Interactions between the cholinergic and dopaminergic systems during the production of ultrasonic vocalizations in rats

Rats produce ultrasonic vocalizations that can be categorized into two types of ultrasonic calls based on their sonographic structure. One group contains 22-kHz ultrasonic vocalization (USVs), characterized by relatively constant (flat) frequency with peak frequency ranging from 19 to 28-kHz, and a call duration ranging between 100 – 3000 ms. These vocalization can be induced by cholinomimetic agents injected into the ascending mesolimbic cholinergic system that terminates in the anterior hypothalamic-preoptic area (AH-MPO) and lateral septum (LS). The other group of USVs contains 50-kHz USVs, characterized by high peak frequency, ranging from 39 to 90-kHz, short duration ranging from 10-90 ms, and varying frequency and complex sonographic morphology. These vocalizations can be induced by dopaminergic agents injected into the nucleus accumbens, the target area for the mesolimbic dopaminergic system. 22-kHz USVs are emitted in situations that are highly aversive, such as proximity of a predator or anticipation of a foot shock, while 50 kHz USVs are emitted in rewarding and appetitive situations, such as juvenile play behaviour or anticipation of rewarding electrical brain stimulation. The activities of these two mesolimbic systems were postulated to be antagonistic to each other. The current thesis is focused on the interaction of these systems indexed by emission of relevant USVs. It was hypothesized that emission of 22 kHz USVs will be antagonized by prior activation of the dopaminergic system while emission of 50 kHz will be antagonized by prior activation of the cholinergic system. It was found that injection of apomorphine into the shell of the nucleus accumbens significantly decreased the number of carbachol-induced 22 kHz USVs from both AH-MPO and LS. Injection of carbachol into the LS significantly decreased the number of apomorphine-induced 50 kHz USVs from the shell of the nucleus accumbens. The results of the study supported the main hypotheses that the mesolimbic dopaminergic and cholinergic systems function in antagonism to each other.

Interactions between the cholinergic and dopaminergic system during the production of ultrasonic vocalizations in rats

Rats produce ultrasonic vocalizations that can be categorized into two types of ultrasonic calls based on their sonographic structure. One group contains 22-kHz ultrasonic vocalization (USVs), characterized by relatively constant (flat) frequency with peak frequency ranging from 19 to 28-kHz, and a call duration ranging between 100 – 3000 ms. These vocalization can be induced by cholinomimetic agents injected into the ascending mesolimbic cholinergic system that terminates in the anterior hypothalamic-preoptic area (AH-MPO) and lateral septum (LS). The other group of USVs contains 50-kHz USVs, characterized by high peak frequency, ranging from 39 to 90-kHz, short duration ranging from 10-90 ms, and varying frequency and complex sonographic morphology. These vocalizations can be induced by dopaminergic agents injected into the nucleus accumbens, the target area for the mesolimbic dopaminergic system. 22-kHz USVs are emitted in situations that are highly aversive, such as proximity of a predator or anticipation of a foot shock, while 50 kHz USVs are emitted in rewarding and appetitive situations, such as juvenile play behaviour or anticipation of rewarding electrical brain stimulation. The activities of these two mesolimbic systems were postulated to be antagonistic to each other. The current thesis is focused on the interaction of these systems indexed by emission of relevant USVs. It was hypothesized that emission of 22 kHz USVs will be antagonized by prior activation of the dopaminergic system while emission of 50 kHz will be antagonized by prior activation of the cholinergic system. It was found that injection of apomorphine into the shell of the nucleus accumbens significantly decreased the number of carbachol-induced 22 kHz USVs from both AH-MPO and LS. Injection of carbachol into the LS significantly decreased the number of apomorphine-induced 50 kHz USVs from the shell of the nucleus accumbens. The results of the study supported the main hypotheses that the mesolimbic dopaminergic and cholinergic systems function in antagonism to each other.

