Naslov
Effects of microinjection of GABA-a receptor agonist/antagonist into the ventral respiratory group of the rat

Autori
Pecotić, Renata ; Valić, Maja ; Vučković, Meri ; Đogaš, Zoran

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Periodicum biologorum / Vitale, Branko - Zagreb : Periodicum biologorum, Hrvatsko prirodoslovno društvo, 2004, 90-90

Skup
Fourth Croatian Congress of Pharmacology

Mjesto i datum
Split, Hrvatska, 15.09.2004. - 18.09.2004

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
GABA; frenički živac; ventralna respiracijska skupina neurona; štakor
(GABA; phrenic nerve; ventral respiratory group; rat)

Sažetak
Introduction: Ventral respiratory group (VRG) forms longitudinal column of respiratory neurons in the ventrolateral medulla, extending from the first cervical segment to the caudal end of the facial nucleus. It has been demonstrated that in cats and rats, chemical activation of different areas of VRG elicit different types of excitatory or inhibitory respiratory responses depending on the injection site. GABA as the main inhibitory neurotransmitter in vertebrate brain is thought to be mediator of fast synaptic inhibition in the breathing control. This study was performed to investigate different types of respiratory responses following unilateral microinjections of specific GABAA receptor agonist/antagonist in the VRG at the different depths from the dorsal brain surface. Materials and Methods: Experiments were performed on urethane anaesthetized, spontaneously breathing, vagotomized adult male Wistar rats weighing 300-330g. Femoral artery was cannulated and blood pressure was continuously monitored. Central respiratory activity was monitored by the phrenic nerve recordings. The rats were placed in a prone position in a stereotaxic instrument. Glass micropipettes were used for drug delivery. The single micropipettes were filled with GABA (0.5 M) and bicuculline (250 mM). The reference depth points were 6.0 mm (RDP1) and 6.5 mm (RDP2) from the dorsal brain surface. The rostro-caudal reference point used in this dorsal approach was 13 mm caudal to bregma, and 1.5 mm lateral to the midline. Results: Unilateral microinjection of GABA into the VRG produced decrease in respiratory rate in average 3.65% when microinjected at RDP1 and 7.55% in average when microinjected at RDP2, due to prolongation in duration of respiratory cycle duration (Ttot) 4.69% in average at RDP1 and 6.72% in average at RDP2. Amplitude of phrenic nerve discharge increased when GABA was microinjected at RDP1, 17.9% in average (SD 13.8) and decreased 6.33% in average (SD 2.89) at RDP2. Unilateral microinjection of bicuculline into the VRG resulted in several types of responses. Mostly, bicuculline microinjection reversibly augmented respiratory rate 7.76% in average (SD 25.33) at RDP1, and 1.94% in average (SD 4.96) at RDP2. Microinjection of bicuculline at RDP2 elicited increase in the phrenic nerve discharge amplitude of 32.5% in average (SD 38.71) and increase of 9.64% in average (SD 16.73) when microinjected at RDP1. Respiratory cycle duration (Ttot) was decreased when bicuculline was microinjected at RDP1 2.83% in average (SD 18.7) and 2.03% in average (SD 6.26) at RDP2. In four animals unilateral microinjection of bicuculline elicited transitional apnea followed by rhythmic breathing pattern. Transitional dysrhytmic breathing pattern was elicited by bicuculline microinjection in three animals followed by rhythmic breathing pattern. Conclusion: These results suggest that GABA activity in the VRG is important for respiratory rhythm generation, and respiratory neurons of the central pattern generator may vary at different depths from the dorsal brain surface.

Izvorni jezik
Engleski

Znanstvena područja
Kliničke medicinske znanosti

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