Influence of Frequency of Stimulus Upon Response to Hypothalamic Stimulation

Hare, Kendrick; Geohegan, William A.

doi:10.1152/jn.1941.4.3.266

Cited by 37 publications

(6 citation statements)

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“…Responses are altered qualita tively as well as quantitatively as shown in figure 4 in which the same rat re sponded to a standard hypothalamic stimulus with a pressure fall during amobar bital anesthesia but with pressure rises of different magnitudes in the awake state and during urethane anesthesia. Since in those experiments we used a constant current of 0.25 mA with a frequency of 90/sec to stimulate a fixed hypo thalamic electrode in the same animal, our results could not have been due to changes in strength (16) or frequency of the electrical stimulus (7,9), nor in area of the hypothalamus being stimulated (18). A possible explanation is that even if the tip of the electrode was only 0.5 mm in diameter, it was in contact with several neurons differing in function, stimulation thresholds, and anesthetic sus ceptibility.…”

Section: Discussionmentioning

confidence: 99%

Reduced Cardiovascular Responsiveness to Hypothalamic Stimulation during Urethane and Amobarbital Anesthesia

Buñag¹,

Eferakeya²

1973

Pharmacology

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Graded pressor responses to electrical stimulation of the posterior hypothalamus were accompanied by variable changes in heart rate. Tachycardia caused by weak currents was prevented by propranolol while reflex bradycardia associated with pressor responses to strong currents was abolished by atropine. Rats anesthetized with urethane were generally more responsive to hypo thalamic stimulation than those anesthetized with amobarbital. Stimulation thresholds were significantly lower when rats were awake than when they were anesthetized with either anesthetic. In some experiments, responses that were initially depressor during amobarbital anesthesia, later became pressor when the rats were awake or anesthetized with urethane. Our findings indicate that general anesthesia alters cardiovascular responsiveness to hypothalamic stimulation qualitatively as well as quantitatively.

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Section: Discussionmentioning

confidence: 99%

Reduced Cardiovascular Responsiveness to Hypothalamic Stimulation during Urethane and Amobarbital Anesthesia

Buñag¹,

Eferakeya²

1973

Pharmacology

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“…It is also possible that the depressor areas in the fetal forebrain develop much later than pressor areas or are perhaps under inhibitory influences in ulrro. The threshold frequency for the pressor-tachycardia response was from 40-50 Hz and decreasing below this value was never associated with conversion to a depressor response as in the adult cat (12). It would seem that the fetal cardiovascular system may be protected against neurogenic hypotension mediated at a hypothalamic level.…”

Section: Discussionmentioning

confidence: 90%

Cardiovascular Effects of Electrical Stimulation of the Forebrain in the Fetal Lamb

et al. 1976

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“…It should be borne in mind that the above-described observations are based on acute experiments and that in chronic conditions secondary adjustments may take place. Throughout this paper the anterior hypothalamus has been considered to be the source of parasympathetic and the posterior hypothalamus the source of sympathetic discharges, although it is well known (Hare & Geohagan, 1941, and others) that through variations of stimulus frequencies parasympathetic and sympathetic effects may be produced from both anterior and posterior…”

Section: Discussionmentioning

confidence: 99%

The influence of lesions in the anterior and posterior hypothalamus on tonic and phasic autonomic reactions

Gellhorn¹,

Nakao²,

Redgate³

1956

The Journal of Physiology

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In previous papers from this laboratory Redgate, 1954; Redgate & Gelihorn, 1955, 1956a it was shown that the intrahypothalamic injection of minute quantities of drugs altered the autonomic effects of hypo-and hypertensive drugs (injected intravenously) in a characteristic manner. If the excitability of the posterior hypothalamus was raised by the injection of strychnine or metrazol into this structure, the hypotensive action of acetylcholine, mecholyl and histamine was lessened. Also, the hypotensive phase was frequently followed by a brief hypertensive phase which was not seen under control conditions. Moreover, the acceleration of the heart rate and the contraction of the nictitating membrane (N.M.) which appeared during the hypotensive phase were intensified. When, however, thiopentone was injected into the posterior hypothalamus the opposite effects were obtained. In addition, it was noted that when through a subthreshold electrical stimulation the excitability of the posterior hypothalamus was increased, the same changes in the effect of the hypotensive drugs were obtained as were seen following the injection of metrazol or strychnine into the posterior hypothalamus. The described effects were reversible.In another group of experiments, thiopentone or pentobarbitone was injected into the anterior hypothalamus and the action of hypertensive drugs such as noradrenaline was tested. It was found that the reflex pulse rate deceleration resulting from the rise of blood pressure was greatly diminished. This diminution in the pulse-slowing reflex was likewise reversible.Finally, it was shown that injection into the hypothalamus of drugs which diminished its excitability revealed a tonic action of the hypothalamus on the cardio-vascular system. Injection of thiopentone into the posterior hypothalamus led to a temporary fall of blood pressure which was associated with a

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Influence of Frequency of Stimulus Upon Response to Hypothalamic Stimulation

Cited by 37 publications

References 0 publications

Reduced Cardiovascular Responsiveness to Hypothalamic Stimulation during Urethane and Amobarbital Anesthesia

Reduced Cardiovascular Responsiveness to Hypothalamic Stimulation during Urethane and Amobarbital Anesthesia

Cardiovascular Effects of Electrical Stimulation of the Forebrain in the Fetal Lamb

The influence of lesions in the anterior and posterior hypothalamus on tonic and phasic autonomic reactions

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