The Role of Orexin-A in Anxiety and the Emission of Ultrasonic Vocalizations in Rats

Central administration of orexin-A has been shown to activate autonomic arousal in rats, reliably inducing anxiety-like behaviours in the open field. To date, there has yet to be a study investigating the role of orexin-A in the communication of such negative affective state. In the current study, forty-six adult male rats were chronically cannulated and administered orexin-A into the medial preoptic area/anterior hypothalamic area to determine the effect of this neuropeptide on anxiety-like behaviour and the production of 22 kHz aversive ultrasonic vocalizations. It was found that intracerebral administration of orexin-A increased autonomic arousal as measured by a significant increase in fecal boli output, however orexin-A did not significantly affect locomotor activity or induce 22 kHz calling. These data suggest that orexin-A is involved in the regulation of the autonomic aspect of anxiety-like behaviour but not in the vocal communication of such negative affect

Investigation of the role of the nucleus accumbens in amphetamine-induced 50 kHz ultrasonic vocalizations in the rat

There is extensive evidence that the mesolimbic dopamine system underlies the production of 50 kHz ultrasonic vocalizations in rats. In particular, the shell of the nucleus accumbens is associated with generation of frequency modulated 50 kHz calls (a specific type of 50 kHz call which can be subdivided into various subtypes). There is also evidence that amphetamine administered systemically preferentially increases the proportion of trill and step calls compared to other frequency modulated 50 kHz subtypes. The purpose of this study was to investigate the effect of drug administration route and the role of the nucleus accumbens shell in amphetamine-induced 50 kHz call profile in the rat. Three experiments investigated this by using subcutaneous and intra-accumbens microinjections of amphetamine, as well as procaine (a local anesthetic) blockade of the nucleus accumbens. Ultrasonic vocalizations were recorded digitally from 24 rats and were analysed for sonographic structure based on general call parameters. The results of the three experiments were partially supportive of the hypotheses. Systemic amphetamine was found to induce greater bandwidth in 50 kHz calling compared to spontaneous calls in a vehicle condition. Systemic amphetamine was also found to preferentially increase the proportion of trill and step subtypes compared to vehicle. Moreover, there was no difference in the proportions of 50 kHz subtypes resulting from intracerebral or systemic application of amphetamine. There was, however, a significant difference for bandwidth, with systemic amphetamine inducing greater bandwidth over intraaccumbens application. Procaine blockade of the nucleus accumbens shell paired with subcutaneous amphetamine produced no difference in bandwidth of calls compared with those after a vehicle pre-treatment similarly paired. There was no reduction in the proportions of trill and step 50 kHz subtypes as well, with the procaine condition showing significantly greater proportion of step calls. The results of the study support a role for the iii nucleus accumbens shell in the amphetamine-induced changes on 50 kHz call profile. They also indicate there are more regions and pathways involved in generating 50 kHz calls than the projections from the ventral tegmental area to the nucleus accumbens. The implications of this work are that frequency modulated 50 kHz subtypes may be generated by distinct neurophysiological mechanisms and may represent a profitable avenue for investigating different circuits of 50 kHz call categories in the rat.

Of mice, birds, and men: the mouse ultrasonic song system has some features similar to humans and song-learning birds.

Humans and song-learning birds communicate acoustically using learned vocalizations. The characteristic features of this social communication behavior include vocal control by forebrain motor areas, a direct cortical projection to brainstem vocal motor neurons, and dependence on auditory feedback to develop and maintain learned vocalizations. These features have so far not been found in closely related primate and avian species that do not learn vocalizations. Male mice produce courtship ultrasonic vocalizations with acoustic features similar to songs of song-learning birds. However, it is assumed that mice lack a forebrain system for vocal modification and that their ultrasonic vocalizations are innate. Here we investigated the mouse song system and discovered that it includes a motor cortex region active during singing, that projects directly to brainstem vocal motor neurons and is necessary for keeping song more stereotyped and on pitch. We also discovered that male mice depend on auditory feedback to maintain some ultrasonic song features, and that sub-strains with differences in their songs can match each other's pitch when cross-housed under competitive social conditions. We conclude that male mice have some limited vocal modification abilities with at least some neuroanatomical features thought to be unique to humans and song-learning birds. To explain our findings, we propose a continuum hypothesis of vocal learning.

