Chemogenetic modulation of histaminergic neurons in the tuberomamillary nucleus alters territorial aggression and wakefulness

Fumito Naganuma,Nobuyuki Okamura,Masato Tanaka,Takeo Yoshikawa,Tadaho Nakamura,Hiroshi Kuroyanagi,Kazuhiko Yanai

doi:10.1038/s41598-021-95497-3

Fumito Naganuma, Nobuyuki Okamura + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-95497-3

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Abstract

Designer receptor activated by designer drugs (DREADDs) techniques are widely used to modulate the activities of specific neuronal populations during behavioural tasks. However, DREADDs-induced modulation of histaminergic neurons in the tuberomamillary nucleus (HATMN neurons) has produced inconsistent effects on the sleep–wake cycle, possibly due to the use of Hdc-Cre mice driving Cre recombinase and DREADDs activity outside the targeted region. Moreover, previous DREADDs studies have not examined locomotor activity and aggressive behaviours, which are also regulated by brain histamine levels. In the present study, we investigated the effects of HATMN activation and inhibition on the locomotor activity, aggressive behaviours and sleep–wake cycle of Hdc-Cre mice with minimal non-target expression of Cre-recombinase. Chemoactivation of HATMN moderately enhanced locomotor activity in a novel open field. Activation of HATMN neurons significantly enhanced aggressive behaviour in the resident–intruder test. Wakefulness was increased and non-rapid eye movement (NREM) sleep decreased for an hour by HATMN chemoactivation. Conversely HATMN chemoinhibition decreased wakefulness and increased NREM sleep for 6 h. These changes in wakefulness induced by HATMN modulation were related to the maintenance of vigilance state. These results indicate the influences of HATMN neurons on exploratory activity, territorial aggression, and wake maintenance.

Highlights

Designer receptor activated by designer drugs (DREADDs) techniques are widely used to modulate the activities of specific neuronal populations during behavioural tasks
Abbreviations AAV Adeno-associated virus Arch Archaerhodopsin bed nucleus of the stria terminalis (BNST) Bed nucleus of the stria terminalis central amygdala (CeA) Central amygdala clozapine N-oxide (CNO) Clozapine N-oxide DAB Diaminobenzidine DREADDs Designer receptor activated by designer drugs EEG Electroencephalogram EMG Electromyogram HA Histamine histidine decarboxylase (Hdc) Histidine decarboxylase histamine N-methyltransferase (Hnmt) Histamine N-methyltransferase lateral hypothalamus (LH) Lateral hypothalamus non-rapid eye movement (NREM) Non-rapid eye movement OF Open field REM Rapid eye movement suprachiasmatic nucleus (SCN) Suprachiasmatic nucleus
We first confirmed that expression of chemogenetic receptors was exclusive to HATMN neurons in the posterior hypothalamus by scanning brain slices obtained after behavioural experiments for immunoreactivity to the vector marker mCherry

Summary

Introduction

Designer receptor activated by designer drugs (DREADDs) techniques are widely used to modulate the activities of specific neuronal populations during behavioural tasks. Chemogenetic and optogenetic techniques allow for the modulation of neuronal activities with regional, cellular and temporal s pecificity[3,4] Such techniques applied to HATMN neurons have yielded inconsistent effects on the sleep–wake cycle. Chemogenetic inhibition decreased wakefulness and increased non-rapid eye movement (NREM) sleep without changing REM sleep during active periods[5]. Another optogenetic study reported that acute silencing of H ATMN neurons during wakefulness promoted NREM sleep, but not REM s leep[6]. Genetic deletion (knockout, KO) of histamine N-methyltransferase (Hnmt) (EC 2.1.1.8), which metabolises histamine into inactive 1-methylhistamine, induced a sustained elevation of extracellular histamine concentration in the mouse CNS and concomitantly reduced locomotor activity during the dark periods, enhanced aggressive behaviours and disrupted the normal sleep–wake cycle without changing the total amount of w akefulness[8]

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