title: Sex differences in the response of postnatal rat lumbar lamina X neurons to exogenously applied galanin recorded in vitro.
abstract: Intracellular recording techniques were used in a horizontal slice preparation of postnatal rat lumbar spinal cord to compare the responses of male and female lamina X neurons to exogenously applied galanin. Although there was no significant sex difference in the resting membrane potential or input resistance of neurons, superfusion of galanin 1-16 (1 microM) produced a membrane hyperpolarization that averaged -5.3 mV in males and only -2.0 mV in females. The galanin-induced membrane hyperpolarization of lamina X neurons was accompanied by an inconsistent and varied change in input resistance. No depolarizing effect of galanin was detected in either sex. Galanin did not significantly alter the spike shape, amplitude, after hyperpolarization or locally evoked synaptic responses. The more than 2.5 fold significant sex difference in response to galanin occurred at a developmental timepoint at which lamina X expressed a comparably higher amount of galanin-like immunoreactivity in males compared to females. These results provide the first indication of a sex difference in the response of lamina X neurons to any neuropeptide. Given the antinociceptive role of galanin in the spinal cord, these results raise the possibility for the presence of distinct physiological and anatomical substrates for sex-dependent differences in nociceptive processing in lamina X of the lumbosacral spinal cord.
authors.affiliation: Department of Anatomy/Slot 510, University of Arkansas for Medical Sciences, 4301 West Markham St., Little Rock, AR 72205, USA. phelankevind@exchange.uams.edu
authors.forename: K D
authors.initials: KD
authors.lastname: Phelan
authors.forename: B W
authors.initials: BW
authors.lastname: Newton
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D017097:Electric Impedance; D004594:Electrophysiology; D019004:Galanin / Q000494:pharmacology*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008159:Lumbar Vertebrae; D009474:Neurons / Q000187:drug effects*; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects*
chemical_list: D010446:Peptide Fragments; C062019:galanin (1-16); D019004:Galanin