The role of the dopaminergic system in the production of ultrasonic calls in adult rats /

Ultrasonic vocalizations (USV) are emitted by rats in a number of social situations such as aggressive encounters, during sexual behavior, and during play in young rats, situations which are predominantly associated with strong emotional responses. These USV typically involve two distinct types of calls: 22 kHz calls, which are emitted in aversive situations and 50 kHz calls, which are emitted in non-aversive, appetitive situation. The 50 kHz calls are the focus of the present study and to date both the glutamatergic and the dopaminergic systems have been independently implicated in the production of these 50 kHz calls. The present study was conducted to examine a possible relationship between glutamate (GLU) and dopamine (DA) in mediating 50 kHz calls. It was hypothesized that the dopaminergic system plays a mediating role in 50 kHz calls induced by injections ofGLU into the anterior hypothalamic/preoptic area (AHPOA) in adult rats. A total of 68 adult male rats were used in this study. Rats' USV were recorded and analyzed in five experiments that were designed to test the hypothesis: in experiment 1, rats were treated with systemic amphetamine (AMPH) alone; in experiment 2, intra- AHPOA GLU was pretreated with systemic AMPH; in experiment 3, intra-AHPOA GLU was pretreated with intra-AHPOA AMPH; in experiment 4, rats were treated with high and low doses of intra-AHPOA AMPH only; in experiment 5, rats were treated with systemic haloperidol (HAL) as a pretreatment for intra-AHPOA GLU. Analysis of the results indicated that AMPH has a facilitatory effect on 50 kHz USV and that a relationship between DA and GLU in inducing 50 kHz calls does exist. The effect, however, was only observed when DA receptors were antagonized with HAL and was not seen with systemic AMPH pretreatments of intra-AHPOA GLU. The DAGLU relationship at the AHPOA was unclear.

Effects of low doses of quinpirole on production of 50 kHz vocalizations in Wistar rats

Rats emit two distinct types of ultrasonic vocalizations in adulthood: 22 kHz (aversive situation), and 50 kHz calls (appetitive situation). The present project is focussed on pharmacological studies of 50 kHz vocalizations. The 50 kHz calls are elicited from dopaminergic activation in the meso limbic pathway and are emitted in such appetitive situations as social contact(s), sexual encounters, food reward, etc. Eighty-five male rats were stereotaxically implanted with bilateral guide cannulae in the nucleus accumbens shell (A= 9.7, L= 1.2, V= 6.7). Quinpirole, a D2/D3 dopaminergic agonist, was injected in low doses to the nucleus accumbens shell in an attempt to elicit 50 kHz vocalizations. A dose response was obtained for the low dose range of quinpirole for six doses: 0.025 Jlg, 0.06 Jlg, 0.12 Jlg, 0.25 Jlg, 0.5 Jlg, and 1.0 Jlg. It was found that only application of the 0.25 Jlg dose of quinpirole and the 7 Jlg dose of amphetamine (positive control) significantly increased the total number of 50 kHz calls (p < 0.006 and p < 0.004 respectively); and particularly significantly increased the frequency modulated type of these calls (p < 0.01, and p < 0.006 respectively). In a double injection procedure, the dose of 0.25 Jlg quinpirole was antagonized with raclopride (D2 antagonist) or U99194A maleate (D3 antagonist) in an attempt to antagonize the response. The 0.25 Jlg dose of quinpirole was successfully antagonized by pre-treatment with an equimolar dose of U99194A maleate (p < 0.008) but not with raclopride. The 7Jlg amphetamine response was also antagonized with an equimolar dose of raclopride. Based on these results, it seems that low doses of quinpirole, particularly the 0.25 Jlg dose, are capable of increasing 50 kHz vocalizations in rats and do so by activation of the D3 dopamine receptor. This is not a biphasic response as seen with locomotor studies. Also noteworthy is the increase in frequency modulated 50 kHz calls elicited by the 0.25 Jlg dose of quinpirole indicating a possible increase in positive affect.

