PMID- 7776233
OWN - NLM
STAT- MEDLINE
DCOM- 19950712
LR  - 20190512
IS  - 0022-3751 (Print)
IS  - 1469-7793 (Electronic)
IS  - 0022-3751 (Linking)
VI  - 483 ( Pt 1)
IP  - Pt 1
DP  - 1995 Feb 15
TI  - Central inhibitory effects of muscimol and bicuculline on the milk ejection 
      reflex in the anaesthetized rat.
PG  - 211-24
AB  - 1. In order to determine whether GABAergic mechanisms are involved in the control 
      of the milk ejection reflex in the rat, we examined the effects of central 
      administration of a GABAA receptor agonist (muscimol) and antagonist 
      (bicuculline) on the milk ejection reflex in the urethane-anaesthetized rat. 2. 
      Intracerebroventricular (i.c.v.) injection of both muscimol (n = 17), at doses of 
      5, 10 and 20 ng, and bicuculline (n = 15), at doses of 0.01, 0.1 and 0.3 
      microgram, inhibited the milk ejection reflex in a dose-dependent manner. The 
      bicuculline-induced inhibition was accompanied by desynchronization of the 
      electroencephalogram and, at the highest dose, by alteration in the sensitivity 
      of the mammary gland to oxytocin. No significant effect on the milk ejection 
      reflex was seen with i.c.v. isotonic saline (n = 5). 3. Injection of 20 (n = 5) 
      or 40 ng (n = 2) muscimol or 0.1 microgram bicuculline (n = 5) i.c.v. did not 
      significantly alter the rise in intramammary pressure evoked by electrical 
      stimulation of the neurohypophysis. 4. Bilateral 400 nl microinfusions directly 
      into the supraoptic nuclei of either muscimol (20-100 ng microliter(-1); n = 10) 
      or bicuculline (0.15 micrograms microliter(-1); n = 5) [corrected] resulted in an 
      inhibition of the milk ejection reflex, which was not accompanied by 
      desynchronization of the electroencephalogram. 5. The effects of i.c.v. 
      injections of muscimol (15 and 20 ng) and bicuculline (0.01, 0.12 and 0.3 
      microgram) on the electrical activity of twenty-seven antidromically identified 
      supraoptic magnocellular neurones were examined. Both compounds resulted in an 
      inhibition of the background firing of oxytocinergic and vasopressinergic cells, 
      and delayed the occurrence of high frequency bursts in oxytocin neurones. In five 
      supraoptic neurones, bicuculline induced a transient activation before 
      inhibition. 6. The powerful inhibitory action on the milk ejection reflex of both 
      muscimol and bicuculline provides evidence for the importance of GABA neurones in 
      maintaining the functional integrity of the mechanisms which allow the 
      intermittent and pulsatile release of oxytocin during suckling.
FAU - Voisin, D L
AU  - Voisin DL
AD  - INSERM U 378, Universite de Bordeaux II, France.
FAU - Herbison, A E
AU  - Herbison AE
FAU - Poulain, D A
AU  - Poulain DA
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - England
TA  - J Physiol
JT  - The Journal of physiology
JID - 0266262
RN  - 0 (Receptors, GABA)
RN  - 2763-96-4 (Muscimol)
RN  - 50-56-6 (Oxytocin)
RN  - Y37615DVKC (Bicuculline)
SB  - IM
EIN - J Physiol (Lond) 1995 Jun 15;485(Pt 3):873
MH  - Action Potentials/physiology
MH  - Animals
MH  - Bicuculline/administration & dosage/*pharmacology
MH  - Electric Stimulation
MH  - Electroencephalography/drug effects
MH  - Female
MH  - Injections, Intraventricular
MH  - Mammary Glands, Animal/*physiology
MH  - Milk Ejection/*drug effects
MH  - Muscimol/administration & dosage/*pharmacology
MH  - Neurons/drug effects/physiology
MH  - Oxytocin/pharmacology
MH  - Pituitary Gland, Posterior/physiology
MH  - Rats
MH  - Rats, Wistar
MH  - Receptors, GABA/*physiology
MH  - Reflex/drug effects
MH  - Supraoptic Nucleus/drug effects/*physiology
PMC - PMC1157883
EDAT- 1995/02/15 00:00
MHDA- 1995/02/15 00:01
PMCR- 1995/02/15
CRDT- 1995/02/15 00:00
PHST- 1995/02/15 00:00 [pubmed]
PHST- 1995/02/15 00:01 [medline]
PHST- 1995/02/15 00:00 [entrez]
PHST- 1995/02/15 00:00 [pmc-release]
AID - 10.1113/jphysiol.1995.sp020579 [doi]
PST - ppublish
SO  - J Physiol. 1995 Feb 15;483 ( Pt 1)(Pt 1):211-24. doi: 
      10.1113/jphysiol.1995.sp020579.