Brain Research, 525 (1990) 165-169 Elsevier
165
BRES 24226
Excitatory and inhibitory effects of adenosine on the neurotransmission in the hippocampal slices of guinea pig Shunji Nishimura, Mitsuhiro Mohri, Yasuhiro Okada and Masahiro Mori Department of Physiology, School of Medicine, Kobe University, Kobe (Japan)
(Accepted 1 May 1990) Key words: Hippocampalslice; Neurotransmission;Postsynapticpotential; Adenosine; Adenosine triphosphate; Excitation; Inhibition
Postsynaptic potentials (PSPs) were recorded from the granular cell layer of guinea pig hippocampal slices. Application of adenosine at a concentration of more than 10/~M in the incubation medium depressed the amplitude of the PSP, but adenosine at a concentration of 10 nM to 1/~M enhanced the amplitude of the PSP. The dose-response curve of the effect of adenosine showed an excitatory and inhibitory biphasic pattern. Adenosine analogues such as adenosine triphosphate (ATP), adenosine diphosphate (ADP) and nicotinamide adenine dinucleotide (NAD) showed similar biphasic effects, howeverfl-y-methyleneadenosinetriphosphate(fl-y-ATP),5"-N-ethylcarboxamidoadenosine(NECA), N~-cyclohexyladenosine(CHA) and N~-R-phenylisopropyladenosine(RPIA) revealed only inhibitory effects. Adenosine has been considered as an inhibitory neurotransmitter in the gut I and neuromodulator in the CNS on synaptic transmission 14. Using tissue slices incubated in a bath, Okada et al. observed distinct inhibitory effects with adenosine and its derivatives on the neurotransmission of hippocampal and olfactory cortex slices 1~-13. Phillis et al. reported that microiontophoretic application of adenosine showed potent inhibitory action on the transmission in the cortical neurons ~5. The inhibitory action of adenosine has been attributed to be mediated through the inhibition of transmitter release at the presynaptic site or through changes of the potassium conductance in the postsynaptic cell4'6. On the other hand, the excitatory effect of adenosine triphosphate (ATP), an adenine nucleotide, has been reported in cuneate neurons in vivo and in spinal ganglion cells in vitro 5'9. In this paper, we are reporting concentrationdependent excitatory and inhibitory biphasic effects of adenosine on neurotransmission in hippocampal slices. Guinea pigs weighing 250-300 g were used. Hippocampal slices were prepared and preincubated for at least 20 rain in standard medium (in mM): NaCI 125, NaHCO 3 26, KC1 5, CaCI2 2, KH2PO 4 1.2, MgSO 4 1.3, glucose 10. The details of the techniques used to prepare slices have been reported elsewhere 13. The slices were placed in the observation chamber and fully submerged in the standard medium continuously perfused (5 ml/min). The temperature was kept at 36 °C throughout the experiment. Under a stereomicroscope, the perforant path was stimulated electrically by means of a pair of silver wire
electrodes, and the postsynaptic field potential (PSP; population spike) was recorded in the granular cell layer of the dentate gyrus with a glass microelectrode. The stimulation was given every 2 s (square pulse 0.1 ms in duration) and the strength of electrical stimulation was adjusted to obtain the PSP at half of the maximum amplitude elicited by supramaximal stimulation. A stable PSP was recorded at least 30 min before the addition of adenosine and its analogues to the medium. Drugs were applied to the perfusion medium in the circulatory unit, and removed by washing the slices. Only one slice was used for one trial to test the effect of adenosine at single concentration applied. Adenosine, ATP, adenosine diphosphate (ADP), nicotinamide adenine dinucleotide (NAD), fl-y-methyleneadenosinetriphosphate (fl-y-ATP) and N6-R-phenylisopropyladenosine (RPIA) were purchased from Sigma. 5"-N-Ethylcarboxamidoadenosine (NECA) was purchased from Research Biochemicals Inc. N~-Cyclohexyladenosine (CHA) was purchased from Kohjin Co. Other chemicals were obtained from Nakarai, Kyoto. A typical PSP recorded from the granular cell layer is shown in Fig. 1A. After obtaining the supramaximal response of the PSP, the amplitude of the PSP was adjusted to half of the maximum amplitude (Fig. 1A-l). The amplitude of PSP increased gradually after the application of adenosine at a concentration of 0.5/~M (Fig. 1A-2), and reached a plateau after 15 min (Fig. 1A-3). After washing the slices, the PSP returned to near the original level within 15 min (Fig. 1A-4). In addition to the
Correspondence: Y. Okada, Department of Physiology,School of Medicine, Kobe University, 7-5-1 Kusunoki-cho,Chuoku, Kobe, Japan.
0006-8993/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)
166
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..•5m=ecImV 200.