Pharmacological analysis of 50 kHz vocalizations in the male rat

The production of 50 kHz ultrasonic vocalizations in rats has been associated with both positive social interactions and appetitive behavioural situations. Furthermore, there is significant evidence showing that these vocalizations are controlled by the meso-limbic dopamine system. The purpose of this study was to perform a pharmacological analysis of 50 kHz calls by using dopamine and two dopamine agonists amphetamine and apomorphine, to induce calls. The acoustic parameters of the different call types were compared across each agonist. All three agonists were able to significantly induce more 50 kHz vocalizations compared to the vehicle control. Furthermore, calls elicited by apomorphine had a significantly higher bandwidth compared to those elicited by dopamine and amphetamine. All three agonists also had significantly different pharmacokinetic properties. These observations suggest that the D2 receptor sub-type is involved in the length of call bandwidths.

海马环路中的组合突触可塑性与大鼠情绪研究

海马在某些类型的学习和记忆中起着关键的作用，而突触可塑性（synaptic plasticity）为学习和记忆的模型提供了理论基础。在海马环路中，分布着各种类型的可塑性，包括突触特异的Hebbian形式的可塑性，如长时程增强（long-term potentiation，LTP）和长时程抑制（long-term depression，LTD）；稳态可塑性（homeostatic plasticity），如突触缩放（synaptic scaling）。稳态可塑性是一种整体的调控过程，它可以调节神经元甚至神经网络的平衡；而Hebbian可塑性则是突触特异的，即每个突触进行单独调控的过程。 越来越多的研究提示稳态可塑性和Hebbian可塑性之间存在着空间间隙（spatial gap），那么，如何使得神经元可以通过Hebbian可塑性的过程来维持细胞整体的兴奋性就变得尤为重要。一些报道揭示了LTP和LTD可以在同一突触通路中同时被激活，因此，我们提出组合突触可塑性的概念，即LTP和LTD的组合，它在赋予系统灵活性的同时又可以降低噪音维持系统的稳定性。基于此，本文将围绕这个问题而开展实验工作。 通过对海马CA1区锥体神经元的微小兴奋性突触后电流（miniature excitatory synaptic current, mEPSC）进行测定分析，我们发现mEPSC的幅度分布符合双峰正态分布（double-peak normal distribution）。Theta节律刺激（theta burst stimuli, TBS）诱导后，mEPSC的幅度分布发生改变，呈现右移趋势。随后，采用干扰肽Pep-A2特异地阻断LTP而不影响LTD，我们发现Pep-A2不影响基础状态下mEPSC的幅度分布。在干扰肽Pep-A2存在下，TBS诱导对基础状态下mEPSC的幅度分布也没有影响。结果为揭示LTP和LTD的组合可塑性提供了初步的证据，对进一步理解记忆的编码过程提供了一定的基础。社交隔离可以引起实验大鼠产生焦虑样和抑郁样的行为，而性经历可以改变动物的情绪状态，降低焦虑样和抑郁样的反应。然而，性经历后进行社交隔离对大鼠情绪的影响并没有报道。在这部分工作中，雄性大鼠经历一周的社交活动（male-male paired housing）或者性活动（male-female paired housing），随后进行一段时间的隔离（1天，2天或者7天）。我们发现，经历过性活动的大鼠，无论隔离与否都表现出相似的情绪反应，包括焦虑样和抑郁样行为以及超声波（ultrasonic vocalizations，USVs）发放；而未经历过性活动的大鼠，其情绪反应随着隔离时间的不同而不同。这一现象提示我们，先前的性经历可以对抗实验动物对环境应激事件，如社交隔离的反应。

Male mice song syntax depends on social contexts and influences female preferences.

