Role of perineuronal nets in the anterior dorsal lateral hypothalamic area in the acquisition of cocaine-induced conditioned place preference and self-administration

Abstract

Addiction involves drug-induced neuroplasticity in the circuitry of motivated behavior, which includes the medial forebrain bundle and the lateral hypothalamic area. Emerging at the forefront of neuroplasticity regulation are specialized extracellular matrix (ECM) structures that form perineuronal nets (PNNs) around certain neurons, mainly parvalbumin positive (PV⁺), fast-spiking interneurons (FSINs), making them a promising target for the regulation of drug-induced neuroplasticity. Despite the emerging significance of PNNs in drug-induced neuroplasticity and the well-established role of the lateral hypothalamic area (LHA) in reward, reinforcement, and motivation, very little is known about how PNN-expressing neurons control drug-seeking behavior. We found that a discrete region of the anterior dorsal LHA (LHAad) exhibited robust PNN and dense ECM expression. Approximately 87% of parvalbumin positive (PV⁺) neurons co-expressed the PNN marker Wisteria floribunda agglutinin (WFA), while 62% of WFA positive (WFA⁺) neurons co-expressed PV in the LHAad of drug naïve rats. Removal of PNNs within this brain region via chrondroitinase ABC (Ch-ABC) administration abolished acquisition of cocaine-induced CPP and significantly attenuated the acquisition of cocaine self-administration (SA). Removal of LHAad PNNs did not affect locomotor activity, sucrose intake, sucrose-induced CPP, or acquisition of sucrose SA in separate groups of cocaine naïve animals. These data suggest that PNN-dependent neuroplasticity within the LHAad is critical for the acquisition of both cocaine-induced CPP and SA but is not general to all rewards, and that PNN degradation may have utility for the management of drug-associated behavioral plasticity and memory in cocaine addicts.

Keywords: Addiction; Cocaine; Conditioned place preference; Dorsal anterior lateral hypothalamic area; Drug-associated memory; Extracellular matrix; Perineuronal nets; Self-administration.

Figure 1. Characterization of the lateral hypothalamic area, anterior region, dorsal/intermediate zones expressing robust PNNs [107]

(A) Depiction of the targeted region characterized by robust PNN expression using the PNN marker WFA. (B) This area correlates with the lateral hypothalamic area (LHA), anterior region (LHAa), including the dorsal (LHAad) and intermediate zones (LHAai) found dorsolateral to the fornix [29]. (C) Areas of strong PNN expression in the LHAad [29] (D) is abolished by Ch-ABC administration. (E) Patterns of distribution of WFA and PV in the rat lateral hypothalamic area, anterior region, dorsal zone (LHAad). (F) Approximately 87% of PV⁺ neurons colocalize with WFA and 62% of WFA⁺ neurons colocalize with PV (n = 6). (G) PNN expression in the LHAa ventral zone (LHAav) is comparatively sparse. (H-I) Similar patterns of sparse expression are also found just caudally in the lateral hypothalamic area (LHA) dorsal region (LHAd) of the middle LHA [29, 94].

Figure 2. Injection of Ch-ABC within the LHAad blocks the acquisition of cocaine- but not sucrose-induced CPP

Data represent time spent on cocaine- or sucrose-paired side (mean ± SEM) recorded during initial preference (IP) and test day following injections of vehicle and Ch-ABC (0.054 U/side). (A) Timeline of the CPP experiment. (B) Acquisition of cocaine-induced CPP was observed following vehicle pretreatment but not following injections of Ch-ABC into the LHAad (P < 0.05). (C) Injections sites in cocaine CPP trained animals that received vehicle (black circles) and Ch-ABC (gray circles) microinjections within the LHAad. (D) Sucrose-induced CPP was observed following injection of both vehicle and Ch-ABC into the LHAad. (E) Injection sites in sucrose CPP trained animals that received vehicle (black circles) and Ch-ABC (gray circles) microinjections within the LHAad. (F) Ch-ABC injections into brain regions adjacent, outside, but not within the LHAad failed to block the acquisition of cocaine-induced CPP. (G) Injection sites in rats tested for cocaine CPP that received vehicle (black circles) and Ch-ABC (gray circles) microinjections.

Figure 3. Injection of Ch-ABC within the LHAad attenuates the acquisition of cocaine-induced self-administration

(A) Timeline of the experiment. Data are mean ± SEM of (B) active lever presses, (C) rewards, (D) inactive lever presses, (E) active lever presses during extinction, and (F) active lever presses during the first 30-min of cue-induced reinstatement. (G) Injection sites in the LHAad for vehicle (black circles) and Ch-ABC (gray circles) cohorts.

Figure 4. Injection of Ch-ABC within the LHAad does not attenuate the acquisition of sucrose-induced self-administration

(A) The timeline of the experiment. Data are mean ± SEM of (B) active lever presses, (C) rewards, (D) inactive lever presses, (E) active lever presses during extinction, and (F) active lever presses during the first 30-min of cue-induced reinstatement. (G) Injection sites in the LHAad for vehicle (black circles) and Ch-ABC (gray circles) cohorts.