Selective enhancement of shock avoidance responding elicited by GABA blockade in the posterior hypothalamus of rats

Anantha Shekhar, J. N. Hingtgen, J. A. DiMicco

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Recent studies have shown that blockade of γ-aminobutyric acid (GABA) in the posterior hypothalamus in anesthetized rats elicits cardio-respiratory stimulation similar to that seen in emotional defense reactions and, in conscious rats, locomotor arousal suggesting a flight response. The present study was conducted in order to test the hypothesis that the behavioral effects by GABA blockade in the posterior hypothalamus were the results of disinhibiting a mechanism whose activation selectively enhances reactivity to aversive stimuli. Male rats were trained on a Sidman shock avoidance schedule (RS20:SS10) as well as a food-reinforced approach schedule (VI 1). Under anesthesia, guide cannulae were stereotaxically implanted bilaterally in the posterior hypothalamus at sites where microinjection of the GABA antagonist, bicuculline methiodide (BMI) 25 ng, increased heart rate. After recovery, rats were tested in both the avoidance and VI 1 schedules after hypothalamic microinjection of saline, BMI 25 ng, and the GABA agonist, muscimol 25 ng. Microinjection of BMI significantly increased the avoidance responses but had no effect on the approach responses. Muscimol decreased both the avoidance and approach responses. When microinjected into the lateral hypothalamic area, BMI had no effect on the response rates in either schedule while muscimol decreased the approach responding only. Therefore, GABA blockade at the discrete area of the posterior hypothalamic nucleus appears to elicit a selective enhancement of avoidance responses. These results suggest that an endogenous GABAergic system in the posterior hypothalamus may tonically inhibit a constellation of autonomic, locomotor and motivational responses that are necessary for some types of defense reaction.

Original languageEnglish
Pages (from-to)118-128
Number of pages11
JournalBrain Research
Volume420
Issue number1
DOIs
StatePublished - Sep 8 1987

Fingerprint

Posterior Hypothalamus
Muscimol
gamma-Aminobutyric Acid
Shock
Appointments and Schedules
Microinjections
Lateral Hypothalamic Area
GABA Antagonists
GABA Agonists
Aminobutyrates
Arousal
Anesthesia
Heart Rate
Food
bicuculline methiodide

Keywords

  • Approach
  • Aversive drive
  • Avoid
  • Bicuculline
  • Defense reaction
  • Hypothalamus
  • Muscimol
  • γ-aminobutyric acid

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

Cite this

Selective enhancement of shock avoidance responding elicited by GABA blockade in the posterior hypothalamus of rats. / Shekhar, Anantha; Hingtgen, J. N.; DiMicco, J. A.

In: Brain Research, Vol. 420, No. 1, 08.09.1987, p. 118-128.

Research output: Contribution to journalArticle

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