to electrical and chemical activation of vagal afferent nerve fibers

1993 ◽  
Vol 70 (5) ◽  
pp. 1950-1961 ◽  
Author(s):  
A. R. Evans ◽  
R. W. Blair
Keyword(s):  
Electrical Stimulation ◽  
Chemical Activation ◽  
Vagal Afferents ◽  
Frequency Dependent ◽  
Afferent Fibers ◽  
Vagal Afferent ◽  
Mixed Responses ◽  
Excitatory Responses ◽  
Dose Dependent ◽  
Stimulation Of

1. Various intensities, frequencies, and pulse widths of electrical stimulation of vagal afferent fibers were used to assess the responses of 87 medullary raphe neurons to vagal afferent fiber input in pentobarbital sodium-anesthetized, barodenervated paralyzed cats. Thirty-seven neurons were antidromically activated from the T2-T3 segments of the thoracic spinal cord, and 40 neurons could not be antidromically activated. Neurons were located in the nucleus raphe magnus (79%) and the nucleus raphe obscurus (15%). The remaining 6% of the neurons were not found; however, their locations were comparable in depth and position on the midline with other neurons in the same animals whose locations were identified. 2. The responses of 60 neurons to electrical stimulation of vagal afferent fibers were classified as excitatory (38%), inhibitory (24%), or mixed, (7%). The mixed responses were characterized by excitation at one frequency or intensity and inhibition at another frequency or intensity. The remaining 27 neurons did not clearly respond. 3. The excitatory responses to electrical stimulation of the cervical vagus nerve were intensity and frequency dependent. Inhibitory responses were frequency dependent at lower frequencies of stimulation and both frequency and intensity dependent at higher frequencies. The mixed responses were frequency dependent. Overall, longer pulse widths produced significantly greater responses than shorter pulse widths. 4. Thirty-three neurons were tested for responses to chemical stimulation of vagal afferents with intra-atrial injections of three doses of veratridine. Twenty-one percent were excited, 55% were inhibited, and 6% had mixed responses. For the mixed responses, excitation occurred at one dose and inhibition at another. The remaining 18% of the neurons were unresponsive to veratridine. The excitatory responses were dose dependent, but the inhibitory responses were not. Three doses of phenybiguanide (PBG) were also used to chemically activate vagal afferents in 27 neurons. Eleven percent were excited, 44% were inhibited, and 4% had mixed responses. The remaining 41% were unresponsive to PBG. The excitatory and inhibitory responses were dose dependent. 5. When comparing responses in projection and nonprojection neurons, inhibition was seen significantly more often in projection neurons and excitation in nonprojection neurons. Sixty-three percent of the neurons inhibited by electrical stimulation were raphespinal neurons, and 78% of the neurons excited by vagal stimulation were nonprojection neurons. Similar observations were made with the responses to chemical activation of the vagus. 6. Neurons with lower spontaneous discharge rates were more often excited by vagal stimulation and neurons with higher rates were more often inhibited.(ABSTRACT TRUNCATED AT 400 WORDS)

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