Adenosine
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165
BRES 24226
Excitatory and inhibitory effects of adenosine on the neurotransmission in the hippocampal slices of guinea pig Shunji Nishimura, Mitsuhiro Mohri, Yasuhiro Okada and Masahiro Mori Department of Physiology, School of Medicine, Kobe University, Kobe (Japan)
(Accepted 1 May 1990) Key words: Hippocampalslice; Neurotransmission;Postsynapticpotential; Adenosine; Adenosine triphosphate; Excitation; Inhibition
Postsynaptic potentials (PSPs) were recorded from the granular cell layer of guinea pig hippocampal slices. Application of adenosine at a concentration of more than 10/~M in the incubation medium depressed the amplitude of the PSP, but adenosine at a concentration of 10 nM to 1/~M enhanced the amplitude of the PSP. The dose-response curve of the effect of adenosine showed an excitatory and inhibitory biphasic pattern. Adenosine analogues such as adenosine triphosphate (ATP), adenosine diphosphate (ADP) and nicotinamide adenine dinucleotide (NAD) showed similar biphasic effects, howeverfl-y-methyleneadenosinetriphosphate(fl-y-ATP),5"-N-ethylcarboxamidoadenosine(NECA), N~-cyclohexyladenosine(CHA) and N~-R-phenylisopropyladenosine(RPIA) revealed only inhibitory effects. Adenosine has been considered as an inhibitory neurotransmitter in the gut I and neuromodulator in the CNS on synaptic transmission 14. Using tissue slices incubated in a bath, Okada et al. observed distinct inhibitory effects with adenosine and its derivatives on the neurotransmission of hippocampal and olfactory cortex slices 1~-13. Phillis et al. reported that microiontophoretic application of adenosine showed potent inhibitory action on the transmission in the cortical neurons ~5. The inhibitory action of adenosine has been attributed to be mediated through the inhibition of transmitter release at the presynaptic site or through changes of the potassium conductance in the postsynaptic cell4'6. On the other hand, the excitatory effect of adenosine triphosphate (ATP), an adenine nucleotide, has been reported in cuneate neurons in vivo and in spinal ganglion cells in vitro 5'9. In this paper, we are reporting concentrationdependent excitatory and inhibitory biphasic effects of adenosine on neurotransmission in hippocampal slices. Guinea pigs weighing 250-300 g were used. Hippocampal slices were prepared and preincubated for at least 20 rain in standard medium (in mM): NaCI 125, NaHCO 3 26, KC1 5, CaCI2 2, KH2PO 4 1.2, MgSO 4 1.3, glucose 10. The details of the techniques used to prepare slices have been reported elsewhere 13. The slices were placed in the observation chamber and fully submerged in the standard medium continuously perfused (5 ml/min). The temperature was kept at 36 °C throughout the experiment. Under a stereomicroscope, the perforant path was stimulated electrically by means of a pair of silver wire
electrodes, and the postsynaptic field potential (PSP; population spike) was recorded in the granular cell layer of the dentate gyrus with a glass microelectrode. The stimulation was given every 2 s (square pulse 0.1 ms in duration) and the strength of electrical stimulation was adjusted to obtain the PSP at half of the maximum amplitude elicited by supramaximal stimulation. A stable PSP was recorded at least 30 min before the addition of adenosine and its analogues to the medium. Drugs were applied to the perfusion medium in the circulatory unit, and removed by washing the slices. Only one slice was used for one trial to test the effect of adenosine at single concentration applied. Adenosine, ATP, adenosine diphosphate (ADP), nicotinamide adenine dinucleotide (NAD), fl-y-methyleneadenosinetriphosphate (fl-y-ATP) and N6-R-phenylisopropyladenosine (RPIA) were purchased from Sigma. 5"-N-Ethylcarboxamidoadenosine (NECA) was purchased from Research Biochemicals Inc. N~-Cyclohexyladenosine (CHA) was purchased from Kohjin Co. Other chemicals were obtained from Nakarai, Kyoto. A typical PSP recorded from the granular cell layer is shown in Fig. 1A. After obtaining the supramaximal response of the PSP, the amplitude of the PSP was adjusted to half of the maximum amplitude (Fig. 1A-l). The amplitude of PSP increased gradually after the application of adenosine at a concentration of 0.5/~M (Fig. 1A-2), and reached a plateau after 15 min (Fig. 1A-3). After washing the slices, the PSP returned to near the original level within 15 min (Fig. 1A-4). In addition to the
Correspondence: Y. Okada, Department of Physiology,School of Medicine, Kobe University, 7-5-1 Kusunoki-cho,Chuoku, Kobe, Japan.
0006-8993/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)
166
A
..•5m=ecImV 200.
Adenosine
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