**2.3. Anesthesia**

20 Neuroendocrinology and Behavior

**2. Materials and methods** 

**2.2. Experimental protocol** 

**2.1. Animal care** 

instance, a research has indicated that mCPP (a serotonin receptor agonist) microinjections to amygdala increased behavioral indices of anxiety without altering general activity level. In other words, it decreased open arm time and entries, but increased the closed arm ones (Cornelio and Nunes de Souza, 2007). In another study, Herdade et al. (2006) injected locally muscimol (a GABAA receptor agonist) to the medial nucleus of the amygdala and found that

In addition to the regulatory role of amygdala in anxiety, amygdala is of great importance in regulating memory and learning functions. The amygdala is responsible for determining what memories are stored and where the memories are stored in the brain. The removal of the temporal lobe in animals leads to an impairment in memory and this impairment is global and thus none of the sensory memory is developed. For instance, the subjects experience difficulties in learning new material (i.e., anterograde amnesia) after the removal of amygdala (Almonte et al., 2007). One research has shown that amygdala damage leads to an impairment of learning an association between an auditory cue and food reward. When scopolamine, the muscarinic receptor antagonist, was injected to amygdala, it impaired performance on conditioned place preference task but not a spatial radial maze task (McIntyre et al., 1998). Moreover, the infusion of nicotinic receptor antagonists methyllycaconitine (MLA) or dihydro-b-erythroidine (DHbE) impaired working memory (Addy et al., 2003). Taken together, these findings suggest that amygdala damage has detrimental effect on the cognitive performance. However, the effect of melatonin administration to amygdala was not well known prior to the research mentioned below. The administration of melatonin to amygdala with the abolishment of melatonin hormone via pinealectomy might produce different effects on anxiety-like and learning behaviors. In other words, the endogeneous melatonin concentration and the rhythm of melatonin release

might affect the effects of exogeneous melatonin administration on such behaviors.

facilities were held constant at 22 2 C in air-ventilated rooms.

A total of forty seven adult male Wistar rats (200 – 250 g) were obtained from our laboratory colony maintained at the Abant Izzet Baysal University (AIBU). They were exposed from birth to 12L (12 hour of light, 12 hour of darkness, lights off at 1800 hr). Animals were maintained in plastic cages (16x31x42 cm) with pine shavings used as bedding. Food pellets and tap water were accessible ad libitum. The procedures in this study were carried out in accordance with the Animal Scientific procedure and approved by the Institutional Animal Care and Use Committee. All lighting was provided by the cool-white fluorescent tubes controlled by automatic programmable timers. The ambient temperatures in the animal

A total of the forty seven male adult rats were used and were randomly divided into two groups as control (sham –pinealectomy) and pinealectomy in this study. In the control

such treatment inhibited escape behavior in elevated T maze.

Before surgery, rats were anesthetized subcutaneously with Ketamine (20 mg/kg BW, Sigma Chemical Company, MO, USA) and intraperiotoneally with pentobarbitol (32.5 mg/kg BW). The depth of anesthesia was monitored by frequent testing for the presence of leg flexion reflexes and active muscle tonus. After awaking from anesthesia, the animals were placed in their cages.
