The effects of GABA(A) receptor blockade in the dorsomedial hypothalamic nucleus on corticotrophin (ACTH) and corticosterone secretion in male rats

Stanley R. Keim, Anantha Shekhar

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Experiments were conducted to test if blockade of GABA(A) receptors in the dorsomedial hypothalamic nucleus (DMH) of rats, which is known to elicit cardiovascular and anxiety responses, would also elicit changes in the plasma levels of adrenocorticotrophic hormone (ACTH) and corticosterone. Male Sprague-Dawley rats were anesthetized with pentobarbital, fitted with femoral arterial catheters and implanted with microinjection cannulae into the DMH or the sites anterior to the DMH (i.e., closer to the paraventricular nucleus (PVN) of the hypothalamus). The rats were then injected with either artificial cerebrospinal fluid (aCSF; 100 nl) or the GABA(A) antagonist, bicuculline methiodide (BMI; 50 pmol in 100 nl) and their plasma samples obtained at 5, 30, 60, and 120 min after microinjection. Plasma ACTH and corticosterone were measured by using a radioimmunoassay. Rats injected with BMI, but not aCSF, into the DMH showed significant increases in heart rate (HR, 110 ± 16 beats/min), blood pressure (BP; 30 ± 4 mmHg), and plasma levels of both ACTH (64 ± 10 pg/ml) and corticosterone (170 ± 25 ng/ml) from baseline. BMI injections into the anterior sites closer to the PVN did not elicit significant increases in HR, BP, or plasma levels of ACTH and corticosterone. These results suggest that a tonic GABA(A) receptor-mediated inhibition system regulates a coordinated physiological and neuroendocrine response in the DMH and that this neuroendocrine response is not due to diffusion of BMI to the PVN of rats.

Original languageEnglish
Pages (from-to)46-51
Number of pages6
JournalBrain Research
Volume739
Issue number1-2
DOIs
StatePublished - Nov 11 1996

Fingerprint

Dorsomedial Hypothalamic Nucleus
GABA-A Receptors
Corticosterone
Adrenocorticotropic Hormone
Paraventricular Hypothalamic Nucleus
Microinjections
GABA-A Receptor Antagonists
Pentobarbital
Thigh
Hypothalamus
Radioimmunoassay
Sprague Dawley Rats
Cerebrospinal Fluid
Catheters
Anxiety
Heart Rate
Blood Pressure
Injections

Keywords

  • adrenal hormone
  • anxiety
  • bicuculline
  • blood pressure
  • heart rate
  • stress

ASJC Scopus subject areas

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

Cite this

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abstract = "Experiments were conducted to test if blockade of GABA(A) receptors in the dorsomedial hypothalamic nucleus (DMH) of rats, which is known to elicit cardiovascular and anxiety responses, would also elicit changes in the plasma levels of adrenocorticotrophic hormone (ACTH) and corticosterone. Male Sprague-Dawley rats were anesthetized with pentobarbital, fitted with femoral arterial catheters and implanted with microinjection cannulae into the DMH or the sites anterior to the DMH (i.e., closer to the paraventricular nucleus (PVN) of the hypothalamus). The rats were then injected with either artificial cerebrospinal fluid (aCSF; 100 nl) or the GABA(A) antagonist, bicuculline methiodide (BMI; 50 pmol in 100 nl) and their plasma samples obtained at 5, 30, 60, and 120 min after microinjection. Plasma ACTH and corticosterone were measured by using a radioimmunoassay. Rats injected with BMI, but not aCSF, into the DMH showed significant increases in heart rate (HR, 110 ± 16 beats/min), blood pressure (BP; 30 ± 4 mmHg), and plasma levels of both ACTH (64 ± 10 pg/ml) and corticosterone (170 ± 25 ng/ml) from baseline. BMI injections into the anterior sites closer to the PVN did not elicit significant increases in HR, BP, or plasma levels of ACTH and corticosterone. These results suggest that a tonic GABA(A) receptor-mediated inhibition system regulates a coordinated physiological and neuroendocrine response in the DMH and that this neuroendocrine response is not due to diffusion of BMI to the PVN of rats.",
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N2 - Experiments were conducted to test if blockade of GABA(A) receptors in the dorsomedial hypothalamic nucleus (DMH) of rats, which is known to elicit cardiovascular and anxiety responses, would also elicit changes in the plasma levels of adrenocorticotrophic hormone (ACTH) and corticosterone. Male Sprague-Dawley rats were anesthetized with pentobarbital, fitted with femoral arterial catheters and implanted with microinjection cannulae into the DMH or the sites anterior to the DMH (i.e., closer to the paraventricular nucleus (PVN) of the hypothalamus). The rats were then injected with either artificial cerebrospinal fluid (aCSF; 100 nl) or the GABA(A) antagonist, bicuculline methiodide (BMI; 50 pmol in 100 nl) and their plasma samples obtained at 5, 30, 60, and 120 min after microinjection. Plasma ACTH and corticosterone were measured by using a radioimmunoassay. Rats injected with BMI, but not aCSF, into the DMH showed significant increases in heart rate (HR, 110 ± 16 beats/min), blood pressure (BP; 30 ± 4 mmHg), and plasma levels of both ACTH (64 ± 10 pg/ml) and corticosterone (170 ± 25 ng/ml) from baseline. BMI injections into the anterior sites closer to the PVN did not elicit significant increases in HR, BP, or plasma levels of ACTH and corticosterone. These results suggest that a tonic GABA(A) receptor-mediated inhibition system regulates a coordinated physiological and neuroendocrine response in the DMH and that this neuroendocrine response is not due to diffusion of BMI to the PVN of rats.

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