Dopamine enhances fast excitatory synaptic transmission in the extended amygdala by a CRF-R1-dependent process

Abstract

A common feature of drugs of abuse is their ability to increase extracellular dopamine levels in key brain circuits. The actions of dopamine within these circuits are thought to be important in reward and addiction-related behaviors. Current theories of addiction also posit a central role for corticotrophin-releasing factor (CRF) and an interaction between CRF and monoaminergic signaling. One region where drugs of abuse promote robust rises in extracellular dopamine levels is the bed nucleus of the stria terminalis (BNST), a CRF-rich component of the extended amygdala. We find that dopamine rapidly enhances glutamatergic transmission in the BNST through activation of a combination of D(1)- and D(2)-like receptors. This enhancement is activity-dependent and requires the downstream action of CRF receptor 1 (CRF-R1), suggesting that dopamine induces CRF release through a local network mechanism. Furthermore, we found that both in vivo and ex vivo cocaine induced a dopamine receptor and CRF-R1-dependent enhancement of a form of NMDA receptor-dependent short-term potentiation in the BNST. These data highlight a direct and rapid interaction between dopamine and CRF systems that regulates excitatory transmission and plasticity in a brain region key to reinforcement and reinstatement. Because a rise in extracellular dopamine levels in the BNST is a shared consequence of multiple classes of drugs of abuse, this suggests that the CRF-R1-dependent enhancement of glutamatergic transmission in this region may be a common key feature of substances of abuse.

Figure 1.

Dopamine enhances glutamatergic transmission in the dlBNST. A, Diagram of a coronal slice adapted from mouse brain atlas outlining the position of the region of interest, the dlBNST. Immunofluorescent image demonstrates the presence of both TH+ (green) fibers and CRF+ (red) neurons within this region. B, Representative sEPSC recordings in the dlBNST demonstrating the ability of dopamine to enhance glutamatergic transmission. Calibration: 25 pA, 250 ms. C, A brief (5 min) application of 1 μm dopamine transiently increases sEPSC frequency in the dlBNST. D, A brief (5 min) application of 1 μm dopamine transiently increases sEPSC amplitude in the dlBNST. Inset, Representative normalized sEPSC traces, demonstrating the lack of effect on the kinetics of the response. Calibration: 5 ms. E, Bar graph demonstrating the concentration-dependent effects of dopamine on sEPSC frequency in the dlBNST. F, Bar graph demonstrating the effects of multiple concentrations of dopamine on sEPSC amplitude in the dlBNST.

Figure 2.

Activation of both D₁-like and D₂-like receptors is required for dopamine enhancement of spontaneous glutamatergic transmission in the dlBNST. A, A brief application of dopamine (1 μm) does not alter sEPSC frequency in the presence of either the D₁-like receptor antagonist SCH23390 or the D₂-like receptor antagonist sulpiride. B, Bar graph demonstrating dopamine does not enhance sEPSC amplitude in the presence of the D1-like receptor antagonist SCH23390 (3 μm) and the D₂-like receptor antagonist sulpiride (1 μm) or in slices obtained from D₁R knock-out mice. C, A brief application of dopamine (1 μm) does not alter sEPSC amplitude in the presence of either the D₁-like receptor antagonist SCH23390 or the D₂-like receptor antagonist sulpiride. D, Bar graph demonstrating dopamine does not enhance sEPSC amplitude in the presence of the D₁-like receptor antagonist SCH23390 and the D₂-like receptor antagonist sulpiride or in slices obtained from D₁R knock-out mice. E, A brief (5 min) application of 1 μm dopamine does not alter the frequency of mEPSCs in the BNST. F, A brief (5 min) application of 1 μm dopamine does not alter the amplitude of mEPSCs in the BNST.

Figure 3.

Dopamine increases excitability in a subpopulation of neurons in the BNST. A, Representative current-clamp recording from a neuron in the dBNST that was depolarized by dopamine. Each individual trace reflects a current injection ranging from −30 to 40 pA with a 10 pA interval. Calibration: 20 mV, 200 ms. B, Scatter plot demonstrating that dopamine application resulted in a depolarization in a subpopulation of neurons. Neurons that were dramatically depolarized by dopamine are highlighted by a dashed box. C, Representative recording in a dopamine-responsive neuron demonstrating the depolarizing shift following bath application of 1 μm dopamine. Calibration: 5 mV, 1 min.

Figure 4.