In 2005, Holy and Guo advanced the idea that male mice produce ultrasonic vocalizations (USV) with some features similar to courtship songs of songbirds. Since then, studies showed that male mice emit USV songs in different contexts (sexual and other) and possess a multisyllabic repertoire. Debate still exists for and against plasticity in their vocalizations. But the use of a multisyllabic repertoire can increase potential flexibility and information, in how elements are organized and recombined, namely syntax. In many bird species, modulating song syntax has ethological relevance for sexual behavior and mate preferences. In this study we exposed adult male mice to different social contexts and developed a new approach of analyzing their USVs based on songbird syntax analysis. We found that male mice modify their syntax, including specific sequences, length of sequence, repertoire composition, and spectral features, according to stimulus and social context. Males emit longer and simpler syllables and sequences when singing to females, but more complex syllables and sequences in response to fresh female urine. Playback experiments show that the females prefer the complex songs over the simpler ones. We propose the complex songs are to lure females in, whereas the directed simpler sequences are used for direct courtship. These results suggest that although mice have a much more limited ability of song modification, they could still be used as animal models for understanding some vocal communication features that songbirds are used for.

Hypoactivity of the central dopaminergic system and autistic-like behavior induced by a single early prenatal exposure to lipopolysaccharide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação do estado emocional associado à catalepsia causada pela administração intraperitoneal de haloperidol

Haloperidol is a dopamine receptor antagonist used to treat schizophrenia. When systemically administered in rodents, haloperidol induces catalepsy, a state of immobility very similar to that seen in Parkinson's disease. It is known that many of Parkinson's disease symptoms are dependent on the emotional state since patients are still able to respond to external triggers such as loud noise or visual signaling. Recent data highlighted the importance of glutamatergic neurotransmission in the inferior colliculus (IC) on the cataleptic state induced by haloperidol in rats. Given the importance of IC in the brain aversion system and its connections to motor pathways, and based on the clinical reports of the emotional influence on the motor aspect of Parkinson's disease, the objective of the present study was to evaluate the emotional aspect related to catalepsy induced by intraperitoneal administration of haloperidol. To this end, we analysed ultrasonic vocalizations (UVs) of 22 kHz (indicative of aversion) in rats during the tests of catalepsy, open field and contextual conditioned fear. Systemic administration of haloperidol affected the motor activity, inducing catalepsy and decreasing exploratory activity in the open field. There were no UVs of 22 kHz resulting from treatment with haloperidol in catalepsy or open field tests. In the contextual conditioned fear test, haloperidol increased freezing when administered before the test, but decreased freezing on test day when administered before training. In this same test, haloperidol decreased the UVs on the day it was administered (training or test). The catalepsy induced by systemic administration of haloperidol seems to have also affected the motor aspect of UVs. In this way, it was not possible to clarify the existence of an aversive emotional state associated haloperidol induced catalepsy

Analysis of the chronic intake of and withdrawal from diazepam on emotional reactivity and sensory information processing in rats

It has been demonstrated that, on abrupt withdrawal, patients with chronic exposure can experience a number of symptoms indicative of a dependent state. In clinical patients, the earliest to arise and most persistent signal of withdrawal from chronic benzodiazepine (Bzp) treatment is anxiety. In laboratory animals, anxiety-like effects following abrupt interruption of chronic Bzp treatment can also be reproduced. In fact, signs that oscillate from irritability to extreme fear behaviours and seizures have been described already. As anxiety remains one of the most important symptoms of Bzp withdrawal, in this study we evaluated the anxiety levels of rats withdrawn from diazepam. Also studied were the effects on the motor performance and preattentive sensory gating process of rats under diazepam chronic treatment and upon 48-h withdrawal on three animal models of anxiety, the elevated plus-maze (EPM), ultrasonic vocalizations (USV) and startle + prepulse inhibition tests. Data obtained showed an anxiolytic- and anxiogenic-like profile of the chronic intake of and withdrawal from diazepam regimen in the EPM test, 22-KHz USV and startle reflex. Diazepam chronic effects or its withdrawal were ineffective in promoting any alteration in the prepulse inhibition (PPI). However, an increase of PPI was achieved in both sucrose and diazepam pretreated rats on 48-h withdrawal, suggesting a procedural rather than a specific effect of withdrawal on sensory gating processes. It is also possible that the prepulse can function as a conditioned stimulus to informing the delivery of an aversive event, as the auditory startling-eliciting stimulus. All these findings are indicative of a sensitization of the neural substrates of aversion in diazepam withdrawn animals without concomitant changes on the processing of sensory information