Editor’s choice :  PTA, DPOAE & VIBRATORY BC...?

Developing rat ac & serotonin...?

This interesting animal study from USA (GJ Basura et al, Hearing Research 244 (2008) 45–50) which utilized immunocytochemistry with confocal imaging to locate 2-HT_2A receptors represents the first attempt to evaluate 5-HT_2A receptor levels and 5-HT metabolite content specifically in the developing rat auditory cortex.

 

october 16  2008

Vol 8 No 10

Otorhinolaryngology news

In this issue

· PTA, DPOAE, & VIBRATORY BC…?

· Developing Rat AC & Serotonin…?

· Prelingually deafened adults and CI..?

· Case of The week

Coming Events of Importance to Otorhinolaryngologists in Africa

Journal Watch: TORP-Vibroplasty: A New Alternative for the Chronically Disabled Middle Ear. Kahl-Bernd Huttenbrick et al, 2008

 1. Home page of otolaryngologyinafrica.net re-designed for accessibility

2.    A new forum for ENT patients and clinicians launched, For Details, click HERE

3. Receive the latest newsletter info. On your cell phone. Simply point your phone browser http://mobile.otolaryngologyinafrica.net

 Till Next Week,

 Biodun

Abstract:

To clarify the contribution of the skull contents to the transmission of bone vibratory stimuli, and to examine the characteristics of such stimuli, we compared auditory thresholds and distortion-product otoacoustic emission (DPOAE) levels with a bone vibrator placed on various sites of the head, including the eye. The best audiometric thresholds and the highest DPOAE levels were obtained with the vibrator placed on the mastoid of the measuring side, or on the “ultrasound-window” of the temple. The audiometric thresholds obtained with the bone vibrator on the eye were similar to those of the forehead, and about 10 dB higher than at the best sites. DPOAEs were clearly present when elicited by a combination of air-conducted stimuli presented through an insert earphone and with the bone vibrator placed on the eye. These results indicate that vibratory sounds can be transmitted through the skull contents to the inner ear. The intracranial transmission pathway of the vibratory stimuli may play a significant role, particularly at low frequencies, and possibly also when the vibratory stimuli are applied on the skull bone.

© Copyright Dr 'Biodun Olusesi,  2005 - 2008

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Abstract:

Maturation of the mammalian cerebral cortex is, in part, dependent upon multiple coordinated afferent neurotransmitter systems and receptor-mediated cellular linkages during early postnatal development. Given that serotonin (5-HT) is one such system, the present study was designed to specifically evaluate 5-HT tissue content as well as 5-HT2A receptor protein levels within the developing auditory cortex (AC). Using high performance liquid chromatography (HPLC), 5-HT and the metabolite, 5-hydroxyindoleacetic acid (5-HIAA), was measured in isolated AC, which demonstrated a developmental dynamic, reaching young adult levels early during the second week of postnatal development. Radioligand binding of 5-HT2A receptors with the 5-HT2A/2C receptor agonist, 125I-DOI ((+/-)-1-(2,5-dimethoxy-4-iodophenyl)- 2-aminopropane HCl; in the presence of SB206553, a selective 5-HT2C receptor antagonist, also demonstrated a developmental trend, whereby receptor protein levels reached young adult levels at the end of the first postnatal week (P8), significantly increased at P10 and at P17, and decreased back to levels not significantly different from P8 thereafter. Immunocytochemical labeling of 5-HT2A receptors and confocal microscopy revealed that 5-HT2A receptors are largely localized on layer II/III pyramidal cell bodies and apical dendrites within AC. When considered together, the results of the present study suggest that 5-HT, ikely through 5-HT2A receptors, may play an important role in early postnatal AC development.