Central amygdala input circuits control stress-induced anxiety after chronic ETOH

Project: Research project

Description

During abstinence from alcohol, stress in alcoholics can result in negative affect and craving (1), a response which is accompanied by a change in brain functional magnetic resonance imaging (fMRI)—effects of stress not seen in social drinkers (2). Additionally, an extended period of chronic intermittent alcohol (CIA) exposure was found to cause an enduring adaptation that sensitizes stress-induced negative affect during ethanol abstinence. These series of clinical and basic findings are consistent with the kindling/stress hypothesis of alcoholism. Even though the central amygdala (CeA) is known to play an important role in stress-induced negative affect after CIA exposure, unknown is the role input circuits to the CeA have in facilitating this stress-induced anxiety. Among the inputs that synapse on CeA neurons include the basolateral amygdala (BLA) glutamate (GLU)-, hypothalamic oxytocin (OXY)- and vasopressin (VP)-containing terminals. Nonetheless, the influence of these inputs on the stress-induced anxiety after CIA exposure has not been identified. Likewise unidentified is whether CeA medial division (CEM) neurons that output terminals to the periaqueductal gray (PAG) are a critical component of the neural circuit that supports stress-induced anxiety associated with CIA. To address these unknowns, the hypothesis tested is that stress facilitates anxiety during abstinence from CIA exposure by influencing a neural circuit composed of terminal inputs to the lateral (CEL) and medial (CEM) divisions of the CeA that modulate CEM output to the periaqueductal gray (PAG). First, an AAV5-eYFP vector with a CAMKII promoter containing the rhodopsin derivatives halorhodopsin (NpHR3.0) or channel-rhodopsin (ChR2) will be placed in the BLA to document localization of GLU terminals from the BLA to the lateral (CEL) and the medial (CEM) divisions of the CeA. Subsequently determined with optogenetics is whether ChR2 activation or NpHR3.0 inhibition of BLA terminal release of GLU on CEL neurons will influence facilitation of stress-induced anxiety after CIA exposure. This latter optogenetic strategy will be complemented by determining if activation of CEL neurons with an OXY receptor agonist will block facilitation of stress-induced anxiety after CIA exposure. After investigating CEL neural inputs, optogenetic inhibition or excitation of GLU-containing BLA terminals synapsing on CEM neurons will assess if the stress-induced anxiogenic action after CIA exposure is affected. Because VP-containing terminals synapse on CEM neurons to induce anxiety-like behavior, it is reasoned that activation of CEM neurons with VP receptors may contribute to the anxiety induced by stress following CIA exposure. To confirm a direct involvement of CEM neurons in VP action, an AAV-eYFP vector with NpHR3 expressed in CEM neurons will test if optogenetic inhibition of CEM neurons will prevent both stress- as well as VP-induced anxiety after CIA exposure. To confirm that VP action contributes to stress-induced anxiety after CIA exposure, VP receptor subtypes in the CEM will be pharmacologically antagonized prior to stress to determine if the stress-induced anxiety after CIA exposure is prevented. Upon confirmation of CEM terminal presence in the PAG, PAG involvement in stress- and VP-induced anxiety observed after CIA exposure will be assessed by optogenetic inhibition or excitation of neural activity of CEM terminals in the PAG—an approach to implicate both the CEM and the PAG in facilitation of the stress-induced anxiety after CIA exposure. Collectively, the proposed pharmacological and optogenetic strategies utilized can be expected to define whether neural involvement of specific neural inputs to the CEL and CEM as well as the CEM output to the PAG form a circuit that influences facilitation of stress-induced negative affect after CIA exposure. This proposed circuit involving the CeA is felt to be responsible for the neuropathology responsible for the faci
StatusFinished
Effective start/end date7/15/136/30/18

Funding

  • NIH National Institute on Alcohol Abuse and Alcoholism (NIAAA)

Fingerprint

Anxiety
Alcohols
Optogenetics
Periaqueductal Gray
Neurons
Vasopressins
Glutamic Acid
Vasopressin Receptors
Rhodopsin
Central Amygdaloid Nucleus
Synapses
Halorhodopsins
Alcohol Abstinence
Oxytocin Receptors
Oxytocin
Alcoholics
Alcoholism
Ethanol
Magnetic Resonance Imaging
Basolateral Nuclear Complex