CRF signaling is required for dopamine modulation of glutamatergic transmission in the BNST. A, Close up of a CRF-positive neuron (red) within the dlBNST in which TH-positive puncta (green) are localized on to the soma. Scale bar, 20 μm (see supplemental Methods for details, available at www.jneurosci.org as supplemental material). B, Bath application of the CRF-R1 antagonist, NBI27914 (1 μm), blocks the ability of 1 μm dopamine to enhance sEPSC frequency in the dlBNST. C, A brief (5 min) application of 300 nm CRF enhances sEPSC frequency in the dlBNST. D, A brief (5 min) application of 300 nm CRF does not alter sEPSC amplitude in the dlBNST. E, Bar graph demonstrating the concentration-dependent effects of CRF on sEPSC frequency in the dlBNST. F, Bar graph demonstrating the effect of a range of concentrations of CRF on sEPSC amplitude. G, A 10 min application of 300 nm Urocortin 1 enhances sEPSC frequency in the dlBNST. H, A 10 min application of 300 nm Urocortin 1 does not alter sEPSC amplitude in the dlBNST.

Figure 5.

CRF acts via CRF-R1 receptors to enhance glutamate release in the dlBNST. A, CRF induced increase in sEPSC frequency is blocked by preapplication of the CRF-R1 selective antagonist, NBI27914, but persists in the presence of the CRF-R2 selective antagonist, Astressin-2B. B, Bar graph demonstrating the effects of CRF-R1 and CRF-R2 antagonism on the ability of 300 nm CRF to alter sEPSC frequency. C, CRF does not alter sEPSC amplitude in the presence of either NBI27914 or Astressin-2B. D, Bar graph demonstrating the effects of CRF-R1 and CRF-R2 antagonism on the ability of 300 nm CRF to alter sEPSC amplitude. E, Bath application of 300 nm CRF results in a significant increase in mEPSC frequency as denoted by the shift in the cumulative probability distribution of the interevent interval. Inset, Bar graph demonstrating the average normalized increase in frequency (*p < 0.05). F, Bath application of 300 nm CRF does not result in a significant increase in mEPSC amplitude as denoted by the lack of a shift in the cumulative probability distribution of mEPSC amplitude.

Figure 6.

Cocaine produces an enhancement of NMDAR-dependent plasticity following tetanization in the dlBNST. A, Synaptic potentiation following tetanization (two 100 Hz 1 s trains with a 20 s interstimulus interval) in mice receiving an acute injection of cocaine (20 mg/kg) or saline 30 min before being killed. Inset, Representative traces 10 min after the tetanus depicting the enhancement of the N2 portion. B, Cocaine (3 μm) was bath applied for 30 min followed by a 60 min washout before tetanus. Following tetanization enhanced potentiation was observed. Time-matched controls in which no drug was applied to the slice (n = 4) are included in the time course over minutes 0–100. C, Bath application of 100 μm APV for 30 min before the tetanus attenuates LTP both when cocaine was preapplied to slices and in slices naive to cocaine application. D, Quantification of effects in C and D (0–20 min post-tetanus, **p < 0.01).

Figure 7.

Cocaine-induced enhancement of plasticity is dependent on dopamine and CRFR1 signaling. A, Diagrammatic representation of the time course of experiments shown in this figure. The arrow indicates tetanization. i, GBR12909 (10 nm) was bath applied for 30 min followed by a 60 min wash-out before tetanization. ii, Flupenthixol (10 μm) was applied 30 min before cocaine followed by coapplication with cocaine. Antagonist was removed 10 min following the removal of cocaine, and tetanization was performed 50 min following removal of antagonist. iii, NBI27914 (1 μm) was applied 30 min before cocaine followed by coapplication with cocaine. Antagonist was removed 10 min following the removal of cocaine, and tetanization was performed 50 min following removal of antagonist. B, Following tetanization, enhanced short-term potentiation was observed following exposure to GBR12909. C, Following application of cocaine in the presence of the pan-dopamine receptor antagonist, flupenthixol, there was no alteration in plasticity following tetanus. D, Following application of cocaine in the presence of the CRFR1 antagonist, NBI27914, there was no alteration in plasticity following tetanus. E, Quantification of effects of flupenthixol and NBI27914 on alterations in tetanus evoked plasticity following cocaine exposure (0–20 min post-tetanus, *p < 0.05). F, Synaptic potentiation following tetanization (two 100 Hz 1 s trains with a 20 s interstimulus interval) in D₁R KO mice receiving an acute injection of cocaine (20 mg/kg) or saline 30 min before being killed.